Assessment of weathering and subterranean termite resistance in three thermally modified wood species in Portugal

Assessment of weathering and subterranean termite resistance in three thermally modified wood species in Portugal | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Assessment of weathering and subterranean termite resistance in three thermally modified wood species in Portugal Delfina Godinho, Ana Lourenço, Solange Oliveira Araújo, José Saporiti Machado, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5137187/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Jan, 2025 Read the published version in European Journal of Wood and Wood Products → Version 1 posted 9 You are reading this latest preprint version Abstract The main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were Maritime Pine, Ash, and Blackwood acacia. All wood samples were exposed to two different environments (urban and maritime/industrial) for 24 months. Then, its physical and mechanical properties were evaluated (modulus of elasticity (MOE), modulus of rupture (MOR), compression strength (CS), and modulus of compression (MOC)). Thermally modified woods revealed a lower density, which could explain the loss of MOE and MOR. In compression, no significant changes were verified. The weathered samples revealed changes in mechanical properties, mostly verified in MOE and MOR, where some decreases were reported in both locations. Tests were performed to evaluate biodegradation and the resistance of all wood samples to subterranean termites. The grade of attack (≈ 4) and termite survival rate were similar in all wood species (above 75% and lower than 80%), except for Modified Acacia (59%), which could indicate that thermal modification increased toxic substances. The cellulose degradation was reflected in FTIR-ATR and Py/GC-MS in natural and thermally modified woods. Py/GC-MS showed a decrease in levoglucosan, while lignin suffered some modifications with slight changes in monomeric composition reflected by the reduction of the S/G ratio. No changes were found between the two environments, and thermal modification did not give extra protection against termites and weathering. Figures Figure 1 Figure 2 Figure 3 1. Introduction Wood is one of the most ancient materials used by humans in construction. Its flexibility, strength, elasticity, and workability make it an extremely versatile material. Today, wood is used in a wide range of applications, from indoor furniture to outdoor uses in building construction. However, when applied outdoors, wood is exposed to various conditions, such as weathering and biodegradation. Thermal treatment can increase wood durability and overcome weathering and biodegradation. Over the years, different wood protection technologies have been developed to protect wood against these environmental aggressions. One type of wood protection technology is wood modification, which changes wood chemically and helps protect wood against degradation (Ormondroyd et al. 2015 ). One of the most common wood modification technologies worldwide is thermal modification (Esteves and Pereira 2009 ; Jones et al. 2019 ; Godinho et al. 2021 ; Hill et al. 2021 ). Wood weathering is a slower degradation caused by sun radiation, rain, humidity, and wind, among other climatic factors (Nuopponen et al. 2004 ; Williams 2005 ; Godinho et al. 2021 , 2024 ). Usually, it causes wood surface alterations, namely color, chemical, physical, mechanical, and morphological changes (Tomak et al. 2018 ; Cui and Matsumura 2019 ; Humar et al. 2019 ; Godinho et al. 2024 ). The main biodegradation factors that attack wood are wood decay fungi and xylophages. In the xylophage group, insects such as subterranean termites ( Reticulitermes grassei Clément) negatively impact some wood structures. They live and reproduce in soil; their food is wood (Cárdenas et al. 2020 ). In nature, subterranean termites are very important in the organic decomposition process, either in the plant decomposition or by direct consumption (Nunes 2008 ), promoting nitrogen fixation and helping the nutrient deposition in the soil (Nunes 2008 ; Cárdenas et al. 2020 ). This termite species is distributed in the Iberian Peninsula's northern, western, and southern parts of France (Clément et al. 2001 ; Cárdenas et al. 2020 ). These insects have particular bacteria in their digestive system that help to degrade cellulose, causing severe damage to the strength properties of wood (Deka et al. 2002 ). The main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were maritime pine ( Pinus pinaster ), Ash ( Fraxinus excelsior ), and blackwood acacia ( Acacia melanoxylon ). 2. Materials and Methods 2.1. Material - natural and thermal-modified wood specimens The wooden material tested comprised two hardwood species, Acacia ( Acacia melanoxylon R. Br.) and Ash ( Fraxinus excelsior L.), and one softwood species, maritime pine ( Pinus pinaster Aiton), which served as reference. All wood samples used in this research were sourced from Portugal. Each specimen underwent thermal modification in an industrial facility using the Thermowood ® process, specifically under Thermo-D conditions. Each wood was subjected to a temperature of 210°C during approximately 6 h. 2.2. Weathering conditions To compare the degradation in different environments, the samples were exposed in two locations in Portugal, Lumiar (Lisbon) and Sines test sites (Table 1 ), between October 2019 and November 2021. The specimens for natural exposure had two different sizes, 100x320x20mm and 100x 320x40mm (width x length x thickness), according to the standards EN 927-3:2019 and ISO 13061-4:2014 standard. All wood samples were exposed at 45°, according to EN 927-3:2019. The corrosivity of the environments was evaluated according to ISO 9223:2012. The Sines test site is a location with strong industrial and maritime influence and is classified as C5 (very high corrosivity) and Lumiar, an urban test site classified as C2 (low corrosivity) during the exposure period (Table 1 ). Table 1 Characterization of the exposure test sites. The samples were exposed between October 2019 and November 2021 (Values as mean ± standard deviation) (Godinho et al. 2024 ). Location Climatic conditions Sines Lumiar Latitude 37.95°N 38.77°N Longitude 8.88°W 9.17°W Altitude (m) 17 116 Temperature (°C) 16.4 ± 2.5 17.0 ± 3.9 Global radiation (J cm − 2 ) 1 663.3 ± 477.7 2 177.2 ± 1036.4 Relative humidity (%) 85.3 ± 17.9 69.0 ± 6.6 Rain (mm) 24.4 ± 31.4 54.0 ± 48.4 Air pollutants deposition (mg day − 1 mm − 2 ) SO 2 36.0 ± 25.9 8.8 ± 5.2 Cl − 116.3 ± 70.2 17.5 ± 16.0 Environment type Maritime/ Industrial Urban Corrosivity category for steel* C5 (very high) C2 (low) *According to ISO 9223: 2012. 2.3. Bending and compression strength The wood samples (natural, thermal-modified wood, and the weathered test pieces) were placed inside a climatic chamber at 20 ± 2°C temperature and 65 ± 5% relative humidity until a constant mass was reached (difference between weight measurements in a period of 24 h ≤ 0.1%). The bending strength (MOR) and modulus of elasticity (MOE) were determined by a three-point bending test according to ISO 13061-4:2014 standard. Compression parallel to the grain was performed in a 250 kN universal testing machine, with 1% load accuracy, and the displacement was measured using the machine crosshead displacement, with a 1% deformation accuracy. Compression strength (CS) and modulus of compression (MOC) were determined according to ISO 13061-5:2020 standard. For each parameter, 10 replicates were tested, and statistical analysis was performed using a t-student test to verify significant differences between the mean values. It established a p < 0.05 significance value. 2.4. Durability assessment 2.4.1. Durability against subterranean termites The susceptibility of thermally modified wood against subterranean termite ( Reticulitermes grassei Clément) was accessed following an adaptation of the European standard EN 117:2012, with natural wood as the control. Each type of thermally modified wood underwent six replicates, alongside six replicates of the control (natural wood), using wood samples measuring 30x10x10 mm. Pine wood was also selected as the control for all species examined in this study, following the EN 117:2012 standard. The assays focused solely on natural and thermally modified woods to evaluate the effectiveness of thermal modification in protecting wood against subterranean termites. The termites were collected in a maritime pine forest in the Sesimbra region, Portugal, and were kept in the laboratory for less than two weeks before the assays. Groups of 150 termite workers were exposed to the samples for four weeks, maintained in a climatic chamber at 24 ± 2°C and relative humidity of 80 ± 5%. At the end of the trial period, the termite survival rate, defined as the percentage of living termites at the end of the test (SR), and visual grading of the test specimens were evaluated using the standard rating system (0 = no attack, 1 = attempted attack, 2 = slight attack, 3 = average attack and 4 = strong attack) were determined. The test is valid if all control test specimens have a strong attack (rating of 4) and the termite's survival rate is above 50%. Additionally, the wood mass loss (%) was also calculated as follows: $$\:ML\:\left(\%\right)=\:\frac{{(m}_{01}-\:{m}_{02})}{{m}_{01}}\times\:100$$ where: ML - is mass loss after termite exposure; m 01 - is the dry mass of samples before termite exposure; m 02 - is the dry mass of wood samples after termite exposure. 2.5. Chemical characterization 2.5.1. FTIR – ATR spectroscopy Samples of each wood (natural and modified) exposed to termite decay were extracted in a Soxhlet apparatus by a sequence of solvents (dichloromethane, ethanol, and water for 6-12h each solvent). Following extraction, FTIR-ATR spectra were acquired using a Perkin Elmer Spectrum Two, equipped with a UATR Two accessory with a diamond crystal, operating at a resolution of 4 cm − 1 with eight scans. Baseline correction was performed at three specific points. Difference spectra were calculated to compare all wood samples subject to varying degrees of attack. Data processing was carried out using Spectragryph 1.2.15 software, and the spectra were analyzed within the range of 1800 − 800 cm − 1 , as this region exhibited the most pronounced changes. 2.5.2. Analytical pyrolysis (Py-GC/MS) The extracted samples were analyzed Py-GC/MS after sample preparation by milling for 10 min in a Retsch MM20 mixer ball mill, then dried at 35°C in a vacuum oven. Around 0.10 mg of each sample was weighted and pyrolyzed at 550°C (for 1 min) in a platinum coil Pyroprobe connected to a CDS 5150 valved interface linked to the GC-MS (Agilent 7890B & 5977B). A fused-silica capillary column (ZB-1701: 60m x 0.25 mm i.d. x 0.25 µm film thickness) was used to separate the volatiles. The chromatographic conditions were 40°C (held for 4 min), 20°C min − 1 to 100°C, and 6°C min − 1 to 270°C (held for 5 min). The temperatures applied were 270°C in the injector and 280°C in the MS interface. Helium was used as the carrier gas with a total flow of 1 mL/min, and the electron ionization energy was set at 70 eV. The compounds were identified using Wiley NIST2014 and personal databases. The pyrogram total area was determined automatically. Then it was calculated the percentage area of each compound identified. Total carbohydrates (TC) were calculated as the sum of all sugar derivatives, total lignin (TL) as the sum of syringyl (S), guaiacyl (G), and p -hydroxyphenyl units (H). The S/G and C/L ratios and the relation between the lignin monomers (H:G:S) were calculated. 3. Results and Discussion 3.1. Mechanical properties 3.1.1. Natural and thermal-modified wood without weathering Table 2 presents the density values and the mechanical properties attained by each sample before weathering. The density and mechanical properties of the three wood species studied are very similar to the values found in the literature (Carvalho 1996 ; Machado et al. 2014 ; Merlo et al. 2014 ). The modified woods showed a decrease in density of 6.9% (Pine), 10.6% (Acacia) to 11.5% (Ash), which may be connected to the mass loss after the thermal modification treatment as mentioned in the literature (Uribe and Ayala 2015; Bonfatti Júnior et al. 2022). Thermal modification induces water evaporation, the extractives become volatile or degrade, and the structural polymers such as hemicelluloses and lignin suffer degradation while cellulose is comparatively more preserved (Esteves and Pereira 2009 ; Korkut and Aytin 2015 ; De Oliveira Araújo et al. 2017 ; Lourenço et al. 2020 ). All these changes could cause a reduction in density, which has also been reported in other species, e.g ., pedunculate oak ( Quercus robur L.) (Čabalová et al. 2018 ), ash ( Fraxinus excelsior L) (Herrera et al. 2016 ; Molinski et al. 2018 ), maritime pine ( Pinus pinaster L.) (Costa et al. 2019 ), eastern red cedar ( Juniperus virginiana L.) (Kasemsiri et al. 2012 ) and wild cherry ( Prunus avium (L.)L.) (Korkut and Aytin 2015 ). Some changes were verified regarding the wood's mechanical properties, as presented in Table 2 . In the natural woods, MOE values ranged from 10 935 to 15 278 N.mm -2 , respectively, for Pine and Ash. MOR values varied from 93 (Acacia) to 133 N.mm -2 (Ash), while the compression strength was similar between species, ranging from 48 (Pine) to 58 N.mm -2 (Ash). In all the thermally modified woods, MOR values decreased, where the highest decrease was obtained by Ash (≈ 49%) and the lowest by Acacia (≈ 18%). A t -Student statistical analysis (p < 0.05) revealed significant differences between natural and thermal-modified woods. Bending strength loss was expected in all thermal modified wood species as reported in the literature (Esteves and Pereira 2009 ; Sandberg et al. 2017 ; Godinho et al. 2021 ), and the same happened in this study with values ranging from 104 N.mm -2 to 70 N.mm -2 for Pine, 133 N.mm -2 to 68 N.mm -2 for Ash and 93 N.mm -2 to 76 N.mm -2 for Acacia. However, Ash wood suffered the most loss compared to the others (68 N.mm -2 ). In the case of MOE and MOC, no significant changes were observed between natural and thermal-modified wood samples, according to t-student statistical analysis ( p > 0.05 ). Even though there are no significant differences, a slight increase of MOE and MOC was verified in thermal-modified woods, except for Ash. This could be caused by thermal degradation of amorphous cellulose and the increase of relative crystallinity (Tomak et al. 2014 ; Lourenço et al. 2020 ). This same behavior was reported by other authors who studied Ash ( Fraxinus excelsior L.), but also iroko ( Chlorophora excelsa (Welw.) Benth. Hook), and Scots pine ( Pinus sylvestris L.) (Tomak et al. 2014 ). The compression strength (CS) increased in Modified Pine (≈ 8%) and decreased in Modified Acacia (≈ 12%), but no significant changes occurred in Modified Ash. This can be explained by the effects of thermal modification on wood, where the low bound water content could cause an increase in crystalline cellulose content and the increase of lignin polymer network cross-linking (Tomak et al. 2014 ; Lourenço et al. 2020 ). Besides, depending on the wood species, the compression strength values could increase or decrease because it depends on wood density (Esteves and Pereira 2009 ; Priadi and Hiziroglu 2013 ; Čabalová et al. 2018 ). Table 2 Mechanical properties of natural and thermal-modified woods (mean values ± standard deviation). Wood Density (kg.m − 3 ) MOE (N.mm − 2 ) MOR (N.mm − 2 ) CS (N.mm − 2 ) MOC (N.mm − 2 ) Pine 620 ± 57 10 935 ± 2 849 104 ± 18 48 ± 8 11 917 ± 4 041 Modified Pine 587 ± 30 11 150 ± 2 189 70 ± 19 52 ± 5 13 767 ± 4 522 Ash 733 ± 17 15 278 ± 935 133 ± 9 58 ± 3 17 867 ± 2 941 Modified Ash 648 ± 34 12 923 ± 1 663 68 ± 19 59 ± 6 16 526 ± 3 681 Acacia 670 ± 44 12 148 ± 2 265 93 ± 22 50 ± 5 15 104 ± 3 791 Modified Acacia 599 ± 67 12 569 ± 2 224 76 ± 20 44 ± 7 16 931 ± 4 458 MOE – modulus of elasticity; MOR – bending strength; CS – compression strength; MOC – modulus of compression. 3.1.2. Natural and thermal-modified wood after Weathering Table 3 presents the density values and the results from the mechanical properties of all wood samples after 24 months of exposure to weathering. As can be seen, significant changes in density were verified in all wood samples exposed in both locations ( p 0.05 ). Table 3 Mechanical properties of natural and modified woods after 24 months of weathering in Lumiar and Sines (mean values ± standard deviation). Density (kg.m − 3 ) MOE (N.mm − 2 ) MOR (N.mm − 2 ) CS (N.mm − 2 ) MOC (N.mm − 2 ) Lumiar Pine 625 ± 16 11 840 ± 975 92 ± 6 49 ± 2 20 318 ± 8 604 Modified Pine 568 ± 33 9 008 ± 1 444 61 ± 17 47 ± 4 14 076 ± 4 740 Ash 679 ± 92 11 266 ± 2 709 90 ± 20 50 ± 5 20 444 ± 7 765 Modified Ash 619 ± 15 11 215 ± 1 278 70 ± 10 52 ± 5 16 226 ± 3 153 Acacia 627 ± 63 9 576 ± 2 481 87 ± 20 53 ± 3 21 165 ± 7 484 Modified Acacia 533 ± 90 9 639 ± 1 898 55 ± 25 46 ± 5 13 806 ± 3 085 Sines Pine 586 ± 33 9 811 ± 1 727 76 ± 11 41 ± 7 15 638 ± 5 042 Modified Pine 558 ± 16 8 773 ± 1 477 48 ± 12 42 ± 4 14 113 ± 2 641 Ash 681 ± 71 13 263 ± 812 98 ± 8 50 ± 2 28 947 ± 5 201 Modified Ash 641 ± 33 10 763 ± 1 164 71 ± 9 53 ± 4 19 505 ± 4 722 Acacia 659 ± 93 13 349 ± 227 118 ± 19 60 ± 8 21 406 ± 5 539 Modified Acacia 517 ± 80 10 425 ± 1 599 77 ± 23 50 ± 9 14 740 ± 4 091 MOE – modulus of elasticity; MOR – bending strength; CS – compression strength; MOC – modulus of compression. All exposed wood samples revealed some changes in both locations regarding mechanical properties. MOE and MOR decreased (≈ 15%) on most wood samples, with significant changes in both locations ( p < 0.05 ). On the contrary, Pine presented an increase of MOE in Lumiar and Modified Ash, Acacia and Modified Acacia presented an increase of MOR in Sines. This could indicate that thermal modification can give a stable elasticity when woods are exposed to different environments, maybe caused by lignin changes that occur in thermal modification (Godinho et al. 2024 ) that could obstruct UV light by the promotion of free radical reactions, the formation of degradation products with a low molecular weight (Nuopponen et al. 2004 ; Tomak et al. 2014 ) and the low equilibrium moisture content in thermally modified woods caused by the decrease of hemicellulose content (Godinho et al. 2024 ) could reduce the leaching of degradation products (Nuopponen et al. 2004 ; Tomak et al. 2014 ). In the case of compression strength and MOC, all exposed wood samples in both locations increased, except for Modified Ash exposed in Lumiar. Significant changes in compression strength in Pine, Modified Pine, and Acacia were found when exposed to the different environments. Pine and Modified Pine compression strength decreased when exposed to Sines, contrary to Acacia, which increased. MOC found a significant difference only in Ash and Modified Ash, where a higher increase in Sines was verified. 3.2. Durability evaluation 3.2.1. Resistance against subterranean termite Table 4 presents the results of termite resistance of all-natural and thermal-modified woods. The average termite survival rate is similar in all thermally modified and natural wood species (above 75% and lower than 80%), except for Modified Acacia, which presented a lower survival rate of 59% but with a higher standard deviation (13.5%). Table 4 Average survival results, average mass loss, final moisture content, and grade of attack after termite exposure (n = 10, mean values ± standard deviation). Moisture Content (%) Survival (%) Mass Loss (%) Grade of Attack Pine 27.7 ± 1.1 79.4 ± 4.7 6.2 ± 1.3 3.8 ± 0.4 Modified Pine 25.8 ± 6.9 76.3 ± 3.1 9.0 ± 1.0 4 Ash 32.9 ± 1.4 79.7 ± 5.0 3.1 ± 1.6 3.4 ± 0.5 Modified Ash 29.3 ± 7.9 79.2 ± 5.6 8.0 ± 1.2 4 Acacia 34.3 ± 6.2 79.1 ± 3.7 4.7 ± 2.6 4 Modified Acacia 24.1 ± 6.3 59.0 ± 13.5 3.5 ± 1.4 3.5 ± 0.6 STDEV – standard deviation An important fact was that the attack grade was almost the same in all wood samples, which shows that the thermal modification did not improve wood for termite resistance. Even though the results look very similar, the statistical analysis showed significant changes in Ash and Acacia ( p < 0.05 ). Thermal treatment has not been shown to improve the durability of other wood species against subterranean in any tests conducted using the same termite species towards thermally modified Paulownia tomentosa (Esteves et al. 2021 ); Reticulitermes banyulensis Clément towards thermally modified ash and European beech (Oliver-Villanueva et al. 2013 ); Reticulitermes santonensis Feytaud towards maritime pine (Surini et al. 2012 ). Therefore, new techniques to improve the performance of thermally modified wood to termite attack have been developed due to the lack of protection against termites, e.g. with the impregnation of bicine and tricine (Jones et al. 2022 ) or impregnation of a boron derivative associated with appropriate vinylic monomers (Salman et al. 2017 ). In Fig. 1 is presented natural and modified Acacia, as an example of the damage caused by termites. 3.2.2. FTIR-ATR analysis Table 6 presents the chosen assignment bands of FTIR spectra as those used in the previous work published by the authors (Godinho et al. 2024 ). Table 6 Assignment of FTIR bands of principal chemical components in wood in the region 1800 − 800 cm − 1 . Wavenumber (cm − 1 ) Assignment Principal band's origin Ref. 1750 − 1720 C = O stretching in conjugated ketones, carbonyls, aldehydes, and ester group Lignin/Polysaccharide (Pozo et al. 2016 ; Gonultas and Candan 2018 ) 1724–1730 Free carbonyl groups, C = O Stretching of acetyl or carboxylic acid Hemicellulose/Lignin (Graham Solomons and Fryhle 2004 ; Srinivas and Pandey 2012 ; Pozo et al. 2016 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1675 − 1655 C = O stretch on conjugated p -substituted aryl ketones Lignin (Pozo et al. 2016 ) 1605 − 1598 C = C Aromatic ring stretching Syringyl Lignin (Huang et al. 2012a ; Cogulet et al. 2016 ; Pozo et al. 2016 ; Čabalová et al. 2018 ; Gonultas and Candan 2018 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1515 − 1506 C = C stretching of the aromatic ring Guaiacyl lignin (Huang et al. 2012a ; Srinivas and Pandey 2012 ; Pozo et al. 2016 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1470 − 1460 -CH 3 and -CH 2 deformation (asymmetric) Lignin/Xylan (Huang et al. 2012b ; Srinivas and Pandey 2012 ; Pozo et al. 2016 ; Gonultas and Candan 2018 ; Tomak et al. 2018 ; Kubovský et al. 2020 ; Hofmann et al. 2022 ) 1430 − 1420 Aromatic skeletal vibration (lignin) and C-H deformation (cellulose) Lignin/Cellulose (Pozo et al. 2016 ; Gonultas and Candan 2018 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1370 − 1365 Phenolic OH, aliphatic C-H stretch in CH 3 , not in O-Me, C-H vibration in polysaccharide CH 2 bending in cellulose and hemicelluloses Lignin/Polysaccharide/Hemicellulose/Cellulose (Pozo et al. 2016 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1330 − 1320 Phenolic OH, C-H vibration in cellulose, and C-O vibration in syringyl and guaiacyl rings Syringyl Lignin/Guaiacyl Lignin/ Polysaccharide/Cellulose (Yilgor et al. 2013 ; Pozo et al. 2016 ; Özgenç et al. 2017 ; Kubovský et al. 2020 ) 1266 − 1261 Guaiacyl ring breathing with C = O-stretching, acetyl, and carboxylic vibration in xylan and esters Guaicyl Lignin/Xylan/Hemicellulose (Cogulet et al. 2016 ; Pozo et al. 2016 ; Tomak et al. 2018 ; Kubovský et al. 2020 ) 1240 − 1220 Syringyl ring and C-O stretch, acetyl, and carboxylic vibration in xylan Syringyl Lignin/Xylan/Polysaccharides (Herrera et al. 2016 ; Pozo et al. 2016 ; Gonultas and Candan 2018 ; Kubovský et al. 2020 ; Hofmann et al. 2022 ) 1210 − 1201 OH-bending, aryl aldehyde, a- and unsaturated aldehyde, lactones, phenols, and diaryl ethers. Associated with crystallized and amorphous cellulose Cellulose (Pozo et al. 2016 ; Özgenç et al. 2017 ; Tomak et al. 2018 ) 1160 − 1155 C-O-C vibration in cellulose and hemicellulose is also associated with crystallized and amorphous cellulose Cellulose/Hemicellulose (Yildiz et al. 2013 ; Pozo et al. 2016 ; Özgenç et al. 2017 ; Gonultas and Candan 2018 ; Tomak et al. 2018 ) 1110 − 1104 OH association, C-O stretching, and CH 2 rocking on cellulose Cellulose (Pozo et al. 2016 ; Özgenç et al. 2017 ; Tomak et al. 2018 ) 1054 − 1052 C-O deformation in aliphatic alcohols and ethers Carbohydrates (Tomak et al. 2018 ) 1051 − 1023 C-H and C-O deformations Polysaccharides/Cellulose (Herrera et al. 2016 ; Pozo et al. 2016 ; Özgenç et al. 2017 ; Gonultas and Candan 2018 ; Tomak et al. 2018 ) 1000 − 985 C-O valence vibration Cellulose (Uçar et al. 1996 ; Schwanninger et al. 2004 ; Lopes et al. 2018 ) Figure 2 presents the difference in the FTIR-ATR spectra between the woods before and after decay attack by termites. It was verified an increase in bands 1750 − 1720 cm − 1 (lignin and polysaccharides), 1370 − 1350 cm − 1 (lignin, polysaccharides, and hemicellulose), 1240 − 1220 cm − 1 (syringyl, xylans and polysaccharides), 1210 − 1201 cm − 1 (cellulose), 1104–1110 cm − 1 (cellulose) and 1051 − 1023 cm − 1 (polysaccharides and cellulose) in Modified Pine. For Pine, Modified, and natural Ash, and Modified and natural Acacia, increases were seen in the bands 1750 − 1720 cm − 1 (lignin and polysaccharides), 1370 − 1350 cm − 1 (lignin, polysaccharides, and hemicellulose), 1240 − 1220 cm − 1 (syringyl, xylans, and polysaccharides). However, decreases were also observed in the bands 1104–1110 cm − 1 (cellulose) and 1051 − 1023 cm − 1 (polysaccharides and cellulose) of Pine, Ash, and Acacia. These bands did not undergo significant changes in the Modified Ash and Acacia. Termites possess enzymes that facilitate the digestion of wood's main components, aided by bacterial symbiosis in their guts (Singhania 2009 ; Duarte et al. 2017 ). The bacteria release cellulolytic enzymes that degrade cellulose and hemicellulose into sugars, also known as cellulases and hemicellulases, which are then converted into acetate, hydrogen, and carbon dioxide (Singhania 2009 ; Duarte et al. 2017 ; Peristiwati et al. 2018). This process could explain the increased bands at 1240 − 1220 cm − 1 in all wood samples, corresponding to the acetyl group. Besides, the natural wood samples revealed decreases in the bands corresponding to cellulose, which confirmed that the termites attack cellulose more easily than lignin (Duarte et al. 2017 ). However, in Modified Pine and Modified Ash, the cellulose bands increased showing that cellulose did not suffer alterations, maybe because thermal modification caused chemical changes in cellulose (Godinho et al. 2024 ), namely the reduction of amorphous cellulose (Lourenço et al. 2020 ), as revealed in bands 1155–1160 cm − 1 , associated with C-O-C vibration (Godinho et al. 2024 ). These results suggest that thermal modification could help prevent the cellulose degradation caused by termites. The band 1750 − 1720 cm − 1 increase in all wood samples corresponds to C = O stretching in ketones, aldehydes, and ester groups associated with lignin and polysaccharides. The increase was similar in all woods, indicating that the thermal modification did not give extra protection for lignin. Subterranean termites could cause rearrangements in lignin by the same symbiosis present in their guts (Talia 2018 ) because they possess ligninase enzymes that degrade lignin by redox mechanisms and release free radicals (Plácido and Capareda 2015 ; Talia 2018 ). Therefore, the increased intensity of bands associated with lignin may suggest a reorganization of the lignin structure (Ke et al. 2011 , 2012 ). This phenomenon was reported in a study involving the termite Coptotermes formasanus Shiraki, where the digestion process led to significant alterations in lignin structure, namely the destruction of the aromatic ring, dihydroxylation, demethylation, and demethoxylation (Ke et al. 2011 , 2012 ). 3.3. Py/GC analysis Figure 3 shows the pyrograms of the woods (natural and modified) before and after decay by termites. At the beginning of the pyrogram, carbohydrate derivatives were identified (Fig. 2, peaks 1–9), and then, after 16 min of running time, lignin derivatives started to appear. The first one was guaiacol (peak 12). Overall, the compounds identified were the same between species, except in pine, where no syringyl-derived units were identified, being a GH type of lignin. At the same time, Ash and Acacia presented guaiacyl and syringyl units (SG type of lignin). Table 8 presents a resume of the pyrolysis analysis of natural and modified wood before and after decay by termites. In natural Pine wood, termites trigger cellulose degradation, evidenced by decreased levoglucosan content from 10.9–7.7%. This suggests alterations to cellulose, although overall sugar content remains unaffected at 38.8% compared to 38.6%. This is in line with studies that mention the ability of termites to degrade cellulose (Marynowska et al. 2023 ). Notably, total lignin content experiences a slight increase, reaching 23.2% upon termite exposure. Conversely, in natural Ash wood, the C/L ratio remains stable (1.8 vs. 1.6), attributed to a simultaneous increase in sugars and lignin. This stability hints at minimal termite impact on this wood. In Acacia, there is a slight reduction in total carbohydrates, notably in cellulose, where levoglucosan levels drop significantly from 12.9–6.8%. However, lignin content remains unchanged post-termite exposure. Consequently, the C/L ratio in Acacia wood was maintained at 2.3, showcasing consistency, while the S/G ratio experienced a slight increase from 1.9 to 2.3. Table 8 Resume of the analytical pyrolysis analysis of the woods before and after termite decay (% of total chromatographic area). Wood samples TC TL H G S S/G ratio C/L ratio Pine 38.8 19.4 0.3 19.1 n.d. n.d. 2.0 Pine termite decay 38.6 23.2 0.5 22.8 n.d. n.d. 1.7 Modified Pine 44.5 17.3 0.3 17.1 n.d. n.d. 2.6 MP termite decay 43.3 18.4 0.4 18.0 n.d. n.d. 2.4 Ash 35.9 20.5 0.1 6.8 13.6 2.0 1.8 Ash termite decay 40.6 24.6 0.2 8.8 15.7 1.8 1.6 Modified Ash 44.4 20.4 0.2 7.0 13.3 1.9 2.2 MA termite decay 41.3 23.4 0.3 9.2 14.0 1.5 1.8 Acacia 43.5 18.9 0.1 6.6 12.2 1.9 2.3 Acacia termite decay 42.1 19.0 0.2 5.8 13.0 2.3 2.2 Modified Acacia 52.4 14.5 0.2 5.1 9.2 1.8 3.6 MAc termite decay 45.9 15.7 0.3 6.0 9.4 1.6 2.9 TC – total carbohydrates; TL – total lignin; H, G, S – Lignin units; n.d. – not detected/not determined. In modified woods like Pine post-termite attack, a notable decrease in levoglucosan content (from 20.2–13.2%) indicates cellulose degradation by termites. This is corroborated by an increase in minor compounds (peaks 1–10), suggesting a breakdown of cellulose, yielding low molecular weight carbohydrate-derived products. Consequently, total carbohydrate content experienced a slight reduction from 44.5–43.3%, while total lignin exhibited a modest increase from 17.3–18.4%. Similarly, Ash wood displayed consistent C/L values (2.2 vs. 1.8) due to concurrent sugars and increased lignin decreases. Notably, cellulose degradation was evident, with a sharp decline in levoglucosan from 19.3–11.7%. In Acacia, total sugars were significantly reduced (from 52.4–45.9%), primarily attributed to decreased levoglucosan content from 31.2–20.6%. While total lignin slightly increased (from 14.5–15.7%), the C/L ratio decreased from 3.6 to 2.9, indicating cellulose degradation. Therefore, termites can degrade cellulose in natural and modified woods, irrespective of the wood species studied. Termites' ability to degrade cellulose was already shown in FTIR data and is following the literature (Deka et al. 2002 ). According to (Jones et al. 2022 ), even thermally treated woods have poorly performed against termites. For example, in Ash wood, only the temperature of 215 ºC during the thermal modification treatment was effective in classifying the wood on a durability rating scale of "durable" and "very durable" for termite degradation (Candelier et al. 2017 ). Also, termites degrade cellulose in E. grandis thermally treated wood (Gallio et al. 2020 ). 4. Conclusions This experimental study allowed us to conclude: Before weathering: Thermal modification caused changes in mechanical and physical properties, namely a decrease in density and bending strength. Concerning compression, no significant changes were reported. After weathering: All weathered wood samples revealed changes in mechanical properties in both locations. The behavior of all wood samples was very similar in both locations, indicating that the environment type does not affect the mechanical changes. Thermal modification also did not contribute to the resistance to weathering. This was verified in the previous study, where the chemical changes revealed very similar results in both locations. No physical and mechanical evidence demonstrates that marine/industrial or urban environments lead to woods (natural and thermal-modified) having different weathering resistance, except in compression. Pine and Modified Pine suffered a decrease of compression strength in Sines. The opposite happens to Acacia where an increase of compression strength was verified. In Ash and Modified Ash MOC increased in Sines. These results showed that Pine and Modified Pine could have some sensibility in maritime/industrial environment. Ash and Acacia, natural and thermal modified apparently, gained some compression strength and flexibility. Even with these results, further studies with a higher exposure period are needed to evaluate if the wood samples or some wood species will show a different behavior in environments with very high corrosivity and strong maritime/industrial influence. Resistance to subterranean termites All wood samples revealed a close grade of attack. Modified Acacia revealed a little more resistance to subterranean termite attack and a lower survival rate, indicating that thermal modification could produce more toxic substances for termites. FTIR-ATR spectrum corroborates that termite degraded, primarily cellulose. However, in modified woods, cellulose degradation was lower, possibly due to alterations in cellulose polymer after thermal treatment. The spectrum also showed that termites could degrade lignin, causing some rearrangements of the polymer. Pyrolysis analysis corroborates the idea that termites can partially degrade all wood components: cellulose degradation reflected in the decrease of levoglucosan but also lignin by the slight changes in monomeric composition reflected in the reduction of the S/G ratio; these observations occurred either in natural or thermally treated woods. Thermal modification did not improve the durability against termites and the resistance to weathering. Further studies will be needed to evaluate if combining other wood protection products could overcome the fragilities found in thermal-modified wood. Declarations Author Contribution Conceptualization, DG, TQ, TCD, JG, LN and JSM; methodology, DG, SdOA, CF, AL, TQ, TCD, JG, LN and JSM; formal analysis, DG, CF, AL, LN, MD, SD and JSM; writing—original draft preparation, DG; writing, review and editing, CF, AL, SdOA, TQ, TCD, JG, LN, SD and JSM; supervision, TQ, TCD, and JG. All authors have read and agreed to the published version of the manuscript. Acknowledgments The authors would like to thank this research funding by FCT (Fundação para a Ciência e Tecnologia, Portugal) by financing the Forest Research Centre (UIDB/00239/2020) and Associate Laboratory TERRA (LA/P/0092/2020). FCT supported Delfina Godinho through PhD fellowship (PD/BD/142987/2018) under the Sustainable Forests and Products (SUSFOR) doctoral program (SUSFOR) (PD/00157/2012). FCT supported Ana Lourenço through a research contract (DL57/2016/CPI382/CT0007) and Solange de Oliveira Araújo through a research contract (DL57/2016/CPI382/CT0018). The authors also would like to thank Parques de Sintra – Monte da Lua (PSML) for providing the acacia wood, Santos & Santos company for providing pine and ash wood, and for the thermal modification of all wood species. A special thanks to Ana Soares Vieira and Rita Gonçalves for providing the Lumiar's and Sines's climatic data. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5137187","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":371163094,"identity":"9169ec7c-ccd7-4a90-8814-532daa941ad6","order_by":0,"name":"Delfina Godinho","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/UlEQVRIiWNgGAWjYFACxsbHfyok5NjAnAIJBgPCWpibDXjOWBhDtBjAtCTg08LeJsHbVpHYANHCQFgLf/vBNgnJNon0Pv7DD5h5DCzszdmbHzAX/sCtReJMYrOFwTmJ3DaJNAOgFonEnT3HDJhn4HPYgcTGGwllIC0MYC0JBjcSgAw8WuTPP2yQOMAmkc7Gf/wDSIu9wY30D3i1GNxIbJJsaJNIYGPIAdvCuOFGDn5bDG88bDZmOCNh2CaRU3BwDtgvZwoOz0jDrUXufPrDxwwVdfLy/cc3PnhTUQcMsfaNjwts8HgfGRyAMQ4TqQEJMJOuZRSMglEwCoYxAABFj0xT8+eCowAAAABJRU5ErkJggg==","orcid":"","institution":"Universidade de Lisboa","correspondingAuthor":true,"prefix":"","firstName":"Delfina","middleName":"","lastName":"Godinho","suffix":""},{"id":371163095,"identity":"696f2731-7241-4686-81ad-9c47c0d74b2a","order_by":1,"name":"Ana Lourenço","email":"","orcid":"","institution":"Universidade de Lisboa","correspondingAuthor":false,"prefix":"","firstName":"Ana","middleName":"","lastName":"Lourenço","suffix":""},{"id":371163096,"identity":"aa5e9d8e-8004-41be-bdc1-3ecb831ea19c","order_by":2,"name":"Solange Oliveira Araújo","email":"","orcid":"","institution":"Universidade de Lisboa","correspondingAuthor":false,"prefix":"","firstName":"Solange","middleName":"Oliveira","lastName":"Araújo","suffix":""},{"id":371163098,"identity":"310a5010-2042-4b45-97a3-2f561b50de56","order_by":3,"name":"José Saporiti Machado","email":"","orcid":"","institution":"Laboratório Nacional de Engenharia Civil","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Saporiti","lastName":"Machado","suffix":""},{"id":371163099,"identity":"22c248ea-a4e6-4007-9f8f-9cec550a6581","order_by":4,"name":"Lina Nunes","email":"","orcid":"","institution":"Laboratório Nacional de Engenharia Civil","correspondingAuthor":false,"prefix":"","firstName":"Lina","middleName":"","lastName":"Nunes","suffix":""},{"id":371163100,"identity":"b4a17ef1-0437-469f-9963-5a750a402cff","order_by":5,"name":"Marta Duarte","email":"","orcid":"","institution":"Laboratório Nacional de Engenharia Civil","correspondingAuthor":false,"prefix":"","firstName":"Marta","middleName":"","lastName":"Duarte","suffix":""},{"id":371163101,"identity":"3356303a-573e-4ab6-be9c-963de6346977","order_by":6,"name":"Sónia Duarte","email":"","orcid":"","institution":"Laboratório Nacional de Engenharia Civil","correspondingAuthor":false,"prefix":"","firstName":"Sónia","middleName":"","lastName":"Duarte","suffix":""},{"id":371163103,"identity":"15bb59ce-651b-4a70-b4a4-b6215b70c849","order_by":7,"name":"Cristina Ferreira","email":"","orcid":"","institution":"Laboratório Nacional de Engenharia Civil","correspondingAuthor":false,"prefix":"","firstName":"Cristina","middleName":"","lastName":"Ferreira","suffix":""},{"id":371163104,"identity":"7db07ce5-be3b-476f-aeff-ab25451aeb7d","order_by":8,"name":"Teresa Quilhó","email":"","orcid":"","institution":"Universidade de Lisboa","correspondingAuthor":false,"prefix":"","firstName":"Teresa","middleName":"","lastName":"Quilhó","suffix":""},{"id":371163106,"identity":"f5e76a31-0600-4df1-8fce-abfd4cf90ebc","order_by":9,"name":"Teresa C. 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(LNEG)","correspondingAuthor":false,"prefix":"","firstName":"Teresa","middleName":"C.","lastName":"Diamantino","suffix":""},{"id":371163109,"identity":"8c558d94-1cea-4305-9279-2bd8902b7b4b","order_by":10,"name":"Jorge Gominho","email":"","orcid":"","institution":"Universidade de Lisboa","correspondingAuthor":false,"prefix":"","firstName":"Jorge","middleName":"","lastName":"Gominho","suffix":""}],"badges":[],"createdAt":"2024-09-23 10:06:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5137187/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5137187/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00107-024-02199-4","type":"published","date":"2025-01-15T15:58:01+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":69860745,"identity":"609e6b0f-db11-451e-9f05-f7d73e3ba404","added_by":"auto","created_at":"2024-11-26 05:27:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":151313,"visible":true,"origin":"","legend":"\u003cp\u003eNatural (a) and modified Acacia (b) after the termite resistance assay\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5137187/v1/73e362af5dc05cf61ed1f27a.png"},{"id":69861114,"identity":"30fb1891-5a91-4eac-b2b4-c9ab32bc40ab","added_by":"auto","created_at":"2024-11-26 05:35:29","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":61268,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR-ATR spectra difference of the wood samples (natural and after modification) after decay by termite \u003cem\u003eReticulitermes grassei\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5137187/v1/db44887f2acdeaea033bf893.png"},{"id":69860747,"identity":"002b67b2-9ec3-468e-b41a-08f8cb9dfb33","added_by":"auto","created_at":"2024-11-26 05:27:29","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":169180,"visible":true,"origin":"","legend":"\u003cp\u003ePyrograms of the woods before and after decay by thermites. Legend: 1) 2-oxo-propanal; 2) hydroxyacetaldehyde; 3) acetic acid; 4) 1-hydroxy-2-propanone (acetol); 5) 3-hydroxypropanal; 6) CH\u003csub\u003e3\u003c/sub\u003e-CO-CHOH-CHO; 7) furfural \u0026amp; 2-cyclopenten-1-one; 8) 2-hydroxy-2-cyclopenten-1-one; 9) 4-hydroxy-5,6-dihydro-(2H)-pyran-2-one; 12) guaiacol; 13) 4-methylguaiacol; 15) not identified sugar; 16) 4-vinylguaiacol; 18) syringol; 19) not identified sugar; 20) \u003cem\u003etrans\u003c/em\u003e isoeugenol; 21) 4-methylsyringol; 22) vanillin; 25) acetoguaiacone; 26) 4-vinylsyringol; 29) 1,6-anhydro-β-D-glucopyranose (levoglucosan); 32) syringaldehyde; 33) acetosyringone; 36) \u003cem\u003etrans\u003c/em\u003e coniferaldehyde; 38) \u003cem\u003etrans\u003c/em\u003e sinapaldehyde.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5137187/v1/64be5c211132f9077198f042.png"},{"id":74285727,"identity":"45643239-8dd9-4bf8-83e7-4d5f8712ed1c","added_by":"auto","created_at":"2025-01-20 16:14:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1946592,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5137187/v1/a827047c-8676-4e14-b101-da5d6bf9e7d8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessment of weathering and subterranean termite resistance in three thermally modified wood species in Portugal","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eWood is one of the most ancient materials used by humans in construction. Its flexibility, strength, elasticity, and workability make it an extremely versatile material. Today, wood is used in a wide range of applications, from indoor furniture to outdoor uses in building construction. However, when applied outdoors, wood is exposed to various conditions, such as weathering and biodegradation. Thermal treatment can increase wood durability and overcome weathering and biodegradation. Over the years, different wood protection technologies have been developed to protect wood against these environmental aggressions. One type of wood protection technology is wood modification, which changes wood chemically and helps protect wood against degradation (Ormondroyd et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). One of the most common wood modification technologies worldwide is thermal modification (Esteves and Pereira \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Jones et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Godinho et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Hill et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWood weathering is a slower degradation caused by sun radiation, rain, humidity, and wind, among other climatic factors (Nuopponen et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Williams \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Godinho et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Usually, it causes wood surface alterations, namely color, chemical, physical, mechanical, and morphological changes (Tomak et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Cui and Matsumura \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Humar et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Godinho et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe main biodegradation factors that attack wood are wood decay fungi and xylophages. In the xylophage group, insects such as subterranean termites (\u003cem\u003eReticulitermes grassei\u003c/em\u003e Cl\u0026eacute;ment) negatively impact some wood structures. They live and reproduce in soil; their food is wood (C\u0026aacute;rdenas et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In nature, subterranean termites are very important in the organic decomposition process, either in the plant decomposition or by direct consumption (Nunes \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), promoting nitrogen fixation and helping the nutrient deposition in the soil (Nunes \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; C\u0026aacute;rdenas et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). This termite species is distributed in the Iberian Peninsula's northern, western, and southern parts of France (Cl\u0026eacute;ment et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; C\u0026aacute;rdenas et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These insects have particular bacteria in their digestive system that help to degrade cellulose, causing severe damage to the strength properties of wood (Deka et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2002\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were maritime pine (\u003cem\u003ePinus pinaster\u003c/em\u003e), Ash (\u003cem\u003eFraxinus excelsior\u003c/em\u003e), and blackwood acacia (\u003cem\u003eAcacia melanoxylon\u003c/em\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Material - natural and thermal-modified wood specimens\u003c/h2\u003e \u003cp\u003eThe wooden material tested comprised two hardwood species, Acacia (\u003cem\u003eAcacia melanoxylon\u003c/em\u003e R. Br.) and Ash (\u003cem\u003eFraxinus excelsior\u003c/em\u003e L.), and one softwood species, maritime pine (\u003cem\u003ePinus pinaster\u003c/em\u003e Aiton), which served as reference. All wood samples used in this research were sourced from Portugal. Each specimen underwent thermal modification in an industrial facility using the Thermowood \u0026reg; process, specifically under Thermo-D conditions. Each wood was subjected to a temperature of 210\u0026deg;C during approximately 6 h.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Weathering conditions\u003c/h2\u003e \u003cp\u003eTo compare the degradation in different environments, the samples were exposed in two locations in Portugal, Lumiar (Lisbon) and Sines test sites (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), between October 2019 and November 2021. The specimens for natural exposure had two different sizes, 100x320x20mm and 100x 320x40mm (width x length x thickness), according to the standards EN 927-3:2019 and ISO 13061-4:2014 standard. All wood samples were exposed at 45\u0026deg;, according to EN 927-3:2019. The corrosivity of the environments was evaluated according to ISO 9223:2012. The Sines test site is a location with strong industrial and maritime influence and is classified as C5 (very high corrosivity) and Lumiar, an urban test site classified as C2 (low corrosivity) during the exposure period (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacterization of the exposure test sites. The samples were exposed between October 2019 and November 2021 (Values as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation) (Godinho et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eLocation\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClimatic conditions\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSines\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLumiar\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLatitude\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.95\u0026deg;N\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.77\u0026deg;N\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLongitude\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.88\u0026deg;W\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.17\u0026deg;W\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAltitude (m)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e116\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eTemperature (\u0026deg;C)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.0\u0026thinsp;\u0026plusmn;\u0026thinsp;3.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eGlobal radiation (J cm\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;2\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 663.3\u0026thinsp;\u0026plusmn;\u0026thinsp;477.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 177.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1036.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRelative humidity (%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e85.3\u0026thinsp;\u0026plusmn;\u0026thinsp;17.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e69.0\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRain (mm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24.4\u0026thinsp;\u0026plusmn;\u0026thinsp;31.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e54.0\u0026thinsp;\u0026plusmn;\u0026thinsp;48.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAir pollutants deposition (mg day\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e \u003cb\u003emm\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;2\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSO\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.0\u0026thinsp;\u0026plusmn;\u0026thinsp;25.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCl\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e116.3\u0026thinsp;\u0026plusmn;\u0026thinsp;70.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.5\u0026thinsp;\u0026plusmn;\u0026thinsp;16.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eEnvironment type\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMaritime/ Industrial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eUrban\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCorrosivity category for steel*\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC5 (very high)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC2 (low)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e*According to ISO 9223: 2012.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Bending and compression strength\u003c/h2\u003e \u003cp\u003eThe wood samples (natural, thermal-modified wood, and the weathered test pieces) were placed inside a climatic chamber at 20\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C temperature and 65\u0026thinsp;\u0026plusmn;\u0026thinsp;5% relative humidity until a constant mass was reached (difference between weight measurements in a period of 24 h\u0026thinsp;\u0026le;\u0026thinsp;0.1%). The bending strength (MOR) and modulus of elasticity (MOE) were determined by a three-point bending test according to ISO 13061-4:2014 standard. Compression parallel to the grain was performed in a 250 kN universal testing machine, with 1% load accuracy, and the displacement was measured using the machine crosshead displacement, with a 1% deformation accuracy. Compression strength (CS) and modulus of compression (MOC) were determined according to ISO 13061-5:2020 standard. For each parameter, 10 replicates were tested, and statistical analysis was performed using a t-student test to verify significant differences between the mean values. It established a \u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e significance value.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Durability assessment\u003c/h2\u003e \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e \u003ch2\u003e2.4.1. Durability against subterranean termites\u003c/h2\u003e \u003cp\u003eThe susceptibility of thermally modified wood against subterranean termite (\u003cem\u003eReticulitermes grassei\u003c/em\u003e Cl\u0026eacute;ment) was accessed following an adaptation of the European standard EN 117:2012, with natural wood as the control. Each type of thermally modified wood underwent six replicates, alongside six replicates of the control (natural wood), using wood samples measuring 30x10x10 mm. Pine wood was also selected as the control for all species examined in this study, following the EN 117:2012 standard.\u003c/p\u003e \u003cp\u003eThe assays focused solely on natural and thermally modified woods to evaluate the effectiveness of thermal modification in protecting wood against subterranean termites. The termites were collected in a maritime pine forest in the Sesimbra region, Portugal, and were kept in the laboratory for less than two weeks before the assays. Groups of 150 termite workers were exposed to the samples for four weeks, maintained in a climatic chamber at 24\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C and relative humidity of 80\u0026thinsp;\u0026plusmn;\u0026thinsp;5%. At the end of the trial period, the termite survival rate, defined as the percentage of living termites at the end of the test (SR), and visual grading of the test specimens were evaluated using the standard rating system (0\u0026thinsp;=\u0026thinsp;no attack, 1\u0026thinsp;=\u0026thinsp;attempted attack, 2\u0026thinsp;=\u0026thinsp;slight attack, 3\u0026thinsp;=\u0026thinsp;average attack and 4\u0026thinsp;=\u0026thinsp;strong attack) were determined. The test is valid if all control test specimens have a strong attack (rating of 4) and the termite's survival rate is above 50%.\u003c/p\u003e \u003cp\u003eAdditionally, the wood mass loss (%) was also calculated as follows:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:ML\\:\\left(\\%\\right)=\\:\\frac{{(m}_{01}-\\:{m}_{02})}{{m}_{01}}\\times\\:100$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere:\u003c/p\u003e \u003cp\u003eML - is mass loss after termite exposure;\u003c/p\u003e \u003cp\u003em\u003csub\u003e01\u003c/sub\u003e - is the dry mass of samples before termite exposure;\u003c/p\u003e \u003cp\u003em\u003csub\u003e02\u003c/sub\u003e - is the dry mass of wood samples after termite exposure.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Chemical characterization\u003c/h2\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.5.1. FTIR \u0026ndash; ATR spectroscopy\u003c/h2\u003e \u003cp\u003eSamples of each wood (natural and modified) exposed to termite decay were extracted in a Soxhlet apparatus by a sequence of solvents (dichloromethane, ethanol, and water for 6-12h each solvent). Following extraction, FTIR-ATR spectra were acquired using a Perkin Elmer Spectrum Two, equipped with a UATR Two accessory with a diamond crystal, operating at a resolution of 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with eight scans. Baseline correction was performed at three specific points. Difference spectra were calculated to compare all wood samples subject to varying degrees of attack. Data processing was carried out using Spectragryph 1.2.15 software, and the spectra were analyzed within the range of 1800\u0026thinsp;\u0026minus;\u0026thinsp;800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as this region exhibited the most pronounced changes.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.5.2. Analytical pyrolysis (Py-GC/MS)\u003c/h2\u003e \u003cp\u003eThe extracted samples were analyzed Py-GC/MS after sample preparation by milling for 10 min in a Retsch MM20 mixer ball mill, then dried at 35\u0026deg;C in a vacuum oven. Around 0.10 mg of each sample was weighted and pyrolyzed at 550\u0026deg;C (for 1 min) in a platinum coil Pyroprobe connected to a CDS 5150 valved interface linked to the GC-MS (Agilent 7890B \u0026amp; 5977B). A fused-silica capillary column (ZB-1701: 60m x 0.25 mm i.d. x 0.25 \u0026micro;m film thickness) was used to separate the volatiles. The chromatographic conditions were 40\u0026deg;C (held for 4 min), 20\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 100\u0026deg;C, and 6\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 270\u0026deg;C (held for 5 min). The temperatures applied were 270\u0026deg;C in the injector and 280\u0026deg;C in the MS interface. Helium was used as the carrier gas with a total flow of 1 mL/min, and the electron ionization energy was set at 70 eV. The compounds were identified using Wiley NIST2014 and personal databases. The pyrogram total area was determined automatically. Then it was calculated the percentage area of each compound identified. Total carbohydrates (TC) were calculated as the sum of all sugar derivatives, total lignin (TL) as the sum of syringyl (S), guaiacyl (G), and \u003cem\u003ep\u003c/em\u003e-hydroxyphenyl units (H). The S/G and C/L ratios and the relation between the lignin monomers (H:G:S) were calculated.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Mechanical properties\u003c/h2\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1. Natural and thermal-modified wood without weathering\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e presents the density values and the mechanical properties attained by each sample before weathering. The density and mechanical properties of the three wood species studied are very similar to the values found in the literature (Carvalho \u003cspan class=\"CitationRef\"\u003e1996\u003c/span\u003e; Machado et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Merlo et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). The modified woods showed a decrease in density of 6.9% (Pine), 10.6% (Acacia) to 11.5% (Ash), which may be connected to the mass loss after the thermal modification treatment as mentioned in the literature (Uribe and Ayala 2015; Bonfatti J\u0026uacute;nior et al. 2022). Thermal modification induces water evaporation, the extractives become volatile or degrade, and the structural polymers such as hemicelluloses and lignin suffer degradation while cellulose is comparatively more preserved (Esteves and Pereira \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Korkut and Aytin \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; De Oliveira Ara\u0026uacute;jo et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Louren\u0026ccedil;o et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). All these changes could cause a reduction in density, which has also been reported in other species, \u003cem\u003ee.g\u003c/em\u003e., pedunculate oak (\u003cem\u003eQuercus robur\u003c/em\u003e L.) (Čabalov\u0026aacute; et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), ash (\u003cem\u003eFraxinus excelsior\u003c/em\u003e L) (Herrera et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Molinski et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), maritime pine (\u003cem\u003ePinus pinaster\u003c/em\u003e L.) (Costa et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), eastern red cedar (\u003cem\u003eJuniperus virginiana\u003c/em\u003e L.) (Kasemsiri et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e) and wild cherry (\u003cem\u003ePrunus avium\u003c/em\u003e (L.)L.) (Korkut and Aytin \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eSome changes were verified regarding the wood\u0026apos;s mechanical properties, as presented in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. In the natural woods, MOE values ranged from 10 935 to 15 278 N.mm\u003csup\u003e-2\u003c/sup\u003e, respectively, for Pine and Ash. MOR values varied from 93 (Acacia) to 133 N.mm\u003csup\u003e-2\u003c/sup\u003e (Ash), while the compression strength was similar between species, ranging from 48 (Pine) to 58 N.mm\u003csup\u003e-2\u003c/sup\u003e (Ash).\u003c/p\u003e\n \u003cp\u003eIn all the thermally modified woods, MOR values decreased, where the highest decrease was obtained by Ash (\u0026asymp;\u0026thinsp;49%) and the lowest by Acacia (\u0026asymp;\u0026thinsp;18%). A \u003cem\u003et\u003c/em\u003e-Student statistical analysis (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) revealed significant differences between natural and thermal-modified woods. Bending strength loss was expected in all thermal modified wood species as reported in the literature (Esteves and Pereira \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Sandberg et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Godinho et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e), and the same happened in this study with values ranging from 104 N.mm\u003csup\u003e-2\u003c/sup\u003e to 70 N.mm\u003csup\u003e-2\u003c/sup\u003e for Pine, 133 N.mm\u003csup\u003e-2\u003c/sup\u003e to 68 N.mm\u003csup\u003e-2\u003c/sup\u003e for Ash and 93 N.mm\u003csup\u003e-2\u003c/sup\u003e to 76 N.mm\u003csup\u003e-2\u003c/sup\u003e for Acacia. However, Ash wood suffered the most loss compared to the others (68 N.mm\u003csup\u003e-2\u003c/sup\u003e). In the case of MOE and MOC, no significant changes were observed between natural and thermal-modified wood samples, according to t-student statistical analysis (\u003cem\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/em\u003e). Even though there are no significant differences, a slight increase of MOE and MOC was verified in thermal-modified woods, except for Ash. This could be caused by thermal degradation of amorphous cellulose and the increase of relative crystallinity (Tomak et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Louren\u0026ccedil;o et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). This same behavior was reported by other authors who studied Ash (\u003cem\u003eFraxinus excelsior\u003c/em\u003e L.), but also iroko (\u003cem\u003eChlorophora excelsa\u003c/em\u003e (Welw.) Benth. Hook), and Scots pine (\u003cem\u003ePinus sylvestris\u003c/em\u003e L.) (Tomak et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). The compression strength (CS) increased in Modified Pine (\u0026asymp;\u0026thinsp;8%) and decreased in Modified Acacia (\u0026asymp;\u0026thinsp;12%), but no significant changes occurred in Modified Ash. This can be explained by the effects of thermal modification on wood, where the low bound water content could cause an increase in crystalline cellulose content and the increase of lignin polymer network cross-linking (Tomak et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e; Louren\u0026ccedil;o et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e). Besides, depending on the wood species, the compression strength values could increase or decrease because it depends on wood density (Esteves and Pereira \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Priadi and Hiziroglu \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Čabalov\u0026aacute; et al.\u0026nbsp;\u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMechanical properties of natural and thermal-modified woods (mean values\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWood\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDensity (kg.m\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOE\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOR\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCS\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOC\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e620\u0026thinsp;\u0026plusmn;\u0026thinsp;57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10 935\u0026thinsp;\u0026plusmn;\u0026thinsp;2 849\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e104\u0026thinsp;\u0026plusmn;\u0026thinsp;18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11 917\u0026thinsp;\u0026plusmn;\u0026thinsp;4 041\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Pine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e587\u0026thinsp;\u0026plusmn;\u0026thinsp;30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11 150\u0026thinsp;\u0026plusmn;\u0026thinsp;2 189\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e70\u0026thinsp;\u0026plusmn;\u0026thinsp;19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13 767\u0026thinsp;\u0026plusmn;\u0026thinsp;4 522\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e733\u0026thinsp;\u0026plusmn;\u0026thinsp;17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15 278\u0026thinsp;\u0026plusmn;\u0026thinsp;935\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e133\u0026thinsp;\u0026plusmn;\u0026thinsp;9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e58\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17 867\u0026thinsp;\u0026plusmn;\u0026thinsp;2 941\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Ash\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e648\u0026thinsp;\u0026plusmn;\u0026thinsp;34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12 923\u0026thinsp;\u0026plusmn;\u0026thinsp;1 663\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e68\u0026thinsp;\u0026plusmn;\u0026thinsp;19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e59\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16 526\u0026thinsp;\u0026plusmn;\u0026thinsp;3 681\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e670\u0026thinsp;\u0026plusmn;\u0026thinsp;44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12 148\u0026thinsp;\u0026plusmn;\u0026thinsp;2 265\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e93\u0026thinsp;\u0026plusmn;\u0026thinsp;22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15 104\u0026thinsp;\u0026plusmn;\u0026thinsp;3 791\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Acacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e599\u0026thinsp;\u0026plusmn;\u0026thinsp;67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12 569\u0026thinsp;\u0026plusmn;\u0026thinsp;2 224\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e76\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16 931\u0026thinsp;\u0026plusmn;\u0026thinsp;4 458\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eMOE \u0026ndash; modulus of elasticity; MOR \u0026ndash; bending strength; CS \u0026ndash; compression strength; MOC \u0026ndash; modulus of compression.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2. Natural and thermal-modified wood after Weathering\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e presents the density values and the results from the mechanical properties of all wood samples after 24 months of exposure to weathering. As can be seen, significant changes in density were verified in all wood samples exposed in both locations (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e), except on Modified Ash and in Acacia exposed in Lumiar (\u003cem\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/em\u003e).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMechanical properties of natural and modified woods after 24 months of weathering in Lumiar and Sines (mean values\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDensity (kg.m\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOE\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOR\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCS\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMOC\u003c/p\u003e\n \u003cp\u003e(N.mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eLumiar\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e625\u0026thinsp;\u0026plusmn;\u0026thinsp;16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11 840\u0026thinsp;\u0026plusmn;\u0026thinsp;975\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e92\u0026thinsp;\u0026plusmn;\u0026thinsp;6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e49\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20 318\u0026thinsp;\u0026plusmn;\u0026thinsp;8 604\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Pine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e568\u0026thinsp;\u0026plusmn;\u0026thinsp;33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9 008\u0026thinsp;\u0026plusmn;\u0026thinsp;1 444\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e61\u0026thinsp;\u0026plusmn;\u0026thinsp;17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e47\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14 076\u0026thinsp;\u0026plusmn;\u0026thinsp;4 740\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e679\u0026thinsp;\u0026plusmn;\u0026thinsp;92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11 266\u0026thinsp;\u0026plusmn;\u0026thinsp;2 709\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e90\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20 444\u0026thinsp;\u0026plusmn;\u0026thinsp;7 765\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Ash\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e619\u0026thinsp;\u0026plusmn;\u0026thinsp;15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11 215\u0026thinsp;\u0026plusmn;\u0026thinsp;1 278\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e70\u0026thinsp;\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16 226\u0026thinsp;\u0026plusmn;\u0026thinsp;3 153\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e627\u0026thinsp;\u0026plusmn;\u0026thinsp;63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9 576\u0026thinsp;\u0026plusmn;\u0026thinsp;2 481\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e87\u0026thinsp;\u0026plusmn;\u0026thinsp;20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e53\u0026thinsp;\u0026plusmn;\u0026thinsp;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21 165\u0026thinsp;\u0026plusmn;\u0026thinsp;7 484\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Acacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e533\u0026thinsp;\u0026plusmn;\u0026thinsp;90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9 639\u0026thinsp;\u0026plusmn;\u0026thinsp;1 898\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e55\u0026thinsp;\u0026plusmn;\u0026thinsp;25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e46\u0026thinsp;\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13 806\u0026thinsp;\u0026plusmn;\u0026thinsp;3 085\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSines\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e586\u0026thinsp;\u0026plusmn;\u0026thinsp;33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9 811\u0026thinsp;\u0026plusmn;\u0026thinsp;1 727\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e76\u0026thinsp;\u0026plusmn;\u0026thinsp;11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e41\u0026thinsp;\u0026plusmn;\u0026thinsp;7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15 638\u0026thinsp;\u0026plusmn;\u0026thinsp;5 042\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Pine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e558\u0026thinsp;\u0026plusmn;\u0026thinsp;16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8 773\u0026thinsp;\u0026plusmn;\u0026thinsp;1 477\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e42\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14 113\u0026thinsp;\u0026plusmn;\u0026thinsp;2 641\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e681\u0026thinsp;\u0026plusmn;\u0026thinsp;71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13 263\u0026thinsp;\u0026plusmn;\u0026thinsp;812\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e98\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28 947\u0026thinsp;\u0026plusmn;\u0026thinsp;5 201\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Ash\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e641\u0026thinsp;\u0026plusmn;\u0026thinsp;33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10 763\u0026thinsp;\u0026plusmn;\u0026thinsp;1 164\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e71\u0026thinsp;\u0026plusmn;\u0026thinsp;9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e53\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19 505\u0026thinsp;\u0026plusmn;\u0026thinsp;4 722\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e659\u0026thinsp;\u0026plusmn;\u0026thinsp;93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13 349\u0026thinsp;\u0026plusmn;\u0026thinsp;227\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e118\u0026thinsp;\u0026plusmn;\u0026thinsp;19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e60\u0026thinsp;\u0026plusmn;\u0026thinsp;8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21 406\u0026thinsp;\u0026plusmn;\u0026thinsp;5 539\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Acacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e517\u0026thinsp;\u0026plusmn;\u0026thinsp;80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10 425\u0026thinsp;\u0026plusmn;\u0026thinsp;1 599\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e77\u0026thinsp;\u0026plusmn;\u0026thinsp;23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e50\u0026thinsp;\u0026plusmn;\u0026thinsp;9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14 740\u0026thinsp;\u0026plusmn;\u0026thinsp;4 091\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eMOE \u0026ndash; modulus of elasticity; MOR \u0026ndash; bending strength; CS \u0026ndash; compression strength; MOC \u0026ndash; modulus of compression.\u003c/p\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eAll exposed wood samples revealed some changes in both locations regarding mechanical properties. MOE and MOR decreased (\u0026asymp;\u0026thinsp;15%) on most wood samples, with significant changes in both locations (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e). On the contrary, Pine presented an increase of MOE in Lumiar and Modified Ash, Acacia and Modified Acacia presented an increase of MOR in Sines. This could indicate that thermal modification can give a stable elasticity when woods are exposed to different environments, maybe caused by lignin changes that occur in thermal modification (Godinho et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e) that could obstruct UV light by the promotion of free radical reactions, the formation of degradation products with a low molecular weight (Nuopponen et al. \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e) and the low equilibrium moisture content in thermally modified woods caused by the decrease of hemicellulose content (Godinho et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e) could reduce the leaching of degradation products (Nuopponen et al. \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2014\u003c/span\u003e). In the case of compression strength and MOC, all exposed wood samples in both locations increased, except for Modified Ash exposed in Lumiar. Significant changes in compression strength in Pine, Modified Pine, and Acacia were found when exposed to the different environments. Pine and Modified Pine compression strength decreased when exposed to Sines, contrary to Acacia, which increased. MOC found a significant difference only in Ash and Modified Ash, where a higher increase in Sines was verified.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Durability evaluation\u003c/h2\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1. Resistance against subterranean termite\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e presents the results of termite resistance of all-natural and thermal-modified woods. The average termite survival rate is similar in all thermally modified and natural wood species (above 75% and lower than 80%), except for Modified Acacia, which presented a lower survival rate of 59% but with a higher standard deviation (13.5%).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAverage survival results, average mass loss, final moisture content, and grade of attack after termite exposure (n\u0026thinsp;=\u0026thinsp;10, mean values\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMoisture Content (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSurvival\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMass Loss\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGrade of Attack\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.4\u0026thinsp;\u0026plusmn;\u0026thinsp;4.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.2\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Pine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;6.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e76.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32.9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Ash\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e34.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e79.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Acacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e24.1\u0026thinsp;\u0026plusmn;\u0026thinsp;6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e59.0\u0026thinsp;\u0026plusmn;\u0026thinsp;13.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003eSTDEV \u0026ndash; standard deviation\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eAn important fact was that the attack grade was almost the same in all wood samples, which shows that the thermal modification did not improve wood for termite resistance. Even though the results look very similar, the statistical analysis showed significant changes in Ash and Acacia (\u003cem\u003ep\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/em\u003e). Thermal treatment has not been shown to improve the durability of other wood species against subterranean in any tests conducted using the same termite species towards thermally modified \u003cem\u003ePaulownia tomentosa\u003c/em\u003e (Esteves et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e); \u003cem\u003eReticulitermes banyulensis\u003c/em\u003e Cl\u0026eacute;ment towards thermally modified ash and European beech (Oliver-Villanueva et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e); \u003cem\u003eReticulitermes santonensis\u003c/em\u003e Feytaud towards maritime pine (Surini et al. \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). Therefore, new techniques to improve the performance of thermally modified wood to termite attack have been developed due to the lack of protection against termites, e.g. with the impregnation of bicine and tricine (Jones et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e) or impregnation of a boron derivative associated with appropriate vinylic monomers (Salman et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). In Fig. 1 is presented natural and modified Acacia, as an example of the damage caused by termites.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2. FTIR-ATR analysis\u003c/h2\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e presents the chosen assignment bands of FTIR spectra as those used in the previous work published by the authors (Godinho et al.\u0026nbsp;\u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAssignment of FTIR bands of principal chemical components in wood in the region 1800\u0026thinsp;\u0026minus;\u0026thinsp;800 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWavenumber\u003c/p\u003e\n \u003cp\u003e(cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAssignment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePrincipal band\u0026apos;s origin\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRef.\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1750\u0026thinsp;\u0026minus;\u0026thinsp;1720\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u0026thinsp;=\u0026thinsp;O stretching in conjugated ketones, carbonyls, aldehydes, and ester group\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLignin/Polysaccharide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1724\u0026ndash;1730\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFree carbonyl groups, C\u0026thinsp;=\u0026thinsp;O Stretching of acetyl or carboxylic acid\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHemicellulose/Lignin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Graham Solomons and Fryhle \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Srinivas and Pandey \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1675\u0026thinsp;\u0026minus;\u0026thinsp;1655\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u0026thinsp;=\u0026thinsp;O stretch on conjugated \u003cem\u003ep\u003c/em\u003e-substituted aryl ketones\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLignin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1605\u0026thinsp;\u0026minus;\u0026thinsp;1598\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u0026thinsp;=\u0026thinsp;C Aromatic ring stretching\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSyringyl Lignin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Huang et al. \u003cspan class=\"CitationRef\"\u003e2012a\u003c/span\u003e; Cogulet et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Čabalov\u0026aacute; et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1515\u0026thinsp;\u0026minus;\u0026thinsp;1506\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u0026thinsp;=\u0026thinsp;C stretching of the aromatic ring\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGuaiacyl lignin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Huang et al. \u003cspan class=\"CitationRef\"\u003e2012a\u003c/span\u003e; Srinivas and Pandey \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1470\u0026thinsp;\u0026minus;\u0026thinsp;1460\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-CH\u003csub\u003e3\u003c/sub\u003e and -CH\u003csub\u003e2\u003c/sub\u003e deformation (asymmetric)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLignin/Xylan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Huang et al. \u003cspan class=\"CitationRef\"\u003e2012b\u003c/span\u003e; Srinivas and Pandey \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Hofmann et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1430\u0026thinsp;\u0026minus;\u0026thinsp;1420\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAromatic skeletal vibration (lignin) and C-H deformation (cellulose)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLignin/Cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1370\u0026thinsp;\u0026minus;\u0026thinsp;1365\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePhenolic OH, aliphatic C-H stretch in CH\u003csub\u003e3\u003c/sub\u003e, not in O-Me, C-H vibration in polysaccharide CH\u003csub\u003e2\u003c/sub\u003e bending in cellulose and hemicelluloses\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLignin/Polysaccharide/Hemicellulose/Cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1330\u0026thinsp;\u0026minus;\u0026thinsp;1320\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePhenolic OH, C-H vibration in cellulose, and C-O vibration in syringyl and guaiacyl rings\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSyringyl Lignin/Guaiacyl Lignin/ Polysaccharide/Cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Yilgor et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u0026Ouml;zgen\u0026ccedil; et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1266\u0026thinsp;\u0026minus;\u0026thinsp;1261\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGuaiacyl ring breathing with C\u0026thinsp;=\u0026thinsp;O-stretching, acetyl, and carboxylic vibration in xylan and esters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGuaicyl Lignin/Xylan/Hemicellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Cogulet et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1240\u0026thinsp;\u0026minus;\u0026thinsp;1220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSyringyl ring and C-O stretch, acetyl, and carboxylic vibration in xylan\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSyringyl Lignin/Xylan/Polysaccharides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Herrera et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Kubovsk\u0026yacute; et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e; Hofmann et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1210\u0026thinsp;\u0026minus;\u0026thinsp;1201\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOH-bending, aryl aldehyde, a- and unsaturated aldehyde, lactones, phenols, and diaryl ethers. Associated with crystallized and amorphous cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u0026Ouml;zgen\u0026ccedil; et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1160\u0026thinsp;\u0026minus;\u0026thinsp;1155\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC-O-C vibration in cellulose and hemicellulose is also associated with crystallized and amorphous cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCellulose/Hemicellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Yildiz et al. \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u0026Ouml;zgen\u0026ccedil; et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1110\u0026thinsp;\u0026minus;\u0026thinsp;1104\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOH association, C-O stretching, and CH\u003csub\u003e2\u003c/sub\u003e rocking on cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u0026Ouml;zgen\u0026ccedil; et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1054\u0026thinsp;\u0026minus;\u0026thinsp;1052\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC-O deformation in aliphatic alcohols and ethers\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCarbohydrates\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1051\u0026thinsp;\u0026minus;\u0026thinsp;1023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC-H and C-O deformations\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolysaccharides/Cellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(Herrera et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Pozo et al. \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; \u0026Ouml;zgen\u0026ccedil; et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Gonultas and Candan \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tomak et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1000\u0026thinsp;\u0026minus;\u0026thinsp;985\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC-O valence vibration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCellulose\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e(U\u0026ccedil;ar et al. \u003cspan class=\"CitationRef\"\u003e1996\u003c/span\u003e; Schwanninger et al. \u003cspan class=\"CitationRef\"\u003e2004\u003c/span\u003e; Lopes et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eFigure 2 presents the difference in the FTIR-ATR spectra between the woods before and after decay attack by termites. It was verified an increase in bands 1750\u0026thinsp;\u0026minus;\u0026thinsp;1720 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (lignin and polysaccharides), 1370\u0026thinsp;\u0026minus;\u0026thinsp;1350 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (lignin, polysaccharides, and hemicellulose), 1240\u0026thinsp;\u0026minus;\u0026thinsp;1220 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (syringyl, xylans and polysaccharides), 1210\u0026thinsp;\u0026minus;\u0026thinsp;1201 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (cellulose), 1104\u0026ndash;1110 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (cellulose) and 1051\u0026thinsp;\u0026minus;\u0026thinsp;1023 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (polysaccharides and cellulose) in Modified Pine. For Pine, Modified, and natural Ash, and Modified and natural Acacia, increases were seen in the bands 1750\u0026thinsp;\u0026minus;\u0026thinsp;1720 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (lignin and polysaccharides), 1370\u0026thinsp;\u0026minus;\u0026thinsp;1350 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (lignin, polysaccharides, and hemicellulose), 1240\u0026thinsp;\u0026minus;\u0026thinsp;1220 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (syringyl, xylans, and polysaccharides). However, decreases were also observed in the bands 1104\u0026ndash;1110 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (cellulose) and 1051\u0026thinsp;\u0026minus;\u0026thinsp;1023 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (polysaccharides and cellulose) of Pine, Ash, and Acacia. These bands did not undergo significant changes in the Modified Ash and Acacia. Termites possess enzymes that facilitate the digestion of wood\u0026apos;s main components, aided by bacterial symbiosis in their guts (Singhania \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Duarte et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). The bacteria release cellulolytic enzymes that degrade cellulose and hemicellulose into sugars, also known as cellulases and hemicellulases, which are then converted into acetate, hydrogen, and carbon dioxide (Singhania \u003cspan class=\"CitationRef\"\u003e2009\u003c/span\u003e; Duarte et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e; Peristiwati et al. 2018). This process could explain the increased bands at 1240\u0026thinsp;\u0026minus;\u0026thinsp;1220 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in all wood samples, corresponding to the acetyl group. Besides, the natural wood samples revealed decreases in the bands corresponding to cellulose, which confirmed that the termites attack cellulose more easily than lignin (Duarte et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). However, in Modified Pine and Modified Ash, the cellulose bands increased showing that cellulose did not suffer alterations, maybe because thermal modification caused chemical changes in cellulose (Godinho et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e), namely the reduction of amorphous cellulose (Louren\u0026ccedil;o et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e), as revealed in bands 1155\u0026ndash;1160 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, associated with C-O-C vibration (Godinho et al. \u003cspan class=\"CitationRef\"\u003e2024\u003c/span\u003e). These results suggest that thermal modification could help prevent the cellulose degradation caused by termites.\u003c/p\u003e\n \u003cp\u003eThe band 1750\u0026thinsp;\u0026minus;\u0026thinsp;1720 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e increase in all wood samples corresponds to C\u0026thinsp;=\u0026thinsp;O stretching in ketones, aldehydes, and ester groups associated with lignin and polysaccharides. The increase was similar in all woods, indicating that the thermal modification did not give extra protection for lignin. Subterranean termites could cause rearrangements in lignin by the same symbiosis present in their guts (Talia \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e) because they possess ligninase enzymes that degrade lignin by redox mechanisms and release free radicals (Pl\u0026aacute;cido and Capareda \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Talia \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). Therefore, the increased intensity of bands associated with lignin may suggest a reorganization of the lignin structure (Ke et al. \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e). This phenomenon was reported in a study involving the termite \u003cem\u003eCoptotermes formasanus\u003c/em\u003e Shiraki, where the digestion process led to significant alterations in lignin structure, namely the destruction of the aromatic ring, dihydroxylation, demethylation, and demethoxylation (Ke et al. \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Py/GC analysis\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eFigure 3 shows the pyrograms of the woods (natural and modified) before and after decay by termites. At the beginning of the pyrogram, carbohydrate derivatives were identified (Fig. 2, peaks 1\u0026ndash;9), and then, after 16 min of running time, lignin derivatives started to appear. The first one was guaiacol (peak 12). Overall, the compounds identified were the same between species, except in pine, where no syringyl-derived units were identified, being a GH type of lignin. At the same time, Ash and Acacia presented guaiacyl and syringyl units (SG type of lignin).\u003c/p\u003e\n \u003c/div\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e presents a resume of the pyrolysis analysis of natural and modified wood before and after decay by termites. In natural Pine wood, termites trigger cellulose degradation, evidenced by decreased levoglucosan content from 10.9\u0026ndash;7.7%. This suggests alterations to cellulose, although overall sugar content remains unaffected at 38.8% compared to 38.6%. This is in line with studies that mention the ability of termites to degrade cellulose (Marynowska et al. \u003cspan class=\"CitationRef\"\u003e2023\u003c/span\u003e). Notably, total lignin content experiences a slight increase, reaching 23.2% upon termite exposure.\u003c/p\u003e\n \u003cp\u003eConversely, in natural Ash wood, the C/L ratio remains stable (1.8 vs. 1.6), attributed to a simultaneous increase in sugars and lignin. This stability hints at minimal termite impact on this wood. In Acacia, there is a slight reduction in total carbohydrates, notably in cellulose, where levoglucosan levels drop significantly from 12.9\u0026ndash;6.8%. However, lignin content remains unchanged post-termite exposure. Consequently, the C/L ratio in Acacia wood was maintained at 2.3, showcasing consistency, while the S/G ratio experienced a slight increase from 1.9 to 2.3.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab6\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eResume of the analytical pyrolysis analysis of the woods before and after termite decay (% of total chromatographic area).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"8\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWood samples\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTC\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTL\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eH\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eG\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eS\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eS/G ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC/L ratio\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e38.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePine termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e38.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Pine\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMP termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003en.d.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAsh termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e40.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e24.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Ash\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e44.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMA termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e41.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAcacia termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e42.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eModified Acacia\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMAc termite decay\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e45.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eTC \u0026ndash; total carbohydrates; TL \u0026ndash; total lignin; H, G, S \u0026ndash; Lignin units; n.d. \u0026ndash; not detected/not determined.\u003c/p\u003e\n \u003cp\u003eIn modified woods like Pine post-termite attack, a notable decrease in levoglucosan content (from 20.2\u0026ndash;13.2%) indicates cellulose degradation by termites. This is corroborated by an increase in minor compounds (peaks 1\u0026ndash;10), suggesting a breakdown of cellulose, yielding low molecular weight carbohydrate-derived products. Consequently, total carbohydrate content experienced a slight reduction from 44.5\u0026ndash;43.3%, while total lignin exhibited a modest increase from 17.3\u0026ndash;18.4%. Similarly, Ash wood displayed consistent C/L values (2.2 vs. 1.8) due to concurrent sugars and increased lignin decreases. Notably, cellulose degradation was evident, with a sharp decline in levoglucosan from 19.3\u0026ndash;11.7%. In Acacia, total sugars were significantly reduced (from 52.4\u0026ndash;45.9%), primarily attributed to decreased levoglucosan content from 31.2\u0026ndash;20.6%. While total lignin slightly increased (from 14.5\u0026ndash;15.7%), the C/L ratio decreased from 3.6 to 2.9, indicating cellulose degradation. Therefore, termites can degrade cellulose in natural and modified woods, irrespective of the wood species studied. Termites\u0026apos; ability to degrade cellulose was already shown in FTIR data and is following the literature (Deka et al. \u003cspan class=\"CitationRef\"\u003e2002\u003c/span\u003e). According to (Jones et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e), even thermally treated woods have poorly performed against termites. For example, in Ash wood, only the temperature of 215 \u0026ordm;C during the thermal modification treatment was effective in classifying the wood on a durability rating scale of \u0026quot;durable\u0026quot; and \u0026quot;very durable\u0026quot; for termite degradation (Candelier et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e). Also, termites degrade cellulose in \u003cem\u003eE. grandis\u003c/em\u003e thermally treated wood (Gallio et al. \u003cspan class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis experimental study allowed us to conclude:\u003c/p\u003e\n\u003cp\u003eBefore weathering:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eThermal modification caused changes in mechanical and physical properties, namely a decrease in density and bending strength. Concerning compression, no significant changes were reported.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eAfter weathering:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eAll weathered wood samples revealed changes in mechanical properties in both locations. The behavior of all wood samples was very similar in both locations, indicating that the environment type does not affect the mechanical changes. Thermal modification also did not contribute to the resistance to weathering. This was verified in the previous study, where the chemical changes revealed very similar results in both locations.\u003c/li\u003e\n \u003cli\u003eNo physical and mechanical evidence demonstrates that marine/industrial or urban environments lead to woods (natural and thermal-modified) having different weathering resistance, except in compression. Pine and Modified Pine suffered a decrease of compression strength in Sines. The opposite happens to Acacia where an increase of compression strength was verified. In Ash and Modified Ash MOC increased in Sines. These results showed that Pine and Modified Pine could have some sensibility in maritime/industrial environment. Ash and Acacia, natural and thermal modified apparently, gained some compression strength and flexibility. Even with these results, further studies with a higher exposure period are needed to evaluate if the wood samples or some wood species will show a different behavior in environments with very high corrosivity and strong maritime/industrial influence.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eResistance to subterranean termites\u003c/strong\u003e\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eAll wood samples revealed a close grade of attack. Modified Acacia revealed a little more resistance to subterranean termite attack and a lower survival rate, indicating that thermal modification could produce more toxic substances for termites.\u003c/li\u003e\n \u003cli\u003eFTIR-ATR spectrum corroborates that termite degraded, primarily cellulose. However, in modified woods, cellulose degradation was lower, possibly due to alterations in cellulose polymer after thermal treatment. The spectrum also showed that termites could degrade lignin, causing some rearrangements of the polymer.\u003c/li\u003e\n \u003cli\u003ePyrolysis analysis corroborates the idea that termites can partially degrade all wood components: cellulose degradation reflected in the decrease of levoglucosan but also lignin by the slight changes in monomeric composition reflected in the reduction of the S/G ratio; these observations occurred either in natural or thermally treated woods.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThermal modification did not improve the durability against termites and the resistance to weathering. Further studies will be needed to evaluate if combining other wood protection products could overcome the fragilities found in thermal-modified wood.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, DG, TQ, TCD, JG, LN and JSM; methodology, DG, SdOA, CF, AL, TQ, TCD, JG, LN and JSM; formal analysis, DG, CF, AL, LN, MD, SD and JSM; writing\u0026mdash;original draft preparation, DG; writing, review and editing, CF, AL, SdOA, TQ, TCD, JG, LN, SD and JSM; supervision, TQ, TCD, and JG. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments\u003c/h2\u003e \u003cp\u003eThe authors would like to thank this research funding by FCT (Funda\u0026ccedil;\u0026atilde;o para a Ci\u0026ecirc;ncia e Tecnologia, Portugal) by financing the Forest Research Centre (UIDB/00239/2020) and Associate Laboratory TERRA (LA/P/0092/2020). FCT supported Delfina Godinho through PhD fellowship (PD/BD/142987/2018) under the Sustainable Forests and Products (SUSFOR) doctoral program (SUSFOR) (PD/00157/2012). FCT supported Ana Louren\u0026ccedil;o through a research contract (DL57/2016/CPI382/CT0007) and Solange de Oliveira Ara\u0026uacute;jo through a research contract (DL57/2016/CPI382/CT0018). The authors also would like to thank Parques de Sintra \u0026ndash; Monte da Lua (PSML) for providing the acacia wood, Santos \u0026amp; Santos company for providing pine and ash wood, and for the thermal modification of all wood species. A special thanks to Ana Soares Vieira and Rita Gon\u0026ccedil;alves for providing the Lumiar's and Sines's climatic data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eČabalov\u0026aacute; I, Kac\u0026iacute;k F, Lagaňa R, et al (2018) Effect of thermal treatment on the chemical, physical, and mechanical properties of pedunculate oak (\u003cem\u003eQuercus robur\u003c/em\u003e L.) wood. BioResources 13:. https://doi.org/10.15376/biores.13.1.157-170\u003c/li\u003e\n\u003cli\u003eCandelier K, Hannouz S, Th\u0026eacute;venon MF, et al (2017) Resistance of thermally modified ash (\u003cem\u003eFraxinus excelsio\u003c/em\u003er L.) wood under steam pressure against rot fungi, soil-inhabiting micro-organisms and termites. 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Maderas Cienc y Tecnol 20:431\u0026ndash;442. https://doi.org/10.4067/S0718-221X2018005031301\u003c/li\u003e\n\u003cli\u003eGraham Solomons TW, Fryhle CBF (2004) Qu\u0026iacute;mica Org\u0026acirc;nica Cap\u0026iacute;tulo 2: Composto de Carbono Representativos: Grupos Funcionais, For\u0026ccedil;as Intermoleculares e Espectroscopia no Infravermelho (IV), 8th Editio. LTC - Livros T\u0026eacute;cnicos e Cient\u0026iacute;ficos Editora, S.A., Rio de Janeiro\u003c/li\u003e\n\u003cli\u003eHerrera R, Labidi J, Krystofiak T, Llano-Ponte R (2016) Characterization of thermally modified wood at different industrial conditions. Drewno 59:151\u0026ndash;164. https://doi.org/10.12841/wood.1644-3985.C05.15\u003c/li\u003e\n\u003cli\u003eHill C, Altgen M, Rautkari L (2021) Thermal modification of wood \u0026mdash; a review : chemical changes and hygroscopicity. 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Forests 10:. https://doi.org/10.3390/f10100903\u003c/li\u003e\n\u003cli\u003eInternational Organization for Standardization (ISO) (2014) ISO 13061-4 - Physical and mechanical properties of wood \u0026mdash; Test methods for small clear wood specimens \u0026mdash; Part 4: Determination of modulus of elasticity in static bending\u003c/li\u003e\n\u003cli\u003eInternational Organization for Standardization (ISO) (2020) ISO 13061-5 - Physical and mechanical properties of wood \u0026mdash; Test methods for small clear wood specimens \u0026mdash; Part 5: Determination of strength in compression perpendicular to grain\u003c/li\u003e\n\u003cli\u003eInternational Organization for Standardization (ISO) (2012) ISO 9223 Corrosion of metals and alloys \u0026mdash; Classification , determination and. Geneva, Switzerland\u003c/li\u003e\n\u003cli\u003eJones D, Nunes L, Duarte S (2022) Improving Performance of Thermal Modified Wood against Termites with Bicine and Tricine. In: Bio-Based Building Materials. Trans Tech Publications Ltd, pp 735\u0026ndash;742\u003c/li\u003e\n\u003cli\u003eJones D, Sandberg D, Gicomo G (2019) Wood modification in Europe: A state-of-the-art about processes, products, applications. Firenze University Press, Firenze, Italy\u003c/li\u003e\n\u003cli\u003eKasemsiri P, Hiziroglu S, Rimdusit S (2012) Characterization of heat treated eastern redcedar (\u003cem\u003eJuniperus virginiana\u003c/em\u003e L .). J Mater Process Tech 212:1324\u0026ndash;1330. https://doi.org/10.1016/j.jmatprotec.2011.12.019\u003c/li\u003e\n\u003cli\u003eKe J, Laskar DD, Gao D, Chen S (2012) Advanced biorefinery in lower termite-effect of combined pretreatment during the chewing process. Biotechnol Biofuels 5:11. https://doi.org/10.1186/1754-6834-5-11\u003c/li\u003e\n\u003cli\u003eKe J, Laskar DD, Singh D, Chen S (2011) In situ lignocellulosic unlocking mechanism for carbohydrate hydrolysis in termites: Crucial lignin modification. Biotechnol Biofuels 4:17. https://doi.org/10.1186/1754-6834-4-17\u003c/li\u003e\n\u003cli\u003eKorkut S, Aytin A (2015) Evaluation of physical and mechanical properties of wild cherry wood heat-treated using the thermowood process. Maderas Cienc y Tecnol 17:171\u0026ndash;178. https://doi.org/10.4067/S0718-221X2015005000017\u003c/li\u003e\n\u003cli\u003eKubovsk\u0026yacute; I, Kač\u0026iacute;kov\u0026aacute; D, Kač\u0026iacute;k F (2020) Structural changes of oak wood main components caused by thermal modification. Polymers (Basel) 12:. https://doi.org/10.3390/polym12020485\u003c/li\u003e\n\u003cli\u003eLopes J de O, Garcia RA, de Souza ND (2018) Infrared spectroscopy of the surface of thermally-modified teak juvenile wood. Maderas Cienc y Tecnol 20:737\u0026ndash;746. https://doi.org/10.4067/S0718-221X2018005041901\u003c/li\u003e\n\u003cli\u003eLouren\u0026ccedil;o A, Ara\u0026uacute;jo S, Gominho J, Evtuguin D (2020) Cellulose structural changes during mild torrefaction of Eucalyptus wood. Polymers (Basel) 12:1\u0026ndash;17. https://doi.org/10.3390/polym12122831\u003c/li\u003e\n\u003cli\u003eMachado JS, Louzada JL, Santos AJA, et al (2014) Variation of wood density and mechanical properties of blackwood (\u003cem\u003eAcacia melanoxylon\u003c/em\u003e R. Br.). Mater Des 56:975\u0026ndash;980. https://doi.org/10.1016/j.matdes.2013.12.016\u003c/li\u003e\n\u003cli\u003eMarynowska M, Sillam-Duss\u0026egrave;s D, Untereiner B, et al (2023) A holobiont approach towards polysaccharide degradation by the highly compartmentalised gut system of the soil-feeding higher termite \u003cem\u003eLabiotermes labralis\u003c/em\u003e. BMC Genomics 24:1\u0026ndash;20. https://doi.org/10.1186/s12864-023-09224-5\u003c/li\u003e\n\u003cli\u003eMerlo E, Alvarez-Gonzalez JG, Santaclara O, Riesco G (2014) Modelling modulus of elasticity of \u003cem\u003ePinus pinaster\u003c/em\u003e Ait. in northwestern Spain with standing tree acoustic measurements, tree, stand and site variables. For Syst 23:153\u0026ndash;166. https://doi.org/10.5424/fs/2014231-04706\u003c/li\u003e\n\u003cli\u003eMolinski W, Roszyk E, Jablonski A, et al (2018) Mechanical parameters of thermally modified ash wood determined on compression in tangential direction. Maderas Cienc y Tecnol 20:267\u0026ndash;276. https://doi.org/10.4067/S0718-221X2018005021001\u003c/li\u003e\n\u003cli\u003eNunes L (2008) Termite infestation risk in Portuguese historic buildings. Wood Sci Conserv Cult Heritage Braga, Port 117\u0026ndash;122\u003c/li\u003e\n\u003cli\u003eNuopponen M, Wikberg H, Vuorinen T, et al (2004) Heat-treated softwood exposed to weathering. J Appl Polym Sci 91:2128\u0026ndash;2134. https://doi.org/10.1002/app.13351\u003c/li\u003e\n\u003cli\u003eOliver-Villanueva JV, Gasc\u0026oacute;n-Garrido P, Ibiza-Palacios MDS (2013) Evaluation of thermally-treated wood of beech (\u003cem\u003eFagus sylvatica\u003c/em\u003e L.) and ash (\u003cem\u003eFraxinus excelsior\u003c/em\u003e L.) against Mediterranean termites (\u003cem\u003eReticulitermes\u003c/em\u003e spp.). Eur J Wood Wood Prod 71:391\u0026ndash;393. https://doi.org/10.1007/s00107-013-0687-2\u003c/li\u003e\n\u003cli\u003eOrmondroyd G, Spear M, Curling S (2015) Modified wood: Review of efficacy and service life testing. Proc Inst Civ Eng Constr Mater 168:187\u0026ndash;203. https://doi.org/10.1680/coma.14.00072\u003c/li\u003e\n\u003cli\u003e\u0026Ouml;zgen\u0026ccedil; \u0026Ouml;, Durmaz S, Boyaci IH, Eksi-Kocak H (2017) Determination of chemical changes in heat-treated wood using ATR-FTIR and FT Raman spectrometry. Spectrochim Acta - Part A Mol Biomol Spectrosc 171:395\u0026ndash;400. https://doi.org/10.1016/j.saa.2016.08.026\u003c/li\u003e\n\u003cli\u003ePeristiwati, Natamihardja YS, Herlini H (2018) Isolation and identification of cellulolytic bacteria from termites gut (\u003cem\u003eCryptotermes\u003c/em\u003e sp.). J Phys Conf Ser 1013:. https://doi.org/10.1088/1742-6596/1013/1/012173\u003c/li\u003e\n\u003cli\u003ePl\u0026aacute;cido J, Capareda S (2015) Ligninolytic enzymes: A biotechnological alternative for bioethanol production. Bioresour. Bioprocess. 2:23 https://10.1186/s40643-015-0049-5\u003c/li\u003e\n\u003cli\u003ePozo C, D\u0026iacute;az-Visurraga J, Contreras D, et al (2016) Characterization of Temporal Biodegradation of Radiata Pine by \u003cem\u003eGloeophyllum trabeum\u003c/em\u003e through principal component analysis-based two dimensional correlation FTIR spectroscopy. J Chil Chem Soc 61:2878\u0026ndash;2883\u003c/li\u003e\n\u003cli\u003ePriadi T, Hiziroglu S (2013) Characterization of heat treated wood species. Mater Des 49:575\u0026ndash;582. https://doi.org/10.1016/j.matdes.2012.12.067\u003c/li\u003e\n\u003cli\u003eSalman S, Th\u0026eacute;venon MF, P\u0026eacute;trissans A, et al (2017) Improvement of the durability of heat-treated wood against termites. Maderas Cienc y Tecnol 19:317\u0026ndash;328. https://doi.org/10.4067/S0718-221X2017005000027\u003c/li\u003e\n\u003cli\u003eSandberg D, Kutnar A, Mantanis G (2017) Wood modification technologies - A review. IForest 10:895\u0026ndash;908. https://doi.org/10.3832/ifor2380-010\u003c/li\u003e\n\u003cli\u003eSchwanninger M, Rodrigues JC, Pereira H, Hinterstoisser B (2004) Effects of short-time vibratory ball milling on the shape of FT-IR spectra of wood and cellulose. Vib Spectrosc 36:23\u0026ndash;40. https://doi.org/10.1016/j.vibspec.2004.02.003\u003c/li\u003e\n\u003cli\u003eSinghania RR (2009) Cellulolytic enzymes. Biotechnol Agro-Industrial Residues Util Util Agro-Residues 371\u0026ndash;381. https://doi.org/10.1007/978-1-4020-9942-7_20\u003c/li\u003e\n\u003cli\u003eSrinivas K, Pandey KK (2012) Photodegradation of thermally modified wood. J Photochem Photobiol B Biol 117:140\u0026ndash;145. https://doi.org/10.1016/j.jphotobiol.2012.09.013\u003c/li\u003e\n\u003cli\u003eSurini T, Charrier F, Malvestio J, et al (2012) Physical properties and termite durability of maritime pine \u003cem\u003ePinus pinaster\u003c/em\u003e Ait., heat-treated under vacuum pressure. Wood Sci Technol 46:487\u0026ndash;501. https://doi.org/10.1007/s00226-011-0421-3\u003c/li\u003e\n\u003cli\u003eTalia P (2018) Termites and Sustainable Management. Termit Sustain Manag. https://doi.org/10.1007/978-3-319-72110-1\u003c/li\u003e\n\u003cli\u003eTomak ED, Ustaomer D, Ermeydan MA, Yildiz S (2018) An investigation of surface properties of thermally modified wood during natural weathering for 48 months. Meas J Int Meas Confed 127:187\u0026ndash;197. https://doi.org/10.1016/j.measurement.2018.05.102\u003c/li\u003e\n\u003cli\u003eTomak ED, Ustaomer D, Yildiz S, Pesman E (2014) Changes in surface and mechanical properties of heat treated wood during natural weathering. Meas J Int Meas Confed 53:30\u0026ndash;39. https://doi.org/10.1016/j.measurement.2014.03.018\u003c/li\u003e\n\u003cli\u003eU\u0026ccedil;ar G, Staccioli CG, Stoll M (1996) Chemical composition and ultrastructure of a fossil wood from the genus of ancestral sequoia. Holz als Roh - und Werkst 54:411\u0026ndash;421. https://doi.org/10.1007/s001070050212\u003c/li\u003e\n\u003cli\u003eWilliams RS (2005) Weathering of wood. In: Rowell RM (ed) Handbook of Wood Chemistry and Wood Composites. CRC Press Taylor and Francis Group, Florida, pp 142\u0026ndash;185\u003c/li\u003e\n\u003cli\u003eYildiz S, Tomak ED, Yildiz UC, Ustaomer D (2013) Effect of artificial weathering on the properties of heat treated wood. Polym Degrad Stab 98:1419\u0026ndash;1427. https://doi.org/10.1016/j.polymdegradstab.2013.05.004\u003c/li\u003e\n\u003cli\u003eYilgor N, Dogu D, Moore R, et al (2013) Evaluation of fungal deterioration in Liquidambar orientalis Mill. heartwood by FT-IR and light microscopy. BioResources 8:2805\u0026ndash;2826. https://doi.org/10.15376/biores.8.2.2805-2826\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-wood-and-wood-products","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"harw","sideBox":"Learn more about [European Journal of Wood and Wood Products](http://link.springer.com/journal/107)","snPcode":"107","submissionUrl":"https://submission.nature.com/new-submission/107/3","title":"European Journal of Wood and Wood Products","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5137187/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5137187/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe main objective of this study was to evaluate the mechanical properties of three thermal-modified wood species when exposed to weathering in urban and maritime/industrial environments and their durability against subterranean termites. The wood species studied were Maritime Pine, Ash, and Blackwood acacia. All wood samples were exposed to two different environments (urban and maritime/industrial) for 24 months. Then, its physical and mechanical properties were evaluated (modulus of elasticity (MOE), modulus of rupture (MOR), compression strength (CS), and modulus of compression (MOC)). Thermally modified woods revealed a lower density, which could explain the loss of MOE and MOR. In compression, no significant changes were verified. The weathered samples revealed changes in mechanical properties, mostly verified in MOE and MOR, where some decreases were reported in both locations. Tests were performed to evaluate biodegradation and the resistance of all wood samples to subterranean termites. The grade of attack (\u0026asymp;\u0026thinsp;4) and termite survival rate were similar in all wood species (above 75% and lower than 80%), except for Modified Acacia (59%), which could indicate that thermal modification increased toxic substances. The cellulose degradation was reflected in FTIR-ATR and Py/GC-MS in natural and thermally modified woods. Py/GC-MS showed a decrease in levoglucosan, while lignin suffered some modifications with slight changes in monomeric composition reflected by the reduction of the S/G ratio. No changes were found between the two environments, and thermal modification did not give extra protection against termites and weathering.\u003c/p\u003e","manuscriptTitle":"Assessment of weathering and subterranean termite resistance in three thermally modified wood species in Portugal","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-26 05:27:24","doi":"10.21203/rs.3.rs-5137187/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-10-28T09:50:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-19T11:51:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-13T12:50:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"310282206748068659202142909890918751210","date":"2024-10-09T20:57:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"53613767748752445881705533673267661520","date":"2024-10-09T15:29:34+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-10-09T15:09:44+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-09T15:01:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-09-24T05:29:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Wood and Wood Products","date":"2024-09-23T10:02:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-wood-and-wood-products","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"harw","sideBox":"Learn more about [European Journal of Wood and Wood Products](http://link.springer.com/journal/107)","snPcode":"107","submissionUrl":"https://submission.nature.com/new-submission/107/3","title":"European Journal of Wood and Wood Products","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a3526960-6006-460b-a0b0-c239c87866df","owner":[],"postedDate":"November 26th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-01-20T16:11:10+00:00","versionOfRecord":{"articleIdentity":"rs-5137187","link":"https://doi.org/10.1007/s00107-024-02199-4","journal":{"identity":"european-journal-of-wood-and-wood-products","isVorOnly":false,"title":"European Journal of Wood and Wood Products"},"publishedOn":"2025-01-15 15:58:01","publishedOnDateReadable":"January 15th, 2025"},"versionCreatedAt":"2024-11-26 05:27:24","video":"","vorDoi":"10.1007/s00107-024-02199-4","vorDoiUrl":"https://doi.org/10.1007/s00107-024-02199-4","workflowStages":[]},"version":"v1","identity":"rs-5137187","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5137187","identity":"rs-5137187","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}