Development of Low Smoke Environmental friendly Fire Retardant Intumescent Coatings for GI and Steel Structures

Development of Low Smoke Environmental friendly Fire Retardant Intumescent Coatings for GI and Steel Structures | 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 Development of Low Smoke Environmental friendly Fire Retardant Intumescent Coatings for GI and Steel Structures Charu Mehta, Aravind Kumar, Mahesh Kumar Tiwari, Rakesh Kumar, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3621335/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Steel begins to lose its mechanical strength above 500 ºC and tends to distort, leading to the collapse of building structures during fire accidents. Fire retardant intumescent coating can protect the steel structure as it swells upon exposure to fire several times its original thickness producing a carbonaceous protective char. The carbonaceous char acts as a heat transfer barrier and protects the structure of steel physically and thermally The objective of the experimental work is to develop the composition of fire retardant intumescent coating with low smoke emission on reaction to fire. Specific fire retardant intumescent coatings were formulated with various compositions using additives (acid source, carbon source, and blowing agent), binder (water-based), and fillers. All the formulations were examined with the non-luminous premixed flame gas torch preliminary test, and the thickness of the char layer formed at the end of the experiment was observed and measured. It was observed that the composition formulated with a water-based binder can form a char layer of a maximum of 70 times the coating thickness. Various standard tests were performed to examine the water-based coating formulations. The results showed that coating composed of a water-based binder with a 50% addition of epoxy and hardener achieved the criteria of ignitability evaluation as per BS 476 Part 5 as it was not easily ignitible. Fire propagation index BS 476 Part 6 showed a Fire propagation index value of less than 12 which signifies that the heat generation rate was low. According to the surface spread of flame of products as per BS 476-Part 7, the coating was classified as class 1 as no flame spread was observed on the surface. Specific optical density value at 1.5 min was found to be less than 100 and less than 200 at 4 min as per ASTM E 662 which was meeting the criteria as per NFPA 230. Sample IC3 was found to nearly meet Non-combustibility criteria. It can be concluded that an environmental friendly fire retardant intumescent coating can be achieved with a water-based binder, additives, and fillers. Intumescent coatings fire retardant char expansion binders additives fillers Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 1. Introduction Steel and galvanized iron (GI) are the most used metallic alloys and are used in several applications. They are widely used in the construction of structures and many other industry sectors.GI is an iron ore, galvanized with zinc, which protects it from rust and corrosion while also retaining its initial strength over an extended period. Tariq and Bhargava studied the behavior of steel bars at elevated temperatures and observed that steel and GI lose their mechanical strength in case of accidental fires when they reach temperatures above 500 o C (Tariq and Bhargava, 2018; de Silva et al., 2023). The safe evacuation of people from the building is ensured by the prevention of the structural failure of the building structures. Hence, it becomes an important issue in the construction industry to protect the structures during fire accidents. Traditionally used halogenated fire retardant coatings increased environmental concerns and health anxieties; hence they were replaced with non-halogenated fire retardants. Intumescent fire retardant coatings are used to protect the steel and GI-made structures at high temperatures as they form a thick protective char on reaction to fire. Intumescent coatings have several advantages. It can be manufactured using non-toxic chemicals, is affordable, easy to process, eco-friendly, and does not alter the inherent properties of the substrate. Steel and buildings can be protected with fire-retardant intumescent coating, which expands when exposed to fire several times its original thickness to form a carbonaceous protective char. (de Silva et al. , 2022). The carbonaceous char acts as a heat transfer barrier and protects the structure of the substrate physically and thermally. To produce an effective char layer on the substrate, the composition of the coating is formulated. An intumescent coating is composed of the following components: an acid donor, a carbon donor, a blowing agent, a binder (thermoplastic resins), pigments, and fillers (Zeng et al. , 2020). An acid donor releases acid to initiate the chemical reactions which begin with the dehydration of carbon compounds. The carbon donor releases an organic material that reacts with fire to produce an inorganic carbonaceous layer. An expanding (blowing) agent decomposes to liberate a large volume of non–flammable gases which include carbon dioxide, ammonia, and water vapor which makes the binder foam and expand creating a thicker insulating char layer (Metz and Data, 2015). A thermoplastic resin binder is a synthetic polymer that can be remolded at high temperatures (Duquesne et al. , 2005). Fillers are necessary to provide fire resistance, reduce the expansion rate of the carbon layer, minimize gas emissions, and strengthen the char structure.(Nasirzadeh, Yahyaei and Mohseni, 2023). When an intumescent coating is exposed to fire, the following reactions take place: Initially, the polymer binder starts to turn soft and melt when exposed to heat. Then, the acid source in the coating decomposes with the release of inorganic mineral acid at T > 250°C. Further, the reaction of a carbon source (for example pentaerythritol) with the inorganic acid triggers the carbonization process of forming a carbonaceous char layer. Finally, the decomposition of the blowing agent (such as melamine) releases the gaseous products which leads to the expansion (swelling) of the char layer up to a certain thickness (Mariappan, 2016). Resins are used as binders as they contribute to the formation of char structure, and its expansion and ensure the uniformity of the formed layer (Mohd Sabee et al. , 2022). There are various types of intumescent coatings available based on various binders used viz .solvent–based, epoxy–based, and water–based. Although solvent–based and epoxy–based coatings have many advantages such as being resistant to weather conditions and drying faster, however, they show a disadvantage of high smoke production and the evolution of toxic gases. Water–based coatings are eco–friendly, chemically less smelling, and less expensive (Gadhave, Mahanwar and Gadekar, 2018). Also, water–epoxy hybrid coatings can be advantageous for fully exposed steel structures that provide corrosion resistance (Jomy, Prabhu and Prabhu, 2022). Although numerous studies on fire retardant intumescent coatings have been conducted, very few sample studies were reported as per the British standard test procedures to meet the NBC criteria, which are the essential conditions for industrial development. This study focuses on the preliminary development of fire retardant intumescent coating formulations based on water–based binder and their performance in various standard test methods. This was done by comparison of three coating compositions based on the addition of smoke suppressant fillers and changing the binder. 2. Materials and Methods Three different compositions of IC1, IC2, and IC3as shown in Table 1 of intumescent coatings were prepared using binder (water–based polyvinyl acetate), fire–retardant fillers, and fire–retardant additives i.e., acid source, a carbon source, and a blowing agent. Water–based binder was added to additives and fillers to form a mixture which was applied on the steel and GI sheets and were dried for 24 hours before the tests. The difference in the three coatings was due to the addition of binder or smoke suppressant fillers. Table 1 Description of different compositions Sample Binder Used Smoke suppressant fillers (%) Acid source (%) Carbon source (%) Blowing agent (%) Fillers (%) Binder + solvent (%) IC1 Water-based binder 0 21.95 13.72 13.72 12.89 37.37 IC2 Water-based binder 0.15 21.83 13.64 13.64 13.37 37.52 IC3 Water-epoxy hybrid-based binder 0.15 21.83 13.64 13.64 13.37 37.52 2.1. Preliminary test A preliminary test is done to measure the thickness of the char layer formed which is used to indicate the fire protection performance of coating samples. The coating compositions were applied on sheets with approximately 1 mm coating thickness. A preliminary test was done using a non–luminous premixed flame gas torch (flame temperature of nearly 1000 o C) as shown in Figs. 1, 2, and 3. The compositions were made to achieve char with higher thickness as well as high strength to protect the underlying steel sheet. The char layer thickness was measured using a metric scale and char strength was examined by poking a wooden stick in the char. 2.2. Ignitability evaluation as per BS 476 Part 5 The coating compositions of IC1, IC2, and IC3 were applied on GI sheets of 228 \(\times\) 228 mm ( \(\pm\) 1.2 mm) with approximately 1 mm coating thickness. The exact thicknesses of IC1, IC2, and IC3 are shown in Fig. 4. The tendency of a material to get ignited by a small flame at ambient temperature was determined using the ignitability apparatus as shown in Fig. 5. This evaluation enables the identification of ‘easily ignitable’ and ‘not easily ignitable’ materials. If any specimen flames for more than 10 seconds after the removal of the test flame or if the burning of the specimen extends to the edge within this period, the material is classified as ‘Easily Ignitable’ and its performance is indicated by the letter ‘X’. If no specimen flames for more than 10 seconds after the removal of the test flame and burning does not extend to the edge within this period, the material is classified as ‘Not Easily Ignitable ’and the letter ‘P’ indicates its performance. (Read, 2015) 2.3. Fire propagation index- BS 476 Part 6 The coating compositions were applied on GI sheets of 225 X 225 mm (± 1.5 mm) with approximately 1 mm coating thickness. The exact thickness of IC1, IC2, and IC3 are shown in Fig. 6. The fire Propagation index of a material was used to determine the ability of a material to contribute to the spread of fire within a building. It depends on ignition characteristics, amount and rate of heat release, and thermal properties of the product. The higher the Fire Propagation Index, the greater the ability of the material to accelerate the growth of fire. For Fire Propagation Index determination, the time–temperature values were recorded using the calibration board for 20 minutes. For Fire Propagation Index determination, a comparison of the time–temperature history of the specimens of a material with time–temperature history of the calibration is used to compute the fire propagation index (I).FPI values for the samples IC1, IC2, and IC3 were calculated using the Fire propagation index evaluation apparatus (Fig. 7)(British standard 476 part 6, 1989). 2.4. Surface spread of flame of products as per BS 476-Part 7 The coating compositions were applied on GI sheets of 900 mm (L) x 270 mm (W) with approximately 1 mm coating thickness. Samples IC1, IC2, and IC3 with exact thickness are shown in Fig. 8. The surface spread of flame evaluation was used for assessing the tendency of materials that once ignited can support the spread of flame across their surfaces thereby allowing fire to travel. Materials are classified based on the rate and distance of spread of flame over their surfaces as evaluated by the apparatus shown in Fig. 9.For Surface Spread of Flame measurement on the surface of each sample, the time at which the flame front crosses each vertical reference line (Fig. 9a), and the maximum extent of flame spread during the first 1.5 minutes from the start of the evaluation and during the whole evaluation period i.e. 10 minutes or less were noted. (British Standard 476 part, 1997) 2.5. Specific optical density as per ASTM E 662 The coating compositions were applied on GI sheets of 75 mm (L) x 75 mm (W) with approximately 1 mm coating thickness. The exact coating thickness of samples IC1, IC2, and IC3 are shown in Fig. 10. The smoke density evaluation of the material was determined to investigate the smoke suppression performance of the coatings. Measurement was made of the attenuation of a light beam by smoke accumulating within a closed chamber as shown in Fig. 11 due to non-flaming pyrolytic decomposition and flaming combustion. In the case of non-flaming mode, the sample was exposed to radiant heat, and six small flames from a multi-flame-let burner along with the radiant energy were used in flaming mode. For each experimental run, the lowest percent transmittance obtained and the time for the smoke to reach this value were recorded. The maximum specific optical density (Dm) by converting the average lowest percent transmittance obtained to its equivalent DS (from the standard conversion chart) was recorded. 1.1. Non-combustibility test as per BS 476- Part 4 The coating compositions were applied on GI sheets and a stack of 40 mm (L) x 40 mm (W) x 50 mm (H)was prepared for each formulation. Stack height measured using a metric scale (cm) of samples IC1, IC2, and IC3 are shown in Fig. 12. This test is used to evaluate the non-combustible properties of materials using an open, vertically positioned cylindrical furnace as shown in Fig. 13. The furnace is preheated to approximately 750°C before the specimen is introduced. A material is evaluated to be non-combustible from the following data: The average furnace thermocouple temperature rise, the average surface thermocouple temperature rise, the mean duration of sustained flaming, and the average mass loss. (British Standard 476 part 4, 1970) 3. Results and discussions 3.1. Preliminary Test The thickness of the char layer formed at the end of the preliminary test was observed and measured. The thickness and the strength of the char layer formed are used to indicate the fire protection performance of coating samples. During the optimization of the water-based coating compositions, a few coatings were observed with char expansion of 70 times the thickness of the coating applied on the surface of the specimen but with low char strength was observed as shown in Fig. 14a. Hence, samples IC1, IC2, and IC3 were tested which showed good char thickness as well as strength. It was observed that char layers of thickness 40 mm, 30 mm, and 35 mm were formed in samples IC1, IC2, and IC3 respectively as shown in Fig. 14b. Hence, all the samples were found to be effective in fire resistance as a sufficient amount of char with good char strength was formed in all the samples. 3.2. Ignitability evaluation as per BS 476 Part 5 This evaluation was performed to identify if the material is easily ignitable or not. No flame was observed on any of the samples and all were identified as ‘not easily ignitable’ and their performance can be indicated by ‘P’.A char thickness of 35 mm was observed in all the samples as shown in Fig. 15. Hence, all the samples were found to be effective as per the Ignitibility evaluation. 3.3. Fire propagation index as per BS 476 Part 6 The Fire Propagation Index (FPI) of materials was used to identify the materials in terms of their tendency to contribute towards the growth of fire inside the buildings. The FPI values were calculated for the samples IC1, IC2, and IC3 as 0.2, 1.6, and 2.5 respectively. It can be concluded that the values of FPI for all the samples were less than 12 as per the standardized value. The char thickness of 40 mm, 40mm, and 35 mm were formed in samples IC1, IC2, and IC3 respectively as shown in Fig. 16 . Temperature- time plots for samples as shown in Fig. 17 depict an increase in smoke temperature till the complete char formation and a slow increase after the char formation. Hence, all the samples were found to be effective according to the Fire propagation index evaluation method. 3.4. Surface spread of flame of products as per BS 476-Part 7 The surface spread of flame evaluation was used to classify materials based on the rate and distance of spread of flame over their surfaces. All the samples IC1, IC2, and IC3 were tested under standard conditions of the surface spread of flame evaluation and all were classified as Class 1 according to the standard observations as no flame spread was observed during the test over any sample. Although all samples passed the evaluation, coating detachment was observed during the test in samples IC1 and IC2 as shown in Fig. 18. Hence, it can be concluded that the addition of epoxy as a binder in water-based coating can enhance the adhesion of the coating to the substrate. 3.5. Specific optical density as per ASTM E 662 The specific optical density evaluation of the material is determined to check whether it will contribute directly to smoke development. Specific optical density values for all the samples were calculated as shown in Table 2 as per the standardized methods and all the values were found to be lower than standardized values i.e. maximum specific optical density (Dm) less than 100 at 1.5 min and less than 200 at 4 min. Char layer thicknesses of 20–30 mm were formed for the samples after the test as shown in Fig. 19. The specific optical density (Ds) curves of the coatings are shown in Fig. 20 . According to Fig. 20 a) and Table 2 , the value of Ds of IC2 is less than IC1 and IC3 shows the lowest value of Ds. It can be concluded that the addition of smoke suppressant fillers decreases Ds values and shows the effect of smoke suppression. The lowest value of IC3 shows its best effect on smoke suppression. According to Fig. 20 b), Ds values of the IC2 and IC3 coatings are higher than IC1 under a radiant heat flux with flame. Hence, it can be inferred that the smoke suppressant fillers can effectively suppress the smoke through a molten protective layer on the surface of the samples during the combustion process. Since there is no effective smoke suppression in the gas phase, the combustible materials produced by the degradation process will burn and constantly produce smoke. These results reveal that the smoke suppressant fillers are mainly effective in the condensed phase(Zhang et al. , 2016). Table 2 – Specific optical density values for samples IC1, IC2 and IC3. Non-flaming Flaming IC1 Dm (max) value- 46 32.9 Dm(1.5 min) 6.6 17.3 Dm(4.0 min) 26 25.2 IC2 Dm (max) value- 42.8 37.8 Dm(1.5 min) 10.6 8.4 Dm(4.0 min) 26.3 17.7 IC3 Dm (max) value- 26.5 38 Dm(1.5 min) 7.5 17.5 Dm(4.0 min) 18.3 30.6 1.2. Non-combustibility test as per BS 476- Part 4 This test was done to evaluate the non-combustible behavior of a material. Samples IC1, IC2, and IC3 were evaluated and the following observations were noted (Table 3 ). The samples after the test are shown in Fig. 21. According to the calculated data for the samples, it was observed that the time of flaming for the samples IC1 and IC3 was less than 10 seconds and a flame of 20 s was observed in IC2. Mass loss in all the samples was less than 50% and was found to be maximum in IC3 and lowest in IC1 as shown in Fig. 22 . Temperature rise for the furnace was least for IC3 as shown in Fig. 23 . It can be concluded that sample IC3 was found to nearly meet the criteria of the standard evaluation method of Non-combustibility as the flaming time was nearly 2 seconds, mass loss was found to be less than 50%, and a rise in temperature of the furnace was found to be 70 o C. Table 3 Observations from Non-combustibility evaluation for samples IC1, IC2 and IC3 Time of Flaming (s) Mass loss (%) Rise in temperature ( o C) Furnace Sp. Centre IC1 - 13.25 120 187 IC2 20 16.29 225 163 IC3 2 17.27 70 31 4. Conclusion Three water-based fire retardant intumescent coatings were developed and evaluated as per the standards. The developed coatings have been found effective in achieving good char strength and high char expansion in preliminary tests on steel sheets. The specimens with these coatings were found to be effective at temperatures nearly 1000 o C in a non–luminous premixed flame gas torch preliminary test. The coatings were evaluated based on various standard evaluation methods such as Ignitability evaluation as per BS 476 Part 5, Fire Propagation Index BS 476 Part 6, Classification of the Surface Spread of Flame of Products as per BS 476- Part 7, specific optical density as per ASTM E 662 and EN ISO 1182 - Non-combustibility test. It was observed that sample IC3 formed a sufficient amount of char in the preliminary test, was classified as ‘ not easily ignitable’ based on Ignitability evaluation, Fire propagation index value was found to be less than 12 as heat generation rate was low, was classified as ‘Class 1’as no flame spread was observed on the surface based on Surface spread evaluation, was found to have specific optical density value less than 100 at 1.5 min, was found to nearly meet non-combustibility criteria. Hence, it was found to nearly meet all the criteria of all the standard test methods. It can be concluded that a water-based intumescent coating can be developed with low smoke production, excellent fire resistance, good coating adhesion, easy application, and environmentally friendly. The coating composition needs to be evaluated with other standard techniques for further analysis as a part of future study. Declarations Ethical approval Not applicable. Consent to participate Not applicable. Consent for publication The authors have given their consent to publish the manuscript. Author Contributions All authors contributed to the study conception and design. Material preparation was done by Charu Mehta and Aravind Kumar, data collection and analysis were performed by Mahesh Kumar Tiwari, Rakesh Kumar and Mohammad Ahmad Shoeb . The first draft of the manuscript was written by Charu Mehta and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Funding The authors would like to show gratitude to CSIR for supporting the research under the Fast Track Translation (FTT) project MLP032204. The authors are grateful to the Director, CBRI for providing the necessary research facilities and for permitting them to publish the paper. Competing Interests The authors have no relevant financial or non-financial interests to disclose. References British standard institution (1970). Fire test on building materials and structures. Part 4. Non-combustibility test for materials. BSI British Standard Institution (1989). Fire test on building materials and structures. Part 6. Method of test for fire propagation of products.BSI British Standard Institution (1997). Fire test on building materials and structures. Part 7. Method of test to determine the classification of the surface spread of flame of products.BSI De Silva, D., Autiero, M., Bilotta, A., &Nigro, E. (2023). 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Recent developments of intumescent fire protection coatings for structural steel: A review. Journal of Fire Sciences, 34(2), 120–163. MohdSabee, M. M. S., Itam, Z., Beddu, S., Zahari, N. M., Mohd Kamal, N. L., Mohamad, D.,& Abdul Hamid, Z. A. (2022). Flame retardant coatings: additives, binders, and fillers. Polymers, 14(14), 2911. Nasirzadeh, M., Yahyaei, H., &Mohseni, M. (2023). Effects of inorganic fillers on the performance of the water-based intumescent fire‐retardant coating. Fire and Materials, 47(1), 51–61. Read, R. E. H. (1981). Standard fire tests for building materials and structures. Royal Society of Health Journal, 101(5), 190–195. Ronnie Peskens, Allison Park, PA (US) (2015). Intumescent coating composition, US 2015/0291810 A1 Tariq, F., &Bhargava, P. (2018). Residual mechanical behavior of (SD 500) hot rolled TMT reinforcing steel bars after elevated temperatures. Construction and Building Materials, 190, 551–559. Zeng, Y., Weinell, C. E., Dam–Johansen, K., Ring, L., &Kiil, S. (2020). Effects of coating ingredients on the thermal properties and morphological structures of hydrocarbon intumescent coating chars. Progress in Organic Coatings, 143, 105626. Zhang, F., Chen, P., Wang, Y., & Li, S. (2016). Smoke suppression and synergistic flame retardancy properties of zinc borate and diantimony trioxide in epoxy-based intumescent fire-retardant coating. Journal of Thermal Analysis and Calorimetry, 123, 1319–1327. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-3621335","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":267262454,"identity":"9f89bb1e-e289-46db-9cc2-b39cef6c3787","order_by":0,"name":"Charu 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08:16:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":264577,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGas torch preliminary test\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"F2.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/152e74706af54cf0a96e1d64.png"},{"id":49738355,"identity":"c12230a4-37f6-44fe-8585-f0c474b328ca","added_by":"auto","created_at":"2024-01-17 08:08:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":240260,"visible":true,"origin":"","legend":"\u003cp\u003eWater-based polyvinyl acetate fire retardant intumescent coating with its char thickness\u003c/p\u003e","description":"","filename":"F3.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/052b4bc24c3ab3b4926d6041.png"},{"id":49738357,"identity":"98dae25c-4279-41ee-898d-8602d65a5165","added_by":"auto","created_at":"2024-01-17 08:08:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":310298,"visible":true,"origin":"","legend":"\u003cp\u003eThickness of coatings (µm)of samples for Ignitibility evaluation\u003c/p\u003e","description":"","filename":"F4.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/e60cf57a6cbf7fc061869948.png"},{"id":49992656,"identity":"e6ba4965-a6c3-43ec-acb9-e426f2a97e15","added_by":"auto","created_at":"2024-01-22 18:58:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":221929,"visible":true,"origin":"","legend":"\u003cp\u003eIgnitability evaluation apparatus\u003c/p\u003e","description":"","filename":"F5.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/3fe6643fcb9e21be9ff51d74.png"},{"id":49738911,"identity":"ab1b0fc6-b44d-4330-876b-78aaf106002e","added_by":"auto","created_at":"2024-01-17 08:24:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":285420,"visible":true,"origin":"","legend":"\u003cp\u003eThickness of coatings(µm) of samples for Fire propagation index evaluation\u003c/p\u003e","description":"","filename":"F6.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/b7345e292cb0a1eb0bfa9cf5.png"},{"id":49737539,"identity":"e2a18d58-5d01-417c-8e9c-8bcf744089d2","added_by":"auto","created_at":"2024-01-17 07:52:59","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":193209,"visible":true,"origin":"","legend":"\u003cp\u003eFire propagation index evaluation apparatus\u003c/p\u003e","description":"","filename":"F7.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/470a1664805779bb9d2fd900.png"},{"id":49737543,"identity":"49cf635c-3c34-4b78-ae3f-979d17e3dddb","added_by":"auto","created_at":"2024-01-17 07:52:59","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":241522,"visible":true,"origin":"","legend":"\u003cp\u003eThickness of coatings (µm) of samples for the Surface spread of flame of products\u003c/p\u003e","description":"","filename":"F8.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/de16ab214d0048ad2c159068.png"},{"id":49738203,"identity":"fcfffc49-de29-4f64-8479-923f5e2cae5f","added_by":"auto","created_at":"2024-01-17 08:00:59","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":251670,"visible":true,"origin":"","legend":"\u003cp\u003eSurface spread of flame of products evaluation apparatus\u003c/p\u003e","description":"","filename":"F9.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/e05024b786cbf8de4c7d77e5.png"},{"id":49738672,"identity":"a5022363-c034-4424-ac7e-eb74f43add89","added_by":"auto","created_at":"2024-01-17 08:16:59","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":535546,"visible":true,"origin":"","legend":"\u003cp\u003eThickness of coatings (µm) of samples for Specific optical density evaluation. a), b), c) –Non-flaming mode samples and d), e), f)- Flaming mode samples\u003c/p\u003e","description":"","filename":"F10.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/0a6d691f1b5372fe393019b5.png"},{"id":49738200,"identity":"cd22c159-7243-42e2-b42a-de090b538338","added_by":"auto","created_at":"2024-01-17 08:00:59","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":247438,"visible":true,"origin":"","legend":"\u003cp\u003eSpecific optical density evaluation apparatus\u003c/p\u003e","description":"","filename":"F11.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/1b0c115293336b7915db917d.png"},{"id":49738359,"identity":"088fa8aa-4535-4e1f-a11e-0a9a7e957d1e","added_by":"auto","created_at":"2024-01-17 08:08:59","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":327578,"visible":true,"origin":"","legend":"\u003cp\u003e40 mm (L) x 40 mm (W) x 50 mm (H) samples to evaluate combustible properties.\u003c/p\u003e","description":"","filename":"F12.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/ebcd13de435328d90ab88430.png"},{"id":49737559,"identity":"7cf7e8a6-b4a9-4400-93ab-3ed9c556863b","added_by":"auto","created_at":"2024-01-17 07:53:00","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":286482,"visible":true,"origin":"","legend":"\u003cp\u003eApparatus for Non-combustibility Evaluation\u003c/p\u003e","description":"","filename":"F13.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/9ea4a90bb6c6653a2212e76d.png"},{"id":49738207,"identity":"8bdf1251-5df7-469e-8443-d1a904a67640","added_by":"auto","created_at":"2024-01-17 08:01:00","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":755004,"visible":true,"origin":"","legend":"\u003cp\u003ea- Preliminary test of a sample during optimization of coating composition with 70 times swelling and low char strength.\u003c/p\u003e\n\u003cp\u003eb- Preliminary test results for samples IC1, IC2, and, IC3\u003c/p\u003e","description":"","filename":"F14.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/28dfc15395b22634a8fe48b1.png"},{"id":49738675,"identity":"6facda0b-8f54-4fec-a4ea-b75f8affe12d","added_by":"auto","created_at":"2024-01-17 08:16:59","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":360866,"visible":true,"origin":"","legend":"\u003cp\u003eChar thickness of samples IC1, IC2 and IC3 in Ignitibility evaluation test\u003c/p\u003e","description":"","filename":"F15.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/b46e5ff2ff75fb324357c26c.png"},{"id":49737547,"identity":"951ea01e-75b8-4bef-a9ee-6f77c8aaa7f1","added_by":"auto","created_at":"2024-01-17 07:52:59","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":341769,"visible":true,"origin":"","legend":"\u003cp\u003eFire propagation index evaluation results for samples IC1, IC2, and IC4\u003c/p\u003e","description":"","filename":"F16.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/6b3eb0925a6e3d3feeba14cb.png"},{"id":49738212,"identity":"20584c2d-03ac-4e23-821f-9457ad1d4d16","added_by":"auto","created_at":"2024-01-17 08:01:04","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":14674,"visible":true,"origin":"","legend":"\u003cp\u003eTime-temperature plot for samples IC1, IC2, and IC3 based on FPI evaluation.\u003c/p\u003e","description":"","filename":"F17.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/24db54d1567b5a534d78bf2d.png"},{"id":49738208,"identity":"95405e8c-13f0-46d9-ba9a-fe1a902a51a4","added_by":"auto","created_at":"2024-01-17 08:01:00","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":610520,"visible":true,"origin":"","legend":"\u003cp\u003eSurface spread of flame results for samples IC1, IC2, IC3, IC4\u003c/p\u003e","description":"","filename":"F18.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/2e68133229afb64210512960.png"},{"id":49737556,"identity":"619508d3-486d-445e-82bc-aacdc0e14476","added_by":"auto","created_at":"2024-01-17 07:53:00","extension":"png","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":585221,"visible":true,"origin":"","legend":"\u003cp\u003eSpecific optical density evaluation results for samples IC1, IC2, and IC3\u003c/p\u003e","description":"","filename":"F19.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/57bb2078af0edc601bf1e6c8.png"},{"id":49738910,"identity":"ab4969ef-403f-45db-909f-de3eb92d1748","added_by":"auto","created_at":"2024-01-17 08:24:59","extension":"png","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":27751,"visible":true,"origin":"","legend":"\u003cp\u003eSpecific optical density (Ds) curves of the coatings a) Non-Flaming mode b)Flaming mode\u003c/p\u003e","description":"","filename":"F20.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/484bd70fcd3b5b01437c9ff5.png"},{"id":49737558,"identity":"f3042217-1f5d-4bf7-bd12-386683527e5b","added_by":"auto","created_at":"2024-01-17 07:53:00","extension":"png","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":392758,"visible":true,"origin":"","legend":"\u003cp\u003eSamples IC1, IC2 and IC3 after Non-combustibility test.\u003c/p\u003e","description":"","filename":"F21.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/678f341e51910ed219934e22.png"},{"id":49738206,"identity":"3b6579a7-e974-47ed-ba99-fa2dd6d48100","added_by":"auto","created_at":"2024-01-17 08:00:59","extension":"png","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":13180,"visible":true,"origin":"","legend":"\u003cp\u003eMass loss of samples IC1, IC2 and IC3 in Non-combustibility evaluation\u003c/p\u003e","description":"","filename":"F22.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/61df2aac8e94f79d2b4c0655.png"},{"id":49737551,"identity":"61d65829-ba06-4cda-b6ef-aeae1a12550c","added_by":"auto","created_at":"2024-01-17 07:52:59","extension":"png","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":21822,"visible":true,"origin":"","legend":"\u003cp\u003eTime-temperature \u0026nbsp;plot for samples IC1, IC2, and IC3 in Non-combustibility evaluation\u003c/p\u003e","description":"","filename":"F23.png","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/1b2907c9ce5098d65d4a5b22.png"},{"id":77731506,"identity":"152d4e4d-465c-4023-8134-3e4e3f31ae15","added_by":"auto","created_at":"2025-03-04 22:56:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7544001,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3621335/v1/dcd6d315-72af-4f76-a497-d76bde31753e.pdf"}],"financialInterests":"","formattedTitle":"Development of Low Smoke Environmental friendly Fire Retardant Intumescent Coatings for GI and Steel Structures","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSteel and galvanized iron (GI) are the most used metallic alloys and are used in several applications. They are widely used in the construction of structures and many other industry sectors.GI is an iron ore, galvanized with zinc, which protects it from rust and corrosion while also retaining its initial strength over an extended period. Tariq and Bhargava studied the behavior of steel bars at elevated temperatures and observed that steel and GI lose their mechanical strength in case of accidental fires when they reach temperatures above 500\u003csup\u003eo\u003c/sup\u003eC (Tariq and Bhargava, 2018; de Silva et al., 2023). The safe evacuation of people from the building is ensured by the prevention of the structural failure of the building structures. Hence, it becomes an important issue in the construction industry to protect the structures during fire accidents. Traditionally used halogenated fire retardant coatings increased environmental concerns and health anxieties; hence they were replaced with non-halogenated fire retardants. Intumescent fire retardant coatings are used to protect the steel and GI-made structures at high temperatures as they form a thick protective char on reaction to fire.\u003c/p\u003e \u003cp\u003eIntumescent coatings have several advantages. It can be manufactured using non-toxic chemicals, is affordable, easy to process, eco-friendly, and does not alter the inherent properties of the substrate. Steel and buildings can be protected with fire-retardant intumescent coating, which expands when exposed to fire several times its original thickness to form a carbonaceous protective char. (de Silva \u003cem\u003eet al.\u003c/em\u003e, 2022). The carbonaceous char acts as a heat transfer barrier and protects the structure of the substrate physically and thermally. To produce an effective char layer on the substrate, the composition of the coating is formulated. An intumescent coating is composed of the following components: an acid donor, a carbon donor, a blowing agent, a binder (thermoplastic resins), pigments, and fillers (Zeng \u003cem\u003eet al.\u003c/em\u003e, 2020). An acid donor releases acid to initiate the chemical reactions which begin with the dehydration of carbon compounds. The carbon donor releases an organic material that reacts with fire to produce an inorganic carbonaceous layer. An expanding (blowing) agent decomposes to liberate a large volume of non\u0026ndash;flammable gases which include carbon dioxide, ammonia, and water vapor which makes the binder foam and expand creating a thicker insulating char layer (Metz and Data, 2015). A thermoplastic resin binder is a synthetic polymer that can be remolded at high temperatures (Duquesne \u003cem\u003eet al.\u003c/em\u003e, 2005). Fillers are necessary to provide fire resistance, reduce the expansion rate of the carbon layer, minimize gas emissions, and strengthen the char structure.(Nasirzadeh, Yahyaei and Mohseni, 2023).\u003c/p\u003e \u003cp\u003eWhen an intumescent coating is exposed to fire, the following reactions take place:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eInitially, the polymer binder starts to turn soft and melt when exposed to heat.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThen, the acid source in the coating decomposes with the release of inorganic mineral acid at T\u0026thinsp;\u0026gt;\u0026thinsp;250\u0026deg;C.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eFurther, the reaction of a carbon source (for example pentaerythritol) with the inorganic acid triggers the carbonization process of forming a carbonaceous char layer.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eFinally, the decomposition of the blowing agent (such as melamine) releases the gaseous products which leads to the expansion (swelling) of the char layer up to a certain thickness (Mariappan, 2016).\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eResins are used as binders as they contribute to the formation of char structure, and its expansion and ensure the uniformity of the formed layer (Mohd Sabee \u003cem\u003eet al.\u003c/em\u003e, 2022). There are various types of intumescent coatings available based on various binders used viz .solvent\u0026ndash;based, epoxy\u0026ndash;based, and water\u0026ndash;based. Although solvent\u0026ndash;based and epoxy\u0026ndash;based coatings have many advantages such as being resistant to weather conditions and drying faster, however, they show a disadvantage of high smoke production and the evolution of toxic gases. Water\u0026ndash;based coatings are eco\u0026ndash;friendly, chemically less smelling, and less expensive (Gadhave, Mahanwar and Gadekar, 2018). Also, water\u0026ndash;epoxy hybrid coatings can be advantageous for fully exposed steel structures that provide corrosion resistance (Jomy, Prabhu and Prabhu, 2022). Although numerous studies on fire retardant intumescent coatings have been conducted, very few sample studies were reported as per the British standard test procedures to meet the NBC criteria, which are the essential conditions for industrial development.\u003c/p\u003e \u003cp\u003eThis study focuses on the preliminary development of fire retardant intumescent coating formulations based on water\u0026ndash;based binder and their performance in various standard test methods. This was done by comparison of three coating compositions based on the addition of smoke suppressant fillers and changing the binder.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eThree different compositions of IC1, IC2, and IC3as shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e of intumescent coatings were prepared using binder (water\u0026ndash;based polyvinyl acetate), fire\u0026ndash;retardant fillers, and fire\u0026ndash;retardant additives i.e., acid source, a carbon source, and a blowing agent. Water\u0026ndash;based binder was added to additives and fillers to form a mixture which was applied on the steel and GI sheets and were dried for 24 hours before the tests. The difference in the three coatings was due to the addition of binder or smoke suppressant fillers.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDescription of different compositions\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"9\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBinder Used\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSmoke suppressant fillers (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAcid source (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCarbon source (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBlowing agent (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFillers (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBinder\u0026thinsp;+\u0026thinsp;solvent (%)\u003c/p\u003e\n \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\u003eIC1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWater-based binder\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e37.37\u003c/p\u003e\n \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\u003eIC2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWater-based binder\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e37.52\u003c/p\u003e\n \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\u003eIC3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWater-epoxy hybrid-based binder\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e37.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1. Preliminary test\u003c/h2\u003e\n \u003cp\u003eA preliminary test is done to measure the thickness of the char layer formed which is used to indicate the fire protection performance of coating samples. The coating compositions were applied on sheets with approximately 1 mm coating thickness. A preliminary test was done using a non\u0026ndash;luminous premixed flame gas torch (flame temperature of nearly 1000\u003csup\u003eo\u003c/sup\u003e C) as shown in Figs. 1, 2, and 3. The compositions were made to achieve char with higher thickness as well as high strength to protect the underlying steel sheet. The char layer thickness was measured using a metric scale and char strength was examined by poking a wooden stick in the char.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2. Ignitability evaluation as per BS 476 Part 5\u003c/h2\u003e\n \u003cdiv class=\"BlockQuote\"\u003e\n \u003cp\u003eThe coating compositions of IC1, IC2, and IC3 were applied on GI sheets of 228 \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\times\\)\u003c/span\u003e\u003c/span\u003e228 mm (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\pm\\)\u003c/span\u003e\u003c/span\u003e1.2 mm) with approximately 1 mm coating thickness. The exact thicknesses of IC1, IC2, and IC3 are shown in Fig. 4. The tendency of a material to get ignited by a small flame at ambient temperature was determined using the ignitability apparatus as shown in Fig. 5. This evaluation enables the identification of \u0026lsquo;easily ignitable\u0026rsquo; and \u0026lsquo;not easily ignitable\u0026rsquo; materials. If any specimen flames for more than 10 seconds after the removal of the test flame or if the burning of the specimen extends to the edge within this period, the material is classified as \u0026lsquo;Easily Ignitable\u0026rsquo; and its performance is indicated by the letter \u0026lsquo;X\u0026rsquo;. If no specimen flames for more than 10 seconds after the removal of the test flame and burning does not extend to the edge within this period, the material is classified as \u0026lsquo;Not Easily Ignitable \u0026rsquo;and the letter \u0026lsquo;P\u0026rsquo; indicates its performance. (Read, 2015)\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3. Fire propagation index- BS 476 Part 6\u003c/h2\u003e\n \u003cp\u003eThe coating compositions were applied on GI sheets of 225 X 225 mm (\u0026plusmn;\u0026thinsp;1.5 mm) with approximately 1 mm coating thickness. The exact thickness of IC1, IC2, and IC3 are shown in Fig. 6. The fire Propagation index of a material was used to determine the ability of a material to contribute to the spread of fire within a building. It depends on ignition characteristics, amount and rate of heat release, and thermal properties of the product. The higher the Fire Propagation Index, the greater the ability of the material to accelerate the growth of fire. For Fire Propagation Index determination, the time\u0026ndash;temperature values were recorded using the calibration board for 20 minutes. For Fire Propagation Index determination, a comparison of the time\u0026ndash;temperature history of the specimens of a material with time\u0026ndash;temperature history of the calibration is used to compute the fire propagation index (I).FPI values for the samples IC1, IC2, and IC3 were calculated using the Fire propagation index evaluation apparatus (Fig. 7)(British standard 476 part 6, 1989).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4. Surface spread of flame of products as per BS 476-Part 7\u003c/h2\u003e\n \u003cp\u003eThe coating compositions were applied on GI sheets of 900 mm (L) x 270 mm (W) with approximately 1 mm coating thickness. Samples IC1, IC2, and IC3 with exact thickness are shown in Fig. 8. The surface spread of flame evaluation was used for assessing the tendency of materials that once ignited can support the spread of flame across their surfaces thereby allowing fire to travel. Materials are classified based on the rate and distance of spread of flame over their surfaces as evaluated by the apparatus shown in Fig. 9.For Surface Spread of Flame measurement on the surface of each sample, the time at which the flame front crosses each vertical reference line (Fig. 9a), and the maximum extent of flame spread during the first 1.5 minutes from the start of the evaluation and during the whole evaluation period i.e. 10 minutes or less were noted. (British Standard 476 part, 1997)\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5. Specific optical density as per ASTM E 662\u003c/h2\u003e\n \u003cp\u003eThe coating compositions were applied on GI sheets of 75 mm (L) x 75 mm (W) with approximately 1 mm coating thickness. The exact coating thickness of samples IC1, IC2, and IC3 are shown in Fig. 10. The smoke density evaluation of the material was determined to investigate the smoke suppression performance of the coatings. Measurement was made of the attenuation of a light beam by smoke accumulating within a closed chamber as shown in Fig. 11 due to non-flaming pyrolytic decomposition and flaming combustion. In the case of non-flaming mode, the sample was exposed to radiant heat, and six small flames from a multi-flame-let burner along with the radiant energy were used in flaming mode. For each experimental run, the lowest percent transmittance obtained and the time for the smoke to reach this value were recorded. The maximum specific optical density (Dm) by converting the average lowest percent transmittance obtained to its equivalent DS (from the standard conversion chart) was recorded.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e1.1. Non-combustibility test as per BS 476- Part 4\u003c/h2\u003e\n \u003cp\u003eThe coating compositions were applied on GI sheets and a stack of 40 mm (L) x 40 mm (W) x 50 mm (H)was prepared for each formulation. Stack height measured using a metric scale (cm) of samples IC1, IC2, and IC3 are shown in Fig. 12. This test is used to evaluate the non-combustible properties of materials using an open, vertically positioned cylindrical furnace as shown in Fig. 13. The furnace is preheated to approximately 750\u0026deg;C before the specimen is introduced. A material is evaluated to be non-combustible from the following data: The average furnace thermocouple temperature rise, the average surface thermocouple temperature rise, the mean duration of sustained flaming, and the average mass loss. (British Standard 476 part 4, 1970)\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussions","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Preliminary Test\u003c/h2\u003e\n \u003cp\u003eThe thickness of the char layer formed at the end of the preliminary test was observed and measured. The thickness and the strength of the char layer formed are used to indicate the fire protection performance of coating samples. During the optimization of the water-based coating compositions, a few coatings were observed with char expansion of 70 times the thickness of the coating applied on the surface of the specimen but with low char strength was observed as shown in Fig.\u0026nbsp;14a. Hence, samples IC1, IC2, and IC3 were tested which showed good char thickness as well as strength.\u003c/p\u003e\n \u003cp\u003eIt was observed that char layers of thickness 40 mm, 30 mm, and 35 mm were formed in samples IC1, IC2, and IC3 respectively as shown in Fig. 14b. Hence, all the samples were found to be effective in fire resistance as a sufficient amount of char with good char strength was formed in all the samples.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. Ignitability evaluation as per BS 476 Part 5\u003c/h2\u003e\n \u003cp\u003eThis evaluation was performed to identify if the material is easily ignitable or not. No flame was observed on any of the samples and all were identified as \u0026lsquo;not easily ignitable\u0026rsquo; and their performance can be indicated by \u0026lsquo;P\u0026rsquo;.A char thickness of 35 mm was observed in all the samples as shown in Fig. 15. Hence, all the samples were found to be effective as per the Ignitibility evaluation.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. Fire propagation index as per BS 476 Part 6\u003c/h2\u003e\n \u003cp\u003eThe Fire Propagation Index (FPI) of materials was used to identify the materials in terms of their tendency to contribute towards the growth of fire inside the buildings. The FPI values were calculated for the samples IC1, IC2, and IC3 as 0.2, 1.6, and 2.5 respectively. It can be concluded that the values of FPI for all the samples were less than 12 as per the standardized value. The char thickness of 40 mm, 40mm, and 35 mm were formed in samples IC1, IC2, and IC3 respectively as shown in Fig. \u003cspan class=\"InternalRef\"\u003e16\u003c/span\u003e. Temperature- time plots for samples as shown in Fig. 17 depict an increase in smoke temperature till the complete char formation and a slow increase after the char formation. Hence, all the samples were found to be effective according to the Fire propagation index evaluation method.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4. Surface spread of flame of products as per BS 476-Part 7\u003c/h2\u003e\n \u003cp\u003eThe surface spread of flame evaluation was used to classify materials based on the rate and distance of spread of flame over their surfaces. All the samples IC1, IC2, and IC3 were tested under standard conditions of the surface spread of flame evaluation and all were classified as Class 1 according to the standard observations as no flame spread was observed during the test over any sample. Although all samples passed the evaluation, coating detachment was observed during the test in samples IC1 and IC2 as shown in Fig. 18. Hence, it can be concluded that the addition of epoxy as a binder in water-based coating can enhance the adhesion of the coating to the substrate.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5. Specific optical density as per ASTM E 662\u003c/h2\u003e\n \u003cp\u003eThe specific optical density evaluation of the material is determined to check whether it will contribute directly to smoke development. Specific optical density values for all the samples were calculated as shown in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e as per the standardized methods and all the values were found to be lower than standardized values i.e. maximum specific optical density (Dm) less than 100 at 1.5 min and less than 200 at 4 min. Char layer thicknesses of 20\u0026ndash;30 mm were formed for the samples after the test as shown in Fig. 19. The specific optical density (Ds) curves of the coatings are shown in Fig. \u003cspan class=\"InternalRef\"\u003e20\u003c/span\u003e. According to Fig. \u003cspan class=\"InternalRef\"\u003e20\u003c/span\u003ea) and Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, the value of Ds of IC2 is less than IC1 and IC3 shows the lowest value of Ds. It can be concluded that the addition of smoke suppressant fillers decreases Ds values and shows the effect of smoke suppression. The lowest value of IC3 shows its best effect on smoke suppression. According to Fig. \u003cspan class=\"InternalRef\"\u003e20\u003c/span\u003eb), Ds values of the IC2 and IC3 coatings are higher than IC1 under a radiant heat flux with flame. Hence, it can be inferred that the smoke suppressant fillers can effectively suppress the smoke through a molten protective layer on the surface of the samples during the combustion process. Since there is no effective smoke suppression in the gas phase, the combustible materials produced by the degradation process will burn and constantly produce smoke. These results reveal that the smoke suppressant fillers are mainly effective in the condensed phase(Zhang\u0026nbsp;\u003cem\u003eet al.\u003c/em\u003e, 2016).\u003c/p\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\u003e\u0026ndash; Specific optical density values for samples IC1, IC2 and IC3.\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\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNon-flaming\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFlaming\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\" rowspan=\"3\"\u003e\n \u003cp\u003eIC1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm (max) value-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(1.5 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(4.0 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eIC2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm (max) value-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e42.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(1.5 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(4.0 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eIC3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm (max) value-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(1.5 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDm(4.0 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e1.2. Non-combustibility test as per BS 476- Part 4\u003c/h2\u003e\n \u003cp\u003eThis test was done to evaluate the non-combustible behavior of a material. Samples IC1, IC2, and IC3 were evaluated and the following observations were noted (Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). The samples after the test are shown in Fig. 21. According to the calculated data for the samples, it was observed that the time of flaming for the samples IC1 and IC3 was less than 10 seconds and a flame of 20 s was observed in IC2. Mass loss in all the samples was less than 50% and was found to be maximum in IC3 and lowest in IC1 as shown in Fig. \u003cspan class=\"InternalRef\"\u003e22\u003c/span\u003e. Temperature rise for the furnace was least for IC3 as shown in Fig. \u003cspan class=\"InternalRef\"\u003e23\u003c/span\u003e. It can be concluded that sample IC3 was found to nearly meet the criteria of the standard evaluation method of Non-combustibility as the flaming time was nearly 2 seconds, mass loss was found to be less than 50%, and a rise in temperature of the furnace was found to be 70\u003csup\u003eo\u003c/sup\u003eC.\u003c/p\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\u003eObservations from Non-combustibility evaluation for samples IC1, IC2 and IC3\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\u003eTime of Flaming (s)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMass loss (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eRise in temperature (\u003csup\u003eo\u003c/sup\u003eC)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\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\n \u003cp\u003eFurnace\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSp. Centre\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\u003eIC1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e187\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIC2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e225\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e163\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIC3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThree water-based fire retardant intumescent coatings were developed and evaluated as per the standards. The developed coatings have been found effective in achieving good char strength and high char expansion in preliminary tests on steel sheets. The specimens with these coatings were found to be effective at temperatures nearly 1000 \u003csup\u003eo\u003c/sup\u003eC in a non\u0026ndash;luminous premixed flame gas torch preliminary test. The coatings were evaluated based on various standard evaluation methods such as Ignitability evaluation as per BS 476 Part 5, Fire Propagation Index BS 476 Part 6, Classification of the Surface Spread of Flame of Products as per BS 476- Part 7, specific optical density as per ASTM E 662 and EN ISO 1182 - Non-combustibility test. It was observed that sample IC3 formed a sufficient amount of char in the preliminary test, was classified as \u0026lsquo; not easily ignitable\u0026rsquo; based on Ignitability evaluation, Fire propagation index value was found to be less than 12 as heat generation rate was low, was classified as \u0026lsquo;Class 1\u0026rsquo;as no flame spread was observed on the surface based on Surface spread evaluation, was found to have specific optical density value less than 100 at 1.5 min, was found to nearly meet non-combustibility criteria. Hence, it was found to nearly meet all the criteria of all the standard test methods. It can be concluded that a water-based intumescent coating can be developed with low smoke production, excellent fire resistance, good coating adhesion, easy application, and environmentally friendly. The coating composition needs to be evaluated with other standard techniques for further analysis as a part of future study.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e Not applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e Not applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e The authors have given their consent to publish the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation was done by Charu Mehta and \u0026nbsp;Aravind Kumar, data collection and analysis were performed by Mahesh Kumar Tiwari, Rakesh Kumar and Mohammad Ahmad Shoeb . The first draft of the manuscript was written by Charu Mehta and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;The authors would like to show gratitude to CSIR for supporting the research under the Fast Track Translation (FTT) project MLP032204. The authors are grateful to the Director, CBRI for providing the necessary research facilities and for permitting them to publish the paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBritish standard institution (1970). Fire test on building materials and structures. Part 4. Non-combustibility test for materials. BSI\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBritish Standard Institution (1989). Fire test on building materials and structures. Part 6. Method of test for fire propagation of products.BSI\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBritish Standard Institution (1997). Fire test on building materials and structures. Part 7. Method of test to determine the classification of the surface spread of flame of products.BSI\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Silva, D., Autiero, M., Bilotta, A., \u0026amp;Nigro, E. (2023). Experimental investigation on galvanized steel elements at elevated temperature. \u003cem\u003eFire Safety Journal\u003c/em\u003e, \u003cem\u003e138\u003c/em\u003e, 103803.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDe Silva, D., Nuzzo, I., Nigro, E., \u0026amp;Occhiuzzi, A. (2022). Intumescent coatings for fire resistance of steel structures: Current approaches for qualification and design. Coatings, 12(5), 696.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuquesne, S., Magnet, S., Jama, C., \u0026amp;Delobel, R. (2005). Thermoplastic resins for thin film intumescent coatings\u0026ndash;towards a better understanding of their effect on intumescence efficiency. Polymer Degradation and Stability, 88(1), 63\u0026ndash;69.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGadhave, R. V., Mahanwar, P. A., \u0026amp;Gadekar, P. T. (2018). Starch-stabilized polyvinyl acetate emulsion. Polymers from Renewable Resources, 9(2), 75\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJomy, J., Prabhu, D., \u0026amp;Prabhu, P. R. (2022). Inhibitors incorporated into the water\u0026ndash;based epoxy coatings on metals for corrosion protection: a review. Journal of Bio\u0026ndash;and Tribo\u0026ndash;Corrosion, 8(2), 44.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMariappan, T. (2016). Recent developments of intumescent fire protection coatings for structural steel: A review. Journal of Fire Sciences, 34(2), 120\u0026ndash;163.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMohdSabee, M. M. S., Itam, Z., Beddu, S., Zahari, N. M., Mohd Kamal, N. L., Mohamad, D.,\u0026amp; Abdul Hamid, Z. A. (2022). Flame retardant coatings: additives, binders, and fillers. Polymers, 14(14), 2911.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNasirzadeh, M., Yahyaei, H., \u0026amp;Mohseni, M. (2023). Effects of inorganic fillers on the performance of the water-based intumescent fire‐retardant coating. Fire and Materials, 47(1), 51\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRead, R. E. H. (1981). Standard fire tests for building materials and structures. Royal Society of Health Journal, 101(5), 190\u0026ndash;195.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRonnie Peskens, Allison Park, PA (US) (2015). Intumescent coating composition, US 2015/0291810 A1\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTariq, F., \u0026amp;Bhargava, P. (2018). Residual mechanical behavior of (SD 500) hot rolled TMT reinforcing steel bars after elevated temperatures. Construction and Building Materials, 190, 551\u0026ndash;559.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeng, Y., Weinell, C. E., Dam\u0026ndash;Johansen, K., Ring, L., \u0026amp;Kiil, S. (2020). Effects of coating ingredients on the thermal properties and morphological structures of hydrocarbon intumescent coating chars. Progress in Organic Coatings, 143, 105626.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang, F., Chen, P., Wang, Y., \u0026amp; Li, S. (2016). Smoke suppression and synergistic flame retardancy properties of zinc borate and diantimony trioxide in epoxy-based intumescent fire-retardant coating. Journal of Thermal Analysis and Calorimetry, 123, 1319\u0026ndash;1327.\u003c/span\u003e\u003c/li\u003e \u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Intumescent coatings, fire retardant, char expansion, binders, additives, fillers","lastPublishedDoi":"10.21203/rs.3.rs-3621335/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3621335/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSteel begins to lose its mechanical strength above 500 \u0026ordm;C and tends to distort, leading to the collapse of building structures during fire accidents. Fire retardant intumescent coating can protect the steel structure as it swells upon exposure to fire several times its original thickness producing a carbonaceous protective char. The carbonaceous char acts as a heat transfer barrier and protects the structure of steel physically and thermally The objective of the experimental work is to develop the composition of fire retardant intumescent coating with low smoke emission on reaction to fire. Specific fire retardant intumescent coatings were formulated with various compositions using additives (acid source, carbon source, and blowing agent), binder (water-based), and fillers. All the formulations were examined with the non-luminous premixed flame gas torch preliminary test, and the thickness of the char layer formed at the end of the experiment was observed and measured. It was observed that the composition formulated with a water-based binder can form a char layer of a maximum of 70 times the coating thickness.\u003c/p\u003e \u003cp\u003eVarious standard tests were performed to examine the water-based coating formulations. The results showed that coating composed of a water-based binder with a 50% addition of epoxy and hardener achieved the criteria of ignitability evaluation as per BS 476 Part 5 as it was not easily ignitible. Fire propagation index BS 476 Part 6 showed a Fire propagation index value of less than 12 which signifies that the heat generation rate was low. According to the surface spread of flame of products as per BS 476-Part 7, the coating was classified as class 1 as no flame spread was observed on the surface. Specific optical density value at 1.5 min was found to be less than 100 and less than 200 at 4 min as per ASTM E 662 which was meeting the criteria as per NFPA 230. Sample IC3 was found to nearly meet Non-combustibility criteria. It can be concluded that an environmental friendly fire retardant intumescent coating can be achieved with a water-based binder, additives, and fillers.\u003c/p\u003e","manuscriptTitle":"Development of Low Smoke Environmental friendly Fire Retardant Intumescent Coatings for GI and Steel Structures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-17 07:52:54","doi":"10.21203/rs.3.rs-3621335/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d61b43ec-8ee3-4f2c-a919-026433a85e83","owner":[],"postedDate":"January 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-03-04T22:48:46+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-17 07:52:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3621335","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3621335","identity":"rs-3621335","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}