Assessing tolerable viscosity differences in polymer-to-polymer welding

Assessing tolerable viscosity differences in polymer-to-polymer welding | 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 Assessing tolerable viscosity differences in polymer-to-polymer welding Miranda Marcus, Elizabeth Drake, Matt Nitsch, Zach Corey This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5269647/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract The welding of dissimilar polymers is becoming increasingly common. There are a couple key drivers to this trend. First, many new plastics applications must be used in environments where adhesives cannot be easily applied, such as for medical products where finding adhesives that pass FDA regulations is nearly impossible. Another key area where dissimilar polymers are joined is for highly engineered applications in which a material is needed for its very specific — and expensive — engineered properties. Often, the expensive material will need to be joined to a lower-cost material to provide some nearby structure that does not require the same specialized properties. A third driver is the need to save space for small or very compact assemblies. Even a thin layer of adhesive can be a significant barrier to performance for some products, such as small electronics. Lastly, an assembly may require the joining of components that must be manufactured via different processes, such as joining an injection-molded frame to an extruded bag. Due to the different plastics production processes used, the two parts can have very different thermal properties even if they are the same type of polymer. One of the most critical properties affecting dissimilar polymer joining is viscosity. If the polymers’ viscosity is not similar enough, intermolecular diffusion cannot occur. The goal of this work is to set clear boundaries on the tolerable limits of the viscosity mismatch that can be accommodated and still result in intermolecular diffusion. Polymers of the same grade of material were heated conductively using a hot plate to different temperatures, then the melt layers were pressed together in the standard hot plate welding approach. The parts were then tensile tested and cross-sectioned to determine relative strength and whether intermolecular diffusion occurred. By using the same grade of material heated to different temperatures, the independent variables are minimized, and the effect of viscosity can be clearly identified. The test data was then analyzed for statistically significant shifts to identify the maximum allowable difference in viscosity. Polymer Welding Dissimilar Polymers Polymer Joining Viscosity Difference Hot Plate Welding 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 Figure 24 1. Introduction The need for dissimilar polymer welding is growing. Of the existing polymer joining techniques, adhesive bonding, solvent welding, mechanical fasteners, and welding are applicable to dissimilar polymer joining. However, these approaches are not always suitable for specific applications. Adhesive bonding utilizes a third material to create a bond. The adhesive material must have a high surface energy and compatible surface chemistry. Often there are limited options for adhesives that are compatible for the joining of dissimilar polymers. Many adhesives do not pass FDA regulations, which makes them unusable for many medical applications. In small electronics, limited space is available for extra joining material. Lasty, for some products, adhesives can be a significant barrier to performance. Solvent welding, like adhesives, requires a third material to be added to the joint. The solvent breaks down the chemical bounds that hold the polymer chains together allowing them to move and achieve some degree of molecular diffusion. However, it is often challenging to find a solvent that is compatible with dissimilar polymers. Mechanical fasteners are often used to join dissimilar polymers as there are little to no materials-based limitations to this technique. Yet a major drawback is the added weight and size that mechanical fasteners require. In many applications existing welding approaches are not suitable for dissimilar polymer joining. In applications in which a polymer has been subjected to different processing methods, i.e., extrusion and injection molding, it will take on different rheological properties. This difference, when using traditional welding processes, can lead to reduced weld strength. For a dissimilar polymer weld to be successful, intermolecular diffusion along the polymers’ melt interface must occur. Intermolecular diffusion is dependent on a polymer’s relative viscosity. Polymers with highly different viscosities do not bound well because the two melts have limited contact time. For dissimilar polymer welding to be a viable joining approach, the tolerable viscosity difference allowed for intermolecular diffusion to occur must be evaluated. This work aims to assess the allowed viscosity difference by evaluating the weld strength of polymer welds at increasing viscosity differences. A custom, dual-temperature hot plate welder will be used to “mismatch” a polymer’s viscosity and create a polymer weld. The polymer weld will then be tensile tested and cross-sectioned. 2. Literature Review Polymer welding occurs when there is molecular diffusion across the melt surfaces of both polymers. This diffusion is only possible when the polymers (in the weld zone) are a viscous fluid [ 1 ]. If diffusion does not occur, the polymers will only adhere to each other through an adhesive bond created by the melt of higher temperature polymer [ 2 ]. For polymers with dissimilar viscosities, the melt will flow across the surface of the other polymer even under pressure, and diffusion will not occur. If the two materials have similar viscosities, then they will spread at similar rates. This increases their contact time which can lead to molecular diffusion. Increasing the viscosity of a polymer is known to increase its weld strength [ 3 ]. When welding dissimilar polymers, blends with a viscosity ratio of less the 21 are known to be brittle, while those above 21 have ductile weld lines [ 4 ]. Bates demonstrates that in vibration welded assemblies of homopolymers, the weld strength of low melt flow indices (MFI), meaning higher molecular weight polymers, decreases significantly with increased pressure [ 5 ]. This effect is not as significant with high MFI, (low molecular weight) polymers, implying a relationship between a polymer’s molecular weight and its rate of molecular diffusion. A polymer’s carbon chain length and melting point, properties related to polymer viscosity, are also known to affect weld strength [ 6 ]. Additionally, the thickness of a polymer’s heat-affected zone (HAZ) decreases with pressure, suggesting that a molecular weight dependent HAZ is required to maximize a polymer’s weld strength [ 7 ]. The flow of molten polymers in hot plate welding depends on the movement of chain segments. Sufficient thermal energy is required to overcome the energy barriers of the chain segments to allow for molecular diffusion. Low flow results in weak bonding, while excessive flow causes shape deformation during welding. For optimal weld strength a polymer’s flow pattern must be controlled. The Arrhenius equation for molten polymers can be rearranged to obtain the needed flow activation energy E a . $$\:\text{ln}\eta\:=\frac{{E}_{a}}{RT}+\text{ln}C$$ Where C is a constant and 𝜂 is the viscosity of a polymer [ 5 ]. In addition to viscosity, compatibilizers and processing temperatures are also found to affect the morphology and mechanical properties of polymer welds [ 8 ]. 3. Materials and Equipment 3.1. Materials Four thermoplastic polymers — Acrylonitrile Butadiene Styrene (ABS), Polystyrene (PS), Polycarbonate (PC) Polyvinyl Chloride (PVC) — were tested. ABS is a common thermoplastic known to be hard, tough, heat resistant, and impact resistant. PS, a clear, hard and brittle thermoplastic, is one of the most wildly used plastics. PC can be easily molded and thermoformed. PVC is another high-strength thermoplastic. Lightweight and durable, PVC has both rigid and flexible forms. All materials were sourced from McMaster Carr in 6.4-mm thickness. Materials properties are in Table 1 below. Table 1 ABS, PVC, PS, and PC material properties Material ABS PVC PS PC Color Natural Clear White Clear Fabrication Molded Extruded Extruded Extruded Glass Transition Temperature (°C) 106.08 56.18 99.15 153.13 Maximum Use Temperature (°C) 71 49 68 82 Tensile Strength (MPa) 29–35 50 17–28 61–66 Hardness R101-R109 84D R70 R118 Density (g/cc) 1.02 1.36 1.08 1.19 Flexural Modulus (MPa) 1860–2620 3170 1520–1860 2210–2410 Water Absorption 0.13–0.3% 0.03 0.05 0.15–0.2 Coefficient of Thermal Expansion (mm/mm/°C × 10 − 5) 9.0-10.1 6.7–7.4 6.7–6.8 3.2. Equipment 3.2.1. Welding EWI built a custom hot plate and infrared (IR) welder that can heat two polymers to different temperatures to control their viscosity (Fig. 1 ). The system was designed to allow for IR and hot plate heating; however, this experiment only utilized hot plate welding. Each hot plate and IR lamp has a dedicated power control to allow for individual temperature control. Thermocouples are used to track and control the temperature of each hot plate so they can be independently adjusted. Once the polymers are at the desired temperature that will correlate to the viscosity of the melt, they are pressed together at a set time and pressure. The closing velocity and holding force are controlled by pneumatic cylinders. 3.2.2. Tensile testing An Instron 5584 universal tensile machine (Fig. 2 ) was used to find the weld strength of each viscosity mismatched sample. All tensile tests were performed at a pull speed of 0.2 inches per minute at room temperature. 3.2.3. Heated After Cross-Section Analysis Heated after cross-section (HACS) analysis is a weld evaluation technique that enables visual assessment of whether intermolecular diffusion has occurred as well as other weld qualities. After the sample is ground and polished, a heat treat step allows the polymer chains on the surface of a sample to thermally recover from the mechanical displacement. HACS can be used to detect weld defects such as a lack of diffusion, voids, cracking, or uneven or misaligned welds. An Olympus BX51 microscope was used to photograph the welded cross sections. A Puhui Infrared reflow system was used to heat the samples for HACS analysis. 4. Experimental Procedure To test the tolerable viscosity differences in polymer-to-polymer welding, four polymers, PS ABS, PC and PVC, were hot plate welded at varying dissimilar viscosities. To create a viscosity mismatch, two 25.4- × 79.2- × 6.4-mm coupons of the same polymer were heated to different temperatures and hot plate welded using a custom dual-temp hot plate welder. During the welding process, each coupon was held against a hot plate for 10 seconds at 50 psi then brought in contact with each other to complete the weld. Welds were completed at each of the following temperature settings shown in Table 2 . Table 2 ABS, PVC, PC , and PS Temperature Settings Material Temperature setting (°C) 1 2 3 4 5 6 ABS 290–290 280–300 270–310 260–320 250–330 240–340 PVC 220 − 200 210–230 200–240 190–250 180–260 170–270 PC 290–290 260–320 240–340 PS 290–290 260–320 240–340 The viscosity versus temperature for all materials was evaluated using a rotational rheometer. The temperature differences could then be correlated to viscosity differences as shown in Table 3 . Table 3 ABS, PVC, PC, and PS Viscosity Mismatch Material Viscosity Mismatch (Pa-s) 1 2 3 4 5 6 ABS 0 283 1439 2205 2833 4827 PVC 0 5767 12462 Not Measured PC 0 975 5330 PS 0 366 1428 Ultimate load tensile testing and cross-section analysis was completed on all samples. The ultimate load tensile testing was performed with an Instron 5584 universal tensile machine with a pull speed of 0.2 inches per minute at room temperature. Cross-section analysis was done using the HACS methodology. 5. Results ABS tensile tests indicate a decrease in the average weld strength as the temperature difference increases. A temperature difference of 60°C produces an average weld strength below the lowest preforming ABS to ABS weld with no temperature difference. However, the ABS to ABS welds with a temperature difference of 100°C performed better than the those with differences of 60°C, which merits further study (see Fig. 3 ). Cross-section analysis reveals a lack of intermolecular diffusion in ABS to ABS welds at all temperature differences. The faint horizontal line in the middle of the weld shows a lack of diffusion between the weld interfaces (see Figs. 4, 5, and 6). This may be a reason the weld strength did not significantly decrease as viscosity mismatch increased. The expectation is that diffusion will occur at the similar temperature welds, but if it does not, then the expected lack of diffusion at greater mismatch will not have the anticipated negative effect on the weld strength. For PC to PC welds, a temperature difference of 260–320°C produced the strongest weld strength with a maximum of 27.8 Mpa; however, this temperature range did produce a wide range of ultimate tensile strength (UTS) values. The most extreme temperature mismatch, 240–340°C, exceeds the tolerable range of viscosity differences, as it has a low standard deviation and averages a weld strength below welds of other temperature differences. See Fig. 7 . A weld interface cannot be seen in the PC to PC welds at 290–290°C and 260–320°C, indicating that molecular diffusion occurred (Figs. 8 and 9). A large void in PC to PC weld 240–340°C is visible (Fig. 10). In the PS to PS welds, an increasing mismatch in temperature leads to a reduction in the weld strength. Temperature differences of 290–290°C and 270–310°C result in a similar UTS. As the weld temperature difference increases, the weld strength decreases (Fig. 11 ). A weld interface can be seen in PS-PS welds of 290–290°C, 280–300°C, 260–320°C, 250 − 230°C, and 240–240°C (Figs. 12, 13, 14, 15, 16, and 17) but no distinct middle line between the two melt layers, indicating intermolecular diffusion did occur. PS to PS weld 270–310°C (Fig. 14) did not show any signs of melt or change in microstructure, which is not aligned with the appearance of flash. This cross-section merits further investigation. Unlike the other polymers tested, the weld strength of PVC to PVC bonds increase as temperature difference increases (Fig. 18 ). The largest temperature difference, 170–270°C breaks this trend and is considered to be outside the tolerable range of viscosity difference. A weld interface can be seen in all PVC to PVC welds (Figs. 19, 20, 21, 22, 23, and 24), but no distinct dividing line is visible across the weld in the matched temperature weld (Fig. 19). No intermolecular diffusion has occurred for most of these welds. The dark spot in the PVC to PVC weld at 180–260°C (Fig. 23) is fluid that has collected in the weld joint from the polishing process, not a void. However, both the highest temperature difference cross-sections show a significant lack of adhesion at the weld interface (Figs. 23 and 24). 6. Discussion The results show that some mismatch in viscosity is tolerable and in the case of PVC, even potentially beneficial to the weld strength. However, there is a difference that is too great to result in good welds for all the materials tested. Analysis of variance (ANOVA) of the date was performed to check for statistical significance of the results. The PC and PS results were found to be likely to be statistically significant, but the ABS and PVC results were not. These results are shown in Table 4 , where the p-unc of < 0.1 indicates statistical significance. Interestingly, the results of this work indicated the traditional limit of viscosity mismatch used in industry today is significantly more restrictive than necessary. The industry rule of thumb is that polymers should have a melt flow index within 10% of each other to be welded. However, at the temperature differences tested here, the viscosity is well outside that range and still produces good, strong welds in many cases. 7. Conclusions A successful polymer weld is achieved when molecular diffusion occurs between the melt interface of two polymers. For this diffusion to occur the two polymer melts must have a similar viscosity. To determine a tolerable range of viscosities differences, ABS, PVS, PC, and PS coupons were welded at varying temperature differences. Tensile testing and HACS analysis were performed on the welds to determine what viscosity differences allowed for molecular diffusion. Results indicate the pre-existing industry standard of a melt flow index of less than 10% is too restrictive. Polymers with viscosities outside that range still produced strong welds. PVC welds increased in strength as their viscosity differences increased. Declarations The authors have no competing interests to declare that are relevant to the content of this article. No funding was received for conducting this study. References Volkov SS, Bigus GA, Remizov, AL (2018) Ultrasonic Welding of Dissimilar Plastics. Russ Engin Res 38:281–284. https://doi.org/10.3103/S1068798X18040238 Ritter GW, EWI (2016) Bonding of plastics. SPE ANTEC Indianapolis, 562-564. Ersoy OG, Nugay N (2004) A new approach to increase weld line strength of incompatible polymer blend composites: selective filler addition. Polymer, 45(4), 1243-1252. https://doi.org/10.1016/j.polymer.2003.12.036 Jarus D, Summers J W, Hiltner A, Baer E (2000) Weld line strength of poly (vinyl chloride)/polyethylene blends. Polymer, 41(8), 3057-3068. https://doi.org/10.1016/S0032-3861(99)00470-X Bates P, Powell A, Kontopoulou M (2009) Vibration welding polypropylene - Effect of MFI on weld strength and microstructure. Annual Technical Conference - ANTEC, Conference Proceedings. 1. 317-322 Kumar R, Singh R, Ahuja IPS (2019) Friction stir welding of ABS-15Al sheets by introducing compatible semi-consumable shoulder-less pin of PA6-50Al. Measurement, 131, 461-472. https://doi.org/10.1016/j.measurement.2018.09.005 Shim MJ, Kim S (1997) Characteristics of polymer welding by healing process. Materials Chemistry and Physics 48:90-93. https://doi.org/10.1016/S0254-0584(97)80084-3 Lim JC, Park JK (2005) Weld‐line characteristics of polycarbonate/acrylonitrile–butadiene–styrene blends. I. Effect of the processing temperature. Journal of applied polymer science, 95(3), 689-699. https://doi.org/10.1002/app.21218 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 23 Dec, 2024 Reviewers invited by journal 17 Dec, 2024 Editor invited by journal 04 Nov, 2024 Editor assigned by journal 30 Oct, 2024 First submitted to journal 30 Oct, 2024 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-5269647","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":391506861,"identity":"4166324c-4f25-4f1e-a31d-4dd10b4d3b17","order_by":0,"name":"Miranda Marcus","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAApUlEQVRIiWNgGAWjYBADOQYGxgbStBiTriWRePW60w4/+/CzrS69XyK5geHjnlrCWsxupxnP7G07nDtzRmID44xnx4nRkmDMzNh2IHfD7cQGZp4Dx4jRkv4ZqKUu3Z4ELTkgW5gTDKTBWmqI0lLM2HPusOGM+w8bDs44cIAoh21m+FFWJ8/fc/zhgw8H6ghrQQFAKw6TqAUISLVlFIyCUTAKRgIAAOoIPdl8aimSAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-6498-1480","institution":"EWI: Edison Welding Institute","correspondingAuthor":true,"prefix":"","firstName":"Miranda","middleName":"","lastName":"Marcus","suffix":""},{"id":391506862,"identity":"79fd5a79-6351-4e50-a1c9-bf834381dbe4","order_by":1,"name":"Elizabeth Drake","email":"","orcid":"","institution":"EWI: Edison Welding Institute","correspondingAuthor":false,"prefix":"","firstName":"Elizabeth","middleName":"","lastName":"Drake","suffix":""},{"id":391506863,"identity":"deb25bdb-5f08-4289-9495-443ada94570a","order_by":2,"name":"Matt Nitsch","email":"","orcid":"","institution":"EWI: Edison Welding Institute","correspondingAuthor":false,"prefix":"","firstName":"Matt","middleName":"","lastName":"Nitsch","suffix":""},{"id":391506864,"identity":"213738ff-8851-4d37-867d-2d25fc6e7a31","order_by":3,"name":"Zach Corey","email":"","orcid":"","institution":"EWI: Edison Welding Institute","correspondingAuthor":false,"prefix":"","firstName":"Zach","middleName":"","lastName":"Corey","suffix":""}],"badges":[],"createdAt":"2024-10-15 14:44:02","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5269647/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5269647/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":71918969,"identity":"a71f00b8-5b05-46e5-b3e1-33f24a993149","added_by":"auto","created_at":"2024-12-19 17:05:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":687661,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEWI's custom dual temperature hot plate welder\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/332d46f0eb30aaa521569919.png"},{"id":71918461,"identity":"dbb6cf5e-ba90-481a-8c91-86265de6f7b3","added_by":"auto","created_at":"2024-12-19 16:57:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":130238,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eInstron 5584 universal tensile machine\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/19704393eb85195f481b6b92.png"},{"id":71918458,"identity":"8fe644d2-b9cc-4f22-8407-ed5f46a07e9d","added_by":"auto","created_at":"2024-12-19 16:57:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":10110,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of temperature difference on ABS to ABS weld strength\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/91af1ab75ed92f62f21c4c12.png"},{"id":71918978,"identity":"2301cd29-1203-459e-9ca8-43de4be8b9de","added_by":"auto","created_at":"2024-12-19 17:05:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":525301,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of ABS 290-290°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/f211409e8dbaa88abc8f2731.png"},{"id":71918965,"identity":"e0d786fc-018c-4297-866c-cd5f321be774","added_by":"auto","created_at":"2024-12-19 17:05:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":519999,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of ABS 260-320°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/ca5faec7df392465b203f53b.png"},{"id":71919839,"identity":"0b58ca8f-acf0-46bb-8d98-42d50b095035","added_by":"auto","created_at":"2024-12-19 17:13:09","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":568421,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of ABS 240-340°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/cfabeb52a9ef0737afa80b36.png"},{"id":71918968,"identity":"d7e8729c-0605-4087-a177-20af4d42de63","added_by":"auto","created_at":"2024-12-19 17:05:08","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":71783,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of temperature difference on PC to PC weld strength\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/f62c42862d7c7d28d4071352.png"},{"id":71918975,"identity":"54ceb138-a747-4e8f-be84-0c6dbf0c248d","added_by":"auto","created_at":"2024-12-19 17:05:09","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":421432,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PC 290-290°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/f740c048b0559729d2a23d17.png"},{"id":71918471,"identity":"d90d80bc-4d3d-43e0-ac69-fac062adfaf6","added_by":"auto","created_at":"2024-12-19 16:57:08","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":472465,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PC 260-320°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/3fb903027093e37dc9b9fef7.png"},{"id":71918498,"identity":"624bf60b-bfc0-477e-921f-6cd589023575","added_by":"auto","created_at":"2024-12-19 16:57:10","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":483373,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PC 240-340°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/fa3766d1a5a11cf28cd36377.png"},{"id":71919836,"identity":"50becdca-25f0-488c-865d-bde509449935","added_by":"auto","created_at":"2024-12-19 17:13:08","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":95182,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of temperature difference on PS to PS weld strength\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/dacaee21873aef29cc63d81a.png"},{"id":71918973,"identity":"b4c1bd29-84b2-413d-88d7-0fa2c42134e0","added_by":"auto","created_at":"2024-12-19 17:05:08","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":339293,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 290-290°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/73e186b1103eefd1562d51bf.png"},{"id":71918974,"identity":"9933e57d-f177-4f2a-89c0-efd8447ef094","added_by":"auto","created_at":"2024-12-19 17:05:08","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":310506,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 280-300°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/9e60ec30f01db59d9a1b9d61.png"},{"id":71918481,"identity":"5916f7bf-0e6b-4d01-8583-50ff9e426631","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":314007,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 270-310°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/5db636dde6a7a5a76d424aca.png"},{"id":71918486,"identity":"8a304fc9-3774-4d06-aa72-62896f12944a","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":343515,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 260-320°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/5ef8d34ab4b498848c4cad09.png"},{"id":71918485,"identity":"4ba42228-42fd-4fe9-9637-006f6ad9043a","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":377502,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 250-330°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/f3eb694535a41d9a9eb7435a.png"},{"id":71918496,"identity":"a511be21-9927-48e2-8969-3f5b0515b76c","added_by":"auto","created_at":"2024-12-19 16:57:10","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":276779,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PS 240-340°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/9e8a3883cc08a67190e9c0f5.png"},{"id":71918477,"identity":"651a1004-e173-43d9-afd5-1cee287f1417","added_by":"auto","created_at":"2024-12-19 16:57:08","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":91231,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEffect of temperature difference of PVC to PVC weld strength\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"18.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/93f7eb4dd5e894211f81490d.png"},{"id":71918488,"identity":"26b24eae-2694-4435-8032-318c72eb1b35","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":410760,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 220-220°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"19.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/0e9430998f607575ee7157dc.png"},{"id":71918480,"identity":"81fb6a75-8e83-4cab-afda-6845808e211f","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":446613,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 210-230°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"20.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/a2bc80e778afa1f6b2b02fc3.png"},{"id":71918482,"identity":"13e9a084-af53-47ab-9053-c3ab967af683","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":332458,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 200-240°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"21.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/f3e686c501866e8d83f40c99.png"},{"id":71918607,"identity":"e8b214e7-d6c1-4a10-9a07-69e5ed179510","added_by":"auto","created_at":"2024-12-19 16:57:10","extension":"png","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":371398,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 190-250°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"22.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/18628f32d460967a99ed1319.png"},{"id":71918493,"identity":"53c3e554-0261-4409-b71d-5962851dfe19","added_by":"auto","created_at":"2024-12-19 16:57:09","extension":"png","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":279597,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 180-260°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"23.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/6e8fde8ad49965b695502c44.png"},{"id":71918597,"identity":"0ea84d03-4d5c-4af3-91b0-92f1c1934279","added_by":"auto","created_at":"2024-12-19 16:57:10","extension":"png","order_by":24,"title":"Figure 24","display":"","copyAsset":false,"role":"figure","size":269798,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHACS of PVC 170-270°C 12×\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"24.png","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/bbb8588fb3dc8d384600ad87.png"},{"id":71921145,"identity":"4d99b668-e73b-4f3e-ae2d-0c98e478953b","added_by":"auto","created_at":"2024-12-19 17:29:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12775838,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5269647/v1/b77b2766-0c25-40af-99ec-1960386743c8.pdf"}],"financialInterests":"","formattedTitle":"Assessing tolerable viscosity differences in polymer-to-polymer welding","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe need for dissimilar polymer welding is growing. Of the existing polymer joining techniques, adhesive bonding, solvent welding, mechanical fasteners, and welding are applicable to dissimilar polymer joining. However, these approaches are not always suitable for specific applications.\u003c/p\u003e \u003cp\u003eAdhesive bonding utilizes a third material to create a bond. The adhesive material must have a high surface energy and compatible surface chemistry. Often there are limited options for adhesives that are compatible for the joining of dissimilar polymers. Many adhesives do not pass FDA regulations, which makes them unusable for many medical applications. In small electronics, limited space is available for extra joining material. Lasty, for some products, adhesives can be a significant barrier to performance. Solvent welding, like adhesives, requires a third material to be added to the joint. The solvent breaks down the chemical bounds that hold the polymer chains together allowing them to move and achieve some degree of molecular diffusion. However, it is often challenging to find a solvent that is compatible with dissimilar polymers. Mechanical fasteners are often used to join dissimilar polymers as there are little to no materials-based limitations to this technique. Yet a major drawback is the added weight and size that mechanical fasteners require.\u003c/p\u003e \u003cp\u003eIn many applications existing welding approaches are not suitable for dissimilar polymer joining. In applications in which a polymer has been subjected to different processing methods, i.e., extrusion and injection molding, it will take on different rheological properties. This difference, when using traditional welding processes, can lead to reduced weld strength.\u003c/p\u003e \u003cp\u003eFor a dissimilar polymer weld to be successful, intermolecular diffusion along the polymers\u0026rsquo; melt interface must occur. Intermolecular diffusion is dependent on a polymer\u0026rsquo;s relative viscosity. Polymers with highly different viscosities do not bound well because the two melts have limited contact time. For dissimilar polymer welding to be a viable joining approach, the tolerable viscosity difference allowed for intermolecular diffusion to occur must be evaluated. This work aims to assess the allowed viscosity difference by evaluating the weld strength of polymer welds at increasing viscosity differences. A custom, dual-temperature hot plate welder will be used to \u0026ldquo;mismatch\u0026rdquo; a polymer\u0026rsquo;s viscosity and create a polymer weld. The polymer weld will then be tensile tested and cross-sectioned.\u003c/p\u003e"},{"header":"2. Literature Review","content":"\u003cp\u003ePolymer welding occurs when there is molecular diffusion across the melt surfaces of both polymers. This diffusion is only possible when the polymers (in the weld zone) are a viscous fluid [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. If diffusion does not occur, the polymers will only adhere to each other through an adhesive bond created by the melt of higher temperature polymer [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. For polymers with dissimilar viscosities, the melt will flow across the surface of the other polymer even under pressure, and diffusion will not occur. If the two materials have similar viscosities, then they will spread at similar rates. This increases their contact time which can lead to molecular diffusion.\u003c/p\u003e \u003cp\u003eIncreasing the viscosity of a polymer is known to increase its weld strength [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. When welding dissimilar polymers, blends with a viscosity ratio of less the 21 are known to be brittle, while those above 21 have ductile weld lines [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Bates demonstrates that in vibration welded assemblies of homopolymers, the weld strength of low melt flow indices (MFI), meaning higher molecular weight polymers, decreases significantly with increased pressure [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This effect is not as significant with high MFI, (low molecular weight) polymers, implying a relationship between a polymer\u0026rsquo;s molecular weight and its rate of molecular diffusion. A polymer\u0026rsquo;s carbon chain length and melting point, properties related to polymer viscosity, are also known to affect weld strength [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Additionally, the thickness of a polymer\u0026rsquo;s heat-affected zone (HAZ) decreases with pressure, suggesting that a molecular weight dependent HAZ is required to maximize a polymer\u0026rsquo;s weld strength [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe flow of molten polymers in hot plate welding depends on the movement of chain segments. Sufficient thermal energy is required to overcome the energy barriers of the chain segments to allow for molecular diffusion. Low flow results in weak bonding, while excessive flow causes shape deformation during welding. For optimal weld strength a polymer\u0026rsquo;s flow pattern must be controlled. The Arrhenius equation for molten polymers can be rearranged to obtain the needed flow activation energy E\u003csub\u003ea\u003c/sub\u003e.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\text{ln}\\eta\\:=\\frac{{E}_{a}}{RT}+\\text{ln}C$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere C is a constant and \u0026#120578; is the viscosity of a polymer [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn addition to viscosity, compatibilizers and processing temperatures are also found to affect the morphology and mechanical properties of polymer welds [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e"},{"header":"3. Materials and Equipment","content":"\u003cdiv id=\"Sec4\"\u003e\n \u003ch2\u003e3.1. Materials\u003c/h2\u003e\n \u003cp\u003eFour thermoplastic polymers \u0026mdash; Acrylonitrile Butadiene Styrene (ABS), Polystyrene (PS), Polycarbonate (PC) Polyvinyl Chloride (PVC) \u0026mdash; were tested. ABS is a common thermoplastic known to be hard, tough, heat resistant, and impact resistant. PS, a clear, hard and brittle thermoplastic, is one of the most wildly used plastics. PC can be easily molded and thermoformed. PVC is another high-strength thermoplastic. Lightweight and durable, PVC has both rigid and flexible forms. All materials were sourced from McMaster Carr in 6.4-mm thickness. Materials properties are in Table \u003cspan\u003e1\u003c/span\u003e below.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eABS, PVC, PS, and PC material properties\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\n \u003cp\u003eMaterial\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eABS\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePVC\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePS\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePC\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\u003eColor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNatural\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eClear\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWhite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eClear\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFabrication\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMolded\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExtruded\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExtruded\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExtruded\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGlass Transition Temperature (\u0026deg;C)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e106.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e99.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e153.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMaximum Use Temperature (\u0026deg;C)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTensile Strength (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29\u0026ndash;35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17\u0026ndash;28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e61\u0026ndash;66\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHardness\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR101-R109\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e84D\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eR118\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDensity (g/cc)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.19\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFlexural Modulus (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1860\u0026ndash;2620\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1520\u0026ndash;1860\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2210\u0026ndash;2410\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWater Absorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.13\u0026ndash;0.3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u0026ndash;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCoefficient of Thermal Expansion (mm/mm/\u0026deg;C \u0026times; 10\u0026thinsp;\u0026minus;\u0026thinsp;5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.0-10.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.7\u0026ndash;7.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.7\u0026ndash;6.8\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=\"Sec5\"\u003e\n \u003ch2\u003e3.2. Equipment\u003c/h2\u003e\n \u003cdiv id=\"Sec6\"\u003e\n \u003ch2\u003e3.2.1. Welding\u003c/h2\u003e\n \u003cp\u003eEWI built a custom hot plate and infrared (IR) welder that can heat two polymers to different temperatures to control their viscosity (Fig. \u003cspan\u003e1\u003c/span\u003e). The system was designed to allow for IR and hot plate heating; however, this experiment only utilized hot plate welding. Each hot plate and IR lamp has a dedicated power control to allow for individual temperature control. Thermocouples are used to track and control the temperature of each hot plate so they can be independently adjusted. Once the polymers are at the desired temperature that will correlate to the viscosity of the melt, they are pressed together at a set time and pressure. The closing velocity and holding force are controlled by pneumatic cylinders.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec7\"\u003e\n \u003ch2\u003e3.2.2. Tensile testing\u003c/h2\u003e\n \u003cp\u003eAn Instron 5584 universal tensile machine (Fig. \u003cspan\u003e2\u003c/span\u003e) was used to find the weld strength of each viscosity mismatched sample. All tensile tests were performed at a pull speed of 0.2 inches per minute at room temperature.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec8\"\u003e\n \u003ch2\u003e3.2.3. Heated After Cross-Section Analysis\u003c/h2\u003e\n \u003cp\u003eHeated after cross-section (HACS) analysis is a weld evaluation technique that enables visual assessment of whether intermolecular diffusion has occurred as well as other weld qualities. After the sample is ground and polished, a heat treat step allows the polymer chains on the surface of a sample to thermally recover from the mechanical displacement. HACS can be used to detect weld defects such as a lack of diffusion, voids, cracking, or uneven or misaligned welds. An Olympus BX51 microscope was used to photograph the welded cross sections. A Puhui Infrared reflow system was used to heat the samples for HACS analysis.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. Experimental Procedure","content":"\u003cp\u003eTo test the tolerable viscosity differences in polymer-to-polymer welding, four polymers, PS ABS, PC and PVC, were hot plate welded at varying dissimilar viscosities. To create a viscosity mismatch, two 25.4- \u0026times; 79.2- \u0026times; 6.4-mm coupons of the same polymer were heated to different temperatures and hot plate welded using a custom dual-temp hot plate welder. During the welding process, each coupon was held against a hot plate for 10 seconds at 50 psi then brought in contact with each other to complete the weld. Welds were completed at each of the following temperature settings shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eABS, PVC, PC\u003c/em\u003e, \u003cem\u003eand PS Temperature Settings\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e \u003cp\u003eTemperature setting (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eABS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e290\u0026ndash;290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e280\u0026ndash;300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e270\u0026ndash;310\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e260\u0026ndash;320\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e250\u0026ndash;330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e240\u0026ndash;340\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePVC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e220\u0026thinsp;\u0026minus;\u0026thinsp;200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e210\u0026ndash;230\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e200\u0026ndash;240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e190\u0026ndash;250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e180\u0026ndash;260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e170\u0026ndash;270\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e290\u0026ndash;290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e260\u0026ndash;320\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e240\u0026ndash;340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e290\u0026ndash;290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e260\u0026ndash;320\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e240\u0026ndash;340\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe viscosity versus temperature for all materials was evaluated using a rotational rheometer. The temperature differences could then be correlated to viscosity differences as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eABS, PVC, PC, and PS Viscosity Mismatch\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaterial\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e \u003cp\u003eViscosity Mismatch (Pa-s)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eABS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e283\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1439\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2205\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2833\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4827\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePVC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5767\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12462\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eNot Measured\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e975\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" morerows=\"1\" nameend=\"c7\" namest=\"c5\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e366\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1428\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\u003eUltimate load tensile testing and cross-section analysis was completed on all samples. The ultimate load tensile testing was performed with an Instron 5584 universal tensile machine with a pull speed of 0.2 inches per minute at room temperature. Cross-section analysis was done using the HACS methodology.\u003c/p\u003e"},{"header":"5. Results","content":"\u003cp\u003eABS tensile tests indicate a decrease in the average weld strength as the temperature difference increases. A temperature difference of 60\u0026deg;C produces an average weld strength below the lowest preforming ABS to ABS weld with no temperature difference. However, the ABS to ABS welds with a temperature difference of 100\u0026deg;C performed better than the those with differences of 60\u0026deg;C, which merits further study (see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCross-section analysis reveals a lack of intermolecular diffusion in ABS to ABS welds at all temperature differences. The faint horizontal line in the middle of the weld shows a lack of diffusion between the weld interfaces (see Figs.\u0026nbsp;4, 5, and 6). This may be a reason the weld strength did not significantly decrease as viscosity mismatch increased. The expectation is that diffusion will occur at the similar temperature welds, but if it does not, then the expected lack of diffusion at greater mismatch will not have the anticipated negative effect on the weld strength.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFor PC to PC welds, a temperature difference of 260\u0026ndash;320\u0026deg;C produced the strongest weld strength with a maximum of 27.8 Mpa; however, this temperature range did produce a wide range of ultimate tensile strength (UTS) values. The most extreme temperature mismatch, 240\u0026ndash;340\u0026deg;C, exceeds the tolerable range of viscosity differences, as it has a low standard deviation and averages a weld strength below welds of other temperature differences. See Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e7\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA weld interface cannot be seen in the PC to PC welds at 290\u0026ndash;290\u0026deg;C and 260\u0026ndash;320\u0026deg;C, indicating that molecular diffusion occurred (Figs.\u0026nbsp;8 and 9). A large void in PC to PC weld 240\u0026ndash;340\u0026deg;C is visible (Fig.\u0026nbsp;10).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn the PS to PS welds, an increasing mismatch in temperature leads to a reduction in the weld strength. Temperature differences of 290\u0026ndash;290\u0026deg;C and 270\u0026ndash;310\u0026deg;C result in a similar UTS. As the weld temperature difference increases, the weld strength decreases (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA weld interface can be seen in PS-PS welds of 290\u0026ndash;290\u0026deg;C, 280\u0026ndash;300\u0026deg;C, 260\u0026ndash;320\u0026deg;C, 250\u0026thinsp;\u0026minus;\u0026thinsp;230\u0026deg;C, and 240\u0026ndash;240\u0026deg;C (Figs.\u0026nbsp;12, 13, 14, 15, 16, and 17) but no distinct middle line between the two melt layers, indicating intermolecular diffusion did occur. PS to PS weld 270\u0026ndash;310\u0026deg;C (Fig.\u0026nbsp;14) did not show any signs of melt or change in microstructure, which is not aligned with the appearance of flash. This cross-section merits further investigation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUnlike the other polymers tested, the weld strength of PVC to PVC bonds increase as temperature difference increases (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e18\u003c/span\u003e). The largest temperature difference, 170\u0026ndash;270\u0026deg;C breaks this trend and is considered to be outside the tolerable range of viscosity difference.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA weld interface can be seen in all PVC to PVC welds (Figs.\u0026nbsp;19, 20, 21, 22, 23, and 24), but no distinct dividing line is visible across the weld in the matched temperature weld (Fig.\u0026nbsp;19). No intermolecular diffusion has occurred for most of these welds. The dark spot in the PVC to PVC weld at 180\u0026ndash;260\u0026deg;C (Fig.\u0026nbsp;23) is fluid that has collected in the weld joint from the polishing process, not a void. However, both the highest temperature difference cross-sections show a significant lack of adhesion at the weld interface (Figs.\u0026nbsp;23 and 24).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"6. Discussion","content":"\u003cp\u003eThe results show that some mismatch in viscosity is tolerable and in the case of PVC, even potentially beneficial to the weld strength. However, there is a difference that is too great to result in good welds for all the materials tested. Analysis of variance (ANOVA) of the date was performed to check for statistical significance of the results. The PC and PS results were found to be likely to be statistically significant, but the ABS and PVC results were not. These results are shown in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, where the p-unc of \u0026lt;\u0026thinsp;0.1 indicates statistical significance.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1734625036.png\"\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eInterestingly, the results of this work indicated the traditional limit of viscosity mismatch used in industry today is significantly more restrictive than necessary. The industry rule of thumb is that polymers should have a melt flow index within 10% of each other to be welded. However, at the temperature differences tested here, the viscosity is well outside that range and still produces good, strong welds in many cases.\u003c/p\u003e"},{"header":"7. Conclusions","content":"\u003cp\u003eA successful polymer weld is achieved when molecular diffusion occurs between the melt interface of two polymers. For this diffusion to occur the two polymer melts must have a similar viscosity. To determine a tolerable range of viscosities differences, ABS, PVS, PC, and PS coupons were welded at varying temperature differences. Tensile testing and HACS analysis were performed on the welds to determine what viscosity differences allowed for molecular diffusion. Results indicate the pre-existing industry standard of a melt flow index of less than 10% is too restrictive. Polymers with viscosities outside that range still produced strong welds. PVC welds increased in strength as their viscosity differences increased.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors have no competing interests to declare that are relevant to the content of this article. No funding was received for conducting this study.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eVolkov SS, Bigus GA, Remizov, AL (2018) Ultrasonic Welding of Dissimilar Plastics. Russ Engin Res 38:281\u0026ndash;284. https://doi.org/10.3103/S1068798X18040238\u003c/li\u003e\n\u003cli\u003eRitter GW, EWI (2016) Bonding of plastics. SPE ANTEC Indianapolis, 562-564. \u003c/li\u003e\n\u003cli\u003eErsoy OG, Nugay N (2004) A new approach to increase weld line strength of incompatible polymer blend composites: selective filler addition. Polymer, 45(4), 1243-1252. https://doi.org/10.1016/j.polymer.2003.12.036\u003c/li\u003e\n\u003cli\u003eJarus D, Summers J W, Hiltner A, Baer E (2000) Weld line strength of poly (vinyl chloride)/polyethylene blends. Polymer, 41(8), 3057-3068. https://doi.org/10.1016/S0032-3861(99)00470-X\u003c/li\u003e\n\u003cli\u003eBates P, Powell A, Kontopoulou M (2009) Vibration welding polypropylene - Effect of MFI on weld strength and microstructure. Annual Technical Conference - ANTEC, Conference Proceedings. 1. 317-322 \u003c/li\u003e\n\u003cli\u003eKumar R, Singh R, Ahuja IPS (2019) Friction stir welding of ABS-15Al sheets by introducing compatible semi-consumable shoulder-less pin of PA6-50Al. Measurement, 131, 461-472. https://doi.org/10.1016/j.measurement.2018.09.005\u003c/li\u003e\n\u003cli\u003eShim MJ, Kim S (1997) Characteristics of polymer welding by healing process. Materials Chemistry and Physics 48:90-93. https://doi.org/10.1016/S0254-0584(97)80084-3\u003c/li\u003e\n\u003cli\u003eLim JC, Park JK (2005) Weld‐line characteristics of polycarbonate/acrylonitrile\u0026ndash;butadiene\u0026ndash;styrene blends. I. Effect of the processing temperature. Journal of applied polymer science, 95(3), 689-699. https://doi.org/10.1002/app.21218\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Polymer Welding, Dissimilar Polymers, Polymer Joining, Viscosity Difference, Hot Plate Welding","lastPublishedDoi":"10.21203/rs.3.rs-5269647/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5269647/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe welding of dissimilar polymers is becoming increasingly common. There are a couple key drivers to this trend. First, many new plastics applications must be used in environments where adhesives cannot be easily applied, such as for medical products where finding adhesives that pass FDA regulations is nearly impossible. Another key area where dissimilar polymers are joined is for highly engineered applications in which a material is needed for its very specific \u0026mdash; and expensive \u0026mdash; engineered properties. Often, the expensive material will need to be joined to a lower-cost material to provide some nearby structure that does not require the same specialized properties. A third driver is the need to save space for small or very compact assemblies. Even a thin layer of adhesive can be a significant barrier to performance for some products, such as small electronics. Lastly, an assembly may require the joining of components that must be manufactured via different processes, such as joining an injection-molded frame to an extruded bag. Due to the different plastics production processes used, the two parts can have very different thermal properties even if they are the same type of polymer.\u003c/p\u003e \u003cp\u003eOne of the most critical properties affecting dissimilar polymer joining is viscosity. If the polymers\u0026rsquo; viscosity is not similar enough, intermolecular diffusion cannot occur. The goal of this work is to set clear boundaries on the tolerable limits of the viscosity mismatch that can be accommodated and still result in intermolecular diffusion. Polymers of the same grade of material were heated conductively using a hot plate to different temperatures, then the melt layers were pressed together in the standard hot plate welding approach. The parts were then tensile tested and cross-sectioned to determine relative strength and whether intermolecular diffusion occurred. By using the same grade of material heated to different temperatures, the independent variables are minimized, and the effect of viscosity can be clearly identified. The test data was then analyzed for statistically significant shifts to identify the maximum allowable difference in viscosity.\u003c/p\u003e","manuscriptTitle":"Assessing tolerable viscosity differences in polymer-to-polymer welding","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-19 16:57:03","doi":"10.21203/rs.3.rs-5269647/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-12-23T08:57:57+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-12-17T16:22:44+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2024-11-04T08:59:18+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-30T23:08:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2024-10-30T12:30:19+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"52a7aaea-7ca8-475f-8211-b4f928faa8df","owner":[],"postedDate":"December 19th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-12-19T16:57:03+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-19 16:57:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5269647","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5269647","identity":"rs-5269647","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}