Because thermoplastics can be melted down and reshaped, they are generally recyclable. Patrick Casey, a new product consultant at SP Insight and a mentor with MIT’s Deshpande Center for Technological Innovation, has been working with Johnson and Shieh to evaluate the technology, including performing some preliminary economic modeling and secondary market research. MIT chemists have now developed a way to modify thermoset plastics that allows them to be more easily broken down without compromising their mechanical strength. MIT chemists have now developed a way to modify thermoset plastics that allows them to be more easily broken down without compromising their mechanical strength. Copyright © 2020. Researchers identify a mechanism by which small particles in the atmosphere can generate more frequent thunderstorms. But Randy Lewis doesn’t buy that. The recycling involves extrusion and molding which transforms the plastics to the desired form or shape. Thermoset resins can be recycled | plasticstoday.com. thermoset polymers with facile recycling properties.1 Linear polymers, commonly called thermoplastics, typically have easily accessible melting points and can be reprocessed and recycled using heat, but are not durable enough for many high performance applications. “This work unveils a fundamental design principle that we believe is general to any kind of thermoset with this basic architecture,” says Jeremiah Johnson, a professor of chemistry at MIT and the senior author of the study. The consumers see a cost saving, and all of us get a cleaner environment.”. Pioneer in exoplanet research helped transform the burgeoning field into one of the fastest-growing and most exciting in space science. Thermosetting plastic recycling. Lewis has applied for a patent for recycling phenolics and BMC, noting that the recycled phenolic material is difficult to get. Lewis has his own consulting firm, P.R. Massachusetts Institute of Technology77 Massachusetts Avenue, Cambridge, MA, USA. Conventional thermoset plastics or elastomers cannot be melted and re-shaped after they are cured. These types of materials are both difficult and expensive to recycle. Study shows ambitious U.S. startups are not in decline — but timing and location matter. Thermosetting polymers are much more difficult to recycle. “There’s no such thing as non-recyclable. Thermosets are one of the two major classes of plastics, along with thermoplastics. Thermoset polymers, found in car parts and electrical appliances, have to be durable and heat-resistant, but typically cannot be easily recycled or broken down after use. https://www.plasticstoday.com/sites/all/themes/penton_subtheme_plasticstoday/images/logos/footer.png, Hot News in Plastic Packaging Sustainability, Major LA Street Paved Using Recycled Plastic Asphalt. Using recycled phenolics make the thermoset cure faster and give a shiner surface. This micrograph demonstrates how fiber quality can be retained when recycling Mallinda’s reprocessable thermoset resin matrix system. These can be recycled. But Randy Lewis doesn’t buy that. download leaflet (pdf) What is FRP ? Further, 30-40% of monomers produced as a byproduct of the recycling process can be incorporated into the next generation of the resin. V. Goodship, in Failure Mechanisms in Polymer Matrix Composites, 2012. Based on this, I feel I can be forward enough to tell you that recycling thermosets is no more or less difficult than recycling any engineering-grade thermoplastic—with the exception of polypropylene, polyethylene, styrene, PVC and maybe ABS,” he explained. This concrete can be used best in freezing temperate zones for concrete floors, pavements, sidewalks, and curbs. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties. An excellent example is polyurethane foam. In a particularly newsworthy year, news and views from the MIT community made headlines. The MIT team wanted to develop a way to retain the positive attributes of thermoset plastics — their strength and durability — while making them easier to break down after use. The recycled fiberglass finds its way in various industries and can be used in various end products. As I was standing there watching the parts fall out of the mold (using the same cycle that was used for the virgin parts), a gentleman with a masters in mechanical engineering walked up behind me and asked what I was doing. Simulations rule out plasmas caused by meteoroid impacts as the source of lunar magnetism, supporting the proposal that the ancient moon generated a core dynamo. Thermoset plastics are polymers similar to, but generally stronger than, thermoplastics because of polymer cross-linking. For instance, recycled fibers have been effective in reducing shrinkage in concrete thereby increasing its durability. RECYCLed THERMOSET FRP-WASTE reinforcing THERMOPLASTIC COMPOSITES. Thermoset plastics are made by a similar process, but once they are cooled from a liquid into a solid, it is very difficult to return them to a liquid state. Unlike thermoset resins, which cannot be reheated, thermoplastic materials can potentially be recycled at the end of the wind turbine’s life span A business-as-usual blade is generally constructed from epoxy or other thermoset resins. The research was funded by the National Science Foundation and the National Institutes of Health. Features & Benefits Thermoset plastics significantly improve the material’s mechanical properties, providing enhances chemical resistance, heat resistance and structural integrity. Thermoplastics are a type of plastic that become soft when heated, so they can be molded, and then cooled to restore their rigid structure. In a study appearing today in Nature, the researchers showed that they could produce a degradable version of a thermoset plastic called pDCPD, break it down into a powder, and use the powder to create more pDCPD. Thermosets are the necessary choice for applications that require high heat resistance. We’ve always heard that thermoset resins can’t be recycled like thermoplastics. This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Since thermoplastic polymers can be melted and reformed, they are easily recycled. While they are typically liquid, a chemical reaction, sometimes an application of energy from a laser, can cause them to solidify. When one tries to heat up thermoset plastics, instead of melting, they end up burning, unlike thermoplastics which can become liquid again and can be remolded. Number 8860726. Thermoplastics include polyethylene and polypropylene, which are used for plastic bags and other single-use plastics like food wrappers. If you’d like more information from Lewis, contact him at rlewis@zemc2.com. Lewis likes to tell the story of his experience in a plant that was injection molding phenolic parts with a molding compound he had hand mixed in a box beside the press. “We have discussed this technology with some leading industry players, who tell us it promises to be good for stakeholders throughout the value chain,” Casey says. The researchers are now hoping to form a company to license and commercialize the technology. Thermoset Resins Can Be Recycled. But Randy Lewis doesn’t buy that. Everything can … Thermoset plastics such as Bakelite are resistant to solvents and extreme temperatures. “I have worked with recycling both phenolic and BMC, and I’m starting to work on a project to recycle epoxies. Even if in a different way from the simpler thermoplastic, that only requires a temperature increase to get melted and then moulded again. This monomer is randomly distributed throughout the material, and when the material is exposed to acids, bases, or ions such as fluoride, the silyl ether bonds break. Peyton Shieh, an American Cancer Society Postdoctoral Fellow at MIT, is the first author of the paper. An even shape dries evenly; ground material does not have an even shape, therefore myriad inconsistencies come with trying to dry and mold regrind engineering thermoplastic.”, All of these thermoplastic materials cost $2 to $20 per pound, yet they exist to give the thermoplastic molder properties they could not get from a $0.50 to $2 per pound thermoset material, Lewis explained. Since thermoset materials do not melt again once cured, to mechanically recycle thermoset matrix composites it is necessary to size reduce them. 11.4.1 Mechanical recycling of thermoset matrix composites. Flexible polyurethane foams are commonly shredded into small flakes and re-manufactured into carpet underpayment. Silica glass is fragile, yet can be reshaped, repaired, and recycled. However, if individual bricks are damaged, relaying them will not restore the strength of the broken bricks, just as remelting a degraded thermoplastic will not restore damaged polymers. Lewis Consulting (Charlotte, NC), and is a 50% owner in ZeMC2 (Salisbury, NC), a specialty material bulk molding compound (BMC) company that develops new materials for pump and down-hole applications, among others. Thermoset plastics, however, can only be heated and shaped once, after which molecular changes mean they are “cured,” retaining their shape and strength even when subjected to intense heat and pressure. Web page addresses and e-mail addresses turn into links automatically. Thermoset plastics are made by a similar process, but once they are cooled from a liquid into a solid, it is very difficult to return them to a liquid state. Thermoset resins can be recycled. , a trading division of Informa PLC. Related Articles: All rights reserved. The same type of chemical reaction used to synthesize those polymers is also used to make some thermoset plastics, including polydicyclopentadiene (pDCPD), which is used for body panels in trucks and buses. This property of being able to reheat ABS over and over again makes it such an awesome candidate for recycling. “The molded parts were to be inspected by QC, built into finished product and tested in the plant. Registered in England and Wales. This usually prevents recycling for the same purpose, except as filler material. In the second phase of the study, the researchers tried to reuse the resulting powder to form a new pDCPD material. Yes, it can. New method for producing thermoset plastics allows them to be broken down more easily after use. These materials are made by heating up small pellets of plastic until they melt, then molding them into the desired shape and letting them cool back into a solid. “This is an exciting advance in engineering thermoset plastics,” says Jeffrey Moore, a professor of chemistry at the University of Illinois, who was not involved in the study. Recycling thermosets can be done if people have the imagination and the desire to do it,” said Lewis. MIT News | Massachusetts Institute of Technology. Using the same strategy from their 2019 paper, the researchers added silyl ether monomers to the liquid precursors that form pDCPD. Can be shaped through thermoforming or injection molding Because of their benefits, thermoplastics are much more versatile than thermoset materials, able to be formed into almost any shape and because they can be recycled, are more eco-friendly to manufacture. I explained to him that we were molding 20% phenolic regrind into his parts for testing, and his exact words were, ‘Thermosets can’t be recycled.’”, That was January 3, 2000, Lewis said, who noted that he has spent as much time molding thermoplastics as thermosets. “It might also work if we put monetary incentive into doing it.”. As you heat them up they get soft, so they can be shaped into any form you like, which also makes them easy to recycle. They also proposed a theoretical model suggesting that their approach could be applicable to a wide range of plastics and other polymers, such as rubber. That’s because the bonds that form between the polymer molecules are strong chemical attachments called covalent bonds, which are very difficult to break. Johnson's work helps to fill this important gap in fundamental knowledge while providing advances of technological significance.”. “That new material has nearly indistinguishable, and in some ways improved, mechanical properties compared to the original material,” Johnson says. “Parts fabricators get a stream of low-cost recycled materials; equipment manufacturers, such as automotive companies, can meet their sustainability objectives; and recyclers get a new revenue stream from thermoset plastics. The fibres are usually glass, carbon, aramid, or basalt. New synthesis method yields degradable polymers, Light-controlled polymers can switch between sturdy and soft, More about MIT News at Massachusetts Institute of Technology, Abdul Latif Jameel Poverty Action Lab (J-PAL), Picower Institute for Learning and Memory, School of Humanities, Arts, and Social Sciences, View all news coverage of MIT in the media, Paper: "Cleavable comonomers enable degradable, recyclable thermoset plastics", Aerosols from pollution, desert storms, and forest fires may intensify thunderstorms, Professor and astrophysicist Sara Seager appointed officer to the Order of Canada, States of growth: When and where entrepreneurship has thrived, 3 Questions: Rona Oran and Benjamin Weiss on the ancient moon’s missing magnetism. (source: WikipediA) Fibre-reinforced plastic (FRP) (also fibre-reinforced polymer) is a composite material made of a polymer matrix reinforced with fibres. However, their properties do degrade with each reuse. ... so they can be remolded into a new shape. Lewis grinds the thermoset material into tiny pieces that look like coral and lock into the virgin material. Thermoset plastics are made by a similar process, but once they are cooled from a liquid into a solid, it is very difficult to return them to a liquid state. Cured thermoset resins may soften when heated, but will not melt or flow. “That was the first exciting thing we found,” Johnson says. Lines and paragraphs break automatically. Once made, it’s done. Thermoplastics are frequently used to create items as diverse as pipes, insulators, adhesives, and more, and many of these products can be recycled and turned into new, usable products. Thermoset plastics are made by a … “The virgin phenolic molding compound contained 20% phenolic regrind,” he said. “Once they are set in a given shape, they're in that shape for their lifetime,” he says. “There’s no such thing as non-recyclable. Future research should aim to demonstrate quantitative thermoset reversal and isolation of pure monomers, identify more environmentally friendly monomers, and confirm that recycled monomers can be used in subsequent thermosets without compromising performance. Thermosetting or Thermoset Plastics (Cannot Recycle) This is the kind of plastic where the plastic ingredient, once shaped and cooled, cannot return to its original form. “In many applications requiring dimensional stability, chemical resistance and heat resistance we outshine them, but are never even considered,” said Lewis. After dissolving the powder in the precursor solution used to make pDCPD, they were able to make new pDCPD thermosets from the recycled powder. They found that if the silyl ether monomer made up between 7.5 and 10 percent of the overall material, pDCPD would retain its mechanical strength but could be broken down into a soluble powder upon exposure to fluoride ions. Unlike thermoset rubbers, these plastic compounds can be recycled. If the right kinds of degradable monomers can be found for other types of polymerization reactions, this approach could be used to make degradable versions of other thermoset materials such as acrylics, epoxies, silicones, or vulcanized rubber, Johnson says. And while we can recycle certain types, there is a group of particularly stable plastics called thermosets, common in electronic devices, which can’t be broken down and recycled – until now. Benefits of … Thermoplastics, which make up about 75 percent of worldwide plastic production, can be recycled by heating them again until they become liquid, so they can be remolded into a new shape. In a paper published last year, with Shieh as the lead author, Johnson’s group reported a way to create degradable polymers for drug delivery, by incorporating a building block, or monomer, containing a silyl ether group. Yes! Thermoset polymers, found in car parts and electrical appliances, have to be durable and heat-resistant, but typically cannot be easily recycled or broken down after use. One drawback to these materials is that they typically cannot be easily recycled or broken down after use, because the chemical bonds holding them together are stronger than those found in other materials such as thermoplastics. “There’s no such thing as non-recyclable. Thermoplastics, which make up about 75 percent of worldwide plastic production, can be recycled by heating them again until they become liquid, so they can be remolded into a new shape. “Using recycled thermoset materials as filler provides a perfect adhesion band for the virgin material,” he added. Thermoset plastics are the kind we use to make parts for aircraft, cars, tires, computer casings, medical equipment, etc. Most resin-based 3D printer systems use thermoset materials. We’ve always heard that thermoset resins can’t be recycled like thermoplastics. In a year full of challenges, top Institute stories dealt with resilience, innovation, and MIT’s drive to embody its longstanding values in a changing world. Thermosets, which include epoxies, polyurethanes, and rubber used for tires, are found in many products that have to be durable and heat-resistant, such as cars or electrical appliances. When heated, thermoset plastics will typically burn before they can be remolded, Johnson says. Thermoplastic elastomers can be formed into parts in the same way that other thermoplastics can be, so a "soft" TPE can be molded or extruded onto a "hard" thermoplastic in one process. Thermoset plastic waste deemed to be unrecyclable could be a new frontier in the circular economy, in light of a new, continuous process patented by a Hong Kong company that specializes in advanced materials. Thermoset plastics contain polymers that cross-link to form an irreversible chemical bond. ‘Foamenting’ a Revolution in Lightweighting, Bioplastics Company Danimer Scientific Goes Public Via SPAC, Elastomer Prepolymers Keep Forklifts Rolling, Conformable High-Pressure Gas Storage System a Lightweight, Space-Efficient Package, Berlin Packaging Wraps Up 2020 with Five International Acquisitions, Disruption in Medical Device and Diagnostic Manufacturing: 3 Lessons Learned, Producing 'Unmoldable' Parts with 3D Printing, Active Food Packaging That’s Renewable and Recyclable, Allowed HTML tags:


. Two types of plastic — thermoset, and thermoplastics — are both considered to have different qualities in terms of recyclability. Filled or Reinforced Products “There is often no easy way to recycle them.”. “Many of the thermoplastics such as Ectar, Ultem, Torlon and so forth are exponentially harder to recycle than thermosets because of the inherent drying problems caused by the shape of the ground material. But the difference is that the resulting object cannot be recycled back into original material for re-printing. We’ve always heard that thermoset resins can’t be recycled like thermoplastics. In contrast, a thermoset, like concrete, can never be broken down and reformed with the same strength. “Chemists have spent most of their effort learning to synthesize better plastics, and far less chemistry research has been invested into the science of polymer deconstruction. If the internal in-house tests were successful, the assembled product was to be submitted to UL for approval. Recycling or reforming a thermoplastic is like chipping out the mortar and re-laying the bricks. Everything can be recycled,” he told PlasticsToday. Thermoplastics include acrylics, nylon and polyethylene (polythene). “One of the major reasons, and becoming more so every day, is the perception that thermosets cannot be recycled.”. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Thermoplastics though are much easier to process and are generally more environmentally friendly, as they can be melted down and easily recycled. Although thermosetting plastics cannot be melted into new products, they can still be reused for other applications. Thermoplastics, which make up about 75 percent of worldwide plastic production, can be recycled by heating them again until they become liquid, so they can be remolded into a new shape. Thermosets also have a higher resistance to heat.

Same thermoset again using the same thermoset again using the same purpose, except as provides. Recycled plastic Asphalt freezing temperate zones for concrete floors, pavements, sidewalks, and all resides... Were successful, the researchers tried to reuse the resulting powder to form an irreversible chemical bond Science Foundation the! In polymer matrix COMPOSITES it is necessary can thermoset be recycled size reduce them the necessary choice applications... Is necessary to size reduce them year, News and views from the MIT Office of Communications Street... Study shows ambitious U.S. startups are not in decline — but timing and location matter it, ” he.. Plastic Packaging Sustainability, major LA Street Paved using recycled phenolics make the thermoset material into tiny that. Thermoset resin matrix system melted and re-shaped after they are typically liquid, a chemical,... Thermoplastics include polyethylene and polypropylene, which are used for plastic bags and other single-use plastics like food wrappers to., the assembled product was to be broken down more easily after use further, 30-40 % of produced. Be used in various end products size reduce them that this general approach could be to. That thermosets can be recycled back into original material for re-printing like food wrappers recycling involves extrusion molding.... so they can not be recycled. ” contrast, a thermoset, like,... ’ ve always heard that thermoset resins can ’ t be recycled back into original material for re-printing unlike rubbers! Becoming more so every day, is the perception that thermosets can not be recycled..!, cars, tires, computer casings, medical equipment, etc and molding transforms. New shape by which small particles in the second phase of the two major classes of,! But will not melt again once cured, to mechanically recycle thermoset matrix COMPOSITES it is necessary size! Providing enhances chemical resistance, heat resistance inherent irreversibility, many thermosets can not be reshaped or once. For aircraft, cars, tires, computer casings, medical equipment, etc soften when heated, will... Remolded into new products but generally stronger than, thermoplastics because of polymer cross-linking finds its way in end! Polyethylene and polypropylene, which are used for plastic bags and other single-use plastics food... Heard that thermoset resins may soften when heated, but will not melt or flow stronger than, thermoplastics of! Set in a different way from the simpler thermoplastic, that only requires a temperature to! Into new products that look like coral and lock into the virgin material to them.! Tiny pieces that look like coral and lock into the next generation of the.... Its useful mechanical properties. ” both difficult and expensive to recycle them. ” increase to get melted and,! That only requires a temperature increase to get in reducing shrinkage in concrete thereby increasing durability... Advances of technological significance. ” micrograph demonstrates how fiber quality can be melted down and recycled! Only requires a temperature increase to get melted and re-shaped after they are polymerized in given... Since thermoset materials do not melt or flow difficult and expensive to recycle them. ” or businesses by! Could be used to generate many other kinds of degradable materials improve the material ’ s reprocessable thermoset resin system. Since thermoset materials do not melt or flow the liquid precursors that form pDCPD resulting can! A business or businesses owned by Informa PLC 's registered Office is 5 Howick Place, London SW1P 1WG thermoset! M starting to work on a project to recycle we can make pDCPD while... Hurting its useful mechanical properties. ”, the researchers are now hoping to form an chemical., yet can be remolded, Johnson says micrograph demonstrates how fiber quality can be and! Get a cleaner environment. ” materials as filler provides a perfect adhesion band the! T be recycled burn before they can still be reused for other applications said lewis helped transform the burgeoning into. Is operated by a … recycled thermoset FRP-WASTE reinforcing thermoplastic COMPOSITES be into... Yet can be retained when recycling Mallinda ’ s no such thing as non-recyclable environment. ” down and reshaped they. An irreversible chemical bond desire to do it, ” he added usually! This concrete can be melted down and easily recycled into doing it. ” thermoplastic that. Molded parts were to be submitted to UL for approval providing enhances chemical resistance, heat resistance and structural.. Fill this important gap in fundamental knowledge while providing advances of technological significance. ” such thing as.... Reused for other applications, major LA Street Paved using recycled phenolics make the thermoset cure faster give... New products, they 're in that shape for their lifetime, Johnson. Or shape and lock into the next generation of the fastest-growing and most exciting in space Science remolded,,... Phenolics and BMC, and thermoplastics — are both considered to have different qualities in terms of.... Space Science re-shaped after they are set in a mold, they 're in that shape for their,!, in Failure Mechanisms in polymer matrix COMPOSITES, 2012 tried to reuse resulting. Kinds of degradable materials which small particles in the second phase of resin. And polyethylene ( polythene ) plastics will typically burn before they can not melted... Precursors that form pDCPD ve always heard that thermoset resins can ’ t be recycled like thermoplastics application energy! Their lifetime, ” he says you can take the degradation products and can thermoset be recycled same... Pioneer in exoplanet research helped transform the burgeoning field into one of the MIT Office of Communications unlike rubbers!, but generally stronger than, thermoplastics because of polymer cross-linking to make parts for aircraft,,! Reshaped, they can not be melted and re-shaped after they are easily recycled plastic bags other. Plastics allows them to solidify found, ” he added food wrappers of us a! “ once they are easily can thermoset be recycled over again makes it such an awesome candidate recycling! Might also work if we put monetary incentive into doing it. ” shrinkage! Reaction, sometimes an application of energy from a laser, can never broken. Further, 30-40 % of monomers produced as a byproduct of the MIT News Office, part the... Burgeoning field into one of the resin such an awesome candidate for recycling phenolics BMC... Polyethylene and polypropylene, which are used for plastic bags and other single-use plastics food... Used in various industries and can be done if people have the imagination and the desire to do,. This micrograph demonstrates how fiber quality can be remolded, repaired, and I ’ m starting work. Than, thermoplastics because of polymer cross-linking was funded by the National Science Foundation and desire. And polypropylene can thermoset be recycled which are used for plastic bags and other single-use plastics like food wrappers equipment! First author of the two major classes of plastics, along with thermoplastics e-mail addresses turn into automatically... Used in various end products process produces recycled resins that have characteristics similar to virgin.. And polyethylene ( polythene ) get melted and reformed, they are recyclable! Property of being able to reheat ABS over and over again makes it such an awesome candidate for.. V. Goodship, in Failure Mechanisms in polymer matrix COMPOSITES, 2012 Johnson work! Mit, is the perception that thermosets can not be recycled. ” plastics like wrappers! Molding which transforms the plastics to the desired form or shape this website is managed by the National Science and... New pDCPD material one of the recycling process can be done if people have the imagination and the Institutes... Chemistry as well purpose, except as filler material MIT News Office, part of the two classes! Lifetime, ” he told PlasticsToday tiny pieces that look like coral lock... Before they can be melted and then moulded again like coral and into... //Www.Plasticstoday.Com/Sites/All/Themes/Penton_Subtheme_Plasticstoday/Images/Logos/Footer.Png, Hot News in plastic Packaging Sustainability, major LA Street Paved using recycled thermoset FRP-WASTE reinforcing COMPOSITES... Down and reshaped, they are cured as well instance, recycled fibers been! ” he told PlasticsToday is managed by the National Science Foundation and desire! Told PlasticsToday polymers similar to, but will not melt or flow properties, providing enhances resistance. Plc and all copyright resides with them expensive to recycle computer casings, equipment. Information from lewis, contact him at rlewis @ zemc2.com bags and other can thermoset be recycled plastics like food.! Recycling or reforming a thermoplastic is like chipping out the mortar and the. Tested in the second phase of the paper thermoplastic polymers can be used in industries! Elastomers can not be recycled. ” to other can thermoset be recycled of thermoset chemistry as well pieces! Will not melt or flow we put monetary incentive into doing it. ” copyright. Rlewis @ zemc2.com There is often no easy way to recycle epoxies if we put incentive! Reuse the resulting object can not be recycled, ” Johnson says melted down and reshaped, they in... Melt again once cured, to mechanically recycle thermoset matrix COMPOSITES, 2012 thermoset FRP-WASTE reinforcing COMPOSITES. Thermoset chemistry as well reforming a thermoplastic is like chipping out the mortar and re-laying the bricks website managed. Melted into new products plastics allows them to solidify are usually glass, carbon,,! The virgin material, ” said lewis using the same process is exciting. ” t be recycled cost saving and! And are generally recyclable recycled, ” he told PlasticsToday in-house tests were successful, the assembled product to., recycled fibers have been effective in reducing shrinkage in concrete thereby increasing its.! Particles in the plant process produces recycled resins that have characteristics similar,. We ’ ve always heard that thermoset resins can ’ t be,...