@Ann: I don't think it's correct to call this a thermoplastic resin -- at least, the authors don't seem to call it that in the Science article. It's crosslinked, which would make it a thermoset according to the conventional definition. The difference is that, in this material, the crosslinks can rearrange themselves by means of a reversible chemical reaction. In a typical thermoset, the crosslinks are irreversible (which is why normal thermosets have no melting point and can't be recycled).
I also don't think it's correct to say that it could be recycled by pyrolysis. Pyrolysis would mean thermally breaking down the polymer, which would probably render it unusable. (You might be thinking about composite recycling, where pyrolysis can be used to recover fibers by removing the polymer matrix). The authors mention hydrolysis or alcoholysis, which would mean chemically breaking down the crosslinks, while leaving the polymer chains intact.
The method the authors used to recycle the material was simpler -- they just ground up the material and re-molded it. It looks like the properties were not as good as the virgin material -- but they weren't that bad either, and the fact that they were able to do it at all is impressive.
This is a very interesting development in polymer science. I hope that everyone interested in this will follow the link to the Science article.
The idea of having crosslinks which can be turned on and off is a concept which is also used in self-healing and shape memory polymers. It will be interesting to see what uses people come up with for this.
Is this material being used yet? I'm very curious as to its use. Would its use be very specific? Or could it possibly have a wide range of uses? Sounds like it's much more flexible in its potential uses than materials it might replace.
I agree with Rob that the possibilities for a material of this sort are intriguing. I know this is still in the early development stage, but the project must be driven with an eye to possible applications of this kind of material and what sort of issues it might resolve. Any sense of where it might be used and what industries it might impact?
I agree with Beth. This material was probably created with a particular solution in mind. I think it's only in the electronics industry where technology is developed without a specific solution in mind. I wouldn't imagine a "solution looking for a problem" is common in materials.
@Rob: I don't think this was developed for a specific application -- this looks like basic research. (Looking at the ESPCI website which Ann links too, it would appear that basic research is their mission).
I can't emphasize enough that this is a major breakthrough in polymer chemistry. This group has developed an entirely new class of material -- a thermosetting resin with reversible crosslinks. The number of potential applications is enormous -- basically, any application where polymers are used (and probably some where they currently aren't, too).
Is it a "solution looking for a problem"? Not really; it's a solution to very fundamental problems with thermosetting and thermoplastic resins, which the authors express very clearly and succinctly in their introduction. Thermosetting resins don't flow when heated, which, among other things, means they can't be injection molded or extruded. As Ann points out, it also means they can't be recycled. On the other hand, thermoplastics don't have the dimensional stability, mechanical properties, or chemical resistanceof thermosets.
By making a thermoset which behaves like a thermoplastic at high temperatures, they have essentially solved both sets of problems. Not only that, but they have also enabled totally new manufacturing methods which couldn't even be imagined before.
It may be a few years before this class of material starts to make its way into applications. It doesn't seem like cost will be a barrier to adoption, but unfamiliarity will undoubtedly be -- this class of material fundamentally challenges what everybody thinks they know about how polymers behave. But this is a really incredible development which illustrates the value of basic research, and is certain to have a massive impact.
I would think the recyclability of it would be hampered by the fact that it would still be molded into a composite structure with fiber reinforcement. Just like painted PP/TPO is limited in recyclability, this would be too, but still it could still be molded into something useful. If it's based on currently available thermosetting resins, I would think the moldability would be comparable (i.e. low cost tooling, low pressure molding, long cycle times), so the economics would be comparable. If it functions like a thermoset during the design life cycle of the part, I thing the main benefit would be the "green" aspect of its recyclability at the end of its life cycle.
This is an interesting material. I agree that the processability of the new material should be significantly better than existing thermoset materials. The article is a little misleading in that it states that the material has glass like properties. True, the material will melt and flow like glass, but per the atricle, the materiala at room temperature is more like conventional rubber than glass.
Reading this article and others like it around the net, it looks like the folks at ESPCI ParisTech are not exaggerating when they describe their development as a "new class" of material. While it does appear to be the result of basic research, it was supported in part by the Arkema Group. I anticipate this material and its reaction chemistry will be part of a large patent portfolio. At its face, it reminds me of the fictional "Transparent Aluminum" appearing in Start Trek IV: The Voyage Home. But rather than being a metal with glass-like qualities, the fine folks at the Laboratoire "Matière Molle et Chimie" have developed a thermoset polymer with glass-like qualities. Both would be fantastically revolutionary.
I like the reference to Star Trek, William. A lot of those show, I think particularly Star Trek, focused on what technology might be available in the future. Star Trek really cam out of the tradition of science fiction -- as opposed to fantasy like Star Wars. One of the great aspects of the early science fiction was the emphasis on science.
Rob, the material has just been invented in R&D. And Dave is right, this is basic research sponsored by the French government, like the U.S. government used to sponsor. (The link is actually to a lab that is funded by CNRS and ESPCI.)
However, some applications are mentioned in a press release
They include aircraft, electronic circuits, and automobiles. So I suspect this was done with at least some applications in mind. I agree with Dave, I suspect because it's a new class of materials it will be a few years before we see it commercialized. Look how long it's taken for carbon fiber composites!
@Tim: The authors actually discuss two formulations in their article. One behaves like an elastomer at room temperature, the other behaves like a glass.
@williamlweaver: I laughed when you mentioned Star Trek IV, but your comment absolutely captures the potential impact of this development. By the way, while transparent aluminum as a construction material is still science fiction, a couple of years ago a group succeeded in making aluminum transparent for a tiny fraction of a second by using an extremely high powered laser to knock out all of the free electrons. And another group found that sodium can become transparent under very high pressures. It transforms from a metal into something called an "elemental ionic solid."
@William K.: Science magazine is actually published by the American Association for the Advancement of Science; it's not specifically for plastics industry professionals. In fact, plastics industry professionals probably comprise a very small portion of its readership (which is why coverage of this development in trade publications like Design News is so important). It is an academic journal which covers an incredibly wide range of topics. For some reason I have access to the full text at work.
A magazine which covers a similarly broad range of topics, but on a level accessible to the general reader, is Science News. Pretty much all of their content is available fre online.
I love the Star Trek references, also. Dave, thanks for the update on that transparent aluminum concept. And I'm with you about Science News--I've received it as a subscriber for several decades, and most of its content is accessible online without charge.
To answer your question, Dave, recycling usually refers to what happens to the material at the end of its useful life, rather than reusing it during its useful life, as in the (implicitly linear) mantra Reduce, Reuse, Recycle. Biodegradation is only one of several recycling possibilities. Others include converting waste to fuel. And pyrolysis is one of several waste-to-energy (WTE) methods for that conversion.
@Ann: You seem to be using the words "reuse" and "recycle" in a very unusual way. To me (and, I think, to most people) reusing a plastic bottle would mean washing it out and putting something else in it. Recycling a plastic bottle would mean grinding it up and remolding it into a new plastic bottle.
By your definition, if I take a plastic bottle, grind it up, and remold it into a new plastic bottle -- which is what most people, whether they are consumers or people in the plastics industry, would call "recycling" -- I'm reusing it, not recycling it. But if I burn it (waste to fuel), I'm recycling it.
I see your logic, but I don't think your usage agrees at all with the commonly accepted definition.
Your definition would also imply that anything which is flammable is recyclable, which would stretch the definition of "recyclable" considerably for plastics (and would also imply that most metals are not recyclable).
I think some of the confusion has to do with what is considered reuse, and whether we're discussing single-use or multi-use (a confusing term) plastics. Since multi-use is confusing, the SPI and other industry bodies usually use the term "durables". The definition of single use in a plastic, such as a plastic water bottle, is that you drink your water and then either throw it away, whence it goes to the landfill, or recycle it. But the Reduce, Reuse, Recycle mantra suggests we reuse a plastic bottle several times before recycling it. In any case, you don't recycle an item made of single-use plastic until the end of its life as that product, in this case a bottle.
An appliance or a phone is made of durable plastics. You don't throw away either one after using it once, hence the other term, multi-use. But at the end of its life as a phone or an appliance, it can then be recycled, and its material be used in another type of product.
Most of the discussions I've read distinguish between a thermoplastic and a thermoset depending on their behavior, not on their structure. Regarding pyrolysis, I've read a lot about its use in recycling for a variety of plastics, not just CFRP composites. And yes, I do understand that it breaks down the polymers. The other two methods you mention, alcoholysis and hydrolysis, make a lot more sense if they can keep polymer chains intact.
But I think you are merging two different categories. The authors talk about both reusing and recycling. The first is re-shaping the material, which they did indeed do by grinding it up and remolding it. Recycling is described separately as an end-of-life process.
@Ann: Fair enough -- this material challenges the generally accepted notions of thermoplastic and thermoset, so I suppose one term is as good (or as bad) as the other. However, the title "Thermoplastic resin has glass-like qualities" does not do justice to this material, since amorphous thermoplastics (i.e. thermoplastics with glass-like properties!) are extremely common. In fact, the title of this article would accurately describe most cheap commodity plastics such as polyethylene. It doesn't communicate what a profound development this is.
You're right that the authors distinguish between grinding up the material and remolding it, and chemically deactivating and reactivating the crosslinks. But I think the term "recycling" would be applicable to both -- after all, grinding up a polymer and remolding it is how most current plastics recycling is done.
I'd be interested to know what your reading has taught you about the use of pyrolysis in recycling polymers. From what I know, pyrolysis (thermal degradation in a non-oxidizing atmosphere) produces gas and char. I have a little experience with pyrolysis as a polymer analysis technique -- basically, identifying a polymer by the "fingerprint" of gases it gives off when it is pyrolyzed. I have hard that in some cases, the gas can be burned as fuel, and the char -- which is basically just carbon -- might have some potential uses as well. But neither of these is really recycling, at least in the sense in which most people use the term.
I wanted to read the article but I am unwilling to sign up for the association, or even to register. I am not a "plastics professional" and don't want to be treated like one. I was hoping to extend my education a bit, and be able to be better prepared for design decisions in the future. But I am not in the plastics industry.
So why not let others read about what sounds like a great advance?
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