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.
@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).
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.
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.
@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.
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!
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.
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.
@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.
Although plastics make up only about 11% of all US municipal solid waste, many are actually more energy-dense than coal. Converting these non-recycled plastics into energy with existing technologies could reduce US coal consumption, as well as boost domestic energy reserves, says a new study.
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