this post was submitted on 20 Oct 2023
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Where do you get the idea we are made of plastics? Not necessarily throwing shade, just.. I'm a molecular biologist and at first pass that seems like a stretch. I'd be excited to be wrong
Thermosets and thermoplastics, right? Not sure that we have that going on in there...
Cellulose, starch, and chitin are all sugar polymers in plants and crustaceans (may be a broader group, I used chitosan from crustaceans though).
In mammals, collagen is a polymer. It's like 30% of a humans non-water weight. Bones are composites that are tough collagen binding hard and strong fibers of apatite (mostly calcium apatite/ hydroxyapatite). I don't think the apatite system is considered a polymer, though.
Triglycerides aren't polymers in adipose tissue. Although plant triglycerides can split and polymerize. Which make beautiful wood stains.
Yeah but like... not all polymers are plastics, right? Like... they aren't synonyms?
Wikipedia says acrylics, polyesters, silicones, polyurethanes, thermoplastics, and thermosets are plastics. Do those exist in organic tissue? Am I missing an obvious group?
All plastics are polymers, but I really don't think it's a commonly held view that all polymers are plastics
Ah ok. That's probably true. I was under the impression that a polymer that is solid at room temperature is a plastic.
Plastic as a term only makes sense to not include biological polymers if we define it to only be man-made polymers. It's arbitrary semantics, so I find it's better to be inclusive to help show the chemical quirks than to be exclusive on arbitrary lines.
It's fine if you want to draw some conceptual comparisons between biological and synthetic polymers, but it's 100% not true that "plastics" as defined as synthetic, organic polymers (I.e. acrylics, silicones, polyesters, polyurethanes, halogenated plastics, thermosets, thermoplastics et al.) are the same on a chemical basis as most biological polymers.
Like... where are you drawing the line? Are proteins a plastic? Is starch plastic? Is DNA plastic? RNA? Clearly not, by multiple definitions (bioavailability, reactivity, structure and function, persistence in the environment, etc.). Even biological compounds closer to synthetic polymers (cellulose, chitin, etc.) are definitively different, even if they do have longer persistence, lower reactivity, etc. And bioplastics (like what people mean when they say biodegradable plastics) are heat-modified biological polymers. They don't come out of a living thing that way; they are fundamentally altered from their previous form.
I guess I just... disagree that the distinction is "arbitrary semantics"?
All of these types of plastic you're using as counterexamples are more distinct from each other than they are from biological polymers.
Plastics are a ridiculously diverse group of chemicals, not including naturally occurring polymers is anthropocentric and not always useful.
What, in your opinion, is the semantic difference between the words plastic and polymer?
What is your word of choice to distinguish between naturally occurring and lab-made polymers?
It depends on the context. Sometimes plastic is good for that, but in this case I don't believe that it is.
Plastic is not a rigorous term. When discussing specific plastics it's petty much always better to describe specifics, because plastics are too diverse of chemistry to do anything else.