I really want to discuss plastic recycling systems in the U.S. and the issues that exist with them, but before I do that, I must first describe the process by which plastics are produced. I was going to put this all in one post, but like I said in my intro, I get really wordy really fast, and it was going to be an actual full essay just on this one topic. So here is part one: a brief summary of how plastics are produced. It’s time to get science-y.
The American Chemistry Council gives a very detailed description of the chemical makeup of common plastics and how they are produced. Here’s a link for all my chemistry nerds out there, whaddup. https://plastics.americanchemistry.com/How-Plastics-Are-Made/ Plastics of all kinds are generally made using the same key ingredients: oil, natural gas, or coal (really every gross substance that we really shouldn’t be so dependent on anymore, but I digress).
Chemicals from these substances are joined into long chains of molecules called polymers. These polymers, in the case of plastics production, are also called thermoplastics, and appear similar to “long chains of atoms, like pearls on a string of pearls” (https://plastics.americanchemistry.com/How-Plastics-Are-Made/). Different combinations of chemicals and polymers can produce different plastic resins with different properties and characteristics (such as flexibility, temperature resistance, rigidity, tensile strength, and so on).
Different kinds of plastic and the different molecular structures they take.
On top of this, additives are usually used during the final stages of plastic production to improve certain “basic mechanical, physical, or chemical properties” (https://plastics.americanchemistry.com/How-Plastics-Are-Made/). They’re also used to protect the plastic polymers from damage by light, heat, or bacteria (hint, this is part of the reason why plastics don’t decompose on their own). Additives also have the ability to affect color, surface appearance, reduced friction, and flame retardancy.
There are several different methods for converting polymers into finished products. These include extrusion, calendering, film blowing, injection molding, blow molding, expanded bead blowing, rotational molding, compression molding, casting, and thermoforming. For a quick look at how one brand of plastic bags is made from our polymerized starting materials, check out this video here.
So now that we’ve gotten a brief glimpse into how plastics are made, let’s look at the process by which we recycle them.
Sources:
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Cho, R. (2012, January 31). What Happens to All That Plastic? Retrieved April 21, 2017, from http://blogs.ei.columbia.edu/2012/01/31/what-happens-to-all-that-plastic/
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Plastics. (n.d.). Retrieved April 21, 2017, from https://plastics.americanchemistry.com/How-Plastics-Are-Made/
Plastic or More Plastic? 