What Is Plastic?

I always used to think of plastic as a singular material, a transparent cup, for example, or a clear, lightweight bottle. Still, when I hear the word “plastic,” I think of these images rather than picturing the myriad forms that constitute what plastic really is.

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Styrofoam is plastic. Telephones are plastic. Computer keyboards and insulation, shatterproof glass and garden hoses—they’re also plastic. I read a passage from the Encyclopedia Americana that really surprised me. It said that, in every car, there is more than 100 pounds of plastic (Rosen 216). It’s in the dashboard, the taillights, it encases the battery. Without it, cars would be a lot heavier and a lot more expensive to run.

My challenge to get rid of plastic is really futile, as so much of our modern society is literally built and transported on the back of plastic, but how did it get here?

What is it really?

In a word, plastic is a “polymer,” otherwise known as a long chain of molecules that repeat and repeat, sometimes a million or more times. You might think of a polymer as a necklace with a string of identical beads, stretching far out of sight. That necklace, with the beads all in a line, would be akin to a linear polymer. There are many polymers, such as silk or rubber or even the hair on our heads, that occur naturally on our planet, and then there are the polymers that industry has created, synthetic polymers, and those are the building blocks of plastic.

Polymers each have their own unique structure. If you’ve ever noticed the numbers on the bottom of recyclable plastic containers, the ones with a triangle and a #1-7 on it, you are actually looking at the type of polymer that makes up the material you are holding.

For example, the recyclable plastic with the symbol #1 on it is the polymer called polyethylene terephthalate, otherwise known as PET. Here’s a chart from the Encyclopedia Britannica showing the main recyclable plastics (starting with number 1 and going through number six, though it’s a little hard to read) with their respective polymer type listed. You’ll notice that most of these plastics (the ones that can be recycled) consist of a polymer made with ethylene.

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In a future post, I plan to delve a little deeper into each of these different types of recyclable plastic to find out which is the most environmentally friendly. But for now, back to the actual making of plastic…

So, polymers are the basic components of plastic, and to make these various synthetic polymers, we need petroleum. Almost every plastic in existence is a byproduct of crude oil.

The process starts with oil refining. Petroleum is super-heated in a conductor until the various gases in the petroleum start to separate into layers. Those that are lighter float to the top and are collected for plastic production. These lighter gases, which consist of carbon molecules, also known as monomers, are then chemically manipulated to link up and form different kinds of polymers.

The following photo, also from the Encyclopedia Britannica, shows how ethylene gas is processed to create a dry polymer:

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Once we have these polymers, sometimes in the form of a pellet, powder, or flake, we are able to melt or shape them to become the various kinds of plastic we use and recognize. But before they are molded into a finished product, polymers are almost always mixed with other materials. Additives make plastic more flexible, or more fire resistant, or even longer lasting.

After the various additives have been combined with the base polymers, then the plastic is finally shaped: it’s blown into bottles or flattened into sheets, it’s even puffed up into foam, hence, Styrofoam.

This is the process in a nutshell.

What really stayed with me after learning the step-by-step process of plastic manufacturing was thinking about those additives. Often, the additives in plastic are the reason plastic is so hard to destroy. Certain flame retardants or other “stabilizers,” for example, work to do exactly what, in the long term, becomes plastic’s major problem: they try to keep plastics from breaking down naturally. They intentionally try to make plastic live forever.

Plastic already resists environmental degradation. Polymers are unique in their inherent strength. But we don’t manufacture plastic that could be more susceptible to breaking down. Here’s a passage from the Encyclopedia Americana illuminating plastic’s resilience and why we actually like it that way:

“Plastics present a potential environmental problem because…plastics are not normally degraded by environmental processes…It is possible to build certain linkages into the chains of most common plastics and to make these linkages break on exposure to sunlight. The material then degrades to a powder that becomes part of the soil or is more readily broken down by microbes. So far the problems with this approach have been the cost and keeping plastics from degrading on supermarket shelves” (Rosen 218).

If we started to reduce additives that extend the life of plastics, or if we developed plastic that was purposefully subject to environmental decay, then plastic would start to lose some of its inherent appeal—it would leak or disintegrate. Our car might fall apart.

It’s an interesting conundrum that we’ve become so dependent on a material that we intentionally manipulate so that it lasts for a lifetime, but then don’t think about what that means for the health of our planet after our finite time here expires.

At the time that this Encyclopedia Americana article was published, the United States alone produced about 23 billion pounds of plastic on an annual basis (Rosen 216). This from a volume published in 2006. I can only imagine how, in ten years’ time, that figure has grown.


“Industrial Polymers.” The New Encyclopaedia Britannica: Macropaedia. 15th ed. Vol. 21. N.p.: Encyclopaedia Britannica, 2007. Print.

Rosen, Stephen L. “Plastic.” Encyclopedia Americana. International ed. Vol. 22. Danbury, CT: Scholastic Library Pub., 2006. 216-19. Print.

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