What is the process of oil being turned into plastic?
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Oil is made up of molecules called hydrocarbons (they contain only carbon and hydrogen atoms).
Longer molecules can be broken down by a process called “cracking” which creates small molecules, some of which have a smaller hydrogen to carbon ratio (they contain what’s called a carbon-carbon double bond).
Certain molecules (called initiators) can break one of the two bonds in this double bond. They can do this in a variety of ways, one common method is that they have an unpaired electron (they usually hang around in pairs) and these are called “free radicals” and very reactive. When the free radical sees a double bond, it grabs one of the electrons, creating a bond and moving the free radical to the end of the molecule: I* + C=C -> I-C-C*, where the * is the free radical, – is a single bond and = is a double bond).
Because we still have a free radical, the new molecule can react with another double bond, and then another, and another – making a molecule that’s millions of units long: a polymer,
Most of our plastics are these types of polymer (polythene, PVC, polystyrene/styrofoam, rubber, Teflon etc.)
What we think of as “oil” is actually a slurry of different chemical compounds that vary depending on the unique circumstances that created the oil deep under ground. Once we’ve extracted the oil, we separate the useful parts that we can burn for fuel and we’re left with the heavy “waste” leftovers. In the early days, we just threw this stuff out but eventually someone figured out that the waste had some useful compounds that could be heated and molded into shape: **the first plastics**
From there, we rapidly learned that adding some stuff or reacting those compounds in a particular way made new unique and useful plastics that could be modified for seemingly any purpose!
Petroleum (“oil”) is made up of lots of different kinds of molecules, all of which are hydrocarbons: made of hydrogen and carbon atoms. The thing about carbon is that there are *lots* of ways carbon atoms can connect together and with other elements (other kinds of atoms). To make “plastic” out of “oil”, we chemically break up the petroleum hydrocarbon molecules, sort out the resulting molecules (when you break a molecule into two or more parts, all the parts are still molecules if they have more than one atom) using some real “gee wizz” industrial chemistry, and if you do it right they reassemble themselves into very very long repeating chains of the sorted parts all by themselves. The original oil was a chaotic mess of all different parts, but by sorting those parts, some of them have this cool ability to form plastic polymers when it’s just those parts without anything else to make things messy.
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