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What Is Plastic?


Many of the containers you use are made from plastic.

Many of the containers you use are made from plastic.

saw2th, Creative Commons

Question: What Is Plastic?

Have you ever wondered about the chemical composition of plastic or what it is made of? Here's a look a what plastic is and how it is formed.

Answer: Plastic is any synthetic or semi-synthetic organic polymer. While plastics may be made from just about any organic polymer, most industrial plastic is made from petrochemicals. Thermoplastics and thermosetting polymers are the two types of plastic.

Thermosets and Thermoplastics

Thermosetting polymers, also known as thermosets, solidify into a permanent shape. They are amorphous and considered to have infinite molecular weight. Thermoplastics, on the other hand, can be heated and remolded over and over again. Some thermoplastics are amorphous, while some have a partially crystalline structure. Thermoplastics typically have a molecular weight between 20,000 to 500,000 amu.

Examples of Plastics

polyethylene terephthalate - PET or PETE
high-density polyethylene - HDPE
polyvinyl chloride - PVC
polypropylene - PP
polystyrene - PS
low-density polyethylene - LDPE


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