High-Density Polyethylene

High-Density Polyethylene (HDPE)
When you watch television, use a computer, ride on a bus, train, or plane, you are using plastics. When you go to the doctor’s office or hospital or shop at the grocery store, you again are relying on plastics.

So where do plastics come from … and just what are they?

Plastics are derived from materials found in nature, such as natural gas, oil, coal, minerals, and plants. Nature made the very first plastics—did you know that rubber from a rubber tree is a plastic?

Interest in making plastics arose in the 1800s to replace rare materials such as ivory and tortoiseshell. The first synthetic plastics were derived from cellulose, a substance found in plants and trees. Cellulose was heated with chemicals and resulted in a new substance that was extremely durable.

The raw materials for today’s plastics come from many places (some even use salt!), but most plastics can be made from the hydrocarbons that are readily available in natural gas, oil, and coal.

What are Plastics: the Chemistry
The chemistry of plastics can be difficult, but the basics are straightforward. Think back to your high school science lessons about atoms and molecules (groups of atoms). Synthetics are merely chains of identical molecules joined together. These chains are called polymers. This is why many synthetics begin with “poly,” such as polyethylene, polystyrene, and polypropylene. Polymers often are made of carbon and hydrogen and sometimes oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorous, or silicon.

The term “plastics” or "synthetics" encompass all these various polymers.

Although there are many polymers, plastics, in general, are lightweight with significant degrees of strength. Synthetics can be molded, extruded, cast and blown into seemingly limitless shapes and films or foams or even drawn into fibers for textiles. Many types of coatings, sealants, and glues are plastics, too.