SIC 2821 applies to PLASTIC MATERIALS AND RESINS.

The plastic materials and resins industry is comprised of companies primarily engaged in manufacturing various resins and plastics for sale to other industries that create plastic sheets, rods, films, and other products.

The plastics industry comprises about 70 percent of the entire synthetic materials industry, which also encompasses rubber and manmade fibers. Manufacturers produce about 500 different types of resins and compounds.

Duralumin is an aluminum alloy. Composite materials are made of plastic resins and reinforcing fibers (e.g. fiberglass, carbon fiber), not metals.

Plastic resins are composed of hydrocarbons. Two common components are polyethylene and polyvinyl chloride. These are produced during the "cracking" process.