The word "plastic" was originally an adjective describing a material that could flow. Its first use as a noun came with the introduction of Bakelite and Celluloid in the early 1900s. The word is now used to mean a substance which can be pressed into definite shape and retains its shape when the pressure is removed.

Plastics are long-chain molecules known as polymers. The starting materials are called monomers.Proteins, starches, and resins such as frankincense and myrrh are natural polymers. Synthetic polymers are used in fibers and in molded and extruded solids which are commonly called plastics or resins.Hermann Staudinger, who was awarded the Nobel Prize in chemistry in 1953, introduced the term macromolecule in the 1920s. One of his first compounds was polystyrene, with a molecular weight of approximately 600,000, formed by a chain of 5,700 styrene units.

In terms of the chemistry involved, the two main types...