Plastic is essentially any material that can be heated and molded so that it retains the molded shape after it cools. (Animal horn and amber are examples of natural plastics.) The first man-made plastic, called Parkesine, was introduced by its inventor, Alexander Parkes, at the Great Exposition of 1862 in London. Already renowned for his work with rubber, Parkes’ new discovery was part of a scientific movement to find uses for “coal tar,” a byproduct of natural gas production.

Modern Plastics
Today, a wide variety of plastic polymers, also called resins, are derived from natural gas, crude oil or other naturally occurring building blocks. Each polymer is a chain of carbon-based molecules called monomers bonded together through a chemical reaction. What these molecules are made of, their structure and the strength of the bonds between them will affect the plastic’s physical properties. For example, some plastics are flexible while others are rigid; some can be made into crystal-clear items, others into lightweight foam products.

From production through use to waste management, plastics help conserve resources. Their unique properties and characteristics – light weight, durability, formability, enable manufacturers to minimize the raw materials used, energy consumed and waste generated in the production of goods ranging from automobiles to coffee cups. It’s important to think about all those steps in a product’s life cycle, not just what happens when a product’s useful life is over, to get a true picture of its environmental performance.

http://inventors.about.com/od/pstartinventions/a/plastics.htm