If we identify various periods in history in terms of the most widely used materials - as archaeologists refer to the Bronze and Iron Ages - the 20th century could fairly be called the Plastic Age. Although plastics did not become pervasive until after World War II, they had become quite familiar many years earlier.
Plastics, materials made up of large, organic
(carbon-containing) molecules that can be formed into a variety of products.
The molecules that compose plastics are long carbon chains that give plastics
many of their useful properties. In general, materials that are made up of
long, chainlike molecules are called polymers. The word plastic is derived from
the words plasticus (Latin for “capable of molding”) and plastikos (Greek “to
mold,” or “fit for molding”). Plastics can be made hard as stone, strong as steel,
transparent as glass, light as wood, and elastic as rubber. Plastics are also
lightweight, waterproof, chemical resistant, and produced in almost any color.
More than 50 families of plastics have been produced, and new types are
currently under development.
Like metals, plastics come in a variety of grades. For
instance, nylons are plastics that are separated by different properties,
costs, and the manufacturing processes used to produce them. Also like metals,
some plastics can be alloyed, or blended, to combine the advantages possessed
by several different plastics. For example, some types of impact-resistant
(shatterproof) plastics and heat-resistant plastics are made by blending
different plastics together.
Plastics are moldable, synthetic (chemically-fabricated)
materials derived mostly from fossil fuels, such as oil, coal, or natural gas.
The raw forms of other materials, such as glass, metals, and clay, are also
moldable. The key difference between these materials and plastics is that
plastics consist of long molecules that give plastics many of their unique
properties, while glass, metals, and clay consist of short molecules. (Adapted
from ‘Science: A History of Discovery in the Twentieth Century’, and Encarta