Natural polymers (from the Greek poly meaning “many” and meros meaning “parts”) are found in many forms such
as horns of animals, tortoise shell, shellac (from the lac beetle), rosin (from pine trees), asphalt, and tar from
distillation of organic materials. One of the most useful of the natural polymers was rubber, obtained from the sap
of the hevea tree. (Rubber was named by the chemist Joseph Priestley who found that a piece of solidified latex
gum was good for rubbing out pencil marks on paper. In Great Britain, erasers are still called “rubbers”.) Natural
rubber had only limited use as it became brittle in the cold and melted when warmed. In 1839, Charles Goodyear
discovered, through a lucky accident, that by heating the latex with sulfur, the properties were changed making the
rubber more flexible and temperature stable. That process became known as vulcanization.