Page 38 - Carrahers_Polymer_Chemistry,_Eighth_Edition

1 Introduction to Polymers

1.1 HISTORY OF POLYMERS
Since most materials are polymeric and most of the recent advances in science and technology
involve polymers, some have called this the polymer age. Actually, we have always lived in a poly-
mer age. The ancient Greeks classified all matter as animal, vegetable, and mineral. Minerals were

emphasized by the alchemists, but medieval artisans emphasized animal and vegetable matter. All
are largely polymeric and are important to life as we know it. Most chemists, biochemists, and
chemical engineers are now involved in some phase of polymer science or technology.
The word polymer is derived from the Greek poly and meros, meaning many and parts, respec-
tively. Some scientists prefer to use the word macromolecule, or large molecule, instead of poly-
mer. Others maintain that naturally occurring polymers, or biopolymers, and synthetic polymer
should be studied in different courses. Others name these large molecules simply “giant molecules.”
However, the same principles apply to all polymers. If one discounts the end uses, the differences

between all polymers, including plastics, fibers, and elastomers or rubbers, are determined primar-
ily by the intermolecular and intramolecular forces between the molecules and within the individual
molecule, respectively, and by the functional groups present, and most of all, by their size allowing
an accumulation of these forces.
In addition to being the basis of life itself, protein is used as a source of amino acids and energy.
The ancients degraded or depolymerized the protein in meat by aging and cooking, and they dena-
tured egg albumin by heating or adding vinegar to the eggs. Early humans learned how to process,
dye, and weave the natural proteinaceous fibers of wool and silk and the carbohydrate fi bers from

flax and cotton. Early South American civilizations, such as the Aztecs, used natural rubber (Hevea
brasiliensis) for making elastic articles and for waterproofi ng fabrics.

There has always been an abundance of natural fibers and elastomers but few plastics. Of course,
early humans employed a crude plastic art in tanning the protein in animal skins to make leather
and in heat-formed tortoise shells. They also used naturally occurring tars as caulking materials and
extracted shellac from the excrement of small coccid insects (Coccus lacca).
Until Wohler synthesized urea from inorganic compounds in 1828, there had been little progress
in organic chemistry since the alchemists emphasized the transmutation of base metals to gold and
believed in a vital force theory. Despite this essential breakthrough, little progress was made in
understanding organic compounds until the 1850s when Kekule developed the presently accepted
technique for writing structural formulas. However, polymer scientists displayed a talent for making
empirical discoveries before the science was developed.
Charles Goodyear grew up in poverty. He was a Connecticut Yankee born in 1800. He began
work in his father’s farm implement business. Later he moved to Philadelphia where he opened a
retail hardware store that soon went bankrupt. Charles then turned to being an inventor. As a child
he had noticed the magic material that formed a rubber bottle he had found. He visited the Roxbury
India Rubber Company to try and interest them in his efforts to improve the properties of rubber.
They assured him that there was no need to do so.
He started his experiments with a malodorous gum from South America in debtor’s prison. In a
small cottage on the grounds of the prison, he blended the gum, the raw rubber called hevea rubber

with anything he could find—ink, soup, castor oil, and so on. While rubber-based products were
available, they were either sticky or became sticky in the summer’s heat. He found that treatment

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