Page 339 - Carrahers_Polymer_Chemistry,_Eighth_Edition

302 Carraher’s Polymer Chemistry

OH
O H
HO O O H
H
H H HO
H H H O R (9.32)
R H OH H O
Agarose

Glycoproteins contain both saccharide and protein moieties with the protein being the major
component, but both portions are involved in the overall biological activities.

9.9 SYNTHETIC RUBBERS

Natural rubber (NR) has been known for more than one thousand years. The Aztecs played a game
using a “rubber” ball. NR was used by the Mayan civilization in Central and South America before

the twentieth century. In addition to using the latex from the ule tree for waterproofing of cloth-
ing, they played a game called “tlachtli” with large hevea rubber balls. The object of the game was
to insert the ball into a tight-fitting stone hole in a vertical wall using only the shoulder or thigh.

The game ended once a goal was scored, and the members of the losing team could be sacrifi ced
to the gods.
Columbus, on his second voyage to America is reported to have seen the Indians of Haiti using
rubber balls. By the eighteenth century Europeans and Americans used NR to “rub out” marks
made by lead pencils. The “rubbing out” use led to the name “rubber.” Because of the association
of NR with the American Indian, it was also called “Indian rubber.”
Early progress toward its use in Europe is attributed to Charles Macintosh and Thomas Hancock.
NR was dissolved in relatively expensive solvents such as turpentine and camphene. The earliest
applications were made by pouring these solutions containing the NR onto objects to be “rubber-
ized.” Later, other less-expensive solvents were discovered, including the use of coal-tar naphtha.
Macintosh poured naphtha solutions containing the NR onto layers of cloth producing “water-
proof” material, which was the origin of the Macintosh raincoat, misspelled by the English as
“Mackintoshes.” The layering of the NR not only produced a material that was waterproof, but also
got around the problem that NR was sticky, becoming more sticky on hot days. NR also had an
unpleasant odor that was somewhat captured and prevented from smelling up the place by place-
ment between the pieces of cloth. Hancock, an associate of Macintosh, worked to develop other
useful rubbers from NR. One of his fi rst was rubber thread derived from cutting strips of NR and
applied to cloths and footwear. He had lots of scrapes and found that by heating the scrapes he could
reform sheets of the NR from which he could cut more strips. He also developed a crude mixing
machine that allowed him to mix other materials, additives, into the rubber.
The development of rubber technology then shifted to North America in the early to mid-1800s.
Mills were developed that allowed additives to be added to rubber and allowed rubber to be formed
into sheets and small particles. Uses for NR were largely waterproof cloth items in Britain and
waterproof boots in the United States.
But, the problem of stickiness remained until an accidental discovery by Charles Goodyear in
1839. As a young man Goodyear started a lifelong affair with NR to “tame it” for use. He recorded
thousands of experiments with NR mixing materials of the day with it and observing what happened.

When working with sulfur some of his rubber got mixed with sulfur and fire with the resulting mix-
ture no longer sticky. After some effort, he worked with mixtures of NR, sulfur, and lead producing

a “fireproof” gum that was later called “vulcanized rubber” after the god of fire Vulcan. About this
same time, Hancock found a piece of Goodyear’s vulcanized rubber and applied for a patent citing as
the important ingredients heat, sulfur, and NR. Goodyear’s combination included lead that allowed
vulcanization to occur at lower temperatures. Goodyear applied for a British patent on January 30,

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