CHApter 2 An evolutionary perspective
20
Though the evolution of metals is interesting, the history of polymers is rather different. Wood, of course, is a polymeric composite,
one used for construction from the earliest times. The beauty of
amber (petrified resin) and of horn and tortoise shell (the polymer
keratin) attracted designers as early as 80 BC and remained attractive into the 19
th century. (In London there is still a Horners’ Guild,
the trade association of artisans who worked horn and shell.)
Rubber, brought to Europe in 1550, was already used in Mexico for
the Mayan ball game Pok-a-Tok. Rubber grew in importance in the
19
th century, partly because of the wide spectrum of properties
made possible by vulcanization—cross-linking with sulfur that
produced materials as elastic as latex and as rigid as ebonite.
The real polymer revolution, however, had its beginnings in the
early 20
th century with the development of Bakelite, a phenolic, in
1909 and synthetic butyl rubber in 1922. This was followed in
mid-century by a period of rapid development of polymer science.
Almost all the polymers we use so widely today were developed in
a 20-year span from 1940 to 1960, among them the bulk commodity polymers polypropylene (PP), used for food containers; polyethylene (PE), used for children’s toys; polyvinyl chloride (PVC),
used for pipes and fittings; and popyurethane (PU), used for foams
and car dashboards, the combined annual tonnage of which now
approaches that of steel. Designers seized on these attributes—
cheap and easily molded to complex shapes—to produce a spectrum of brightly colored, cheerfully ephemeral products. Design
with polymers has since matured; they are now as important as
metals in household products, automobiles, and, most recently, in
aerospace. The polymers of transport and aerospace are, however,
more complex than “pure” polymers because they do not have the
stiffness and strength these applications demand. They are polymermatrix composites, reinforced with fillers and fibers.
Composite technology is not new. Straw-reinforced mud brick is
one of the earliest of the materials of architecture and remains one
of the traditional materials for building in parts of Africa and Asia
even today. Steel-reinforced concrete—the material of shopping
centers, road bridges, and apartment blocks—appeared just before
1850. Reinforcing concrete with steel to enhance the tensile strength
where previously it had none was easy. Reinforcing metals, already
strong, took much longer, and even today metal matrix composites
are few. But polymers, with many attractive properties but lamentable stiffness, got scientists thinking. The technology for making
glass fibers had existed since 1880, when it was used to make “glass
wool” insulation. Glass wool, or better, woven or layered glass
20
Though the evolution of metals is interesting, the history of polymers is rather different. Wood, of course, is a polymeric composite,
one used for construction from the earliest times. The beauty of
amber (petrified resin) and of horn and tortoise shell (the polymer
keratin) attracted designers as early as 80 BC and remained attractive into the 19
th century. (In London there is still a Horners’ Guild,
the trade association of artisans who worked horn and shell.)
Rubber, brought to Europe in 1550, was already used in Mexico for
the Mayan ball game Pok-a-Tok. Rubber grew in importance in the
19
th century, partly because of the wide spectrum of properties
made possible by vulcanization—cross-linking with sulfur that
produced materials as elastic as latex and as rigid as ebonite.
The real polymer revolution, however, had its beginnings in the
early 20
th century with the development of Bakelite, a phenolic, in
1909 and synthetic butyl rubber in 1922. This was followed in
mid-century by a period of rapid development of polymer science.
Almost all the polymers we use so widely today were developed in
a 20-year span from 1940 to 1960, among them the bulk commodity polymers polypropylene (PP), used for food containers; polyethylene (PE), used for children’s toys; polyvinyl chloride (PVC),
used for pipes and fittings; and popyurethane (PU), used for foams
and car dashboards, the combined annual tonnage of which now
approaches that of steel. Designers seized on these attributes—
cheap and easily molded to complex shapes—to produce a spectrum of brightly colored, cheerfully ephemeral products. Design
with polymers has since matured; they are now as important as
metals in household products, automobiles, and, most recently, in
aerospace. The polymers of transport and aerospace are, however,
more complex than “pure” polymers because they do not have the
stiffness and strength these applications demand. They are polymermatrix composites, reinforced with fillers and fibers.
Composite technology is not new. Straw-reinforced mud brick is
one of the earliest of the materials of architecture and remains one
of the traditional materials for building in parts of Africa and Asia
even today. Steel-reinforced concrete—the material of shopping
centers, road bridges, and apartment blocks—appeared just before
1850. Reinforcing concrete with steel to enhance the tensile strength
where previously it had none was easy. Reinforcing metals, already
strong, took much longer, and even today metal matrix composites
are few. But polymers, with many attractive properties but lamentable stiffness, got scientists thinking. The technology for making
glass fibers had existed since 1880, when it was used to make “glass
wool” insulation. Glass wool, or better, woven or layered glass