| Apart from their use as moulding
materials, synthetic polymers have replaced
natural polymers in many traditional technologies. Adhesives
The heated glue-pot
which traditionally contained glues based on
animal products such as hoof, horn and fish
residues has been replaced by adhesives based on
synthetic polymers. There is now a wide range of
adhesives and sealants suited to a variety of
tasks from PVA wood, board and paper glues to two-part
epoxide resins for rivet-less bonding of metal
panels in aircraft.
Fibres
Animal
fibres, such as wool or silk, and vegetable
fibres, such as cotton, continue to be used
although there is a wealth of synthetic fibres
now available.
The first artificial silk was developed by
Chardonnet in 1884 by spinning cellulose nitrate
from solution. However, this was dangerously
inflammable and the first commercially successful
artificial fibre was developed by Stearn by
spinning regenerated cellulose from viscose. The
rights to this process were acquired by S.
Courtauld & Co. in 1904.
The Dreyfus brothers spun fibres from cellulose
acetate solution in the 1920s and this became the
Celanese Corporation.
The first fibre to be spun from a molten polymer
was nylon in the 1930s and since then a number of
polymers have been produced in fibre form -
including acrylic fibre based on
polyacrylonitrile (PAN) and polyester based on
polyethylene terephthalate (PET). Carbon fibres
for making advanced composites are produced by a
heat treatment of polyacrylonitrile and other
synthetic fibres.
Films
Animal
membranes were the only non-metallic film forming
materials used before the availability of rubber
and these found little application. The
successful development of a drum for casting
films from viscose led in the 1920s to the
production of 'Cellophane' - still a widely used
material.
In the 1930s, unsupported PVC films were
manufactured but it was not until polyethylene
was available in the 1940s that the production of
films for bagging materials became commonplace.
Surface
finishes
The
paint industry was traditionally based on
naturally occurring 'drying' oils such as linseed
but since the 1930s these have gradually been
replaced by synthetic polymers. Because of
toxicity problems from using paints based on
solvents, many more finishes are now water-based polymer emulsions.
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