Polypropylene
Polypropylene is
a highly crystalline thermoplastic polymer
produced by the chain growth polymerisation of
propylene, a gas obtained from petroleum cracking.
It has properties related to polyethylene but has
a much higher melting temperature and is much
stiffer. Polypropylene can be produced with
different molecular chain structures under
controlled conditions (stereo-specific) but only
the "isotactic" form is produced in
large quantities. Here the methyl side groups are
arranged on the same side of the polymer chain.
Isotactic polypropylene was discovered in 1954 by
the Italian chemist Guilio Natta and his
assistant Paulo Chini, working in conjunction
with the Italian company Montecatini. Catalysts
of the type invented by Karl Ziegler, the German
chemist, for the production of polyethylene at
ambient pressure were used. (See K. Ziegler, G. Natta.)
Commercial production of polypropylene began in
1957 with Hercules Incorporated, Montecatini and
Farbwerke Hoechst AG. ICI produced polypropylene
resin as Propathene in 1954. Natta and Ziegler
were awarded the Nobel Prize for Chemistry in
1963 in recognition of their work on "Ziegler-Natta"
catalysts.
Polypropylene is an important plastic and is used
in many different forms and applications through
a range of manufacturing processes. A large
proportion of polypropylene is used in fibres as
constituents of fabrics, upholstery and carpets.
Many industrial uses involve ropes, woven and non-woven
fabrics and reinforcements. Blow moulded
containers, such as bottles for foods, shampoos
and other liquids, form part of everyday
experience. A wide range of injection moulded
items exists in appliance housings, resistant
containers, car components, toys and furniture.
The remarkable fatigue resistance properties of
polypropylene has seen valuable applications in
long life hinge designs in packaging containers
and elsewhere.
Since the 1980s the production, consumption and
applications of this important polymer have
increased through the application of even more
efficient catalysts and property enhancements.
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