Polymers in Sport and Leisure

Polymers in Sport and Leisure
recently is a snow scooter which utilises a glass fibre
reinforced polyurethane hood manufactured by the
RIM process (32).
7 Water Sports
Developments in polymers have led to radical changes in
the design and construction of boats and other water sports
equipment. Probably the two most important contributions
have been in reduced cost and greatly improved strength
to weight ratio. The changes started with glass fibre hulls
and construction has developed to embrace a very wide
range of polymers including carbon and aramid fibre
reinforced materials and rigid foams. Boats account for a
major consumption of glass reinforced materials, which
are used in relatively very large vessels as well as small
pleasure boats and personal jet skis.
At the higher performance end, the advanced
composites give better fatigue resistance and this can
be improved further with sandwich constructions. The
better strength to weight ratio achievable results in
weight saving. An advanced racing boat design involves
carbon fibre reinforced epoxy skins and a polyvinyl
chloride foam core.
A strong sandwich construction is produced by having
a foam core between glass reinforced panels but a
departure from the use of fibre reinforcement is for
one or more of the skins to be made from a
thermoplastic. One design for a catamaran uses a
thermoformed skin, a cellular core and a glass fibre
reinforcing layer (351). The boats are rotomoulded
and produced much faster than by the more
conventional process.
Composites and sandwich constructions have not had
it all their own way in hull construction of smaller craft
and a multipurpose rowing/sailing/motor boat has been
moulded in polypropylene (110). It was reported that a
glass reinforced plastic pedal boat was not
commercially viable and was being replaced with
rotomoulded polyethylene (323).
Glass reinforced plastic canoes were extremely
successful and simple enough that people could build
them at home. For competition, improvements were
made by using carbon and aramid reinforcement such
as in Canadian canoes for the 1996 Olympics (321).
However, rotational moulding from high density
polyethylene is faster and more economic and takes
much of the market for recreational canoes. Kayaks
have been made from recycled high density
polyethylene by thermoforming and rotomoulding
(334) and also from thermoformed acrylonitrilebutadiene-styrene
which is said to produce a lighter
and stiffer craft than from other plastics (1).
Inflatable boats use elastomer-coated polyester or nylon
fabrics. The best rubber for the outer coating to give
long life is generally held to be Hypalon, with
polychloroprene being very satisfactory for the inner
layer, but polyurethane, butyl rubber and, at the lower
end of the market, polyvinyl chloride have also been
used. Some inflatables are composites in the sense that
parts of the hull are rigid, for example, made from glass
reinforced plastic.
Fabrics for sails are another important marine
application of polymers. It is surprising to be reminded
that cotton was replaced by nylon and polyester
something like 45 years ago and Kevlar was introduced
20 years ago. Polyester is considerably stiffer and
stronger than cotton, but for high-performance
applications Kevlar represents a 300% increase in
strength and 1000% increase in modulus.
The most recent materials are carbon fibre and
polybenzoxazole which have shown considerable
promise although there is still uncertainty about their
durability. The use of these newer materials is limited
by their high cost and the fact that their use has not
been sanctioned by some governing bodies.
Another material said to be showing potential (257) is
polyethylene naphthalate, which can be woven but also
heat shrunk to produce a fabric combining the durability
of a woven material with the performance of a laminate.
Apart from the main structural elements, both rubbers
and plastics find use in many marine components from
seats and decorative trim to oars and rowlocks. In boat
engines, glass reinforced nylon has been used in covers
and for the steering arm, and Viton fluoroelastomer
for shaft seals.
Surfboards are produced in the hundreds of thousands
annually from a polyurethane foam core covered with
glass reinforced polyester, the core blanks being carved
to shape before being laminated. A British company is
said to produce the best quality blanks using
methylenediphenyl isocyanate rather than toluene
diisocyanate (42). Alternative constructions are now
being introduced that have origins in windsurfing
technology and involve composite skins over expanded
polystyrene (62).
Elastomers also find outlet in swimming fins, caps and
masks. Thermoplastic elastomers are increasingly used,
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