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Archery
Down
the centuries, archers were important in hunting and in war. The old bows
were made of special woods such as yew, and arrows were tipped with sharpened
bone. Modern archery employs many synthetic materials. Bows are of thermosetting
polyester or epoxy resin,
reinforced with glass or carbon
fibres respectively. Arrows are of drawn aluminium or carbon-fibre
reinforced resin, while the tips are of stainless steel and the "feathers",
if not natural, are of a polymer such as polypropylene
or nylon. The strings are of
a non-stretch polyester,
nylon or polyaramid
fibre.
Climbing
In
climbing, grip is all-important. Modern climbing boots have soles made
of a synthetic butyl rubber
to give excellent grip on mountain or rock, as well as being very flexible.
The uppers may be of natural leather
or canvas, or of nylon. Helmets
may be of glass-reinforced polyester
for strength and rigidity, or be moulded in one of the thermoplastic
polymers such as polypropylene,
built on to a suitable cradle structure. Outer clothing is made waterproof
but breathable by the use of PTFE
membrane (e.g. "Gore-Tex"), whilst underwear is of polyester
fibre treated with a wetting agent to allow perspiration to be transmitted
out through the fabric. Ropes, lines and webbing employ tough synthetic
fibres such as polyester
and nylon.
Cycling
Safety,
comfort and visual appeal are all satisfied by modern cycling gear. The
lightest cycles are of magnesium alloy or a composite of polyaramid
or carbon fibres in epoxy
resin. Components may be moulded in shock-absorbing nylon
or the elastomeric polyether-block-amide,
and these materials are also used along with polyurethanes
for making light, flexible and strong cycling shoes. Tyres of rubber cover
inner tubes of specially-formulated butyl
rubber. The seat cover is of polyurethane and the paint used for the
frame is applied as an electrically-charged powder coating. The cyclist's
helmet can be moulded in polycarbonate,
polyester or ABS,
and the clothing may have a membrane coating in PTFE
to make it waterproof but "breathable".
Fishing
To
make sure that the catch doesn't get away, the angler needs strong lines
made of synthetic fibres. Nylon
monofilament is the dominant material, although braided lines of other
polymers are used, such as polyester
which, being heavier than nylon, is more suitable for sinking lines. Fishing
rods, originally made of wood, are now commonly based on glass-fibre or
carbon-fibre reinforced
polyester or epoxy materials.
Other articles such as floats are often made from plastics such as polypropylene,
with nylon and polyester finding further use in nets and webbing.
Horseriding
At
first sight horseriding, with its traditional image, may seem far removed
from the world of chemicals. But the leather
in the saddle and boots is made by the chemical process of tanning. Special
soaps and cleaners for the leather contain added glycerine.
Some long boots are moulded in PVC,
others in neoprene. PVC is
also used extensively for poles and fences. Coats, blankets and tack such
as straps, may be in acrylic,
polyester or nylon
fibre. A horse's visor needs to be tough and transparent so is made of
polycarbonate. Specialist
veterinary medicines, the result of research by the chemical and pharmaceutical
industries, are essential along with products of more general use such
as antibiotics, antiseptics
and disinfectants.
Photography
Chemistry
and chemicals are at the heart of photography. Film-based photography
relies on the light-sensitive properties of silver halides.
These are suspended in a thin layer of gelatin
emulsion, supported on transparent cellulose
acetate or polyester. Exposure
to light, followed by processing with a developer which is a weak alkaline
solution, converts the silver halide into a metallic form of silver, creating
the "negative". This is "fixed" using a solution of
thiosulphate, which stabilises
the metallic silver and removes residual silver halide. For printing,
the negative is placed on sensitised paper and exposing it to light so
that the silver salts in the paper are affected in the same way as in
the original film, but producing an opposite, positive, image. In video
cameras, images are recorded on magnetic tape, while in digital cameras,
the visual information is captured in binary number form, for converting
into images by means of specially devised computer programs. Chemistry
is still required for these "dry" processes, for example to
make the charge-coupled devices that capture the image, and to produce
inkjet prints.
Sailing
and Windsurfing
Modern
materials provide safe and stylish sailing and surfing. The hulls of most
yachts and dinghies are built in "fibreglass",
a glass-reinforced thermosetting
polyester, to provide rigidity and resistance to the elements. Smaller
dinghies may be moulded in polypropylene,
while surfboards use a rigid polyurethane
or polystyrene foam together
with a rigidifying structure which may be glass-reinforced resin or moulded
nylon. Anti-fouling paints
for sea-going yachts are formulated with maximum attention to their possible
impact on marine wildlife. Sails are made of polyester
or polyaramid for resistance
to wear, high tensile strength and waterproofing. Sailing masts and booms
are of extruded aluminium,
polyaramid or carbon-fibre
reinforced polymers.
Skateboarding
and Rollerblading
The
huge popularity that skateboarding and rollerblading now enjoy owes much
to the performance and style made possible by modern materials. The board,
or deck, of a skateboard is usually made either of glass-reinforced polyester
("Fibreglass")
or of up to seven layers of wood (the best being maple) laminated together
with PVA adhesive. The wheels are
of moulded polyurethane,
which is excellent for abrasion resistance while giving good grip for
control, and high resiliency and rebound to facilitate speed and enhance
the ride. Dyes can be included
to give attractive colours to the transparent wheels although too much
can affect the performance of the urethane.
Roller skates with in-line wheels had been tried many years ago but were
re-invented in modern materials in 1979, by Scott Olsen in the USA, and
given the name rollerblades. The wheels are again of polyurethane.
The frames are of glass-reinforced nylon
or, in the top-performance products, of titanium
alloy. Skateboard parks now exist in many towns and use a variety of plastics
in their construction - with pigments
included to give bright colours - and often also use rubberised materials
for flooring. Safety equipment for skateboarding and rollerblading includes
helmets which have a foam inner such as expanded polystyrene
and a hard shell such as polycarbonate.
Skiing
Few
activities make such demands on equipment as skiing, where materials,
as well as being lightweight, need the strength to stand up to severe
mechanical forces whilst remaining sufficiently flexible in cold weather
to perform as required. The skis themselves are built up in layers. The
core is of a polyurethane
foam formulated to give rigidity and lightness. This is encased in a shell
which may be of polyaramid
to augment rigidity and dynamic response. The underside of the ski has
to be smooth but resistant to abrasion - a combination which high-density
polyethylene can provide.
An upper coating such as ABS or
polypropylene completes
the surface finish and gives resistance to cold and water. Ski sticks
use carbon fibres with epoxy
resin for lightness and strength. Ski boots may be moulded in polyurethane
or polypropylene for strength, resistance to cold and impact, and impermeability,
while their linings use a flexible form of polyurethane foam. Goggles
have lenses in polycarbonate
for clarity and toughness.
Sunbathing
Soaking
up the sun is a favourite holiday or leisure pastime. The
swimming costumes or bikinis usually worn during sunbathing are of polyester
or
nylon, perhaps incorporating PTFE
to repel water, while the reclining
chairs used are of PVC, coloured
with pigments and including
stabilisers to
prevent discolouration by ultraviolet light from the sun's rays. But uv
light can
also harm the skin, especially pale skin. It can cause dermatitis or,
more seriously, a type of skin cancer called melanoma. As well as avoiding
undue exposure to strong sun, people apply sunscreens - with factor numbers
indicating how many times longer you should be able to stay in the sun
without burning, compared with not using the screen. Opaque sunscreens
contain inorganic oxides such as titanium dioxide, to reflect the sun's
rays. Organic compounds used as sunscreens contain large molecules such
as benzophenone-3 that are strong absorbers of uv light. Antioxidants
are
also included in some sunscreens, to act as "scavengers" for
free radicals,
with the intention of minimising cancer risk. See also www.sunscreens.net
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