Polyacrylonitrile
Polyacrylonitrileis used for very few products an average consumer would be
familiar with, except to make another polymer,
carbon fiber. Homopolymers of
polyacrylonitrile have been uses as fibers in hot gas filtration systems,
outdoor awnings, sails for yachts, and even fiber reinforced concrete. But
mostly copolymers containing
polyacrylonitrile are used as fibers
to make knitted clothing, like socks and sweaters, as well as outdoor products
like tents and such. If the label of some piece of clothing says "acrylic", then
it's made out of some copolymer of polyacrylonitrile. Usually they're copolymers
of acrylonitrile and methyl acrylate, or acrylonitrile and
methyl methacrylate:
Also, sometimes we make copolymers of acrylonitrile and
vinyl chloride. These copolymers are
flame-retardant, and the fibers made from them are called modacrylic
fibers.
But the slew of copolymers of acrylonitrile doesn't stop there.
Poly(styrene-co-acrylonitrile) (SAN) and poly(acrylonitrile-co-butadiene-co--styrene)
(ABS), are used as plastics.
SAN is a simple random copolymer of styrene and acrylonitrile. But ABS is more
complicated. It's made by polymerizing styrene and acrylonitrile in the presence
of polybutadiene. Polybutadiene has carbon-carbon double bonds in it, which can
polymerize, too. So we end up with a polybutadiene chain with SAN chains grafted
onto it, like you see below.
ABS is very strong and lightweight. It is strong enough to be used to make
automobile body parts, but it is so light that Wassana can lift this front
bumper fascia over her head with only hand! Using plastics like ABS makes
automobiles lighter, so they use less fuel, and therefore they pollute less.
 ABS is a
stronger plastic than polystyrene
because of the nitrile groups of its acrylonitrile units. The nitrile groups are
very polar, so they are attracted to each other. This allows opposite charges on
the nitrile groups to stabilize each other like you see in the picture on the
left. This strong attraction holds ABS chains together tightly, making the
material stronger. Also the rubbery polybutadiene makes ABS tougher than
polystyrene.
Polyacrylonitrile is a vinyl
polymer, and a derivative of the
acrylate familyof polymers. It
is made from the monomer acrylonitrile by
free radical vinyl polymerization.
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