Styrene acrylonitrile resin (SAN) is a
copolymer plastic
Plastics are a wide range of synthetic polymers, synthetic or Semisynthesis, semisynthetic materials composed primarily of Polymer, polymers. Their defining characteristic, Plasticity (physics), plasticity, allows them to be Injection moulding ...
consisting of
styrene and
acrylonitrile. It is widely used in place of
polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It i ...
owing to its greater thermal resistance. The chains of between 70 and 80% by weight styrene and 20 to 30% acrylonitrile.
Larger acrylonitrile content improves mechanical properties and chemical resistance, but also adds a yellow tint to the normally transparent plastic.
[Charles A. Harper, ed., ''Modern Plastics Handbook'', , 2000.]
Properties and uses
SAN is similar in use to
polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It i ...
. Like polystyrene itself, it is transparent and brittle. The copolymer has a
glass transition temperature greater than 100 °C owing to the
acrylonitrile units in the chain, thus making the material resistant to boiling water. It is structurally related to
ABS plastic, where
polybutadiene is copolymerised with SAN to give a much tougher material. The rubber chains form separate phases which are 10-20 micrometers in diameter. When the product is stressed,
crazing from the particles helps to increase the strength of the polymer. The method of
rubber toughening has been used to strengthen other polymers such as
PMMA and
nylon.
Uses include food containers, water bottles, kitchenware, e.g., blenders and mixers, healthcare materials, cosmetic jars, computer products, packaging material, household equipment e.g., shower trays,
battery cases and
plastic optical fibers.
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References
{{Plastics
Plastics
Household chemicals
Packaging materials
Copolymers