Styrene acrylonitrile resin (SAN) is a

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

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 Styrene is an organic compound with the chemical formula C6H5CH=CH2. Its structure consists of a vinyl group as substituent on benzene. Styrene is a colorless, oily liquid, although aged samples can appear yellowish. The compound evaporates easi ...

and

acrylonitrile Acrylonitrile is an organic compound with the formula and the structure . It is a colorless, volatile liquid. It has a pungent odor of garlic or onions. Its molecular structure consists of a vinyl group () linked to a nitrile (). It is an im ...

. 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

. Like polystyrene itself, it is transparent and brittle. The copolymer has a

glass transition temperature The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rub ...

greater than 100 °C owing to the

units in the chain, thus making the material resistant to boiling water. It is structurally related to ABS plastic, where

polybutadiene Polybutadiene utadiene rubber, BRis a synthetic rubber. It offers high elasticity, high resistance to wear, good strength even without fillers, and excellent abrasion resistance when filled and vulcanized. "Polybutadiene" is a collective name fo ...

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 Crazing is a Yield (engineering), yielding mechanism in polymers characterized by the formation of a fine network of microvoids and fibrils. These structures (known as ''crazes'') typically appear as linear features and frequently precede brittle ...

from the particles helps to increase the strength of the polymer. The method of

rubber toughening Rubber toughening is a process in which rubber nanoparticles are interspersed within a polymer matrix to increase the mechanical robustness, or toughness, of the material. By "toughening" a polymer it is meant that the ability of the polymeric subst ...

has been used to strengthen other polymers such as PMMA and

nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...

. 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 fiber Plastic optical fiber (POF) or polymer optical fiber is an optical fiber that is made out of polymer. Similar to glass optical fiber, POF transmits light (for illumination or data) through the core of the fiber. Its chief advantage over the gl ...

References

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