Styrene acrylonitrile resin 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 ...

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...

consisting of

styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...

and

acrylonitrile Acrylonitrile is an organic compound with the formula and the structure . It is a colorless, volatile liquid although commercial samples can be yellow due to impurities. It has a pungent odor of garlic or onions. In terms of its molecula ...

. It is also known as SAN. It is widely used in place of

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the Aromatic hydrocarbon, aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin pe ...

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.

Properties

SAN is similar in use to

. Like polystyrene itself, it is optically transparent and brittle in mechanical behavior. 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 ru ...

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. Polybutadiene rubber is a polymer formed from the polymerization of the monomer 1,3-butadiene. Polybutadiene has a high resistance to wear and is used especially in the manufacture of ti ...

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 the phenomenon that produces a network of fine cracks on the surface of a material, for example in a glaze layer. Crazing frequently precedes fracture in some glassy thermoplastic polymers. As it only takes place under tensile stre ...

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 PMMA may refer to: * para-Methoxymethamphetamine, a stimulant drug * Philippine Merchant Marine Academy * Poly(methyl methacrylate), a transparent thermoplastic often used as a glass substitute {{disambig ...

and

nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from pet ...

Uses

Uses include food containers, water bottles, kitchenware, computer products, packaging material,

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

cases and plastic optical fibers.

Health risks

The acrylonitrile from SAN containers has been found to migrate to content in variable amounts. Acrylonitrile is classified as a Class 2B carcinogen (possibly carcinogenic) by the International Agency for Research on Cancer (IARC). Acrylonitrile has been shown to increase rates of cancer appearance in high dosage tests in male and female rats and mice."Acrylonitrile: Carcinogenic Potency Database"
''berkeley.edu''.

References

{{Plastics Plastics Household chemicals Packaging materials Copolymers