Styrene-acrylonitrile resin

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Styrene acrylonitrile
Styrene-acrylonitrile.svg
Identifiers
CAS number 9003-54-7 YesY
Properties
Molecular formula (C8H8)n-(C3H3N)m
Molar mass variable
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Styrene acrylonitrile resin is a copolymer plastic consisting of styrene and acrylonitrile. It is also known as SAN. It is widely used in place of polystyrene owing to its greater thermal resistance. The chains of the polymer show alternating repeat units of styrene and acrylonitrile, and it is a copolymer.

The relative composition is typically between 70 and 80% by weight styrene and 20 to 30% acrylonitrile.[1] Larger acrylonitrile content improves mechanical properties and chemical resistance, but also adds a yellow tint to the normally transparent plastic.[2]

Properties[edit]

SAN is similar in use to polystyrene. Like polystyrene itself, it is optically transparent and brittle in mechanical behavior. 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. Uses include food containers, kitchenware, computer products, packaging material, battery cases and plastic optical fibers. 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.

References[edit]

  1. ^ "Ullmann's Encyclopedia of Industrial Chemistry". Vol 29. Polystyrene and Styrene Copolymers. Wiley Online Library. p. 487
  2. ^ Charles A. Harper, ed., Modern Plastics Handbook, ISBN 0-07-026714-6, 2000.

External links[edit]