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 main features of SAN are,
1. Excellent dimensional stability.
2. Very good tensile and flexural strength.
3. Good abrasion resistance and impact strength.
4. High chemical resistance, better resistance to stress cracking and crazing.
5. Resistance to water, acid and alkalis is greater than PS.
Grading of SAN:
- UV stabilized grade
- Antistatic grade
- Glass reinforced grade
The relative composition is typically 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 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. 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.
1. Transparent, ( light transmission up to 89 % )
2. High-gloss ; good mould surface reproduction
3. High Rigidity
4. Good chemical resistance
5. Heat deflection temperature >90 °C
6. High dimensional accuracy and stability
7. Good Electrical insulation
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