ASA

Acrylic-styrene-acrylonitrile (ASA) polymers are amorphous plastics which have mechanical properties similar to those of ABS resins. However, the ASA properties are far less affected by outdoor weathering. ASA is a terpolymer that can be produced by either a patented, proprietary reaction process or by a graft process. In the reaction method, ASA is made by introducing a grafted acrylic ester elastomer during a copolymerization of styrene and acrylonitrile (SAN). The finely divided powder is uniformly distributed in and grafted to the SAN molecular chains. The outstanding weatherability of ASA is due to the acrylic ester elastomer. ASA resins are available in natural, off white, and a broad range of standard and custom-matched colors. Base ASA resins are sold under the trade names Luran S (BASF Plastic Materials), Geloy (General Electric Plastics) and Centrex (Monsanto Chemical Co.). ASA resins can be compounded with other polymers to make alloys and compounds that benefit from ASA's weather resistance. Also, ASA sheet is used as a capstock over other plastics. ASA parts have high gloss, good chemical and heat resistance, and high impact strength, even at low temperatures. Typical heat-deflection temperatures for ASA are 180 to 220 °F (82 to 104 °C) at 264 psi. Tensile strengths are 4,000 to 7,000 psi; elongation at break, 25 to 40%, flexural modulus, 220,000 to 250,000 psi; and notched Izod impact strengths are 9.0 to 11.0 ft-lb/in. (at 73 °F) and 4.0 to 6.0 ft-lb/in. (at -40 °F). ASA is resistant to saturated hydrocarbons, low-aromatic gasoline and lubricating oil, vegetable and animal oils, water, aqueous solutions of salts, and dilute acids and alkalis. However, it is attacked by concentrated inorganic acids, aromatic and chlorinated hydrocarbons, esters, ethers, ketones, and some alcohols. ASA offers better resistance to environmental stress cracking than ABS. With respect to flame resistance, ASA is