Acrylonitrile styrene acrylate (ASA)

Acrylonitrile-styrene-acrylate is the predecessor of ABS (Acrylonitrile- butadiene-styrene). ASA is an acrylate rubber modified styrene acrylonitrile copolymer with an acrylate rubber modifier included at the polymerisation stage. Developed to create similar material as ABS but superior in terms of weather resistance.

Properties

Acrylonitrile styrene acrylate (ASA) has great toughness and rigidity, good chemical resistance and thermal stability, outstanding resistance to weather, aging and yellowing and high gloss.

ASA possesses a similar chemical structure to ABS, since both consist of a SAN matrix containing a graft rubber. However, while the core of the graft rubber of ABS consist of polybutadiene, that of ASA consists of poly(n-butyl acrylate), and this accounts for important differences in the properties of the two plastics.

The butyl acrylate rubber of ASA is free of double bonds which ASA clear advantages in terms of weatherability and resistance against heat ageing. It has higher resistance against environmental stress cracking, especially against alcohols and many cleaning agents.

ASA also exhibits advantages over other thermoplastic housing materials such as polycarbonate, PBT and polypropylene.

Common Application

Because of the enhanced weather resistance, ASA is used extensively in the automotive industries, and further in general for outdoor applications. Asa polymers have been widely applied to glossy coloured outdoor products including;

• Automotive outside parts
• Boats
• Garden furniture
• Household electrical products
• Satellite antennas or
• Street lamps
• Children’s toys
• Window frames
• Sanitary equipment
• Housing for solar collectors and carrier for solar cells
• Sunlight sensors
• Solar-powered battery chargers
• Solar-charged flashlights
• Sensors and transmitter modules for electronic alarms
• Movement detectors
• Safety lighting and alarms
• Housing for access control units
• Housing for fire alarms
• Roof outlets

History

ASA was first introduced to the market by BASF in around 1970 as Luran® S, based on patents from the 1960s (3-6). Developed to create similar material as Acrylonitrile-Butadiene-Styrene (ABS) but superior in terms of weather resistance. ASA polymers are produced by introducing a grafted acrylic ester elastomer during the copolymerization reaction between styrene and acrylonitrile.

References

1. http://www.bpf.co.uk/plastipedia/polymers/SAN.aspx

2. Handbook of Engineering and Specialty Thermoplastic, Polyolefins and Styrenics