4.4 Acrylonitrile-Butadiene-Styrene Copolymer (ABS) Although the impact strength of acrylonitrile-styrene copolymers is higher than that of polystyrene, it is still sufficiently low to make it a limiting factor in many applications. Understandably, therefore, the addition of rubbery materials to SAN copolymers has been extensively investigated and as a result materials based on acrylonitrile, butadiene and styrene have become commercially important. Such materials are commonly referred to as ABS polymers. Commercial ABS polymers are not random copolymers of acrylonitrile, butadiene and styrene but are what have become known as multipolymers or polyblends, similar to high impact polystyrene. * Preparation Two basicprocesses are used commercially to prepare ABS polymers, namely blending, and grafting. These processes give rise to materials which are rather different to each other. Of the two processes, grafting is now the more important.
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