Published December 1972
The original ABS resins introduced in 1948 were simple polyblends of a styrene acrylonitrile copolymer (SAN) with a rubber (SB or nitrile) containing butadiene. While these first resins displayed good impact strength in comparison with other resins such as PVC, polystyrene, or polyolefins, they lacked other qualities necessary for good processing. ABS graft resins, which were developed in the mid-1950s, had much improved properties compared with the polyblends; thus markets for these resins developed quickly. ABS resins will be the first of the so-called engineering plastics to reach a production level of 1 billion lb/yr (by 1975).
ABS graft resins are commonly composed of three monomers--acrylonitrile, butadiene, and styrene. These resins are thermoplastic blends that are made up of two distinct phases: one phase is a styrene acrylonitrile copolymer, and the other is a dispersed rubber phase consisting of a butadiene rubber onto which styrene-acrylonitrile monomers are grafted. The final properties of ABS graft resins can be altered significantly by changing monomer composition, the ratio of the rubber in the final blend, or the molecular structure and physical properties of the two phases. ABS resin manufacturers have taken advantage of this flexibility and have developed many grades of resins having optimum combinations of properties for specific applications.
More recently, ABS manufacturers have begun to use other monomers such as acrylates in grafting, or to blend other resins such as PVC, polycarbonates, and polysulfones into ABS. This has further extended the usefulness of these versatile resins.
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