The ABCs of ABS

Tweaking mix ratios of acrylonitrile/butadiene/styrene in ABS resins lets designers boost a part’s heat stability, chemical resistance, toughness, stiffness, and impact resistance. Edited by Jean M. Hoffman The Kiwi Too travel trailer from Jayco Inc., Middlebury, Ind., sports a durable ground-effects package consisting of a front cap assembly that covers the well for holding LP bottles, wheel-well skirting, and the rear bumper. The parts are coextruded sheets of Lustran ABS resin capped with Centrex 825 weatherable polymer. The front panels and sinks for the QPA-160 and QPA-310 ice dispensers from Manitowoc Ice Inc., Manitowoc, Wis., come from Lustran 456 resin. The opaque, matte-gloss ABS resin has a tensile yield stress of 1,900 lb/in. , a flexural yield stress of 4,100 lb/in. , and a flexural modulus of 173,000 lb/in. The aftermarket golf-cart top from Primex Plastics Corp., Oakwood, Ga., and Piper Plastics Inc., Orlando, is made from Centrex 833 acrylonitrile-styreneacrylic (ASA) and Lustran 752 ABS. The ABS gives the hood its sturdy structure while the high-gloss ASA resists fading, cracking, and yellowing from the sun. Acrylonitrile butadiene styrene (ABS) use has grown over the last 50 years as more and more molders and OEMs take advantage of the resin's processing and property versatility. Applications run the gamut from automotive interiors and exteriors, boat hulls and appliances to food-storage products, garden tools, electrical/electronic components, and industrial equipment. In general, ABS has high impact strength and rigidity, stands up well to chemicals and weather, and may easily be processed with good as-molded surfaces. Properties of specific grades of ABS resin are determined by several factors including acrylonitrile-butadiene-styrene mix ratio, manufacturing method, rubber particle size, and polymer chain length. In setting the mix ratio, designers increase the amount of acrylonitrile for better heat stability and chemical resistance. Likewise, tweaking the amount of butadiene improves