An Engineering Comparison of Die Cast Zinc and Injection Molded Polymers

An engineering evaluation conducted by the International Lead Zinc Research Organization, Inc. (ILZRO) has produced data which verify that die cast zinc is stronger, stiffer, and more thermally resistant than five major engineering thermoplastics-polycarbonate, polyacetal, nylon, ABS (acrylonitrile-butadiene-styrene), and polypropylene-under identical test procedures. However, since zinc is five to eight times more dense than the polymers tested (and most other unfilled polymers), the plastics industry often stresses the high strength-to-weight ratios and low cost per cubic inch of plastics as more than offsetting advantages. The question facing the design engineer, therefore, is: which material is the best choice for the particular application; that is, which will provide the required strength and stiffness at lowest cost? On the basis of the comparative tests performed in this research effort, the SAE 903 zinc die casting alloy is demonstrably the superior material on a cost-performance basis.