Shrinkage behavior and mechanical performances of injection molded polypropylene/talc composites

In this research, the influences of adding talc mineral particles of 10 mu m particle size on the shrinkage and the mechanical properties of injection molded polypropylene (PP)/talc composites were investigated. PP has a crystalline molecular structure and hence it possesses nonisotropic shrinkage along and across the flow directions. Addition of the talc mineral filler to PP induced an isotropic shrinkage in the molded part because of the nonisotropic shape of talc particles. The results of experiments indicated that the maximum flexural strength, maximum impact strength, and isotropic shrinkage were achieved by adding 10, 20, and 30 by weight percent of talc respectively. By incorporating of 10 wt% of talc particles into the PP matrix, the tensile strength was hardly affected but the occurrence of cold drawing phenomena in the tensile test was hindered considerably. The flake-shape structure of talc filler played an important role in determining the molded part shrinkage and mechanical properties. POLYM. ENG. SCI., 47:2124-2128, 2007. (C) 2007 Society of Plastics Engineers.