Effects of filler concentration and geometry on performance of cylindrical injection molded composites pp.1059-1076
Authors: (Kurt A. Rosentrater, Agricultural and Bioprocess Engineer, United States Department of Agriculture, Agricultural Research Service, North Central Agricultural Research Laboratory, Brookings, SD)
Abstract: There is growing interest in using fillers in plastic products to displace petroleum components, reduce cost, and improve mechanical properties. Many studies have examined the use of materials such as clay, talc, paper, wood flour, lignin, flax, and bamboo, to name just a few. For successful utilization in the marketplace, it is essential to optimize resulting physical and mechanical properties of these composite products. And it is also important to understand how both processing behavior and final product quality will be impacted when using fillers. Moreover, all of these will be influenced by the specific manufacturing processes used, the specific plastic used, the specific filler used (and at what level), as well as the mold geometry used. To provide a greater understanding regarding these synergistically-related factors, the objectives of this study were to examine processing behavior and product quality as affected by injection molding parameters, specifically the effects of 1) geometry for a cylindrical mold, and 2) filler concentration levels. With polypropylene as the base plastic, the inclusion of calcium carbonate as a filler (from 20 to 40%), using 10 mold lengths (1.0 to 10.0 cm) for a given diameter (1.0 cm), and thus 10 length-to-diameter ratios, were examined using injection molding computer simulation software. Injection mold processing effects and final product quality were predicted for each of the treatments under investigation. As mold geometry increased, injection time and injection pressure curvilinearly increased as well; an increase in filler level, on the other hand, reduced injection time and pressure, but also in a curvilinear fashion. This study represents an initial step toward understanding the complex relationships between specific factors in the production of plastic composites. Thus the information generated herein will be essential for further efforts to utilize fillers in manufactured products.