Examining the Effects of Filler Concentration and Mold Geometry on Performance of Cylindrical Injection Molded Composites

Authors: Rosentrater, Kurt

Submitted to: Materials Science Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2009
Publication Date: 10/1/2009
Citation: Rosentrater, K.A. 2009. Examining the Effects of Filler Concentration and Mold Geometry on Performance of Cylindrical Injection Molded Composites. Materials Science Research Journal. Volume 3, Issue 1-2, pp. 1-17.

Interpretive Summary: Interest in using fillers in plastics is increasing, because they can be used to displace petroleum, reduce raw material cost, and can even improve mechanical properties. Over the years, many researchers have examined the use of various fillers, including clay, talc, paper, wood flour, lignin, flax, and bamboo; but this is only a small list. To successfully use fillers, however, it is essential to examine the physical and mechanical properties of the resulting composites. It is also important to understand how processing behavior and final product quality will be altered due to the use of fillers. 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 develop greater understanding regarding these related factors, the objectives of this study were to examine processing behavior and product quality as affected by injection molding parameters. Specifically, this study examined the effects of 1) geometry for a cylindrical mold, and 2) filler concentration levels. Polypropylene was the base plastic material for this study, and calcium carbonate was used as the filler (from 20 to 40% inclusion). Three mold lengths (10.0, 20.0, and 30.0 cm) for a given diameter (1.0 cm), and thus three length-to-diameter ratios, were examined using injection molding computer simulation software. Mold processing effects and final product quality were predicted for each of the treatments. As mold geometry increased, injection pressure increased. An increase in filler level, on the other hand, reduced injection time and pressure. This study represents an initial step toward understanding the complex relationships between specific factors in the production of plastic composites, and will hopefully be used to further efforts to utilize fillers.

Technical 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 three mold lengths (10.0, 20.0, and 30.0 cm) for a given diameter (1.0 cm), and thus three 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 pressure increased; an increase in filler level, on the other hand, reduced injection time and pressure. 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.