Experimental study of shrinkage and ejection forces of reinforced polypropylene based on nanoclays and short glass fibers

Abstract

This study presents the influence of nanoclays and glass fibers on the shrinkage and ejection forces of polypropylene-based composites for tubular parts produced by injection molding. An instrumented mold was used to measure cavity pressure, surface temperature and ejection forces in the tubular parts during the injection cycle. The materials used for the study were polypropylene homopolymer Domolen 1100L, nanoclays for polyolefin nanocomposites (P-802 nanoMax, used in percentages of 2%, 6%, and 10%) and reinforced polypropylene homopolymer with a content of 10% and 30% glass fiber (Domolen P1-013-V10-N and Domolen P1-102-V30-N, respectively). Part shrinkage was measured 48 h after production. The results show that the incorporation of nanoclays reduces shrinkage and ejection forces while glass fibers decrease shrinkage and increase ejection forces due to an increase in elastic modulus. Nanoclays decrease the ejection forces when compared to glass fibers and pure PP. The effects of nanoclays are less pronounced than those of glass fibers. Moldings produced with different materials were also analyzed to assess the effect of mold temperature on the ejection forces. Shrinkage rises slightly by increasing the mold temperature while the ejection force decreases.