Impact Resistance of All-polypropylene Composites Composed of Alpha and Beta Modifications

The development of environmental friendly engineering material has received top priority recently. Glass fiber (GF) reinforced polypropylene (PP) composites is one of the most widely used materials in the automotive industry due to its favourable properties. However, the presence of GF has become a major issue in the recycling of GF/PP composites. Considerable efforts have been devoted to find a more environmental friendly material than GF/PP. One of the possibilities is to use natural fibers (wood fiber, hemp, flax, sisal, etc.) as reinforcements. On the other hand, self-reinforced PP (SRPP) composites seem to be a viable alternative to GF/PP composites and their development is an extensively studied topic nowadays. For preparing SRPP composites (hot compaction [1], coextrusion [2], film-stacking [3, 4]) several concepts are used. In these composites the excellent fiber/matrix adhesion is ensured without any coupling agent. Note that the best adhesion and the highest interfacial shear strength can be obtained between identical materials.