Impact toughness of long glass fiber reinforced polypropylene

By using an impregnation device developed at our laboratory, long glass fiber reinforced polypropylene pellets for injection molding were produced. Composites samples were molded with the pellets by a conventional injection machine. Factors affecting the impact toughness were studied by Charpy test. The impact toughness increased with the addition of grafted polypropylene at first, but it decreased slowly when the grafted polypropylene addition exceeded 5%. Nevertheless, a higher impact toughness was obtained with longer pellets and/or wider runner. As to molded planar samples, the impact toughness variation is dependent on the position where the sample was cut. Annealing was an effective method to improve the impact toughness.