Tensile properties of injection molded long glass fiber reinforced polypropylene parts

Using an impregnation device developed at our laboratory, long glass fiber reinforced polypropylene (LGFRP) pellets were produced. Composites parts were injection molded with the pellets by a conventional injection machine. Factors affecting the tensile strength of the parts were studied. Polypropylene grafted with maleic anhydride (PP-MAH) as a surface-modifier was very efficient to improve the tensile strength. The tensile strength reached a maximum value for a grafted PP-MAH content of 0.3% PP. The more the glass fiber impregnated in pellets was, the higher the strength would be. The tensile strength of the parts molded with 10 mm long pellets was lower than those of the parts molded with 5 mm or 15 mm long pellets. Annealing was an efficient way to improve the tensile strength.