Effects of processing conditions of injection molding on the microstructure of long fiber reinforced nylon composites

Long fiber reinforced nylon6 pellets (Verton, PF-700-10HI) were injection molded and the influence of the mold gate thickness was investigated. Microstructure of injection-molded long fiber reinforced thermoplastics (LFRTP) could be roughly subdivided into one core region and two skin regions, We established the criterion for division of the regions, which was 54.7 degrees of orientation angle (theta). The fiber length and the fiber orientation in injection molded specimens were measured in order to investigate the influence by the processing conditions such as holding pressure and injection speed. In spite of the fiber breakage by increasing the holding pressure, the mechanical properties of the specimens were improved by the enhanced fiber orientation. An increase in holding pressure led to denser packing and increased the skin region. Also, a higher injection speed led to fiber breakage and decreased the skin region. The mechanical properties of injection molded specimens could be improved by increasing the holding pressure and decreasing the injection speed.