Development of morphology and properties of injection-molded bars of HDPE/PA6 blends along flow direction

The structure and mechanical properties of injection-molded bars of high-density polyethylene (HDPE)/PA6 blends were studied in this article. The experimental results showed that the morphologies of injection-molded bars change gradually along the flow direction, which is tightly related to the melt viscosity and processing conditions. The higher melt viscosity, lower mold temperature, and shorter packing time, restricting the macromolecular relaxation, enhance the difference in morphologies and properties at near and far parts of a mold. An injection-molded bar (namely H2C5), consisting of 75 wt % of HDPE, 20 wt % of PA6, and 5 wt % of compatibilizer (HDPE-g-MAH), showed a greater difference in mechanical properties at near and far parts because of its higher melt viscosity. A clear interface between the skin and core layers of near part in it leads to a much higher impact strength than that of far part. And tensile tests show that its tensile strength of near part is higher than that of far part due to the higher orientation degrees of HDPE matrix and PA6 dispersed phase in near part. (c) 2006 Wiley Periodicals, Inc.