An effect of mold surface temperature on final product properties in the injection molding of high-density polyethylene materials

Mold surface temperature is one of the most critical process parameters in injection molding. This study aimed to determine the effect of mold surface temperature on plastic parts in injection molding of high-density polyethylene materials. Other process parameters were kept constant, and samples were prepared by changing mold surface temperatures by the injection molding method. The samples' mechanical tests, thermal tests, and gloss measurements by a gloss meter were performed, and the amount of warpage and collapses was measured by a video measuring system. Microstructures were examined under a scanning electron microscope. It was observed that the mold surface temperature increased the crystallization rate, tensile and bending strength of the materials, decreased the thicknesses of the crystal lamella and impact strength, and had an effect on the melting temperature of the crystal. The microstructure investigations demonstrated that as the mold surface temperature increased, the cavity formation in the structure increased, and fibrillation decreased due to expansion and cooling time. It was determined that the amount of collapse and warpage was affected by the mold surface temperature and that the increase in the mold surface temperature decreased the amount of collapse and increased the amount of warpage and surface gloss. Graphic abstract