Abstract:

In this paper, we simulated the influence of different cooling methods on the performance of injection-molded fittings based on high-density polyethylene. We found that in the actual production process, water-dipping cooling resulted in a too fast cooling rate for the fittings and thus greatly shortened the period of the fittings staying at a maximum growth rate. This led to the formation of more microcrystals inside the fittings, which depressed the growth of larger crystals. As a result, an obviously loosen structure was generated inside the fittings with non-uniform crystals and large internal stress, thus resulting in poor performance. However, the natural cooling could avoid these defects and therefore led to better properties including oxidation induction time, density value, crystallinity, and tensile yield stress for the fittings in comparison with water cooling.

Key words: cooling method, high-density polyethylene, crystallinity, fitting