Material BehaviourStress relaxation behavior of high density polyethylene (HDPE) articles molded by gas-assisted injection molding

The effect of gas pressure, delay time and short-shot size on the stress relaxation behaviour of high density polyethylene (HDPE) parts molded by gas-assisted injection molding (GAIM) was examined using a universal tensile testing machine. The results showed that resistance to stress relaxation of the specimens molded by GAIM is better at higher gas pressure, smaller short-shot size and an appropriate delay time. The stress relaxation behavior of the parts was found to be dependent on the crystallinity, the grain size and grain number of the crystals.