Abstract: By simulation analysis utilizing Flow/3D module in Moldflow MPI5.0 and simultaneous thermal analysis, the effects of melt temperature and injection rate on the distribution of shear rate and melting enthalpy in thin-wall injection molding were studied. Three melt temperatures, 175, 195, and 215 ℃ were selected. Results of the injection moulding experiments of the thin-wall PE-HD part with a thickness of 0.8 mm showed that in the flow direction, the shear rate and the melting enthalpy of the melt close to the gate were much higher than those at other positions and decreased with increasing distance from the gate. For the melt at a distance between1.5 mm from the gate and the end of part, the shear rate stayed somewhere between 2000~4000 s-1 and no significant change in the melting enthalpy was observed when the distance was longer than about 5 mm. The melting enthalpy reached its peak value at the melt temperature of 215 ℃; The shear rate at the gate increased with increasing injection speed.

Key words: thin-wall injection molding, high-density polyethylene, shear rate, crystallization, melt temperature