高密度聚乙烯薄壁件注射成型时的结晶特性研究

Crystallization Properties of Injection Molded PE-HD Thin-wall Parts

用Moldflow MPI5．0软件的Flow3D模块仿真及同步热分析仪分析的方法，研究了熔体温度及注射速率对薄壁件注射成型时结晶特性的影响。结果表明，熔体温度为175、195、215℃时，在厚度为0．8mm的高密度聚乙烯薄壁件的注射成型过程中，在流动方向上，浇口附近的剪切速率和熔融热焓远大于其他各处，且二者均随着与浇口间距离的增加而迅速降低；从距浇口1．5mm处到制品末端，剪切速率稳定在2000-4000s^-1之间；从距浇1215mm处至制品末端，熔融热焓的变化不明显；熔体温度为215℃时，制品的熔融热焓最高；随着注射速率的增加，浇口处的最大剪切速率亦增加。

By simulation analysis utilizing Flow/3D module in Moldflow MPI 5.0 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 parts 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 between 1.5 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.