聚丙烯内聚区银纹断裂时间的预测

文中拟定的聚丙烯(PP)银纹断裂分离标准是根据银纹拉伸产生变形热引起内聚区熔融层的形成和增厚提出的。内聚区分离的数值模拟是基于活性层附近的银纹区和本体区内的非线性热传导和热对流,并伴随均一轴向银纹的力学拉伸。聚丙烯银纹断裂时间的预测是在假定常银纹增厚速率和常内聚力的条件下实现的。研究表明,活性层温度相同时PP材料银纹区和本体区的温度分布不同,前者的热传导较后者快得多。随着应力或拉伸速率增大,无论是银纹区还是本体区的温度分布均呈减小的趋势。随着应力增加或银纹增厚速率的增加,PP的银纹断裂时间呈递减的趋势。实验结果的比对证实了通过热反内聚模型的数值模拟程序可预测聚丙烯的银纹断裂时间。

Crease Fracture Time Prediction in Cohesive Region of Polypropylene

It is proposed that the separate criteria for polypropylene crease fracture is based on the melt layer of cohesive region forming and thickening is due to the formation heat resulted from the crease extension.The numerical simulation for a separate of cohesive region is based on non-linear heat conduction and convection in the crease and the bulk region near to the active layer with a mechanical extension along the crease axis.The prediction of the crease fracture time for PP is possible when crease thickening rate and cohesive stress are assumed as constant.The results indicate that the temperature at the active layer will exhibit that different temperature distribution in crease region and bulk region for PP,which is due to that the heat conduction in the farmer is much faster rather than latter.Thetemperature in the central active layer increases as an increase in stress.Also as an increase in a stress the temperature distribution in either crease region or bulk region shows a decrease.As an increase in an extension rate from 0.1 m/ s to 1.0 m/s,the temperature distribution decrease.As increases in a stress and a crease thickening rate,respectively,the crease fracture time for PP decreases gradually.Compared with experiment results,it is confirmed that the heat de-cohesive model can be used to simulate the crease fracture time for polypropylene.