注射成型工艺对PBT结晶和降解行为的影响

通过采用不同的注射条件,分别考察了熔体温度、模具温度、螺杆转速、注射速率、背压、保压压力、保压时间、滞留时间等多个重要的注射参数对聚对苯二甲酸丁二醇酯(PBT)小型制件降解程度、结晶形态和力学性能的影响。利用偏光显微镜、DSC、黏度计等,着重研究了各注射工艺参数对制件皮层厚度、结晶度、相对分子质量以及断裂伸长率的影响,从而为优化注射成型工艺过程提供依据。结果表明:熔体温度对制件各项性能的影响最为显著,而螺杆转速、背压、保压压力等的影响相对较小;随着熔体温度的提高和滞留时间的延长,PBT的降解程度迅速加剧,相对分子质量急剧下降,从而使制件断裂伸长率严重降低,力学性能变差。

Influence of Injection Moulding Parameters on Crystallization and Degradation Behavior of Polybutylene Terphthalate

The effects of several injection molding parameters on the degradation and crystal morphology of PBT were investigated, including melt temperature, mold temperature, injection speed, holding pressure, dwell time, and so on. Through microscopy, DSC and viscosity number, it was proved that melt temperature has the most significant influence on degradation of PBT. The other parameters, such as injection speed, screw speed, back pressure, and holding pressure had moderate effects. With increasing melt temperature and dwell time, the degree of degradation increased, the average molecular weight decreased rapidly, leading to inferior mechanical properties, especially low elongation at break.