聚碳酸酯反复加工稳定性与结构的关系

通过对4种分别采用光气法和熔融酯交换法生产的、具有代表性的国产和进口聚碳酸酯(PC)的物理力学性能及反复加工后的性能稳定性进行了研究。发现不同聚碳酸酯(PC)原料本身的拉伸强度、断裂伸长率、屈服应力、冲击强度和熔体流动速率并无明显差异,但4种牌号PC的反复加工稳定性差异显著。通过凝胶渗透色谱和核磁共振碳谱对不同PC的分子结构和相对分子质量及其分布进行了表征分析,结合Instron万能材料试验机等的测试结果,首次发现,当相对分子质量相近的PC中小分子链/大分子链所占比例越高、分子链"离散性"越大,其反复加工后物理力学性能的稳定性也越差;PC中的支化链和芳基酮含量越高其反复加工稳定性也越差;熔融酯交换法生产的PC中因Fries重排而存在支化链和芳基酮结构,光气法PC中未检测到支化链和芳基酮。

Changes of Structure and Properties of Different Polycarbonate After Repeated Processing

In this paper,the physical and mechanical properties of representative domestic and imported polycarbonate(PC),produced by phosgene method and melt transesterification method and the stability performance after repeated processing were systematically studied.The results shown that there is no significant difference in elongation at break,yield stress,impact strength and melt flow rate(MFR).However,the repeated processing stability of PC is significantly different.The molecular structure,molecular weight and distribution of different PCs were analyzed by GPC and 13C-NMR.Combined with the results of Instron material testing machine,it is found that the higher the proportion of small molecular chains in PC with similar molecular weight,the greater"discreteness"of molecular chains,the worse stability of physical and mechanical properties after repeated processing.Moreover the higher content of branched chains and aryl ketones,the worse of the repeated processing stability.Branched chain and aryl ketone structures exist in the melt transesterification method PC due to Fries rearrangement,but don’t in the phosgene method PC.