流变学方法研究共聚甲醛分子量及其分布

摘要

According to the conditions of the molecular weight and distribution tests of polyoxymethylene (POM) being difficult,rheological properties of several commercial co-POM were tested by means of rotational rheometer,the zero shear viscosity was obtained by the relationship between the complex viscosity and circular frequency,so the molecular weights of differe nt POM were obtained from the relationship between the zero shear viscosity and weight average molecular weight,meanwhile,the molecular weight distributions of different POM were obtained from Vinogradov model and Carreau-Yasuda model. The results show that the molecular weight and distribution of POM can be characterized easily and quickly by rheological method,comparing with the results of GPC,the results obtained from rheological method show that the errors were very low. The results also show preliminarily that POM with larger zero shear viscosity has the bigger weight average molecular weight,and POM with lower melt flow rate has the wider molecular distribution.%针对聚甲醛(POM)分子量及其分布测试较为困难的情况，采用旋转平板流变仪对不同牌号的市售共聚POM树脂的流变性能进行了测试，利用复合黏度和角频率的关系曲线得到了零切黏度，然后利用零切黏度与重均分子量的关系式得到了不同牌号POM的分子量，同时利用Vinogradov模型和Carreau-Yasuda模型得到了其分子量分布曲线，并与凝胶渗透色谱(GPC)测试结果进行了对比。结果表明，采用流变学的方法可以快速、准确地测试POM树脂的分子量及其分布，其结果与GPC测试结果相差不大。另外，流变学法测试结果初步表明，零切黏度大的POM树脂的重均分子量较大，熔体流动速率较小的POM树脂的分子量分布较宽。