聚烯烃弹性体的结构与熔体黏度关系的研究

Study on Relationship Between Structure and Melt Viscosity of Polyolefin Elastomer

采用凝胶渗透色谱仪和核磁共振仪表征了一系列聚烯烃弹性体(POE)样品的结构,并用毛细管流变仪考察了其挤出稳定性、剪切依赖性和黏温依赖性,分析了熔体黏度与聚合物结构的关系。结果表明,随着剪切速率的提高,高相对分子质量的POE熔体易出现不稳定流动,挤出物表面发生畸变;相对分子质量越大、温度越低、共聚单体含越高,发生不稳定流动的临界剪切速率6)γc越低;POE的剪切黏度很大程度上受相对分子质量的影响,与共聚单体的含量关系不大;不同相对分子质量及组成的POE熔体的黏流活化能相近,约为2.8×10~4 J/mol。基于Carreau、Cross和Arrhenius等方程,分别建立了关联熔体零切黏度与聚合物重均相对分子质量和温度关系的半经验式、关联熔体表观黏度与零切黏度和剪切速率关系的半经验式;两式可用于预测POE熔体的黏度,其适用范围为温度为130~190℃,剪切速率为10~2 000s^(-1),重均相对分子质量(M_w)为4.2×104~1.24×10~5 g/mol。

The chain structure of several polyolefin elastomer(POE)samples was characterized by GPC and NMR,and their melt flow stability at high extrusion rate and their melt viscosities at various shear rates and temperatures were investigated by capillary rheometer.The relationship between the chain structure and melt viscosity were further analyzed.The results indicated that there was an unstable flow in the polymer melt with higher molecular weight with an increase of shear rate,and the surface of the melt extrudate became distorted.The critical shear rate also becomes lower if the molecular weight and co-monomer content were higher and the temperature was lower.The shear viscosity of POE was greatly influenced by the molecular weight and was almost not related to the co-monomer content.The polymer melts with various molecular weights and their compositions have the approximately same viscous flow activation energy around 2.8×10 4 J/mol.Based on the Carreau Equation,Cross Equation and Arrhenius Equation,the semi-model correlated with the zero shear viscosity,weight-average molecular weight and temperature and the semi-model related to correlated with the melt apparent viscosity,zero shear viscosity and shear rate were established.Both of the two equations are available to predict the melt viscosity of POE in the temperature range of 130~190℃,in the shear rate range of 10~2 000 s-1,in the weight-average molecular weigh range of 4.2×10 4~1.24×10 5 g/mol.