聚丙烯／线形双峰聚乙烯共混体系的流变行为、结晶形态与力学性能研究

Rheological Behavior, Crystal Morphology and Mechanical Properties of PP/PE-LB Blend

用毛细管流变仪研究了聚丙烯（PP）与线形双峰聚乙烯（PE-LB）共混体系熔体的流变行为。讨论了共混体系的组成、剪切应力和剪切速率对熔体流变行为、熔体黏度的影响。测定了PE-LB不同含量的共混物熔体的非牛顿指数，并计算了共混熔体的黏流活化能。结果表明：共混体系熔体属假塑性流体，其黏度随PE-LB加入量的增加逐渐增大，但是在PE-LB含量较低时黏度的增幅并不明显；共混体系的非牛顿指数显示出双波谷形，在两者含量比较接近的时候出现峰值。DSC实验证明PE-LB的加入使PP的熔融温度降低，结晶温度提高，说明PE-LB与PP有一定相容性，并对PP有稀释作用；SEM照片显示共混体系没有出现相分离的界面，证明两者有一定的相容性。PE-LB对PP有明显的增韧改性作用，当PE-LB质量含量为20％时，冲击强度比纯PP提高了67％；当含量为40％时，冲击强度提高了3．2倍，拉伸强度分别下降为纯PP的93％和65％。

Melt rheological behaviors of the polypropylene/linear bimodal polyethylene （PP/PE-LB） blend were studied with capillary rheometer. Influences of composition, shear stress, and shearing rate on the melt rheological behavior were discussed. Non-Newtonian index（ n ） and melt flow activation energy of the melt were measured and the results showed that PP/PE-LB blends were pseudoplastic fluids. Melt viscosity of the blends increased with increasing PE-LB content. DSC and SEM showed that addi- tion of PE-LB helped PP crystallize at higher temperatures. The addition of LBPE obviously increased the mechanical properties of PP. While the additions were 20 wt % and 40 wt %, the notched impact strength increased about 67 % and 320%, respectively, however, at the cost of the tensile strength lowered by 7 % and 35 %, respectively.