核壳胶粒增韧改性聚丙烯研究3. 冲击断裂行为和增韧机理

用扫描电子显微方法研究了核壳胶粒与聚丙烯 ( PP)反应共混物试样的冲击断裂行为 .通过对冲击断裂表面分区显微分析 ,揭示了冲击断裂的断面形态和形变特征 .结合冲击测试实验数据和断面显微分析结果 ,对核壳胶粒增韧改性 PP的增韧机理作了探讨 .结果表明 ,PP断面上可以区别出以银纹化机理为主的脆性断裂特征和以剪切屈服为主的韧性断裂特征 ,提高试样冲击断裂韧性主要是基体聚合物的剪切屈服 ,同一断面上可以同时出现脆性断裂与韧性断裂的断裂特征 ;核壳胶粒改性 PP共混物的增韧机理是核壳橡胶粒子的空穴化和 PP基体的剪切屈服

Toughening Polypropylene by Core-Shell Particles 3. Impact Fracture Behavior and Toughening Mechanisms

On the basis of the previous paper, the impact fracture behavior of the reactive blends of core shell particles and polypropylene was farther investigated. The morphology and deformation features of fractured surface under impact were revealed by the microscopic studies on the various zones of impact fractured surface. Considering the impact toughness and the morphology of fractured surface, the toughening mechanisms for core shell rubber modified polypropylene were discussed. The results indicate that the PP matrix is deformed through crazing and shear yielding mechanisms. Two types of deformation characteristics of fractured surface are distinct, i.e., brittle fracture dominated by matrix crazing and tough fracture dominated by matrix yielding. Shear yielding is the main source responding for the improvement in fracture toughness. Both brittle fracture and tough fracture characteristics can exist together on the same fractured surface. The toughening mechanisms for the core shell rubber modified PP are the cavitation of core shell particles and the yielding of matrix polymers.