交联聚苯乙烯刚性粒子增韧聚丙烯研究

Research on Cross-linking Polystyrene Rigid Particles Toughened Polypropylene

为了解交联聚苯乙烯(XPS)微粒增韧聚丙烯的机理,用双螺杆挤出机将乳液聚合法合成的XPS微粒与均聚丙烯(PP)共混复合,并研究了该复合材料的力学性能、断面形貌和结晶特性。电镜观测发现当XPS粒子的交联剂用量不少于6%(wt)时,它们能在PP热熔融加工时均匀地分散在基体材料中而不团聚。力学性能测试表明PP中加入适量的XPS粒子后,该复合材料的拉伸强度基本保持不变,而冲击强度有较大的提高,经SBS弹性体包覆的XPS粒子与PP复合后得到的改性聚丙烯的冲击强度可达纯聚丙烯的3倍。通过X衍射技术和电镜分析表明韧性增加的主要机理是XPS粒子诱导PP的β结晶成核作用和XPS粒子与基材界面间较大的作用力引起的。当XPS粒子经SBS弹性体包覆后,其诱导β结晶作用明显消失,此时PP的增韧可认为是复合材料受到冲击时,XPS粒子通过相容性优良的界面橡胶层产生大形变和空穴化作用耗散能量的结果。

In order to understand the toughening mechanism of homopolypropylene （PP）, the cross-linking polystyrene （XPS） particles, which are synthesized by emulsion polymerization, were blended with PP through a twin-screw extruder, and the mechanical properties, morphology and crystal characteristic of the composite material were studied. SEM observation finds that the XPS particles containing no less than 6%（wt） erosslinker would disperse well in PP matrix without coagulation during melting process. The results of mechanical tests show that the tensile strength of the modified PP changes slightly, while the Charpy notched impact strength is dramatically improved, When the XPS particles are encapsulated with SBS elastomer, the Charpy notched impact strength of the composite material will be almost three times of that of PE XRD analysis and SEM observation indicate that the predominant mechanism of the toughness improvement is due to the nucleation effect of the β crystal in PP induced by XPS particles and the significant interface interaction between XPS particles and PP matrix. However, it is found that after encapsulated with SBS, the XPS particles ean not induce the β crystallization of PP, and in this ease, it is considered that the toughening mechanism comes from the dissipated energy due to the large deformation of the rubber layer interface and a large amount of mierovoid formation, which is caused by the cavitation in the stretched rubber shell under impact load.