α-烯烃基甲基二氯硅烷调控丙烯多相共聚制备高熔体强度高抗冲聚丙烯

Preparation of High-melt-strength,High-impact-strength Polypropylene by α-Alkenylmethyldichlorosilane-mediated Heterophasic Copolymerization of Propylene

作为最重要的热塑性高分子材料之一,聚丙烯在材料力学性能上的缺陷主要表现为冲击韧性尤其是低温韧性差,在熔体加工中的缺陷主要表现为熔体强度低,如何综合改善这两方面的性能是丙烯聚合和聚丙烯结构设计研究的重要问题.本文利用α-烯烃基甲基二氯硅烷调控丙烯多相共聚,在聚合反应完成后通过对聚合物进行水解处理,在共聚物中产生长链支化结构,制备了同时具有高熔体强度和高冲击韧性的新型聚丙烯.共聚物的凝胶渗透色谱(GPC)和熔体流变学测试结果均表明长链支化结构的存在,而试样断面扫描电镜(SEM)则清楚给出其以聚丙烯为基体和以乙丙无规共聚物橡胶(EPR)为分散相的相分离形态.共聚物在拉伸流变测试中表现出高熔体强度和显著的应变强化效应,在力学性能测试中显现出高缺口冲击强度.

As one of the most important thermoplastic polymer materials,polypropylene(PP)is mainly flawed on mechanical properties by low impact strength(particularly at sub-zero temperatures)and on melt processibility by low melt strength,hindering greatly efforts that are aimed to expand its applications.It is thus of great scientific as well as practical importance to address these two issues simultaneously and to prepare both mechanical and processing-proof new PP materials.However,due to the long-standing challenge in propylene polymerization of long chain-branching,the past efforts succeeding in achieving increased impact strengths by heterophasic copolymerization incorporating elastomeric ethylene-propylene copolymer(EPR),have nonetheless failed to make progress in improving the processing side of properties.In this study,we introduce an α-alkenylmethyldichlorosilane-mediated heterophasic copolymerization approach to address the problem.By introducing heterophasic copolymerization of propylene,α-alkenylmethyldichlorosilane can promote resultant PP/EPR heterophasic copolymers to be long chain-branched by an additional facile hydrolysis treatment.Phase-separated PP impact copolymers with long chain-branched structure were prepared by the rendered heterophasic copolymerization of propylene,which were confirmed by GPC,rheology,as well as morphology(SEM)measurements.The LCBed PP impact copolymers simultaneously possess high melt strength and strong strain-hardening effect in extensional rheology test and high impact resistance in mechanical properties test,providing a new platform for developing advanced PP materials with all-round application adaptability.