St存在下MAH熔融接枝PP机理的探讨

Study on the Mechanism of Melt-grafting of Maleic Anhydride and Comonomer Styrene onto Polypropylene

在哈克转矩流变仪和双螺杆挤出机中,对苯乙烯(St)存在下马来酸酐(MAH)熔融接枝聚丙烯(PP)进行了研究。实验表明:St的加入不仅可显著提高MAH的接枝率,而且可减少PP的降解;当St和MAH的摩尔比为1时,MAH接枝率最大。通过反应机理分析得出:没有St时,MAH主要以单分子形式在PP降解之后接枝到PP上;而在St存在下,St与MAH以交替接枝的形式或者配合物(CTC)形式在PP降解之前接枝到PP上,形成St和MAH交替聚合的长链。后者使MAH的接枝率增加,同时增大了PP的交联,减小了PP的降解。

Maleic anhydride and comonomer styrene melt-grafting onto polypropylene was conducted in Haake torque rheometer and twin screw extruder. The result showed that the comonomer styrene might greatly improve the grafting degree of MAH and reduce the degradation of PP. It was found that when nSt / nMAH≈ 1, the grafting degree of MAH reached maximum. Through the study of the mechanism, it was believed that when there wasn＇t styrene in the reactive system, MAH was grafted mostly onto PP as single molecule after the degradation of PP. However, when there was St in the reactive system, MAH and St was grafted onto PP as alternate or CTC, and formed long chain of MAH and St, which increased the grafting degree of MAH. At the same time, the reactive activity of St and CTC was higher than that of MAH, which led to graft onto PP before the degradation of PP. On the other hand, St may increase the cross linkage of PP,which reduced degradation of PP.