马来酸酐熔融接枝聚丙烯及降解机理研究

Degradation Mechanisms of Melt-Grafting Maleic Anhydrid onto Polypropylene

用双螺杆挤出机研究了加入助剂和不加助剂的马来酸酐(MAH)对聚丙烯(PP)的熔融接枝改性。采用正交试验优化了熔融接枝工艺条件。用接枝物的熔融流动速率(MI)来表征PP降解程度,系统研究了单体MAH、引发剂过氧化二异丙苯(DCP)和助剂硫代二丙酸二月桂酯(ABX)用量对PP降解的影响。分析了PP降解机理以及助剂ABX抑制PP降解的机理。分析表明PP降解副反应是由引发剂作用下产生的PP大分子自由基和由MAH作用下产生的PP大分子自由基引起的;ABX助剂一方面由于它的供电子基减小了PP发生分子内和分子间自由基的转移反应,类似于负向催化剂的作用,降低了PP降解,另一方面降低了MAH激态分子的活性,也降低了PP的降解。

Using a double-screw extruder, the characters of polypropylene （PP） melt-grafted by maleic anhydride （MAH） with and without adding the assistant were studied respectively. The operation conditions of melt-grafting MAIl onto PP were optimized by orthogonal experiment. The degradation of PP was characterized by melt flow rate （MI）. The influences of the amounts of MAH, initiator dicumyl peroxide （DCP） and the assistant sulfo-dipropionate dilaurate （ABX） on the degradation of PP were investigated. The degradation mechanism of PP and the mechanism of restraining degradation of PP by the assistant ABX were analyzed. The analysis shows that the degradation reaction of PP is caused by PP macro-radical, which is produced under the effects of the initiator DCP and the MAH. The reason of why the assistant ABX could reduce the degradation reaction of PP is that, on the one hand, electron-donating group of the assistant ABX could reduce the free radical transfer reaction inner and inter the molecules of PP, which works as the negative catalyst, on the other hand, the assistant ABX could reduce the activity of excited state molecules of MAH.