接枝对聚丙烯绝缘材料热氧老化的影响及机理

Influence and Mechanism of Grafting on Thermal Oxidative Aging of Polypropylene

以聚丙烯(polypropylene,PP)为代表的环保型电缆绝缘材料是当前的研究热点。该文研究了接枝改性对聚丙烯材料热氧老化性能的提升效果及作用机理。实验结果表明,在抗氧化剂含量达到阈值之前,热氧老化反应主要局限在非晶区,且氧化反应速率较低。在此过程中,晶区结构在热的作用下趋于完善,使得电气性能有所提升,而非晶区结构的部分降解导致试样的拉伸性能显著降低。在抗氧化剂含量达到阈值之后,氧化反应速率加剧,非晶区及晶区结构严重降解,试样在短时间内失去绝缘性能。研究发现,相较于纯PP,接枝试样能够形成小球晶结构和独特的交联结构,抑制氧气向试样内部扩散,降低了氧化反应速率,因而热氧老化性能得到显著提升。随着接枝基团含量的提高,接枝试样的热氧老化性能单调提升,其中10%含量的苯乙烯(styrene,St)接枝试样具有相对最优的热氧老化性能。研究结果为聚丙烯电缆绝缘长期运行性能的提升提供了理论参考。

The environmental friendly cable insulation material represented by polypropylene(PP)is a research hotspot at present.The influence of graft modification on the thermal oxidative aging properties of PP materials and its mechanism were studied.The results show that before the antioxidant content reaches the threshold,the thermal oxidative aging reaction is mainly limited in the amorphous regions and the oxidation reaction rate is low.In this process,the crystal structure tends to be perfect under the action of heat,which improves the electrical properties,while the partial degradation of the amorphous structure leads to the significant reduction of the tensile properties of the samples.After the antioxidant content reaches the threshold,the oxidation reaction rate intensifies,the structures of amorphous regions and crystalline regions degrade seriously,and the sample loses its insulation performance in a short time.Compared with pure PP,the grafted samples can form small spherulite structure and unique crosslinking structure,inhibit the diffusion of oxygen into the interior of the sample and reduce the oxidation reaction rate,so the thermal oxidative aging performance is significantly improved.As the grafted monomer content increases,the thermal oxidative aging performance of the grafted samples is monotonously improved,and the 10%Styrene(St)grafted sample has the relatively best thermal oxidative aging performance.The research results provide a theoretical reference for improving the long-term operation performance of PP cable insulation.