Chi Xiaohong, Cheng Lu, Liu Wenfeng, Zhang Xiaohong, Li Shengtao
State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China.
Key Laboratory of Engineering Dielectric and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China.
Materials (Basel). 2018 Jul 30;11(8):1321. doi: 10.3390/ma11081321.
Polypropylene (PP) contains promising application prospects in thermoplastic cables for high voltage direct current (HVDC) power transmission because of its outstanding thermal and dielectric properties. However, the problem of poor toughness and space charge has restricted the application of pure PP in HVDC cables. In this paper, polyolefin elastomer (POE) and nano-silica were blended thoroughly and added into a PP mixture by a melting method. Scanning electron microscopy (SEM) was employed to observe the dispersion of POE and nanoparticles. Thermal properties were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Mechanical properties were evaluated by tensile tests. The elastomeric properties of composites were improved as the dispersed POE could transfer and homogenize external mechanical forces. DC breakdown results showed that the fail strength of composite with 10 phr POE and 1 phr nano-silica was obviously enhanced. The pulsed electro-acoustic (PEA) results showed that the injection and accumulation of space charge was increased by the introduction of POE, while it was restrained by the collective effect caused by nano-silica filling. X-ray diffraction (XRD) spectrograms showed that secondary ordered structures existed in the composites of PP, POE, and nano-silica, and that the ordered structure around the nanoparticles contributed to the enhancement of breakdown strength. The mechanical and dielectric properties were modified synergistically, which made the modified PP a propitious insulation material for HVDC cables.
聚丙烯（PP）因其出色的热性能和介电性能，在高压直流（HVDC）输电的热塑性电缆中具有广阔的应用前景。然而，韧性差和空间电荷问题限制了纯PP在HVDC电缆中的应用。本文将聚烯烃弹性体（POE）和纳米二氧化硅充分共混，并通过熔融法加入到PP混合物中。采用扫描电子显微镜（SEM）观察POE和纳米颗粒的分散情况。通过差示扫描量热法（DSC）和动态力学分析（DMA）对热性能进行表征。通过拉伸试验评估力学性能。由于分散的POE能够传递并均匀化外部机械力，复合材料的弹性性能得到改善。直流击穿结果表明，含有10份POE和1份纳米二氧化硅的复合材料的击穿强度明显提高。脉冲电声（PEA）结果表明，POE的引入增加了空间电荷的注入和积累，而纳米二氧化硅填充产生的协同效应抑制了空间电荷的注入和积累。X射线衍射（XRD）光谱图表明，PP、POE和纳米二氧化硅的复合材料中存在二次有序结构，纳米颗粒周围的有序结构有助于提高击穿强度。力学性能和介电性能得到协同改性，使得改性PP成为一种适用于HVDC电缆的绝缘材料。
