【作者】 李霞；

【导师】 高俊国；

【作者基本信息】 哈尔滨理工大学 ， 高电压与绝缘技术， 2019， 硕士

【摘要】 通过掺杂、共混等技术改性电缆用绝缘材料,提高复合材料的击穿电场、绝缘电阻系数、降低其热阻系数,是解决电力电缆绝缘老化的关键所在。纳米填料在抑制聚乙烯内部空间电荷的积聚、提高其击穿电场强度方面效果明显,微米填料由于粒径尺寸较大在耐电腐蚀以及热学性能方面较为突出。而微、纳米填料共同的掺杂是否会因其协同效应对基体材料在空间电荷以及直流击穿方面产生影响未见有进一步的研究。本文以低密度聚乙烯(LDPE)作为基体材料,分别以平均粒径为30nm、1?m的球型氧化锌,直径约为1.5~3μm,长度约为20~30μm的针型氧化锌(ZnO)作为添加剂,采用熔融共混法和二步法制备出含量分别为0.5%、1%、3%的纳米球型、微米球型、微米针型、微米球-纳米球型、微米针-纳米球型ZnO/LDPE复合材料。利用扫描电子显微镜(SEM),偏光显微镜(PLM)对试验所制得的针型ZnO粒子形貌进行了观测,采用傅立叶光谱(FTIR)对复合材料进行Zn-O键的表征,通过差示扫描量热仪(DSC)测量了复合材料的结晶度和熔融峰温度,对比研究了纯低密度聚乙烯以及复合填料的微米、纳米、微-纳米复合材料的介电频谱以及击穿、电导性能。球型ZnO粒子的掺杂在一定程度上改变了复合材料的结晶效果,其中加入纳米球型复合材料结晶度提升效果最明显,而随着针型ZnO粒子含量的增加,微米针型复合材料结晶度有所降低。试验所制得的材料具有明显的针型结构以及氧化锌特征吸收峰。加入针型ZnO粒子复合材料的交、直流击穿场强相比于纯LDPE均有所降低,且随填料含量增加而减小,在含量为3%时击穿场强最低,而球型ZnO粒子的加入使得复合材料的交、直流击穿场强有所提高,微、纳米复合型材料的击穿场强介于微米针和纳米球复合材料之间。随着电场强度和温度的增加,LDPE和各种复合材料的电导率均随之提高,微米针型氧化锌的加入能够显著提高ZnO/LDPE复合材料的电导率并且随着其添加含量的增加而增大。各复合材料的相对介电常数,损耗角正切值均大于或近似等于纯LDPE。但是在整个频率范围内,微米针-纳米球型ZnO/LDPE复合材料的介电常数均低于LDPE,这就为低介质损耗的新型绝缘提供理论基础更多还原

【Abstract】 Modification of insulating materials for cables by doping and blending technology to improve composite materials,breakdown electric field,insulation resistance coefficient and reduction of thermal resistance coefficient are the key to solve insulation aging of power cable.Nano-fillers have obvious effects on inhibiting the accumulation of space charge in polyethylene and improving its breakdown electric field strength.Micron fillers have outstanding electrical corrosion resistance and thermal properties due to their large particle size.Whether the doping of micro and nano fillers will affect the space charge and DC breakdown of the matrix materials due to their synergistic effect has not been further studied.In this paper,low density polyethylene(LDPE)was used as matrix material.The nanospheres,microspheres,microneedles,microspheres-nanospheres and microneedles with an average particle size of 30 nm and a diameter of 1.5-3 um and a length of 20-30 um were prepared by melt blending method and two-step method,respectively,with 0.5%,1% and 3% of nanospheres,microspheres,microspheres and microneedles.-Nanospherical ZnO/LDPE composites.The morphology of needle-shaped ZnO particles was observed by scanning electron microscopy(SEM)and polarized light microscopy(PLM).The Zn-O bonds of the composites were characterized by Fourier transform infrared spectroscopy(FTIR).The crystallinity and melting peak temperature of the composites were measured by differential scanning calorimeter(DSC).The micrometers,nanometers and micrometers of pure low density polyethylene and composite fillers were compared and studied.-Dielectric spectrum,breakdown and conductivity of nanocomposites.The doping of spherical ZnO particles changed the crystallinity of the composites to a certain extent.The crystallinity of nanospherical composites was the most obvious.With the increase of the content of needle-shaped ZnO particles,the crystallinity of micron needle-shaped composites decreased.The material has obvious needle structure and characteristic absorption peak of zinc oxide.The AC and DC breakdown field strengths of the composites with needle-like ZnO particles are lower than those of pure LDPE,and decrease with the increase of filler content.The breakdown field strength is the lowest when the filler content is 3%.The AC and DC breakdown field strengths of the composites with spherical ZnO particles are increased.The breakdown field strengths of micro-and nano-composite materials are between micron needles and nanospherical composites.With the increase of electric field strength and temperature,the conductivity of LDPE and various composites increases.The addition of micron needle zinc oxide can significantly improve the conductivity of ZnO/LDPE composites and increase with the increase of its content.The relative dielectric constant and tangent value of loss angle of all composites are greater or approximately equal to pure LDPE.However,in the whole frequency range,the dielectric constant of micron needle-nano spherical ZnO/LDPE composites is lower than that of LDPE,which provides a theoretical basis for new insulation with low dielectric loss.更多还原