纳米PTFE对低密度聚乙烯空间电荷特性与直流介电性能的影响

Effect of nanometer PTFE on space charge characteristics and DC dielectric properties of low density polyethylene

为研究驻极体材料纳米聚四氟乙烯(PTFE)对低密度聚乙烯(LDPE)空间电荷特性及直流介电性能的影响,选用纳米PTFE粉末与LDPE共混,制备得到不同填料质量分数(0.1wt%、0.3wt%、0.5wt%)的纳米PTFE/LDPE复合材料。SEM图像表明,粒径为20 nm左右的PTFE粒子在LDPE基体中分散性良好,结晶尺寸减小。FTIR表明,掺杂纳米PTFE粒子不会改变LDPE原有的化学结构。DSC结果表明,纳米PTFE粒子作为异相成核剂促进了材料的异相成核,提高了复合材料的结晶度。利用电声脉冲法(PEA)测试了室温下纳米复合材料的空间电荷分布,并测试了纳米复合材料的电导电流特性及直流击穿特性,结果表明,较低掺杂含量的纳米复合材料能明显抑制材料内部的空间电荷积聚,并且提高了复合材料空间电荷注入的阈值场强和材料的耐电强度。热刺激电流(TSC)结果表明掺杂含量较少时,纳米复合材料的陷阱能级最深,并随着掺杂含量的增加,纳米复合材料的陷阱能级逐渐变浅,浅陷阱密度逐渐增大。最后利用Materials Studio软件仿真分析F原子对LDPE陷阱能级的影响,表明F原子较强的电负性是影响纳米PTFE/LDPE复合材料陷阱能级的重要因素。

In order to study the effect of nano polytetrafluoroethylene(PTFE),a electret material,on the space charge characteristics and DC dielectric properties of low density polyethylene(LDPE),nano PTFE powder and LDPE were blended to prepare nano PTFE/LDPE composites with different filler mass fractions(0.1wt%,0.3wt%,0.5wt%).The images of SEM show that PTFE particles with a particle size of about 20 nm are well dispersed in LDPE matrix.The crystal size decreases.FTIR shows that doping nano PTFE particles does not alter the original chemical structure of LDPE.DSC shows that the use of nano PTFE particles as heterogeneous nucleating agents promotes heterogeneous nucleation of the material and improves the crystallinity of the composite material.The space charge distribution of nanocomposites at room temperature was measured using the electroacoustic pulse method(PEA),and the conductivity current characteristics and DC breakdown characteristics of nanocomposites were tested.The results showe that nanocomposites with lower doping content can significantly inhibit the accumula-tion of space charges inside the material,and improve the threshold field strength of space charge injection and the electrical resistance of the material.The thermal stimulation current(TSC)results indicate that when the doping content is low,the trap energy level of the nanocomposite material is the deepest,and as the doping content increases,the trap energy level of the nanocomposite material gradually becomes shallower,and the shallow trap density gradually increases.Finally,the materials studio software is used to simulate and analyze the influence of F atom on the trap energy level of LDPE,indicating that the strong electronegativity of F atom is an important factor affecting the trap energy level of nano PTFE/LDPE composites.