纳米ZnO/低密度聚乙烯复合材料的介电特性

为探讨纳米ZnO/低密度聚乙烯（LDPE）复合材料的介电特性，首先，采用硅烷偶联剂和钛酸酯偶联剂对纳米ZnO进行改性，并利用两步法制备了不同纳米ZnO质量分数、不同纳米ZnO粒径、不同纳米ZnO表面修饰方式和不同冷却方式的纳米ZnO/LDPE复合材料；然后，通过FTIR、SEM、DSC和热激电流（TSC）测试了纳米ZnO在基体中的分散情况、复合材料的等温结晶过程参数变化及陷阱密度；最后，在不同实验温度下分别进行了交流击穿、绝缘电导率、介电常数和空间电荷实验。结果表明:纳米ZnO的加入使纳米ZnO/LDPE复合材料内部陷阱深度和密度均有所增加；当纳米ZnO的粒径为40 nm且质量分数为3%时，复合材料的结晶速度最快，纳米ZnO在基体中的分散性较好，击穿场强达到最高值133.3 kV/mm，电导率及介电常数也相对较低，加压时复合材料内部空间电荷少，短路时释放电荷速度快，介电性能较好；由于纳米粒子增加了材料内部的热传导速率，降低了复合材料随着温度升高而降解的速度，因而相对于纯LDPE，随着实验温度的提高，纳米ZnO/LDPE复合材料的击穿场强下降幅度及电导率上升幅度均较小。 

Dielectric properties of nano ZnO/low density polyethylene composites

In order to investigate dielectric properties of nano ZnO/low density polyethylene (LDPE)composites, silane coupling agent and titanium acid ester coupling agent were used to modify nano ZnO,and nano ZnO/LDPE composites with different nano ZnO mass fractions,different nano ZnO particles sizes,different nano ZnO surface modification methods and different cooling methods were prepared by two step method.Then,the dispersion situa-tions of nano ZnO in the matrix,the parameter changings during isothermal crystallization process and trap densities of the composites were investigated by FTIR,SEM,DSC and thermally stimulated current (TSC).Finally,alter-nate current breakdown,insulation conductivity,permittivity and space charge experiments were conducted under different experimental temperatures respectively.The results show that both the depth and density of trap in nano ZnO/LDPE composites increase due to the addition of nano ZnO.When the particle size of nano ZnO is 40 nm and the mass fraction is 3%,the crystallization rate of the composite is the fastest,the dispersibility of nano ZnO in the matrix is better,the breakdown field strength reaches the highest value 133.3 kV/mm,the conductivity and the die-lectric constant are relatively lower,the space charge in the composite is less when voltage application,and the dis-charge speed is fast when short circuit,and the dielectric properties are better.Since nano particles increase the thermal conduction rate in material and decrease the rate of composites degrading with the temperature increasing, thus comparing with pure LDPE,with experimental temperature rising,the reducing amplitude of breakdown strength and the increasing amplitude of conductivity of nano ZnO/LDPE composites are both smaller.