SiO_(2)粒子的尺度因素对聚乙烯基复合材料的结晶行为及电学性能的影响

Influence of SiO_(2) particle size factors on the crystallization behavior and electrical properties of polyethylene matrix composites

分别选用粒径分别为1μm、30 nm和100 nm的SiO_(2)粒子作添加粒子,以低密度聚乙烯(LDPE)为基体,制备三种SiO_(2)/LDPE复合材料。对各复合材料的结晶行为进行分析,分析各材料的结晶度,同时对每种材料在频率影响下的相对介电常数εr和损耗因子tanδ变化情况进行研究,并探究了各材料的电导电流及空间电荷特性。结果表明,添加粒子的尺寸越小,其所形成的复合材料的晶体尺寸与间距就越小。添加30 nm SiO_(2)粒子后,材料结晶度增加显著;添加100 nm SiO_(2)粒子所构成的微观结构能有效限制分子链运动,使复合材料极化建立困难;大尺寸粒子的添加会对原有结晶结构造成破坏,形成的新结晶结构能促进载流子的迁移;这三种SiO_(2)粒子中,30 nm SiO_(2)粒子的添加能有效抑制空间电荷,100 nm SiO_(2)粒子的加入,则会造成电极附近的异极性电荷积聚。

The SiO_(2) particles with diameter of 1μm,30 nm and 100 nm were used as additive particles and lowdensity polyethylene(LDPE)as matrix to prepare the three kinds of SiO_(2)/LDPE composites.The crystallization behavior and crystallinity of LDPE and three kinds of SiO_(2)/LDPE composites were analyzed,the relative dielectric constantεr and loss factor tanδchanges of each material with frequency were measured,and the conductance current and space charge characteristics of the composites were investigated.The results show that the smaller the particle size is,the smaller the crystal size and grains spacing of the composite materials are.After adding 30 nm SiO_(2) particles,the crystallinity increases significantly.The microstructure formed by adding 100 nm SiO_(2) particles can effectively limit the chain segment movement,which makes it difficult to establish the polarization of the composites.The addition of large size particles can destroy the original crystal structure,and the new crystal structure can promote the carrier migration.Among the three SiO_(2) particles,the addition of SiO_(2) particles at 30 nm can effectively inhibit the space charge,while the addition of SiO_(2) particles at 100 nm can cause the heterogeneous charge accumulation near the electrode.