蒙脱土-弹性体/聚丙烯复合体系纳米颗粒相区分散对结晶形态与介电性能的影响

Influence of interphase dispersion state of nanoparticles on crystal morphology and dielectric properties in montmorillonite elastomer/polypropylene composites

随着电缆需求量日益加大,环保节能绝缘已成为新的发展趋势,研发改进聚丙烯(PP)成为电介质研究学者们的首选。为改善聚丙烯-弹性体共混物的介电性能,采用两步熔融共混法,使用两种不同的增容剂配合有机化处理蒙脱土(MMT)制备MMT-POE/PP纳米改性共混材料,探讨纳米颗粒在共混物材料不同相区内的分散状态,及其对纳米改性效果的影响。利用SEM、静电力显微镜(EFM)、偏光显微镜(PLM)与DSC表征介质的微观结构、结晶形态与结晶参数,并通过对共混物进行击穿性能测试,探讨相区分散对MMTPOE/PP复合材料性能提升的微观机制。实验结果表明:MMT倾向于PP相分散时,其结晶尺寸减小至4.7μm,结晶速度与结晶度有所上升,这使介电常数和绝缘电导率明显下降,且交流击穿场强从82.69 kV/mm提升至95.16 kV/mm。通过调控纳米颗粒倾向于PP相均匀分散,方可对共混物材料的介电性能起到正向提升的作用。

With the increasing demand for cable,environmental protection and energy-saving insulation has become a new development trend,and the research and development of polypropylene(PP)has become the first choice of dielectric researchers.In order to improve dielectric properties of polypropylene-elastomer blends,MMT-POE/PP nano-modified blends were prepared by two-step melting blending method with two different compatibilizers and organically treated montmorillonite(MMT).And then the effects of interphase dispersion states of nanoparticles in different phase zones on dielectric properties of nano-modified blends were investigated.The microstructure,crystalline morphology and crystallization parameters were characterized by SEM,electrostatic force microscopy(EFM),polarizing microscope(PLM)and DSC.The micro-mechanism of phase dispersion on MMT-POE/PP composites was discussed through the breakdown properties test of the blend sample.The experimental results show that when MMT layers tend to disperse in the PP phase,the crystallization size decreases about 5.9μm,the crystallization speed increases,and the crystallinity increases about 2.1%.And then the dielectric constant and insulation conductivity decrease obviously,and the alternating current(AC)breakdown field strength increases from 82.69 kV/mm to 95.16 kV/mm.The dielectric properties of nano-modified blends can be positively improved by regulating the tendency of nanoparticles to disperse uniformly in the PP phase.