Space Charge and DC Breakdown Strength of Propylene-ethylene Copolymer/Polypropylene Composite

By blending elastomers, the mechanical properties of polypropylene can be effectively improved then meet the mechanical performance requirements of cable insulation materials. Common elastomer fillers are POE (Polyolefin Elastomer), SBS (Styrene butadiene styrene) and SEBS(Styrene Ethylene Butylene styrene). However, these fillers either have a certain polarity or are not similar to the structure of the matrix molecules, resulting in poor dispersion of the elastomer in the matrix and a significant decrease in electrical properties. In this paper, propylene-ethylene copolymer plastomer (polyolefin plastomer POP) is selected as the filler. Because its molecule contains propylene units, it can be better compatible with the polypropylene matrix and is expected to obtain better dispersibility. This paper studies the SEM, DSC, DMA, space charge and DC breakdown strength of POP/PP composites, and compared the properties with POE/PP materials. It is found that POP exhibits better dispersibility compared with POE; POP/PP has less space charge and the DC breakdown strength of POP/PP is higher than that of POE/PP; POP has a slightly weaker effect to reduce the elastic modulus of the composite. Since the addition of elastomer will destroy the crystallinity of the PP phase, thereby reducing the DC dielectric properties of the composite system, and as the addition weight of elastomer increases, the dielectric properties of the composite material decrease more significantly. The dispersibility of POP in PP is better than that of POE, and it has good compatibility. It has relatively little negative effect on the crystal regularity of the PP matrix. Therefore, the dielectric properties of POP/PP are better than that of POE/PP system, which has less space charge and has higher DC breakdown strength.