Mechanical and Dielectric Properties with Different Mass Ratio of PP and BPE

In order to research energy-saving and environmently friendly non-crosslinked materials for medium and low voltage cable insulation, polypropylene(PP)and bimodal polyethylene(BPE)composite system with different mass ratio were prepared by melting blend method.Microstructures were observed, mechanical and dielectric properties were also measured to find out the best mass ratio of PP and BPE.Through hot stage polarized microscope, isothermal crystallization of pure PP and 30% PP and 70% BPE (mass fraction) composite system was observed.Grow th of PP spherulites at 140 ℃ and dense crystal structure of 30% PP and 70% BPE composite system were observed, which showed good uniformity of the mixture.In mechanical impact properties measurement of different compsite systems, brittle-ductile transition point occured in 30% PP and 70% BPE composite system.Tensile tests showed that under the stretching speed of 10 mm·min^-1, elastic modulus, tensile strength, tensile elongation at break and fracture energy increased with the rise of PP content.In dielectric properties test of 30% PP and 70% BPE composite system, polymervolume resistivity was basically in the order of 10¹⁴, dielectric constant maintained between 2 and 2.3, and dielectric loss factor was in the order of 10^-4.Besides, a little increase in dielectric loss factor appeared in PP and BPE composites compared to pure PP and pure BPE, electrical performance of which could meet requirements of insulation material for low and medium voltage cables very well.