Dielectric Properties Of Polystyrene Copolymer/LDPE And SEBS/LDPE Composite

Polyethylene is one of the best thermoplastic resin materials because of its dramatic comprehensive performance,however,electrical insulation performance declines gradually on the effect of external electric field.It is found that blending proper additives in PE can effectively improve the nature performance,and it is also a method to improve the long-term insulation performance of polyethylene.Based on the research of polyethylene matrix composite dielectric,LDPE,which is commonly utilized in cable insulation materials,is applied as the base resin,and polystyrene copolymer and SEBS are as fillers,which are the main materials for manufacturing composites of polystyrene-copolymer/LDPE and SEBS/LDPE with different contents by the method of melt blending.Several measurements are required to theoretically interpret the effect of charge behaviors on macroscopic properties of composites,which are DMA and DSC tests,breakdown performance tests that is proceeded at 30?,50?,70? and 90?,and characterizations of the internal structure and the comprehensive properties of composites.Through SEM and DSC tests,it is found that nucleus of LDPE is destroyed by blending polystyrene copolymer or SEBS.Crystallization morphology of LDPE has been altered,therefore,original spherulite has been destroyed.It is also found that the disordering of crystalline increases,which shapes new crystalline crystallized by polystyrene copolymer or SEBS.Moreover,with the increase of mass fraction of polystyrene copolymer or SEBS,the original size of polymer spherulite is reduced,but it improves the crystallinity of composites.Results of DMA test show that polystyrene copolymer and SEBS can be relatively equably fused with LDPE separately by the method of melt blending.Although the original structure of molecular chain of LDPE is altered,the dispersion is satisfied.AC breakdown test shows that LDPE blended with polystyrene copolymer can effectively improve the breakdown field strength of composites.The reason could be that the altered crystalline morphology enhances the dielectric strength,and it may also due to the benzene ring that is absorbed high-energy electrons,which improves the resistance of electrical properties of composites.SEBS,which is blended in LDPE,can effectively improve the breakdown field strength of the composites,but the mechanisms of influenced breakdown by polystyrene copolymer and SEBS may be distinct.TSC test shows that the spectral peak of composites blended by polystyrene copolymer moves towards high temperature,and the shape of spectral peak is similar with that of the composites which is blended by LDPE.With the increasing number of copies of added polystyrene copolymer,a significantly new spectral peak is shaped from 80? to100?.As the increasing amount of added SEBS,the spectral peak shifts to high temperature.This could be due to the introduced benzene substances,which effectively enhance the original trap depth within LDPE.In other words,blending LDPE with polystyrene copolymer or SEBS will enhance the inhibition capability of the space charge.