Study On The Structure And Properties Of PE Based Composites Of Low Dielectric Constant With EVA As Modified Resin

In order to meet the needs of 5G application scenarios,the research and application of new materials with low dielectric,high thermal conductivity and high electromagnetic shielding properties have attracted much attention.Thanks to its low dielectric constant,polyethylene(PE)is widely used in the fields of electronics,energy and communication.In recent years,many studies on thermal conductive polyethylene composites and polyethylene dielectric composites were reported,but polyethylene composites with both thermal conductivity and low dielectric constant are still facing great challenges.In this paper,the thermally conductive filler and the dielectric filler were adopted to prepare the composites by using PE as the matrix resin and ethylene ethyl acetate copolymer(EVA)as modified resin.The effects of the structure of the composites on the dielectric,thermally conductive and mechanical properties of PE based composites were studied.PE foam with low dielectric constant was modified with EVA as the modified resin and borosilicate hollow glass microspheres(BSH)as dielectric filler.The effects of EVA and BSH on the pore structure and properties of PE foam were studied.The results showed that EVA and BSH were favorable for the refining structure and uniform distribution of pore.Under the action of the same foaming agent,the density of the modified foams increased,as well as the dielectric constant and dielectric loss.The combination of EVA and BSH was found to tailor the density,dielectric properties and tensile properties of the modified foams.Compared with the PE foam,the density of the modified foam containing 40 wt.%EVA and 10 wt.%BSH increased by 50%,at 10~3 Hz,the dielectric constant increased by 40%,while the tensile strength and elongation at break increased by 173%and 944%respectively.The PE based thermally conductive composites with low dielectric constant were studied with boron nitride(BN)as thermally conductive filler and EVA grafted silica hollow sphere(m HSG)as dielectric filler.The effects of phase structure on the thermal conductivity and dielectric properties of the composites were studied.The results showed that a co-continuous blend was obtained when the mass ratio of PE:EVA was 1:1(PE5/EVA5).BN and m HSG were revealed to be selectively distributed in PE phase and EVA phase of PE5/EVA5,respectively.As a result,the phase structure formed with PE/BN as thermally conductive phase and EVA/m HSG as dielectric phase.The composites with lower dielectric constant and higher thermal conductivity were obtained by using the selective distribution of fillers and the phase structure of composites.At 10~6 Hz,compared with PE5/EVA5,the thermal conductivity of composites containing 40 wt.%BN and 2 wt.%m HSG was enhanced by 50%,while the dielectric constant was only increased by 7%.