To explore methods for solving the problem that the dielectric properties of low density polyethylene sharply decrease at high temperatures

the polystyrene molecule is grafted onto polyethylene chain by electron irradiation and emulsion polymerization

and the PS-g-LDPE/LDPE composite material of different components is prepared. The AC breakdown strength of composite with 6% polystyrene improves by 20% within temperature span from 80 ℃ to 90 ℃comparing with pure LDPE. The results from differential scanning calorimetry and dynamic mechanical analysis tests show that the crystallinity of the composite with 6% polystyrene increases by 10%; at room temperature

the tensile yield stress and elongation of the composite increase; the storage modulus of the composite material at 85 ℃ reaches 70 MPa. Two main reasons for the obvious improvement of the AC breakdown strength are as follows: 1) the addition of polystyrene increases the elasticity modulus of composite material

enhancing the ability to resist electrical damage. 2) the benzene ring in polystyrene can serve as trapping sites in the composite to constrain the hot electron and consume its energy

which can inhibit the generation of electron-avalanche.