In order to improve the DC dielectric properties of crosslinking polyethylene (XLPE), chloroacetic acid allyl ester (CAAE) with polar groups was grafted on the molecular chain of low density polyethylene (LDPE) during its crosslinking reaction, and dicumyl peroxide (DCP) was used as initiator for grafting reaction. The DC dielectric properties of the prepared materials (XLPE-g-CAAE), including space charge characteristics, conduction current and DC breakdown strength, are studied in this paper. Experimental results prove that CAAE has been grafted successfully on molecular chain of XLPE, and grafting CAAE reaction has little effect on the crosslinking degree and crystallization property of XLPE. Compared with XLPE, XLPE-g-CAAE has a significantly enhanced ability to suppress space charge accumulation, and has lower conduction and higher breakdown strength. XLPE-g-CAAE has the best DC dielectric properties when the mass fraction of CAAE is 1.5%. It is considered that the polar groups of CAAE can introduce uniform and dense deep traps in material, so that charged lattice and coulomb field could be formed through capturing electrons or holes, leading to the suppression of charge injection and carrier mobility. The research in this paper has certain reference value for the development of DC power cable insulation materials.
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