The research progress on the structure,mechanical properties and electrical properties of insulating polypropylene(PP)for high voltage direct current cable upgraded by physical blending and chemical modification is reviewed.Mechanical stretching of PP leads to charge accumulation.Graft modification,antioxidant addition,polycyclic compound and coupling agent modification and blending with other polymers can effectively inhibit the space charge,improve the volume resistivity and DC breakdown field strength.The addition of inorganic oxide nanomaterials exerts significant effects on the spherulite size,crystallization temperature,ductility,space charge behavior and breakdown field strength of PP composites.The thermal properties of random copolymerized PP are relatively excellent,whose elongation at break and breakdown field strength are significantly higher than those of cross linked polyethylene(XLPE),and whose space charge behavior is much better than that of block PP and XLPE.
high voltage direct current cablepolypropylenespace charge accumulationbreakdown field strength
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