Improved DC Properties of Polypropylene HVDC Cable Insulation by Grafting and Blending Combined Modification

Abstract

In order to meet the needs of mechanical properties of cable insulation, polypropylene (PP) needs to be blended with low modulus materials to achieve toughening and softening. However, the compatibility between two or more resins can significantly affect the electrical properties of the composites. To solve this problem, the styrene–ethylene/butylene–styrene block copolymer (SEBS) with high heat resistance is selected as the blending elastomer, and grafted polypropylene (GPP) is prepared to be as basic resin. The morphological structure, thermal properties, mechanical properties and high temperature DC electrical properties of PP, GPP, PP/SEBS and GPP/SEBS are studied. The results demonstrate that compared with PP/SEBS, GPP/SEBS has significantly refined ‘island phase’ structure, further reduced storage modulus and slightly increased tensile strength and elongation at break and higher viscosity at low shear frequency. Electrical properties test results show that the grafted composite exhibits obvious suppression effect on space charge and conductance current, and enhances the DC breakdown strength. The introduction of the grafted material not only effectively improves the compatibility of the composites but also significantly improves the electrical properties of the material. This result can provide a reference for the development of eco-friendly high voltage cable materials.