Dielectric Loss Suppression of Polyethylene Cable Insulation by Motion Restriction of Ultralow‐Content Grafted Maleic Anhydride

ABSTRACT Maleic anhydride (MAH) grafting modification is an effective approach to enhance the insulating performance of polyethylene (PE) cable insulations. However, the high polarity of MAH often causes considerable dielectric loss, making it unsuitable for AC systems. This study proposes a strategy to address this issue by adopting an ultralow‐content MAH grafting to limit polarity introduction while maintaining enhanced electrical performance and by utilising the short‐branch structural differences between linear low‐density polyethylene (LLDPE) and high‐density polyethylene (HDPE) to regulate MAH relaxation and dielectric loss. Experimental results verified the feasibility of this approach: Thermal and mechanical properties were only slightly affected, whereas resistivity increased significantly. The low‐frequency (less than 100 Hz) dielectric loss at 90°C, particularly in short‐branched LLDPE, was effectively suppressed. Molecular dynamics simulations further revealed that the abundant short branches in LLDPE can restrict the motion of MAH groups, thereby reducing the intermolecular friction. Combined with the charge trapping effect of MAH, this yields a substantial suppression of high‐temperature dielectric loss. The results suggest that ultralow‐content MAH‐grafted LLDPE is a promising recyclable cable insulating material for high‐capacity power distribution systems.