New insight on improving electrical strength and toughness of polyethylene blends: Turning point of supramolecular structure

We report an effective approach on improving the electrical strength and mechanical impact toughness in polyethylene blends by locating the composition on a submicroscopic supramolecular structure turning point. The designed linear low density polyethylene (LLDPE)-high density polyethylene (HDPE) blends exhibit the enhanced electrical breakdown strength and toughness with the optimal value of E0=95.48kV/mm and G=54.67 kJ·m-2 respectively, which is around 6% and 18% higher than pure LLDPE. The scanning electron microscopic (SEM) investigation and X-ray diffraction (XRD) study show no obvious variation in mesoscopic and microscopic structure with the change of HDPE content. Further differential scanning calorimetric (DSC) study using successive self-nucleation/annealing (SSA) method reveals that the turning point with optimal performance corresponds with a peculiar supramolecular structure with a high density of tie molecules, which enhances the toughness and the electromechanical breakdown strength. Our work provides a new insight on improving electrical strength and toughness for dielectric polymers, and may aid to enhance the electric insulation performance for dielectric materials in power equipment.