Enhanced temperature stability of cross-linked polyethylene dielectrics enabled by a graftable molecule with multiple...

The temperature stability of semicrystalline polyolefin dielectrics is intrinsically linked to the interplay between crystalline morphology and charge transport, yet their coordinated regulation remains challenging. Here, a graftable molecule with multiple functional units, PXDP, was purpose-designed to coordinate crystallization and charge transport in XLPE. Its terminal vinyl group provides a grafting function, the urethane units provide hydrogen-bond-mediated ordering and nucleation, and the flexible polycaprolactone-derived segments regulate subsequent crystal growth. PXDP grafting further introduces deep traps that impede carrier migration. At a PXDP loading of 0.3 phr, the representative spherulite diameter decreases from 3.4 to 2.1 µm, accompanied by an increased conduction transition threshold and suppressed space-charge accumulation. XLPE-g-PXDP3 achieves a DC breakdown strength of 324.86 kV mm^-1 at 90 °C and an electric-field distortion rate of 3.60% at 80 °C. This work establishes a multiscale molecular-design framework for coordinating crystallization and charge transport in semicrystalline polyolefin dielectrics, thereby reducing the temperature sensitivity of dielectric performance and highlighting its potential for HVDC submarine cable insulation.