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

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.