Enhancing the electrical insulation performance of epoxy resin composites via in situ grafted Cu₂S nanoparticles

With the continuous increase in voltage levels of high-voltage direct current (HVDC) transmission, the requirements for the insulation properties of epoxy resin insulating materials have become increasingly stringent. However, existing methods for enhancing the insulation properties of epoxy resin through nanoparticle modification commonly face bottlenecks such as cumbersome processes, particle agglomeration, and weak interfacial bonding, making it difficult to achieve efficient and stable interfacial charge management. Herein, we report a reaction-induced in situ grafting strategy for nanoparticles. Using copper(II) diethyldithiocarbamate as a single-source precursor, Cu₂S nanoparticles and tetraethylthiourea (TEU) surface-modifying molecules are simultaneously generated via its thermal decomposition reaction, achieving in situ chemical grafting of TEU onto the Cu₂S surface. The resulting TEU@Cu₂S functional nanoparticles were incorporated into the epoxy resin matrix, successfully constructing a stable ternary composite interface. The results demonstrate that this interface can suppress space charge accumulation by introducing deep-level charge traps, thereby significantly enhancing the DC breakdown strength and volume resistivity of the composite, while effectively reducing the surface charge accumulation density. This work provides an innovative and practical solution for the development of high-performance HVDC insulating materials.