Effects of Blending and Grafting Modification with <i>trans</i> , <i>trans</i> -Dibenzalacetone (TTD) on the DC Electrical Properties of Low-Density Polyethylene (LDPE)

-dibenzalacetone (TTD) was prepared via blending and grafting approaches. The DC breakdown strength, electrical conductivity, space charge behavior, surface potential decay, and trap distribution characteristics of the modified LDPE were comparatively investigated. The results indicate that both blending and grafting modification can effectively regulate the DC electrical behavior of LDPE and improve its insulation performance to varying extents. Compared with the blended system, the grafted samples exhibit a significantly higher DC breakdown strength, increasing from 353.20 kV/mm to 403.31 kV/mm, accompanied by a pronounced reduction in electrical conductivity and a markedly lower average volume charge density under a DC electric field of 40 kV/mm, indicating more effective suppression of space charge accumulation. Meanwhile, a slower surface potential decay process is observed in the grafted samples, revealing pronounced differences in charge trapping characteristics within the materials. Combined with quantum chemical calculations and trap formation analysis, it is suggested that the different introduction methods alter the existence state of functional molecules in the polymer matrix, thereby affecting the stability and effectiveness of charge trap structures. Chemical grafting is favorable for stably transforming the electron-capturing capability of TTD into intrinsic charge trapping structures within LDPE, enabling sustained and effective regulation of charge transport under DC electric fields. This study provides useful insights into the molecular design and optimization of polyethylene-based insulation materials for high voltage DC applications.