Theoretical investigation of the reaction of graft maleimide to polyethylene in the UV radiation cross-linking process is accomplished at the B3LYP/6-311+G(d,p) level for high-voltage cable insulation materials. The reaction potential energy surface of the nine reaction channels is identified. The results show that the N,N′-ethylenedimaleimide can connect two 4-methylheptane molecules and act as the cross-linking agent. The calculated reaction potential barrier of forming 4-methylheptane radical by maleimide is higher than that of maleic anhydride. The study is expected to provide a basis for optimizing the UV radiation cross-linking polyethylene process and development more than 500 kV high-voltage cable insulation materials in practical applications.

Cross-linked polyethylene (XLPE) is applied in most advanced high-voltage direct-current (HVDC) power cable insulations, which are produced via dicumyl peroxide (DCP) technology. The electrical conductivity of insulation material can be increased by cross-linking byproducts from the DCP process. Hence, currently much attention is being paid to a new process to produce cross-linking byproduct-free XLPE. The cross-linking in situ between ethylene–glycidyl methacrylate copolymer and 1,5-disubtituted pentane via reactive compounding is a substitute for DCP. The reaction potential energy information of the eighteen reaction channels was obtained at the B3LYP/6-311+G(d,p) level. Results demonstrated that epoxy groups and 1,5-disubtituted reactive groups can react in situ to realize the XLPE-based network structure via covalent linking, and epoxy ring openings yielded ester. 1,5-disubtituted pentane played a cross-linker role. The reactivity of the carboxyl group was stronger than that of the sulfydryl or hydroxyl group. The reaction channel RTS1 was more kinetically favorable due to the lower reaction Gibbs energy barrier height of 1.95 eV. The cross-linking network construction of the new XLPE insulation without byproducts opens up the possibility of DCP substitution, which is beneficial to furthering the design of thermoplastic insulation materials for power cables in the future.

Cross-linked polyethylene (XLPE) insulation is used in most advanced power cable technology. However, in traditional cross-linking, the conductivity of the cross-linking system sharply increases due to the presence of additives (antioxidants and cross-linked agents). Therefore, reducing the number of antioxidants to further reduce conductivity is a very promising method. The structural design of a new dual-functional antioxidant 5-allyloxy-2-hydroxyl-3-tert-butylbenzophenone (5ATB) has been established. The antioxidant behavior and grafting reaction of 5ATB after photocatalysis under ultraviolet (UV) conditions were further studied using density functional theory (DFT). The reaction potential energy information of the six reaction channels at the B3LYP/6-311+G(d,p) level were obtained. The calculation results indicated that the reaction Gibbs energy barrier of 5ATB with O₂ is approximately 0.48 eV lower than that of the polyethylene chain with O₂ to achieve an anti-oxidative effect. Furthermore, the reaction-active site of 5ATB accepting H is located on the C of CH₂ in a C=C double bond, as demonstrated by an analysis of NBO charge populations. The proposed mechanism has the potential to further expand the design concept of insulation materials for advanced future power cables.

An FePc/CeO₂ heterojunction is constructed by hydrogen bonding induced assembly and follows the Z-scheme mechanism of effective charge separation. Fe²⁺ in FePc promotes O₂ activation, thus enhancing the photocatalytic degradation of 2,4-DCP.

The effect of electron-donating and electron-withdrawing groups grafted onto polyethylene on electron mobility was studied using density functional theory. In order to ensure the accuracy of the calculation results, 17 basis sets from six methods were screened. 3-methylpentane was selected as the cross-linked polyethylene model. Compared with the experimental values, the theoretical calculation results show that wB97XD/6-311G(d,p) is more suitable for studying the electron mobility system. The roles of electron-donating and electron-withdrawing functional groups were studied. The results show that the electron mobility of grafting nitrobenzene (Ebnb) to polyethylene is the smallest among the studied molecules. As the ability of electron-donating groups increases, the electron mobility gradually increases, while the addition of the electron-withdrawing group reduces the electron mobility and the electron mobility gradually increases with increasing temperature. This investigation is expected to provide reliable information for the development of insulation materials for cables.