Theoretical study on the reaction mechanism of a new XLPE insulation material without cross-linking byproducts: An alternative to peroxide cross-linking

Objective: Design a new cross-linked polyethylene (XLPE) insulation material without cross-linking by-products (an alternative to peroxide cross-linking). Investigate the process of covalent bonds forming and reaction mechanism of four reaction systems. Method: Theoretical calculation of the reaction potential energy information of the eleven reaction channels is used density functional theory at B3LYP/6-311+G(d,p) level. Results: The calculation results show that the epoxy and reactive functional groups between two poly-ethylene copolymers can react in situ, form covalent bonds, and realize a network XLPE. This reaction process is cross-linking byproduct-free. The reactivity of carboxylic acid functional group is stronger among four reaction systems considered. Discussion: The reaction Gibbs energy barriers of synergistic reaction are lower than that of step by step reaction. The reaction channel of attacking tertiary carbon site -CH- on epoxy is more kinetically favorable than that of attacking secondary carbon site -CH₂- on epoxy. Conclusion: The cross-linking of epoxy and reactive functional groups between two polyethylene copolymers in situ would be beneficial to avoid forming cross-linking byproducts of peroxide cross-linking process, which is a promising method for design thermoplastic insulation materials for power cables.