Electron‐Beam Crosslinking Effects on the Thermal Degradation Behavior and Isoconversional Kinetics of Flame‐Retardant LDPE / EVA Composites

ABSTRACT

Electron‐beam (EB) irradiation provides initiator‐free crosslinking of polyethylene‐based insulation materials, but its influence on the thermal degradation of halogen‐free flame‐retarded composites remains insufficiently understood. This study investigated the thermal stability and conversion‐dependent degradation behavior of EB‐crosslinked low‐density polyethylene/ethylene‐vinyl acetate (LDPE/EVA) composites containing aluminum trihydroxide (ATH), magnesium hydroxide (MH), and supplementary calcium carbonate using thermogravimetric analysis at multiple heating rates. Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Kissinger analyses were applied over α  = 0.1–0.9. EB irradiation progressively enhanced thermal stability, increasing the maximum degradation temperature by approximately 40°C and the average apparent activation energy from approximately 160–165 kJ·mol ⁻¹ for unirradiated materials to above 210 kJ·mol ⁻¹ at the highest dose. Conversion‐dependent activation‐energy profiles varied systematically with irradiation dose, indicating changes in degradation behavior associated with network formation and competing chain‐scission, crystallinity, and filler‐related effects. Under equal‐mass‐loading conditions, MH‐containing formulations exhibited higher degradation temperatures, apparent activation energies, and residue values than corresponding ATH‐containing formulations. Overall, isoconversional analysis provides mechanistic insight into the combined effects of EB‐induced structural modification and flame‐retardant chemistry, supporting the development of thermally stable halogen‐free polyolefin insulation materials for wire and cable applications.