A Kinetic Study on the De-Crosslinking and Decomposition of Silane-Cross-Linked Polyethylene in Supercritical Methanol

De-crosslinking of silane-cross-linked polyethylene (S-XLPE) in supercritical methanol was investigated. Changes in gel content and molecular weight with reaction temperature and reaction time were analyzed in a batch reactor, and kinetic parameters were calculated from the experimental data. The reaction time for de-crosslinking shortened as the reaction temperature increased and the complete de-crosslinking of S-XLPE was achieved at 320 °C and 20 min. The de-crosslinking rate of S-XLPE fit well with the first order reaction model. In addition, the molecular weight of de-cross-linked polyethylene (DXPE) decreased further as reaction temperature and reaction time increased when the reaction temperature exceeded 360 °C relative to that of the original polyethylene before being cross-linked. The decreasing molecular weight trend also fit well with the first order reaction model.