Kinetic and chemorheological evaluation on the crosslinking process of peroxide-initiated low-density polyethylene

Abstract

Peroxide-initiated low-density polyethylene (PLPE) has been extensively used as insulating materials for high-voltage cables, while the lack of comprehensive knowledge on crosslinking process of PLPE seriously limits the development of cable insulation. Here, the crosslinking process and mechanism of PLPE are fully revealed by combining kinetic and chemorheological analysis for the first time. Rheological parameters during crosslinking process of PLPE are obtained by dynamic rheology experiments at different frequencies and temperatures. Crosslinking kinetics of PLPE is explored by rheological conversion method and diffusion-controlled Kamal-Sourour model. Meanwhile, chemorheological behaviors of PLPE are discussed based on percolation theory and Arrhenius law. The results indicate that the crosslinking reaction of PLPE involves complex n-order and autocatalytic reactions. Importantly, the autocatalytic reaction and the gelation formation significantly enhance the reaction rate. Furthermore, physical diffusion of macromolecular chains obviously reduces the reaction rate and prolongs the termination reaction. Based on that, the mutual influences and relationships between the kinetic and chemorheological behaviors are established by combining the apparent activation energy. It is suggested that PLPE crosslinking process is controlled by alternant synergistic action of chemical reaction and physical diffusion. This work can provide a critical theoretical basis for the comprehension and optimization of PLPE crosslinking process.