A novel strategy for construction of multiple dynamic hybrid crosslinking network for polyethylene pipes and self-healing behavior via thermal stimulation

Abstract

Polyethylene (PE) pipes with excellent comprehensive performances have been most widely applied, while endowing PE pipes with self-healing property was conducive to prolong their service life. Due to nonpolar nature of PE molecules, its self-healing functionalization remains extremely challenging. In this work, by introducing amide and carboxyl groups into PE/natural rubber (NR) chains to construct reactive sites and compositing with zinc acrylate (ZDA)/ferric chloride (FeCl3), the hybrid crosslinking network composed of covalent bonds and multiple dynamic bonds, including hydrogen bonds, Fe3+-carboxyl/amide coordination bonds and Zn2+-carboxylate ionic bonds was successfully constructed in PE/NR blend via reactive processing and in-situ vulcanization crosslinking. Upon stretching, the dynamic crosslinking network was first broken, resulting in large energy dissipation, apparent hysteresis loss and stress relaxation, while when removing stress, its residual strain decreased remarkably with increasing waiting time, displaying reversible dynamic characteristic. As a result, the hybrid crosslinking network was reconstructed via thermal stimulation, facilitating diffusion and entanglement of PE/NR chains across interface, and the width/depth of the scratch obviously decreased. The tensile strength and fracture toughness recovered obviously, and the self-healing efficiency of the blends and pipes reached 65–70 %, showing a significantly enhanced self-healing ability with promising application potential.