Characterization of shape memory silane cross‐linked low‐density polyethylene prepared by solid‐phase grafting process

Abstract

Silane cross-linking is a conventional process to improve the properties of polyethylene, and the most common process is completed by two-step methods including melt grafting and hydrolytic cross-linking. In this work, silane crosslinked low-density polyethylene (SXLPE) was prepared via solid-phase grafting copolymerization for the grafting of vinyl trimethoxysilane (VTMS) onto low-density polyethylene (LDPE). The grafting efficiency and cross-linking efficiency were determined by infrared analysis and gel content measurement, and the properties of the materials were evaluated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) studies, thermogravimetric analysis (TGA), mechanical performance test, and shape memory behavior characterization. As the benzoyl peroxide (BPO) content changes from 0.1 to 0.5 phr, the SXLPEs exhibit an increase of cross-linking degree determined by gel content, a slight decrease of crystallinity, an improvement of thermal stability, and enhancement of elastic modulus, and more chain entanglement. The solid-phase grafting copolymerization retains substantial crystal regions of LDPE, which makes it show good shape memory properties, reaching 95% shape fixity ratio and 87% shape recovery ratio.