Physical and chemical transformation of crosslinked polyethylene by super-pressure microchannel liquid collision

Abstract

Recycling of thermosetting material with low energy is still a significant challenge due to their stable and strong chemical bonds existed. In this work, we proposed a super-pressure microchannel liquid collision approach that combined microchannel with super-pressure driving and liquid collision to explore the physical and chemical change of crosslinked polyethylene (XLPE), by which the large bond breaking energy can be obtained and imposed on XLPE particles. Here, a super-pressure microchannel liquid collision generator (SP-MLCG) with 300 MPa input pressure and ~600 m/s output speed was designed to obtain the promising collision energy that calculated from the required energies of breaking the crosslinked bonds in XLPE. The particle size, the surface morphology, the molecular weight, the thermal stability, and the melting properties were evaluated step-by-step by optical image, SEM, GPC, TG, and DSC. By using the SP-MCLG, the size of XLPE particles decreased to ~50 μm. Meanwhile, SP-MLCG can lead to the decrease in the proportion of chains with high molecular weight, and in turn produce the reduction of thermal stable, glass transition temperature and melting temperature of XLPE particles. Especially, melt enthalpy can decrease from −89.65 to −64.14 J·g⁻¹. Hence, our proposed technique might be regarded as a promising method that is able to achieve the recycling and reuse of XLPE due to the considerable transformation of its physical and chemical properties.