One-step reactive processing of vitrimeric thermoplastic polyolefin elastomer with greatly improved thermo-mechanical property

Abstract

Chemically crosslinking can enhance mechanical strength, dimensional stability and heat-resistance of thermoplastic polyolefin elastomers. However, chemically crosslinked elastomers suffer from reduction of flowability and strong shrinkage after reprocessing. In this work, inspired by vitrimer concept, olefin block copolymer (OBC) elastomer was chemically modified with dynamic boronic ester bond through one-step reactive processing. Based on the swelling test, FT-IR sperctra and DMA investigation, OBC vitrimer with tunable composition of dynamic Boron–Oxygen(B–O) bonds has been successfully prepared. Based on classical Arrhenius theory, the calculated activation energy (Ea) of OBC vitrimers ranges from 7.838 kJ/mol to 46.851 kJ/mol due to combined effect of chemical and dyanmic crosslinks. The prepared OBC vitrimers shows good creep-resistance, great reprocessability and good mechanical properties including tensile strength up to 15 MPa, elongation at break of 2300%, and elastic recovery of 90% at 300% strain. Interestingly, OBC vitrimers show significantly improved high-temperature mechancial property, i.e., tensile strength of ∼0.12 MPa and elongation excess 1200% at 120 °C where both OBC and OBC-DCP samples break instantly. Therefore, our work shows a promising industrial-scale strategy to prepare vitrimer elastomers via reactive processing, and provides guidance for molecular design of high-performance vitrimeric polyolefin elastomers.