The utilization of glycerol and xylitol in bio-based vitrimer-like elastomer: Toward more environmentally friendly recyclable and thermally healable crosslinked rubber

Abstract

Eco-friendly rubbers developed from renewable materials and using covalent adaptive networks (CANs) are a family of sustainable materials that has recently attracted enormous interest from both industry and academia. In this study, vitrimer-like elastomers based on epoxidized natural rubber (ENR) were synthesized by cross-linking with dimer fatty acid (DFA). The addition of a small amount of bio-based polyol, namely the sugar alcohol glycerol (GLY) or xylitol (XYL), into the elastomeric vitrimer significantly enhanced its physical and viscoelastic properties. The glycerol-containing vitrimer tended to have reduced maximum torque, modulus, and crosslink density, while the opposite trend was found when xylitol was loaded in ENR50 vitrimer. Therefore, the mechanical and thermal properties of ENR50 vitrimer, as well as H-bond formation, can be manipulated by incorporating different types and concentrations of bio-based polyols. Importantly, a β-hydroxy ester formed in ENR50 can undergo an exchange reaction between the ester and hydroxyl group, a so-called dynamic exchange transesterification reaction, enabling thermo-healing and recycling. The formation of a denser network in polyol-treated ENR50 vitrimer may suppress the mobility of chain segments, affecting speeds of exchange reaction and stress relaxation. The ENR50 vitrimer with sugar alcohols shows several remarkable features in its mechanical performance and dynamic properties and points to an alternative for achieving green production, circular economy, and environmentally friendly processes.