A review on recent approaches to sustainable bio-based epoxy vitrimer from epoxidized vegetable oils

Abstract

Epoxidized vegetable oil (EVO) – based epoxy vitrimer is a promising bio-based material to replace the non-recyclable and ever-increasing petrol-based thermoset. However, the low overall properties of EVO-based epoxy vitrimer are relatively unmatchable to petrol-based thermoset, retarding the substitution of EVO-based epoxy vitrimer into the application range of petrol-based thermoset. To fill the research gap, we review the recent approaches and important characteristics of EVO-based epoxy vitrimer, including the selection of EVO, classification of covalent adaptable network (CANs) and, material properties. Their potential applications and outlooks are discussed as an implication for future development. For EVO-based epoxy vitrimer, EVOs with higher mean epoxy values are suggested to be selected as epoxy monomer in order to produce a vitrimer with greater tensile properties and higher glass transition temperature, Tg. Types of CANs incorporated in EVO-based epoxy vitrimer are not yet fully explored as only 3 types of CANs (transesterification, Schiff base and disulphide exchange) have been reported currently. The mechanical properties and Tg of EVO-based epoxy vitrimer can be improved by using curing agent with rigid structure and avoid using aqueous-based curing agent during synthesis process. Thermal stability of EVO-based epoxy vitrimer is affected by crosslinking density and the structure of curing agent. It is envisaged that EVO-based epoxy vitrimer with greater properties can be developed to replace the traditional petrol-based thermoset, provided that effective EVO, appropriate CANs and suitable curing agent are selected.