Recyclable fire-retardant bio-based thermosets: From molecular engineering to performances and applications

Thermosets play a critical role in aerospace, automotive, electronics, and construction industries due to their mechanical strength, thermal stability, and chemical resistance. Advanced thermoset materials, such as epoxy resins, phenolic resins and unsaturated polyester resins, have significantly contributed to industrial innovation. However, these traditional thermosets heavily rely on petroleum-based resources and suffer non-recyclability and even high flammability. Last years have witnessed the use of many renewable chemicals for developing advanced bio-based thermosets with tunable physical properties, such as recyclability and reprocessability enabled by dynamic covalent chemistries, fire retardancy, mechanical and thermal properties. This review aims to summarize recent advances in recyclable, flame-retardant, bio-based thermosets, and highlights their molecular structures and design strategies for achieving high performances. We also discuss intrinsic flame-retardant modes of action, and degradation/recycling mechanisms based on dynamic covalent chemistry. Following discussions on their applications, some key challenges and opportunities are also proposed for the development of next-generation advanced thermosets. This work is expected to expedite the creation of high-performance recyclable thermosets and to advance the sustainability transition of traditional thermosets.