Review of reversible dynamic bonds containing intrinsically flame retardant biomass thermosets

Thermosets are widely used in the polymer, composite, automobile, aerospace, and electronic industries due to their excellent mechanical, thermal, light weight, and dimensional stability performances. However, most thermosets are made from petroleum resources that deplete petroleum reservoirs and cannot be reused due to their stable linkages, resulting in many waste and environmental problems after their service life. Therefore, repairable, reprocessable, and reworkable thermosets can be produced by incorporating dynamic covalent linkages into polymeric thermosets, which can extend the lifetime and reduce waste. Nevertheless, when a product is recycled multiple times, it is unavoidable that it will decay and become a disposal problem. The use of green and sustainable biomass resources as raw materials for polymer products can assist in mitigating environmental issues by lowering petroleum usage and carbon dioxide emissions. Moreover, thermosets or recyclable biomass thermosets are extremely flammable, limiting their application in automobiles, railways, aircraft, buildings, and electrical products. As a result, flame retardant properties are needed. The purpose of this review paper is to impart a broad summary of the subject by emphasizing and addressing recent advancements as well as future prospects for inherently recyclable flame retardant biomass thermosets. Moreover, synthesis methods have been highlighted to develop the design of internally recyclable fire retardant biomass thermosets. A distinct emphasis will be given on recyclable and inherently fire retardant biomass thermosets in terms of flame retardancy, recycling property, physical properties, and thermal stability. Finally, we will explore the importance and threats that intrinsically recyclable flame retardant biomass thermosets face in the future.