Flame retardancy of biopolymers enhanced by bio-based flame retardants: A review

The demand for sustainable materials has led to the development of biopolymers as alternatives to petroleum-based polymers. However, their high flammability limits their use in applications requiring stringent fire safety. Bio-based additives such as lignin and chitosan among others have charring abilities that enhance flame retardancy by forming protective barriers during combustion. Renewable additives such as phytic acid, tannic acid, casein, and hydrophobins also show potential in improving polymer dehydration, which can help create a stable char layer. Phosphorylation and the use of nitrogen-containing compounds and nanomaterials show promise in improving fire resistance. These advancements make biopolymers more suitable for high-risk fire safety applications while maintaining sustainability. While considerable progress has been made in enhancing the flame retardancy of biopolymers, challenges remain in developing highly effective, non-toxic, and fully biodegradable flame retardants that do not compromise the physical properties and processability of the biopolymers.