Chitin nanofibrils, functionalised with phosphorus, combined or not with nano-clay (montmorillonite), were used to prepare films (approx. 25 µm), and tested for fire resistance and as fire barrier materials. The seafood industry produces millions of tonnes of chitin waste materials annually (crustacean shells and cuticles), already used today in e.g. cosmetics, water treatment or biomedicine, and recognised to be non-toxic, antibacterial and biodegreadable. The nano-crystalline fibril structure of this chitin has been “optimised by nature” for mechanical strength and modulus. Its content in internal amides and surface amines impairs some inherent fire resistance. This research shows that chitin can be surface de-acylated using simply aqueous sodium hydroxide, then functionalised with phosphorus (again with an aqueous reaction). Papers produced with P-functionalised chitin showed significantly improved vertical flame resistance and total heat release, compared to chitin reacted with acetic acid or chlorine. Papers produced from phosphorus-functionalised chitin plus montmorillonite showed both mechanical performance comparable to carbon nanofibre paper but also effectiveness as a fire barrier.
“Sustainable Chitin Nanofibrils Provide Outstanding Flame-Retardant Nanopapers”, F. Riehle et al., Biomacromolecules 2019 https://doi.org/10.1021/acs.biomac.8b01766