Ion – complexed chitosan formulations as effective fire-retardant coatings for wood substrates

•We prepared a flame resistant coating using chitosan and other sustainable materials.•The chitosan based coatings exhibited good intumescence under heat.•The uncrosslinked chitosan based coating exhibited long delays in ignition time.•The ionically crosslinked chitosan coatings did not burn under 50 kW/m2 of heat.•The coatings exhibited good compatibility with an epoxy based, water resistant topcoat.