A facile strategy to fabricate cellulose-based, flame-retardant, transparent and anti-dripping protective coatings

The inherent high flammability and poor processability characteristics of cellulosic materials result in dominant adverse impacts on their practical applications. Here, we proposed a robust strategy for converting highly flammable cellulose into an inherently flame-retardant, halogen-free, anti-dripping and easy-to-process material, DOPO-cellulose acrylate (DCA), by controllably introducing acrylate groups into cellulose chains and later covalently immobilizing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) through an addition reaction between acrylate groups and DOPO. A small number of DOPO groups in DCA significantly reduce the heat release rate and total heat release, and promote the formation of dense and continuous char. Thus, the free-standing and transparent films of the resultant DCA self-extinguish instantly (<1 s) once removed from the flame. Meanwhile, partial acrylate groups are deliberately retained to obtain UV light-crosslinkable DCA, which can form a rigid three-dimensional cross-linked network, thereby inhibiting melt dripping. Benefitting from the excellent formability, the UV light-crosslinkable DCA can easily be processed into flame-retardant, anti-dripping and transparent coatings for protecting various flammable materials from fire, such as paper and wood. The present inherently flame-retardant cellulosic materials show promise for use as novel functional bulk materials and coatings to protect books, buildings and furniture.