Phosphorated cellulose as a cellulose-based filler for developing continuous fire resistant lyocell fibers

Developing a sustainable fire resistant regenerated cellulose fiber for realizing large scale industrial production is an urgent research topic. In this work, a cellulose-based flame retardant filler, phosphorylated microcrystalline cellulose, was successfully synthesized. The acquired phosphorylated cellulose (P-Cell) as a modified bio-based flame retardant was cost-effective and compatible with cellulose spinning dope. The preparation process of fire resistant fiber was the same as the lyocell fibers on a factory scale pilot production. The lyocell fibers loaded with 20 wt% P-Cell exhibited favorable thermal stability and fire retardancy. The char residue amount of fire resistant lyocell fibers remarkably increased by 118% at 700 °C compared with the pure lyocell fibers. As micro combustion calorimetry estimated, the total heat release and peak heat release rate of modified fibers significantly decreased by 87.6% and 82.4%, respectively compared with those of pure lyocell fibers. The flame retardant mechanism was ascribed to the formation of phosphorus-containing oxides and char layer in the condensed phase and the generation of incombustible compounds in the gaseous phase.