Elucidation of cellulose phosphorylation with phytic acid

The worldwide ban on the use of halogenated flame retardants has accelerated the development of non-toxic alternatives from natural feedstock, such as phytic acid. The fire suppressing mechanisms which acidic phosphates impart on cellulosic materials rivals most solutions yet promotes cellulose hydrolysis and degradation. Current attempts to prevent degradation that results from the acid hydrolysis and to improve flame retardancy rely on the use of catalysts without evaluating the effect of curing temperature on cellulose phosphorylation. In this study, the fundamental condensation reaction between cellulose and phytic acid reveals how varying curing temperature affects the phosphorylation and degradation of cellulosic structures. Curing a low concentration of phytic acid on cellulose at 160 °C was shown to promote the phosphorylation of cellulose over the formation of oligo-phosphates. The addition of phytic acid and rise in curing temperature degraded non-crystalline moieties and improved thermo-oxidative stability credit to the char layer formation of the phosphorylated cellulose structure. Increased phosphorus content expectedly led to improved thermal stability, yet cross-linking of phytic acid to cellulose overcame the need for increased phytic acid concentrations. This work thus provides the basis for the application of heat-curing phytic acid at low concentrations to target cellulose fire-retardancy using a chemical catalyst-free and solvent-free approach.