Investigation of Treated Cellulose Filaments as Flame Retardants in Rigid Insulating Polyurethane Foam

The flame retardant commonly used in spray polyurethane foam is tris(1-chloro-2-propyl)phosphate (TCPP), a petroleum-derived chlorinated compound that emits toxic fumes during fires. The objective of this study was to explore the viability of treating cellulose filaments as a sustainable flame-retardant solution to enhance the environmental performance of polyurethane foam and reduce the smoke emission rate in the event of a fire. Cellulose filaments (CFs) were treated using nitrogen- and phosphorus-based compounds, yielding polyelectrolyte complexes (PEC) and layer-by-layer (LbL) products. The morphology, thermogravimetric analysis, fire behavior, and water vapor sorption of the resulting polyurethane foams and treated cellulose were studied. Despite low levels of phosphorus and nitrogen treatment (0.75% and 1.4% phosphorus in PEC, and 7.47% and 4.5% in LbL), the treated CFs showed promising properties. At equivalent phosphorus levels, treated CFs exhibited residue levels comparable to the commercial flame retardant TCPP (28% residue under inert atmosphere in TGA and 44% in cone calorimeter analysis) and produced lower total smoke emissions (TSR of 400 m2/m2 for PEC, 383 m2/m2 for LbL, compared to 432 m2/m2 in TCPP foams and 531 m2/m2 in commercial foams). Further impregnation may be necessary to improve flame-retardant properties.