Synthesis and characterization of hybrid phosphorus-silica films for halogen-free flame retardant cotton fabrics

Diethylphosphatoethyltriethoxysilane has been used as a functional alkoxysilane in consecutive sol-gel depositions on cotton fabrics, for obtaining architectures with a different number of layers (namely, 1, 3 or 6 layers). The role of such architectures has been deeply investigated and correlated with the final properties of the treated fabrics. Afterwards, 3-aminopropyltriethoxysilane and N,N,N',N',N'',N''-hexakis methoxymethyl-[1,3,5]triazine-2,4,6-triamine have been reacted with diethylphosphatoethyltriethoxysilane to investigate the effect of the concurrent presence of Si, P and N on the flame retardancy properties of the cellulosic fabrics. Finally, the synergistic or additive effects due to the concurrent presence of phosphorus and nitrogen-based compounds have been thoroughly investigated. Flammability and cone calorimetry tests have shown that only phosphorus (i.e. bisphosphonate) is able to promote a certain synergism with the sol-gel derived oxide phases in terms of residue, heat release rate and total burning time.