Hybrid phosphorus-doped silica architectures derived from a multistep sol-gel process for improving thermal stability and flame retardancy of cotton fabrics

Hybrid phosphorus-doped silica architectures have been prepared through sol-gel processes in order to enhance the thermal stability and flame retardancy of cotton. To this aim, diethylphosphatoethyltriethoxysilane has been used as a functional phosphate alkoxysilane in a multistep process, consisting of consecutive depositions 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. FT-IR ATR spectroscopy has been exploited for assessing the formation of the silica skeleton on the cotton surface and for evaluating the interactions between the cellulosic fibres and the doped film. The sol-gel treatments have proved to play a protective role on the degradation of the cotton fibres, hindering the formation of volatile species that fuel the further degradation and favouring the formation of char.