DOPO-VTS-based coatings in the realm of fire retardants for cotton textile

The work elucidates the feasibility of incorporation of phosphorus-silicon containing fire retardant (10-(2-trimethoxysilylethyl)- 9-hydro-9-oxa-10-phosphaphenanthrene-10-oxide [DOPO-VTS]) into nanosol coating solutions by cohydrolysis cocondensation reaction of DOPO-VTS with tetraethoxysilane precursor (TEOS). Impregnation of cotton with the organophosphorus silane in a form of nanosol dispersion afforded better fire retardancy of such samples compared to pure DOPO or TEOS-treated cotton indicating synergism between phosphorus and silicon containing species in a condensed phase. The detailed analysis by TGA-MS and SEM pointed to the fact that DOPO-VTS acts as a promoter of cotton degradation which, in turn, results in acceleration of the charring process and formation of compact char in contrast to TEOS-treated samples. Further analysis of the char by XPS confirmed high content of carbonaceous residue in the case of DOPO-VTS-treated samples while mainly siliceous component was left in the char in case of cotton treated with TEOS. Standard flammability test (EN ISO 15025:2008) additionally confirmed the absence of smoldering and better overall fire performance of the DOPO-VTS samples in contrast to TEOS-treated samples.