A polymeric phosphorus, nitrogen and sulphur containing PIN flame retardant was synthesised, based on polyphosphoric acid, an epoxy and thiourea, containing c. 2N:1P:1S. Using a water-soluble cross-linking compound, this PIN FR was applied to nylon fabric. Fire safety performance was compared to market-available P-based flame retardants for nylon.
Fire resistance of the nylon fabric with the sulphur-containing FR (S-PIN FR), measured by LOI (Loss on Ignition) and length of charred fabric, was much better than untreated fabric, and was better, even after ten wash cycles, than with the market FRs. Results also show that the smoke density is significantly lower with the S-PIN FR than for untreated fabric, and that the emissions of various volatile carbon compounds were reduced (the S-PIN FR inhibited pyrolysis of the nylon fabric). Some sulphur containing PIN FR systems are already successful on the market, see e.g. Sony SORPLAS (recycled polycarbonate) in pinfa Newsletter n° 46.
“Synthesis and application of a sulfur-containing phosphoric amide flame retardant for nylon fabric”, Y. Chen, Fie and Materials, 2016 http://dx.doi.org/10.1002/fam.2354