Testing Si P N synergy for PIN FR cotton

Phosphoramidate FRs were compared in cotton coatings, with functionalised silane versus orthosilicate. Silica included into the phosphoramidate (as functionalised silane) only showed fire protection synergy at higher loadings, whereas separate phosphoramidate and orthosilicate, applied together, showed synergies at low and higher loadings. The phosphoramidate PIN FR (containing nitrogen and phosphorus) was Detra-Depa, based on diethylenetriamine. The silane-functionalised variant was based on Triamo (3-[(trimethoxysilyl)propyl] diethylenetriamine). The orthosilicate was TEOS (tetraethyl orthosilicate). They were applied to cotton weave 170 g/m³ by sol-gel and wet finishing at loadings of 0 – 4.5 g/m². The phosphoramidates showed to release TEP (triethyl phosphate) to the gas phase in fire, and to form P-N protective char. At all loadings, the orthosilicate acts in synergy improving char structure without interfering with other FR mechanisms, whereas at low loadings the functionalised silane showed a surface barrier effect preventing the FR dehydration effect and its inhibition of cotton pyrolysis. The authors conclude that silica can offer synergy with N-P phosphoramidate FRs on cotton, but that effectiveness depends on loadings and on the form of the silica.

“A Exploring the impact of siloxane networks on the thermal behavior of P/N-enriched flame-retardant finishes for cotton fabric”, R. Otto et al., Chemical Engineering Journal 520 (2025) 165778 https://doi.org/10.1016/j.cej.2025.165778