P-N-Si PIN FR for non-drip PET fibres

A DOPO – amine - siloxane PIN flame retardant treatment halved burn length and avoided burning drips in PET fabric. The PIN FR was synthesised by the Atherton-Todd reaction, using the well-known PIN FR molecule DOPO (9,10-Dihydro- 9-oxa- 10-phosphaphenanthrene- 10-oxide) with commercially available 3-aminopropyl triethoxysilane (APTES) and with triethylamine, then formulated to a polysiloxane sol. This was applied to PET fabric by dipping-padding-drying. At 15% loading, LOI (limiting oxygen index) was increased from 21.3% (untreated PET) to 26%, vertical flame damage length was reduced to 2.5 cm (untreated PET totally burned) and burning drips were prevented. Fire performance was durable after five wash cycles. The fire performance is attributed to both gas phase action of phosphorus radicals and formation of stable Si-O-Si crosslinked char.

“Synergistic phosphorus-siloxane hybrids for concurrent flame retardancy and anti-dripping of PET fabrics: Mechanistic design and performance optimization”, R. Zhang et al., MTLA Materiialia 45 (2026) 102691 https://doi.org/10.1016/j.mtla.2026.102691

See also “PIN FR no-drip fire performance in PA6” in pinfa Newsletter 156.