Flame-retardant treatment of cotton fabric with organophosphorus derivative containing nitrogen and silicon

A novel environmentally friendly flame-retardant compound, diethyl 3-(triethoxysilanepropyl) phosphoramidate (DTP) was synthesized via a simple one-step procedure with good yield and characterized by FT-IR and H-1-NMR, P-31-NMR and Si-29-NMR. The synthesized compound was coated onto cotton fabrics with different levels of add-ons (5-17 mass%) using the traditional pad-dry-cure method. SEM and XPS were conducted to characterize the surfaces of the coated cotton fabrics. The XPS results showed that DTP was attached to cotton through covalent bond. Cone calorimeter test showed that the cotton fabric treated with DTP became less flammable due to the lower HRR, THR and CO2/CO ratio. The modified cotton fabrics exhibited efficient flame retardancy, which was evidenced by limiting oxygen index (LOI) and vertical flammability test. Cotton fabrics treated with DTP in 5-17 mass% add-ons had high LOI values of 23-32%. Thermogravimetric analysis results show that the usage of DTP promotes degradation of the cotton fabrics and catalyzes its char formation.