A novel durable flame retardant cotton fabric produced by surface chemical grafting of phosphorus- and nitrogen-containing compounds

Phosphorus- and nitrogen-containing compounds were grafted on a cotton fabric surface by three steps. Firstly, the cotton fabric was oxidized by sodium periodate to form aldehyde groups, and then the aldehyde groups were reacted with the organic amine to generate Schiff bases. Finally, the Schiff bases were reacted with dimethyl phosphate by the phosphine hydride addition reaction. The chemical structure of grafted cotton fabric was characterized and confirmed. The results demonstrated that the limiting oxygen index (LOI) value of the modified cotton fabric dramatically increased from 19.5% for pure cotton fabric to 28.1% due to the chemical grafted on the cotton surface. After washing, the LOI value slightly decreased to 27.4%, which indicated that the prepared cotton fabric possessed superior washing durability. Thermogravimetry and cone calorimetry results demonstrated that the grafted flame retardant stimulated the thermal degradation and charring of cotton fabric ahead of time and formed sufficient char residue at high temperature, which efficiently prevented the underlying cotton fabric from degradation and combustion. Consequently, the flame retardancy of the cotton fabric was enhanced.