Synthesis of high-efficiency and durable P-N-rich flame retardant with double functional groups for cotton fabrics

A novel efficient flame retardant 3-dimethyl phosphonate-N,N-dimethyl phosphonate ammonium propanamide (FR-AM) with both -P=O(O-NH4+)(2) reactive groups and -P(=O)-O-C groups was successfully synthesized, and the durable flame-retardant cotton fabrics were prepared by FR-AM. The structure of FR-AM was characterized by nuclear magnetic resonance spectrum (H-1 NMR, C-13 NMR, P-31 NMR). The limited oxygen index (LOI) value of cotton fabric treated by 20 wt% FR-AM increased to 38.8%, which maintained at 27.2% after 50 laundering cycles of home machine washes. The treated cotton fabrics were not ignited in the vertical burning tests and cone calorimeter tests, and the fibers still kept their intact structure after combustion. The heat release rate and total heat release rate of treated cotton fabrics were significantly lower than those of control cotton fabric, especially the reduction of peak heat release rate (186 to 13 kW/m(2)) was 93.01%. The results of TG, TG-FTIR, SEM and EDS showed that FR-AM could release phosphoric acid and polyphosphoric acid, which could catalyze the dehydration of cellulose to form char before the thermal decomposition of cellulose, and reduce the releasing of flammable gases. The mechanical properties of treated cotton fabrics maintained well after treated with FR-AM.

Automated summary

A novel efficient flame retardant FR-AM was successfully synthesized and used to treat cotton fabrics, resulting in durable flame-retardant properties. The treated cotton fabrics showed increased LOI value, reduced heat release rate, and maintained good mechanical properties.