The APEMPPA grafted on cellulose through P–O–C covalent bonds.

Increasing the molecular weight of flame retardants at the same time introducing phosphate ester groups is an effective way to improve washing resistance.

The APEMPPA-treated cotton has high durability, could pass AATCC 61-2013 3A standard 50LCs.

The tensile strength of cotton fabric treated with 40wt%APEMPPA almost did not decrease.

A novel polymer ammonium salt of polyethyleneimine phosphate phosphonic acid (APEMPPA) flame retardant for cotton fabrics was synthesized and characterized by nuclear magnetic resonance (NMR), in which some ammonium phosphoric acid groups were replaced by phosphate ester groups to decrease the phenomena that the ammonium ions in flame retardant would exchange with metal ions such as Ca2+ and Mg2+ in washing water to keep flame retardance well after washing. Energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR) results, and durability of treated cotton fabrics suggested that APEMPPA was grafted onto the cellulose. Limiting oxygen index (LOI) of 40 wt% APEMPPA-treated cotton fabric was 44.5 %, which was still 34.7 % after 50 LCs according to AATCC 61-2013 3A standard. Cone calorimetric and thermogravimetric (TG) results showed the treated cotton fabrics had excellent flame retardancy. TG-FTIR and Raman test results proposed that APEMPPA mainly played a condensed phase flame retardant. EDX results indicated that replacing some ammonium phosphate groups with phosphate ester groups was effective in maintaining flame retardancy during washing. All results showed that increasing the molecular weight and introducing phosphonate group in ammonium phosphorus acid flame retardant can effectively improve flame retardancy and durability. APEMPPA-treated cotton fabrics maintained good tensile strength.

Polyethyleneimine

Phosphate ester

Flame retardant cotton

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