Ultra washing durable flame retardant coating for cotton fabric by the covalent bonding and interface polymerization

Due to fire hazards and environmental concerns, considerable attention has been paid to the design of durable flame retardant fabrics. In this work, a formaldehyde-free flame retardant cotton fabric (Cotton-PEI/APP-TMC) with ultra washing durability was prepared via covalent bonding of ammonium polyphosphate (APP) and polyethyleneimine (PEI) followed by the interface polymerization between PEI and trimesoyl chloride (TMC). The prepared fabric exhibited excellent flame retardancy with a limiting oxygen index value (LOI) of 42.0 % and a damaged length of less than 40 mm in the vertical flammability test (VFT). Besides, the cotton-PEI/APP-TMC sample was not ignited in the 50 kW/m2 cone calorimeter test with a dramatic decrease in both the peak heat release rate and total heat release. Even after 300 washing cycles, the cotton-PEI/APP-TMC sample had an LOI value of 35.3 % and was still self-extinguishing in VFT. It was demonstrated that the interface polymerization between PEI and TMC stabilized the flame retardant coating and shielded the Na+ during washing cycles, which endowed the fabric with durable flame retardancy. It is expected this work paves a promising application prospect for the fabrication of bio-safe durable flame retardant cotton fabrics.