A durable phosphorous-based flame retardant containing double reactive groups for cotton fabrics

Ammonium acryloyl phosphite (AAP) flame retardant with multiple reactive functional groups has been synthesized for use in cotton textiles. Nuclear magnetic resonance was utilized to analyze the structure of AAP flame retardant. The scanning electron microscopy images indicated that some flame retardants penetrated the amorphous region of cotton fibres. The energy-dispersive X-ray and Fourier transform infrared (FTIR) spectroscopy spectra suggested that AAP flame retardant was grafted with cellulose through forming the -N-P(=O)-O-C- connection. The laundering cycles (LCs), limiting oxygen index (LOI), cone calorimetry, and vertical flame test (VFT) suggested that AAP-treated cotton (CF/AAP) possessed exceptional flame retardance and durability. The CF/AAP3 demonstrated an initial LOI value of 47.2%, which remained at 40.7% even after undergoing 50 LCs following the washing standard (AATCC 61-2013 3A). The thermogravimetric and infrared spectroscopy, thermogravimetric, and VFT analyses showed that AAP grafting groups underwent a condensed-phase flame retardance mechanism. The X-ray diffraction patterns indicated that the AAP flame retardant affected the diffraction peak structure of cotton fibres crystal a little during the finishing process. After finishing, the cotton fabrics retained their breaking strength and softness effectively. The overall results indicated that incorporating reactive groups such as -N-P(=O)-(ONH4)2 and CH2=CH- into flame retardants could reinforce the durability of flame-retardant cotton fabrics.