A novel high-molecular-weight flame retardant for cotton fabrics

Abstract

A novel phosphorus-nitrogen based high-molecular-weight flame-retardant ammonium salt of N,N-bis(phosphonomethyl) polyacrylamide (FR-PA) was synthesized for cotton fabrics. The structure of FR-PA was characterized by nuclear magnetic resonance (1H NMR, 13C NMR, and 31P NMR) as well as Fourier-transform infrared spectroscopy, and its viscosity average molecular weight was 3700. FR-PA could be grafted on cotton fabrics by using the dip–pad–cure method. The limiting oxygen index of the treated cotton fabrics reached 40.1%; after 50 laundering cycles, the cotton fabrics still retained an LOI of 28.5%. The treated fiber surface was smooth, as revealed by scanning electron microscopy, and the flame retardant was grafted on the cotton fibers, as determined by energy-dispersive X-ray spectroscopy. Thermogravimetric analysis showed that the treated cotton could leave a large amount of residue, and thermogravimetric infrared analysis indicated that the finished cotton released little flammable gas at high temperatures. Oxygen consumption cone calorimetry showed that the heat release rate and the total heat release of the treated cotton fabrics were significantly lower than those of the control cotton fabrics. Moreover, the stiffness and tensile strength of the treated cotton fabrics were also maintained.