Layer-by-Layer Assembly of Hypophosphorous Acid-Modified Chitosan Based Coating for Flame-Retardant Polyester–Cotton Blends

Hypophosphorous acid-modified chitosan (PCS), as a novel phosphorus-containing chitosan derivative, was first successfully synthesized and characterized by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. Subsequently, thin films of the ecofriendly PCS and branched polyethylenimine were deposited on polyester–cotton (PTCO) blends by the layer-by-layer assembly technique, in an effort to enhance their thermal properties and fire resistance properties. Thermogravimetric analysis, thermogravimetric analysis–Fourier transform infrared spectrometry, scanning electron microscopy, and horizontal flame test (HFT) were used to investigate the quality of the coatings as well as their fire resistance performance. The thermal and thermal oxidation stabilities at high temperature were enhanced for all coated PTCO blends. During the HFT, the afterglow phenomenon was eliminated for all coated blends, and self-extinguishing was achieved for the PCS2-20BL sample. It was found that the enhancement of the intumescent effect by the high phosphorus content in these coatings was conducive to achieving this superior performance.