Chitosan and nano-TiO ₂ coating improves the flame retardancy of dyed and undyed denim fabrics by increasing the charring

In this study, chitosan is obtained from the waste shells of crayfish ( Astacus leptodactylus) and characterized. The crayfish chitosan was coated on cotton fabrics using the padding-drying method. The surface properties, flammability and water and air permeability properties of these coatings based on chitosan and a combination of chitosan and nano-TiO ₂ were determined. The weight of green calico fabric increased to 24.76% after coating with chitosan, while the weight of the blue dyed denim fabric increased to 5.19%. The chitosan coating increased the tear strength of the calico fabric by 20% in the weft direction. Thermogravimetric analysis and vertical burning tests show that chitosan improves the thermal resistance and flame retardancy performance of denim fabrics. While the amount of residue due to thermal degradation of the blue dyed denim fabric was 16.78%, it increased to 34% after coating with chitosan+nano-TiO ₂ . The chitosan coating reduced the mass loss caused by thermal degradation in green calico fabric from 86.3% to 66.0%. Chitosan also improved the post-flame combustion performance of fabrics. While the ember burning time is decreased to 6s in the chitosan-coated dyed calico fabric, this did not occur in the chitosan+nano-TiO ₂ -coated dyed denim fabric.