Preparation of eco-friendly flame-retardant cotton fabrics based on chemical grafting and calcium chelation

In this study, a novel strategy is proposed to prepare eco-friendly flame-retardant cotton fabrics, where chloroacetic acid (MCA) and L-glutamic acid (L-Glu) are used as raw materials to enhance the chelation ability between carboxyl groups (-COO-) and calcium ions (Ca). The morphological and structural characterizations of the prepared cotton fabrics indicate that the three free hydroxy groups (2, 3, 6) in the cellulose macromolecule are chemically modified to graft a large number of carboxyl groups, and Ca ions are successfully chelated on the surface of cotton fabric. The thermal stability of cotton fabrics is greatly improved in both air and nitrogen atmosphere. The residual mass of flame-retardant cotton fabric (COT-Glu–Ca) is much higher than that of original cotton fabric, increasing from 0.03% to 5.6% in air and from 8.1% to 28.2% in N, respectively. At the same time, the limiting oxygen index (LOI) of COT-Glu–Ca fabric is as high as 33.6%. The prepared flame-retardant cotton fabric can undergo vertical combustion tests with a char length of only 53 mm, and afterflame and afterglow are not observed, which proves that the grafted cotton fabric had a good flame retardancy due to a series of modifications and adsorption of Ca ions. The properties of the cotton fabric, including tensile strength, whiteness, and moisture absorption, are all retained at a satisfactory level. Overall, this study provides a promising strategy for manufacturing eco-friendly, phosphorus-free, halogen-free, and fire-resistant cotton fabrics with enhanced metal ion chelation ability. Graphical abstract: (Figure presented.)