Schiff base approach to introduce chitosan-phytic acid complex for flame-retardant cotton fabrics

Abstract

In this study, chitosan was integrated onto cotton fabric fibers through a Schiff base reaction, followed by the in-situ generation of Chitosan-Phytic acid (CH-PA) complex to achieve green flame retardancy. The process began with oxidizing the fabric using sodium periodate (NaIO₄) to create numerous aldehyde groups on the fiber surface. Subsequently, CH was grafted onto the fabric via a Schiff base reaction. The fabric was then immersed in a PA solution to form a CH-PA complex, resulting in a novel and highly efficient flame-retardant (FR) fabric. The structure of the treated fabric was analyzed by using Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), confirming the successful formation of the desired structure. The thermal stability and flame retardancy of the fabric were systematically evaluated using thermogravimetric analysis (TGA), cone calorimetry (CONE), vertical combustion tests, and limiting oxygen index (LOI) measurements. The LOI increased from 17.6 % to 30.6 %, and vertical combustion tests demonstrated self-extinguishing capabilities when the fabric was treated by the NaIO₄ solution at concentrations of 0.02 g/mL or higher. In the CONE test, the modified fabric showed significant improvements, with peak heat release rate (pHRR) and total heat release (THR) decreasing by approximately 80 % and 60 %, respectively. Comprehensive analysis indicated that the FR mechanism involved both gas phase and condensed phase actions. Further characterization of the material included tensile testing and wash resistance assessments. By comparing these findings with recent research on similar topics, the advantages and disadvantages of the materials were thoroughly evaluated. Notably, this work provides a robust experimental foundation and conceptual expansion for the green flame retardancy of cotton fabrics.