Preparation of biobased guar gum polyelectrolyte complex coatings by sol-gel method for improving the flame retardancy of ramie fabrics

In this study, to improve the flame-retardant properties of ramie fabrics (RFs), a polyelectrolyte complex (PEC) was prepared in a one-step process using biobased guar gum (GG), polyethyleneimine (PEI), and ammonium polyphosphate (APP) and deposited on the surface of the RF to construct an intumescent flame-retardant coating. Fabrics treated with PEC coatings exhibited excellent flame-retardant properties. Specifically, the cone calorimeter test results revealed that an increase in sample weight of only 13.23 wt% resulted in significant reductions in the peak heat release rate (pHRR), total heat release (THR), and fire growth rate (FGR) of 91.37%, 65.12%, and 95.28%, respectively. Additionally, the limiting oxygen index (LOI) increased from 19.4% to 33.5%, and the fabrics self-extinguished immediately after the ignition source was removed during the UL-94 test. Scanning electron microscopy (SEM) of the char residue revealed expansion bubbles on the surface, suggesting that the PEC coating provides flame retardancy through a synergistic effect involving both the gas phase and the condensed phase. This study provides a simple and convenient solution for realizing green and efficient flame-retardant coatings on RF.