Facile flame retardant finishing of cotton fabric with hydrated sodium metaborate

Flame retardant (FR) cotton fabric was facilely prepared using hydrated sodium metaborate (SMB) crystalized in situ in the interstices and on the surface of cotton fabric via one-pot impregnation approach, and the thermal, FR and mechanical properties were investigated. TGA results showed that SMB treatment improved the thermal stability of cotton fabric and enhanced the char yield. The treated cotton also had an LOI value of 28.5% with an afterglow time of less than 1 s in the UL-94 test (V-0). Considerable reductions in peak heat release rate (PHRR ~ 91.8%), total heat release (THR ~ 47.2%), peak carbon monoxide and carbon dioxide produced (PCOP ~ 28.6, PCO₂P ~ 85.5%) were obtained. The postburn residues examined by SEM and Raman spectroscopy revealed a preserved fabric structure with high graphite content. SMB treated cotton fabrics demonstrated negligible changes in the tensile strength and the elongation at break. The result demonstrates SMB as an effective flame-retardant for cotton fabrics.