Effect of sodium ligno-sulphonate on flammability of PET woven fabric

Polyethylene terephthalate (PET) polyester fabric has been treated with different concentrations of sodium lignin sulphonate (SLS), a lignin based sustainable flame retarding agent. Treated PET fabric has exhibited different chemical loading on its surface varying from 15 to 60% depending on the concentration used. Treated fabric has shown 40–70% more limiting oxygen index (LOI) value as compared to the control PET fabric. 200 g/L SLS treated PET fabric (with 35% chemical loading) has shown LOI value of 27. In addition to it, melt dripping property of all the treated PET fabrics have been found to be stopped with lower shrinkage during combustion, as observed from the UL94 test results. TG analysis of the said fabric has shown 20–25% more char mass retention and lower rate of weight loss as compared to the control one. Char morphology of the control and the treated fabric has also been examined in different magnifications and analyzed in detail. Forced combustion test of the sodium ligno-sulphonate treated PET fabric has revealed 82% lower peak heat release rate (PHRR) as compared to the control PET fabric with less amount of carbon monoxide liberation during burning. Besides, a possible mechanism lies behind the flame retardancy of the SLS treated PET fabric also has been expressed and discussed scientifically.