Evaluation of three flame retardant (FR) grey cotton blend nonwoven fabrics using micro-scale combustion calorimeter

Abstract

Unbleached (grey or greige) cotton nonwoven fabrics (with 12.5% polypropylene scrim) were treated with three phosphate–nitrogen–based flame retardant formulations and evaluated with micro-scale combustion calorimeter. Heat release rate, peak heat release rate, temperature at peak heat release rate, heat release capacity, total heat release and char yield were determined. The peak heat release rate and total heat release results demonstrated that nonwoven fabrics treated with a formulation having higher diammonium phosphate and no dimethylol dihydroxyethyleneurea were superior to those treated with a formulation containing dimethylol dihydroxyethyleneurea. Nonwoven fabrics treated with these formulations were both superior to the nonwoven fabrics treated with a commercially available flame retardant formulation. These results were supported by the percentages of phosphorus and nitrogen on these fabrics, confirming that P–N synergism imparts high flame retardancy to the nonwoven fabrics. Grey cotton (untreated) consistently showed better flame resistance than (untreated) bleached cotton. As a result, its flame retardant products had lower heat release rate/peak heat release rate and other flammability characteristics than those of the bleached cotton. Additionally, grey cotton is softer than bleached cotton and saves the cost of bleaching and waste disposal. These three flame retardant formulations were used primarily to treat the cotton component of the nonwoven blend to make it flame retardant without flame retardant improvement for the polymer component.