DNA coatings on cotton fabrics: Effect of molecular size and pH on flame retardancy

The results clearly indicate that, despite a similar composition, the coatings containing low molecular size DNA exert a superior fire protection on the fabric substrate, as clearly indicated by horizontal flame spread and cone calorimetry tests. Multiple impregnation treatment turned out to be more performing than the single one, being equal the final add-on achieved. More specifically, the use of multiple impregnations at pH = 4 and 8 allowed achieving self-extinction for 86 and 74% of the tested samples; in addition, 45 and 25% reductions of total heat release and heat release rate peak under 35 kW/m2 have been found with respect to untreated cotton. These findings may be attributed to themorphology of the low molecular size DNA coating, which shows a greater penetration into the microfibrillar surfaces of the component fibres within the fabric and to its higher thermal stability in air.