DNA-chitosan cross-linking and photografting to cotton fabrics to improve washing fastness of the fire-resistant finishing

This work investigates the flammability and antibacterial activity of cotton fabrics treated with DNA and chitosan, which have been deposited either by exploiting impregnation methods (building up two-layer structures or a single mix of the two components) or by the layer-by-layer approach (30 alternating chitosan-DNA bilayers). All the treated fabrics have been subjected to UV-curing and then washed. FTIR and SEM analyses have been employed for assessing the influence of the deposition method and the interactions of the biomacromolecules with the cellulosic substrate. Thermogravimetric analyses, flammability and cone calorimetry tests have been performed for evaluating the thermal stability and the fire behavior of the treated fabrics. The fire performances of the UV-cured and washed fabrics, and the antibacterial activity towards Staphylococcus aureus as well, have been found to be strictly correlated with the deposition method and hence with the presence of DNA or chitosan as the external layer. More specifically, the impregnation of the fabrics with a mixture of DNA and chitosan solution provided good stability in water and enhanced fire retardant properties, but very limited antibacterial activity. The layer-by-layer chitosan-DNA UV-cured architectures have shown the best overall behavior, i.e. enhanced water resistance, self-extinction in flammability tests and good antimicrobial activity.