An environmentally friendly approach to fabricating flame retardant, antibacterial and antifungal cotton fabrics via self-assembly of guanazole-metal complex

Cotton fabrics are prone to ignite fire accidents as well as breed bacteria and fungi, which have hampered their applications in the field of packaging and home decorations. Guanazole complexes with silver and zinc ions were deposited to cotton fabrics through self-assembly to prepare the flame-retardant and antibacterial cotton fabrics. The effect of the guanazole-metal complex on the morphological structure, flammability and thermal degradation of cotton fabrics was studied by field emission scanning electron microscopy (FESEM), limiting oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA). The antibacterial and antifungal activity of the coated fabric was evaluated as well. The guanazole-zinc and guanazole-silver treated cotton fabrics showed a high LOI of 29.5% and 27.5%, respectively. In the vertical burning test, both the guanazole-zinc and guanazole-silver treated cotton fabrics self-extinguished when removing the ignition source, displaying a UL-94 V-0 classification, while the untreated one and the guanazole-treated one completely burned out. Thermogravimetric analysis results confirmed that the guanazole-metal complex promoted the thermal decomposition of cotton and thus improved the char yield significantly. Micro-scale combustion calorimeter measurements clarified that the guanazole-zinc and guanazole-silver treated cotton displayed dramatically decreased peak heat release rate (64.4% and 59.1%, respectively) and total heat release (26.4% and 14.8%, respectively) in comparison to the untreated one. The significantly improved flame retardancy of guanazole-metal complex treated cotton fabrics could be attributed to their enhanced charring capability that blocked flammable volatiles into flame zone. The treated cotton fabric with guanazole-metal complexes exhibited better antibacterial capacity against Staphylococcus aureus and Escherichia coli than untreated and guanazole-treated ones. Furthermore, the guanazole-silver treated cotton fabrics also showed good antifungal activity against Penicillium, Fusarium chlamydosporum and Aspergillus niger.