Combination of bio-based tannic acid, sophora flower extract and metal salts: A facile route towards improving durable flame retardancy and UV resistance of silk fabrics

Environmental engineering placed green demands on the functional modification of textiles. Here, the combination of bio-based tannic acid, sophora flower extract and metal salts was used to manufacture silk fabrics with flame retardancy and UV resistance via a facile impregnation strategy. With different metal salts treated, the modified silk fabrics named silk/TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu achieved self-extinguishing in the vertical burning test, with limiting oxygen index values of 31.7 +/- 0.4 %, 30.2 +/- 0.2 % and 30.9 +/- 0.3 %, respectively. In the cone calorimetry test, the peak heat release rate values of the three silk fabrics modified with metal salts were all significantly suppressed, and the total smoke production values of silk/TA/SFE-TE and silk/ TA/SFE-Fe were reduced from the original 0.178 m2 to 0.126 m2 and 0.138 m2, respectively. Furthermore, silk/ TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu displayed high ultraviolet protection factor values and thus had good UV resistance, owing to the presence of tannic acid and sophora flower extract. Most importantly, the flame retardancy and UV resistance of the three silk fabrics modified with metal salts were still superior to those of the original silk fabrics after 30 washing cycles. In short, this facile route for the preparation of functionalized silk fabrics provides a novel idea for the development of advanced textiles.