Multifunctional modification of silk fabrics via a combination of sophora flower extract, phytic acid and silicone-containing organics: Flame retardancy, water repellency, antibacterial activity and ultraviolet resistance

Herein, a multifunctional composite coating is constructed on silk fabrics by a facile impregnation strategy. In detail, the pre-period involves the aggregation growth of sophora flower extract/phytic acid-lanthanum ion-silk fibroin complex network, while the post-period introduces a water repellent layer that is composed of hydroxyl-terminated polydimethylsiloxane and hexadecyltrimethoxysilane composite. Benefiting from the synergistic effect of P, Si and N elements, the optimized finished silk sample denoted as D/FR/WR-SF exhibits a limiting oxygen index value of up to 29.3%, and shows a damage length as low as 9.4 cm in the vertical burning test. Since the sophora flower extract contains flavonoids such as rutin and quercetin, it confers good antibacterial activity and ultraviolet resistance to silk fabrics. The results display that D/FR/WR-SF inhibits the colony propagation of Escherichia coli and Staphylococcus aureus, and achieves an ultraviolet protection factor value of 38.61 compared with the control silk fabrics. Attributed to the directional arrangement of long-chain alkane and Si-CH3, D/FR/WR-SF exhibits good water repellency with a water contact angle of 138°. Additionally, D/FR/WR-SF also presents satisfactory washing resistance (integrated properties after 25 laundering cycles). Therefore, such a complete multifunctional composite coating scheme shows great potential for expanding advanced textile applications.