Preparation Of Flame-retardant Silk Fabrics By Electrostatic Layer By Layer Self-assembly Using Bio-based Materials

In this paper,the bio-based phosphorus-containing compounds(sodium phytate,sodium tripolyphosphate,riboflavin sodium phosphate)and nitrogen-containing compounds(chitosan)were applied as anionic and cationic flame retardant assembly components,respectively to prepare flame retardant silk fabrics by electrostatic layer by layer self-assembly method.The structure,property and flame-retardant mechanism of the prepared flame retardant silk fabrics were also investigated.The purpose of the research focused on the development of a new and environmentally-friendly method to prepare flame-retardant silk fabrics.Firstly,the flame retardant assembly system was prepared using chitosan/sodium phytate with a concentration ratio of 1:1(w/w).The pH of chitosan solution and sodium phytate solution were adjusted to 5 and 4,respectively.The properties of the silk fabrics prepared through padding layer by layer method were studied as compared with those of the silk fabrics prepared through dipping layer by layer method.The results show that compared with the dipping layer by layer method,the padding layer by layer method showed less time-consuming,and thus treated silk fabrics had higher limiting oxygen index(LOI).A thick and homogeneous layer was observed to deposit on the surface of the treated silk fabrics,indicating the good film forming ability of chitosan/sodium phytate system.Secondly,the flame retardant silk fabrics were prepared using chitosan/sodium tripolyphosphate by the padding layer by layer self-assembly technique.The assembled silk fabric with 10 BL had a high LOI of 33.2%,a weight gain of 25.7%and a char length of 132 mm,reaching the B1 classification for the flame retardant textiles according to GB/T 17591-2006.The TG analysis showed that the treated silk fabrics had high thermal stability.The flame retardant agent could catalyze the dehydration of silk fiber,leading to the decreased weight loss and increased char residue during heating.The surface morphology and elemental analyses showed that the flame retardant with nitrogen and phosphorus element deposited on the surface of the treated silk fabrics.The char residue analysis indicated an intumescent flame retardant mechanism for the treated silk fabrics.The assembled silk fabric with 10 BL had a tensile strength loss of about 16.5%.After 15 washing cycles,the treated silk fabric still had a high LOI of 29.6%.At last,the chitosan/riboflavin sodium phosphate system was applied to prepare colored flame retardant and antibacterial silk fabrics by padding electrostatic layer by layer self-assembly method.The flame retardant and antibacterial properties of the treated silk were investigated.The silk fabric had a high LOI value of 32.8%when assembled with 10 BL.The bacteriostatic rates of the treated silk against S.aureus and E.coli were 93.5%and 97.7%,respectively showing high antibacterial effect.The tensile strength of silk fabric in warp direction decreased by 13.9%.The color of silk fabric turned to orange from yellow due to the introduction of colored riboflavin sodium during the assemble process.The flame retardant mechanism of the treated silk involved in the intumescent mechanism.