Flame Retardant Finish Of Silk Fabric By Boron Modified Silica Sol And Its Properties

Nano scaled silica sol was prepared via sol gel method and modified by the way of physical doping or chemical hybridization, and the influence of the modified silica sol system on silk fabric flame retardency was investigated.Firstly, a series of boron doped silica sols were prepared through sol gel process and applied to silk flame retardancy using boric acid and its salts as flame retardant additives by physical doping. The optimal doping ratio to the tetraethoxysilane(TEOS) of all additives was determined by discussing the influence of the additive dosage on the limiting oxygen index(LOI) and weight gain of the finished silk fabric. The treated samples by boron-silica binary system presented favorable flame retardant, with the increasing LOI value from the original 25.0% to about 30.0%. The results of thermogravimetric analysis(TG), micro calorimeter combustion(MCC) test and smoke density test(NBS) showed that the finished silk had a higher initial pyrolysis temperature and char yield, the heat release rate and total heat release decreased, and the smoke density of the finished samples reduced expressing good smoke suppression. But the boron-silica binary system had a poor washing durability, being a non-durable flame retardant.Secondly, a chemical modified boron hybrid silica sol was prepared via sol gel method using boric acidas flame retardant additiveand then applied to silk flame retardancy with1,2,3,4-butanetetrcarboxylic acid(BTCA) as crosslinking agent.The FT-IR and XPS test results showed that the Si-O-B chemical bond presented in the prepared boron hybrid silica sol system. The SEM results indicated that there was a complete and dense oxide thin film with three demonsional network structure on the surface of treated silk fibers. And the LOI, TG, MCC and NBS test showed that the flame retardancy of finished silk fabric was siganificantly improved, expressing better thermal stability, lower heat release rate and greater smoke suppression. The washing durability test results indicated that the washing durability of silk fabric treated with BTCA first and then the boron hybrid silica sol had a great improvement, and its LOI value maintained around 29.8% even after 30 times washing.At last, a phosphorus or nitrogen doped ternary sol system based on the binary boron hybrid silica sol systemwas preparedvia sol gel method using phosphorus or nitrogen-containing compounds as additives and applied to silk flame retardant finsh. The influence of additives and dosage on LOI value of the treated silk fabric demonstrated that 6% urea(releative to the TEOS) doped nitrogen-boron-silica ternary sol system performed the best flame retardancy with the LOI value of 34.5%. The FT-IR and SEM results showed that the prepared nitrogen-boron-silica ternary sol was successfully entrapped onto the surface of silk fibers. The pretreatment of the BTCA solution to silk could promote the washing durability of the ternary sol effectively, but the LOI of the finished fabrics decreased with respect to the untreated sample by BTCA. And the TG, MCC and NBS test demonstrated that the thermal stability, heat release and smoke suppression of the nitrogen-boron-silica ternary system had certain decrease compared to the boron-silica binary flame retardant system.Furthermore, the whiteness and strength of the treated silk by sol system had a subtle reduce but the handle decreased much.