Pyrolysis Properties and Flame Retardant Effects of Fabrics Finished by Hybrid Silica-based Sols

Abstract

Abstract By using sol-gel process, hybrid sols can be prepared and three dimensional nanoscale or nano-micro networks can be designed and formed onto bulk materials of diverse substrates (such as fabric and wood). Series of pure, composite and hybrid sols like SiO2, SiO2-KH560, SiO2-KH560-MA (Melamine), SiO2-KH560-BB (Boric Acid and Borax) and SiO2-KH560-TPP (Triphenyl Phosphate) including both nano-sols and traditional flame retardant components were prepared and used to finish cotton, polyester and polyester-cotton fabrics, particle size distributions and pH values of as-prepared sols were inspected. Limiting Oxygen Index (LOI), Thermogravimetry Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) experiments were conducted to determine flame retardancy, characterize pyrolysis properties and identify microstructural functional groups on the surfaces of sols-finished fabrics. Effectiveness, synergistic effects and function mechanisms of organically modified hybrid sols and flame retardants were explored. Results show that LOI values are all improved after modifications of cotton, polyester and polyester-cotton fabric, coverage of main pyrolysis stage have been extended to various degrees, and amounts of residual char increase exponentially. The flame retardant effects of cotton and polyester-cotton fabrics treated with SiO2-KH560-BB is most obvious. It shows that the flame retardant hybrid sols affect the pyrolysis courses and heat resistance capacities of fabrics have been improved. It is speculated the sols form coatings on surface of fabrics and inhibit further oxidation, decomposition, and melt dripping, prolong the main pyrolysis process, prevent the fabric further oxidation and decomposition, increase the char yield, improve the thermal stability of polyester fabric. For A3, a broad peak between 650~750cm-1 is seen, indicating that a large number of OH groups exist, and absorption peaks at 1295 cm-1 reveals the presence of Si-C-O groups. The OH groups, boric acid and borax can both strengthen dehydration and char formation capacities by developing thin films surrounding fibers. Superb synergistic effect happens.