Thermal characteristics and physical properties of silk fabrics grafted with phosphorous flame retardant agents

The production of flame retardant silk fabrics is very challenging and there is limited technology available on fire retardant silk applications. In this study, two flame retardant monomers having phosphoric groups, phosmer M and phosmer CL, were applied onto silk fabrics by a graft copolymerization technique. The grafted silk fabrics showed a high level of flame retardancy as evaluated by Japanese Industrial Standard micro-burner test method. It was shown that grafting techniques using phosmer CL are more effective than those using phosmer M to enhance the flame retardant functional properties of the silk fabrics. The differential scanning calorimetry, thermogravimetric analysis and thermomechanical analysis showed that the thermal stability of silk fibroin molecules was greatly enhanced by graft copolymerization with the used phosmers. The position of thermal decomposition for silk fabric shifted toward higher temperature after graft copolymerization with phosmer CL and M. Fourier transform infrared spectra showed evidence of the reaction between the used phosmers and silk. However, the surface morphology of silk fiber was very smooth and fine, and the tensile strength was not significantly affected regardless of the graft copolymerization with phosmer M and CL.