Preparation and flame retardancy of 3-(hydroxyphenylphosphinyl)-propanoic acid esters of cellulose and their fibers

New 3-(hydroxyphenylphosphinyl)-propanoic acid (3-HPP) esters of cellulose were synthesized in N, N-dimethylacetamide/LiCl homogeneously by the method of in situ activation with p-toluenesulfonyl chloride. Chemical structure and thermal properties of the cellulose esters were investigated by FTIR, C-13-NMR, TGA, RT-IR and Py-GC/MS, and their flame retardancy was studied by limiting oxygen index (LOI) test and vertical flammability test. It was found that the degree of substitution (DS) of cellulose esters, in the range from 0.62 to 1.42, had an obvious effect on solubility of cellulose esters. According to the FT-IR and Py-GC/MS results, flame retardant 3-HPP reacting with cellulose could accelerate dehydration action and decrease flammable released products. Besides, ESEM observation also confirmed that flame retardant cellulose (FRC) fibers with 3 wt% cellulose acetate prepared by dry-wet spinning technique possessed good flame resistance.