SynopsisThe reaction of cellulose with phosphorous acid in molten urea afforded a wbite, water-soluble product. The product was a monoester of phosphorous acid, and all the phosphorus residues were in phosphonic form, i.e., cellulose phosphonate. Quantitative addition of acrylonitrile to the P-H bonds in cellulose phosphonate occurred in the presence of sodium ethoxide. By alkali hydrolysis of the adduct, a polyelectrolyte having two different ionization groups, P-OH and COOH, could be prepared. Thermal degradation of three cellulose phosphonates, ammonium cellulose phosphonate (I), ammonium cellulose 2-cyanoethylphosphonate (II), and ammonium cellulose 2-carboxyethylphosphonate (III), was examined. All three samples decomposed at a temperature around 27OoC, but their thermal behaviors were different. Replacement of hydrogen in the phosphonic residue by 2-cyanoethyl and 2-carboxyethyl groups retarded dehydration of cellulose. Sample I had a satisfactory flame retardance; samples I1 and I11 were not flame resistant. Reduction of flame retardance may be due to the electron-withdrawing effect of the cyano and carboxyl groups.
The reaction of cellulose phosphonate and N‐vinyl‐2‐pyrrolidone in ethanol in the presence of sodium ethoxide was investigated and thermal stabilities and flame‐retardant properties for cellulose phosphonate modified with N‐vinyl‐2‐pyrrolidone were discussed. The results in this study point out the following important aspects of flame retardation of cellulose fabrics: (1) The reaction of cellulose phosphonate and N‐vinyl‐2‐pyrrolidone in the presence of sodium ethoxide results in graft polymerization of N‐vinyl‐2‐pyrrolidone at PH sites in cellulose phosphonate; an average chain length of the graft polymer is about five units of vinylpyrrolidone. (2) The graft polymerization of N‐vinyl‐2‐pyrrolidone can improve both stabilities, especially the flame‐retardant properties of cellulose fabrics. (3) Amides, whether noncyclic or cyclic, are suitable for nitrogen compounds that can effectively operate as synergists.
SynopsisThe effects of sulfur atoms on the thermal degradation and flammability of cellulose phenylthiophosphonate were investigated using thermogravimetry, IR spectrometry, and limiting oxygen index flammability tester. Introduction of sulfur atoms instead of oxygen atoms in the phosphonyl groups had little influence on the thermal degradation of cellulose. The thermal reactions were altered by ion exchange with sodium ions, and degradation of the cellulose chains was retarded. Cellulose phenylthiophosphonate was self-extinguishing above 4.64% phosphorus content. The flame-retardant properties remained when the cellulose phosphorus ester was ion exchanged with sodium ions. It was concluded that introduction of sulfur atoms into phosphorus esters of cellulose w& effective in preventing the decrease in flame-retardant properties by ion exchange in laundering.
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