In order to improve the dry-heat process (pad & cure process) with urea and phosphoric acid which is known as a flameproofing treatment of cotton fabrics, the wet-heat process in some organic solvents were examined, and flameproofing effect of cotton fabrics treated by this method was compared with that by the dry-heat process. Among polar organic solvents used in the wet-heat process, dimethylformamide (DMF), dimethylacetoamide, formamide, anilin, and γ-butyrolacton were found to be useful to obtain phosphorylated cottion fabrics with relatively small loss of tensile strength. It was found that there is some optimum ratio among cellulose, urea, phosphoric acid, and DMF, and that the addition of some amines, hexamethylenediamine for example, is effective to prevent tensile strength from depression.
The thermogravimetric analysis shows that the larger the percentage of combined phosphorus, the larger is the weight of the residue after decomposition, and the flameproofing property is proportional to weights of the residues. Insufficient washing of the products leads to the lowering of decomposition temperature. However, the decomposition temperature of the well washed sample is nearly equal to that of the untreated fabrics. This fact disproves the previous assumption that the flameproofing effect is exerted by the carbonization of cellulose, and that the lower the carbonization temperature, the larger is the effect.