The interior of cotton fibers was lightly modified with monochloroacetic acid, and their water absorbency was examined by differential scanning calorimetry. The aim of the selective modification is to prepare cotton fibers which have high water absorbency and yet maintain their natural handling characteristics and other textile properties. The optimal degree of carboxymethylation (DS) for this purpose was in the range of 0.01 to 0.02. The carboxymethylated cotton fibers were transformed into their Na-salts by alkali-treatment, and their water absorbency was compared with that of the acid form fibers. It was found that (1) in the acid form, the modified fibers absorbed about 120-130% as much water as the untreated fibers, (2) the percentage increase in water absorbency of the fibers was further enhanced twice as much as that of the acid form fibers by transforming carboxyl groups into the Na-salts, and (3) the water absorbency of the modified cotton fibers having a DS value of 0.02 was much higher than that of amorphous celluloses, indicating that the cleavage of hydrogen bonds by incorporating substituents, i.e., carboxymethyl groups has a negligible effect on the water absorbency of the modified cotton fibers.
