Effect of liquid ammonia treatment on the pore structure of mercerized cotton and its uptake of reactive dyes

Structural changes in mercerized cotton by liquid ammonia (LA) treatment were investigated and correlated with changes in dyeability of cotton fabrics with reactive dyes. The pore structures of mercerized cotton and mercerized-liquid ammonia (M-LA) treated cotton were characterized by inverse size exclusion chromatography (ISEC). Results showed that when the mercerized cotton was subjected to LA treatment, cumulative accessible volume of smaller pores (e.g., 25.2 Å) increased, whereas that of the larger pores (e.g., 56.7 Å) decreased. These results might be related to the changes in the amorphous region of cotton fiber. The decrease in crystallinity of cotton fiber would increase accessible volume of smaller pores. The larger pores might be compressed by extrusion during swelling of microfibrils or elementary fibrils in water. The change in dyeability of fabrics with reactive dyes of various molecular weights could be rationalized using the observed changes in pore structure. Results also showed that ISEC was more suitable than the method employing Chrastil's diffusion equation for analyzing the pore structure of cotton fiber.