Effect of Scouring / Bleaching, Caustic Mercerization, and Liquid Ammonia Treatment on the Pore Structure of Cotton Textile Fibers

Abstract

The pore structure of cotton was followed through three pretreatments that com monly precede chemical modification for imparting easy care or other functional properties. These treatments included scouring/bleaching, caustic mercerization, and a liquid ammonia treatment with removal by volatilization at elevated temperature. The results include data on the pore structure of the fiber in the greige state. A reverse gel permeation chromatographic technique was used. Columns were prepared from whole cotton fibers in the form of batting, and three series of water soluble solutes were used to study their elution characteristics. The solutes were series of oligomeric sugars, ethylene glycols, and glymes ( ethylene glycol dimethyl ethers) with molecular dimensions in the range of conventional finishing agents for cotton. Scouring/bleaching decreased the water holding capacity of the greige cotton as measured by water of imbibition, but increased it as indicated by gel permeation measurements. The internal volume accessible to water was substantially increased by caustic mercerization, but was only slightly affected by liquid ammonia treatment. The relative accessibility of the cotton fibers to molecules the size of durable press finishing agents was slightly increased by scouring/bleaching, substantially increased by caustic mercerization, but moderately reduced by liquid ammonia treatment. Accessibility to molecules near the permeability limits of the fibers followed similar trends, but differences were greater. Scouring/bleaching increased the permeability limit of the greige fibers, but subsequent mercerization or liquid ammonia treatment decreased it. There was a noteworthy difference in permeability limit and relative accessibility to large molecules. This is accounted for by a decrease in the rate of change in pore size on scouring/bleaching, but substantial increases, to generally more than double, on subsequent caustic mer cerization or liquid ammonia treatment of the scoured / bleached cotton.