SWELLING OF PULP FIBERS IN HOT ALKALINE SOLUTION

Abstract

The degree of swelling of pulp fibers in hot alkaline solution increases with temperature and alkaline concentration. Swelling by hot alkaline solution is influenced by the hydroxyl ion concentration. This can be explained as follows: The selective adsorption of hydroxyl ions by the chain molecules results in an attraction for cations which causes the fibers to swell. Hydroxyl ion adsorption increases at higher hydroxyl ion concentrations, thereby increasing the degree of swelling. The temperature dependency of the degree of swelling seems to be caused by following two reasons: (1) At higher temperatures, the water molecule penetrates into the fiber structure more easily because the strength of association of water molecules is lessened. (2) The motion of molecular chain segmentsis activated at higher temperatures. Investigation of iodine and dye absorption by pulp fibers treated with hot alkaline solution indicated that the fine structure of pulp fibers was altered by the swelling of fibers in hot alkaline solution.