Swelling Capacities of Fibers in Water

Abstract

Swelling in water is one of the important fundamental properties of cellulosic fibers, and is also a factor in determining the proper fiber for a specific utilization. An example of this is the selection of cottons for self-sealing fabrics. Since existing techniques for measuring swelling capacities, as they have been used, are tedious and time-consuming, it was desired to find a rapid method which would be sensitive enough to establish, with certainty, small differences in swelling capacity due to variety, conditions of growth, and state of maturity such as might be decisive in the choice of a cotton for an application dependent upon swelling. In Part I of this study a method is discussed for determining swelling capacities of cotton and other fibers. It is based on the measurement of the rate of loss of moisture from a moisturesaturated sample. Experimentally, this method is exceedingly simple—the fiber samples, fully swollen and containing excess water, are dried very slowly and weighed periodically. It is shown that for a time the moisture is lost at a nearly constant rate. Eventually, however, the drying rate changes and thereafter steadily diminishes. It is believed that this change occurs only after all nonswelling water external to the fiber has evaporated. The moisture regain at this point of transition in the desiccation rate is considered to be indicative of the maximum water-holding capacity of the cellulose— i.e ., the swelling capacity. The moisture regain values determined are in general agreement with the regain values estimated from adsorption isotherms at 100% relative humidity. The maximum regain values from the desiccation rate technique, when expressed in terms of volume increases, agree with the swelling capacities as determined by microscopic measurements.Although the experimental method is simple and direct and more rapid than microscopic methods, the long drying periods required make it suitable mainly for use in research when time is not an important consideration. THESE STUDIES on the measurement of the swelling capacities of textile fibers were carried out with two principal objectives: to contribute to the knowledge of the fundamental properties of cotton, and to contribute to the development of water-resistant fabrics of the type which resist water penetration by self-sealing following wetting. To meet the first objective requires a method that is precise enough and sensitive enough to detect the small differences in swelling capacity that may be due to variety, growth conditions, maturity, etc. To meet the second objective requires a simple and rapid technique for selecting the most suitable cotton in advance of the spinning and weaving operations, since self-sealing has been shown to be materially dependent upon swelling capacity [8].A method is discussed herein for ascertaining swelling capacities which is based on the measurement of the rate of loss of moisture by the fiber sample. Experimentally this method, called the &dquo;desiccation rate&dquo; technique, is excee...

Wet mammals shake at tuned frequencies to dry

“…When fur is spinning, the associated centrifugal force competes with surface tension to decrease the height of the water column to a modified Jurin's height H ¼ 2scos u e /rRv 2 d. Using the definition of RMC, we may write RMC ¼ H/H initial þ D, where D is a free parameter used for fitting the asymptote in figure 5b. This parameter D cannot be predicted with our simple model, as it represents the moisture that soaks into the rough surfaces of the hair and skin, and cannot be removed even under extreme centrifugal forces [44][45][46][47]. The remaining moisture content simplifies to Using our measured trends in moisture content in figure 5b, we may quantify the benefits of the animal's loose dermal tissue, observed in figure 1c.…”

Swelling of wood

“…Reported values of percent swelling of cotton, corrected for lumen area, ranged from 31-33o7o for cotton of different varieties and maturity and 65~ for viscose rayon fibers (Stamm 1964;Moore et al 1950;Welo et al 1952). No such data has been obtained for wood pulp.…”

Moisture Gradients in Centrifuged Samples

“…In analyzing our data in their Table III, Welo et al [9], using their theoretical model and some regain data from their desiccation rate technique measurements [8], arrived at values for the capillary water. In a recent paper [ 1 ] , Ashpole suggested that the saturation regains are very much nearer to the centrifuge values than their desiccation rate data suggest.…”