Liquid Transport in Composite Cellulose—Superabsorbent Fiber Networks
Keywords:
Wicking, absorbency, superabsorbents, fiber swelling, Lucas-Washburn theory, gel blockingAbstract
Wicking flow of water is examined in composite networks of cellulose and carboxymethyl cellulose (CMC) fibers. The rate of advance of water through paper strips and fluff pads of varying composition is reported, while dynamic electrotensiometry is used to measure the wetting and swelling characteristics of the individual cellulose and CMC fibers. Cellulose fibers swell to a small degree almost instantaneously, while CMC fibers swell to more than twice their original diameter over a period of several minutes.
The Lucas-Washburn capillary model adequately describes the imbibition of a nonswelling reference liquid (n-octane) in all of the fiber networks examined. The imbibition of water, however, deviates significantly from Lucas-Washburn kinetics when CMC is present, because of the long-term swelling of the CMC fibers. The net pore restriction effected by fiber swelling is quantified by a "permeability factor," defined as the ratio of the wicking-equivalent radius in the swollen state to that in the unswollen state. A modified capillary model is developed, based on individual fiber swelling characteristics, which describes observed deviations from the Lucas-Washburn model.
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