Development of Measuring Apparatus for the Rate of Capillary Wetting in Fiberous Assemblies.

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The rate of capillary wetting in fiberous assemblies was measured using a newly developed apparatus. The change in electric conductivity with time was measured by using a plug of fiber, fabric or filter paper in a cylinderical Teflon cell of inner radius 10 mm and height 3 mm or 7 mm. The electrodes were platinum disks of diameter 16 mm with 37 holes of radius 0.5 mm, which were placed at the top and bottom of the plug. The head of wetting liquid was adjusted to the bottom level of the plug and then the liquid went up by capillarity. The traveling time in the shortest capillary in the fiberous assembly, <t_0> , which is detected as the yield values in the electric conductivity versus time curves, and the initial slope of the curves, S, were used as parameters of wetting rate. The increase in <t_0> and the decrease in S show the decrease in the capillary wetting rate for the plug. Measurements of capillary wetting rate by this apparatus were successfully carried out using plugs of cellulose filter paper, polyester fabric and nylon fiber. The effect of the alkyl chain length of alkyltrimethyl ammonium chloride on the wetting rate was investigated, The effect of electrolyte (KCl) was also investigated for sodium dodecyl sulfate. The basic studies on wetting were carried out; the capillarity in glass tubes coated with nylon as model capillaries was investigated and the dynamic contact angles were measured by the wilhelmy method.