Development of Apparatus for Evaluating Water Penetration in Vertical and Horizontal Directions of Sanitation Materials

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Attention was paid to the trasient phenomena of liquid penetration in radial direction into porous substances like paper and cloth without depending on external force, and the measuring instrument of tracking this by electric capacitance method was made for trial. On one of two parallel plate electrodes which were set horizontally facing each other, a small hole was drilled, and through it, water was supplied continuously from a liquid vessl. A sample was put between both electrodes, and rectangular waves were applied. From the moment of coming in contact here, the electric capacitance changed sharply. This was recorded, and the penetration characteristics were analyzed. The transient penetration speed of water shorter than 1 s for filter paper (5mm radius) is controlled by the roughness of the surface with which water comes in contact, and it is larger in rough surfaces than in smooth surfaces. The relation of the diameter of water supply holes with penetration speed examined, and as the suitable diameter, 3mm was decided. As the diameter of the holes was larger, the penetration speed in transient period was higher, and the equilibrium penetration quantity was attained earlier. For the radial penetration of a liquid drop on paper, the relation of the penetration A with time t is given by A=Kt^n, where K is a constant related to the properties of paper and liquid. Thereuopn, when the experimental results on the relation of A and t were plotted by both logarithmic scale, it was found that those consisted of three straight lines with different gradient n. First, in the transient period of shorter than 0.5 s, about n=1.8 was detected and it is considerably larger value than the steady state which was published so far. Subsequently, there was the region of n=0.9, and the region of n=0.3 followed. It was known that n and its duration become the indices for determining the penetration characteristics of samples.