Abstract
Kinematics study of liquid diffusion was carried out for disposable diapers using colored salt water. A three-layers model was proposed for disposable diapers, which consists of diffusion, absorption and waterproof layers. It was clarified that liquid diffusion was proceeded horizontally in the diffusion layer at first, and then vertically into the absorbed layer. The equation of diffusion rate of liquid in the horizontal direction was derived on the basis of the disk model of capillary tubes, which were arranged in radial direction. Diffusion rate of liquid in the vertical direction could be calculated from the velocity curves of diffused liquid. The significance of four characteristic parameters, diffusion rate of liquid in the horizontal direction Fw, diffusion rate of liquid in the vertical direction Fh, the maximum area ratio Sm and the remaining area ratio Sr, proposed in our earlier papers were proved to be valuable.
