Visualization of dynamic contact angles on cylinder and fiber

To estimate surface energy of fibrous solids, data on contact angles are required, In this study, microsyringes were used to generate liquid motion along solid cylinders which were partially inserted into the syringe needle. Images of dynamic contact angles were recorded with a microscopic video recording system. Values of these angles were obtained with standard image processing techniques. Platinum wire/glycerin and carbon fiber/epoxy resin were used as sample systems. We demonstrated that the visualization technique provides better results than the Wilhelmy technique. Deteriorated results from the latter may be caused by either inaccurate evaluations of the perimeters of the solid specimen or misestimation of the contact/detaching positions between solid and liquid. Effects of the velocities of the three-phase contact lines and the surface oxidation on fibers are also discussed. (C) 1996 Academic Press, Inc.