methods (26). The Wilhelmy method has been recognized
To estimate surface energy of fibrous solids, data on contact to be superior because (1) the balance technique reduces or angles are required. In this study, microsyringes were used to eliminates operator subjectivity, (2) a much larger surface generate liquid motion along solid cylinders which were partially area is sampled than in the goniometric methods, and (3) it inserted into the syringe needle. Images of dynamic contact angles provides hysteresis data simultaneously. On the other hand, were recorded with a microscopic video recording system. Values although the Wilhelmy technique has been reported to give of these angles were obtained with standard image processing accurate results (27), no systematic comparison has been techniques. Platinum wire/glycerin and carbon fiber/epoxy resin performed on dynamic contact angles with cylindrical and were used as sample systems. We demonstrated that the visualizafibrous solids, to our knowledge. Lack of suitable methods tion technique provides better results than the Wilhelmy technique. Deteriorated results from the latter may be caused by either other than the Wilhelmy technique may be one of the reainaccurate evaluations of the perimeters of the solid specimen or sons. misestimation of the contact/detaching positions between solid In this study, microsyringes were used to generate relative and liquid. Effects of the velocities of the three-phase contact motion between solid cylinders (fiber) and liquid. The milines and the surface oxidation on fibers are also discussed. α§ 1996 croscopically recorded images were analyzed with standard Academic Press, Inc. image processing techniques. Platinum wire/glycerin and Key Words: dynamic contact angle; image processing; carbon carbon fiber/epoxy were used as sample systems. Comparifiber; epoxy.
sons between visualized results and the Wilhelmy data were also made.