Abstract
The contact angle of liquid on a solid surface is important when studying wetting and adhesion phenomena. It is known that the contact angle shows hysteresis and therefore differs depending on the measurement method. The static contact angle of a solid-liquid-liquid system is important because capillary rise and effectiveness of a binder in wet agglomeration are determined by the capillary force, that is, mainly by the static contact angle of the solid-liquid-liquid system. We experimentally investigated the hysteresis of the static contact angle of a polymer solid-water- liquid system. The static contact angle was measured under the condition in which the contact line of the three phases did not move, and the hysteresis was discussed from the viewpoint of difference between an advanced contact angle and a receded contact angle. The contact angle hysteresis of the polymer solid-water-liquid system became larger than that of a polymer solid-vapor-liquid system. Under the condition of advanced contact angle smaller than 40°, most of the receded contact angles became 0°. The advanced contact angle became larger than that estimated by the extended Fowkes' equation. The empirical equations showing the relationship between advanced contact angles and receded contact angles were obtained.
