MEASUREMENTS OF CONTACT ANGLES BETWEEN AN OIL-WATER INTERFACE AND A FIBER BY THE ACDPAC TECHNIQUE

The ACRPAC (Analysis of Capillary Rise Profile Around a Cylinder) meth od was modified and extended to measure the contact angles between an oil-water interface and a fiber. Basically, the accurate image of the partial capillary depression profile was acquired and digitized by app lying computer digital image processing and analysis techniques. The c ontact angle was determined by finding the best fit of the theoretical ly predicted profile, i.e., the curve representing a solution of the L aplace equation of capillarity, to the physically observed liquid-liqu id interface. This analysis of the capillary depression profile around a cylinder (ACDPAC) technique was used to measure the contact angles of different water-oil interfaces on cylindrical glass fibers pre-coat ed with FC725. The wettability of the fiber-water-oil systems with var ying oil and aqueous phases was examined. In particular, the wetting e ffects of a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic surfactant sodium dodecyl sulfate (SDS) dissolved in th e aqueous phase were studied by using the ACDPAC technique. The oil ph ases tested were two dimethyl siloxane liquids, silicone oil A-type an d silicone oil B-type. (C) 1998 Academic Press.