EFFECT OF ADSORBED WATER ON WETTING PROPERTIES OF BOROSILICATE GLASS, QUARTZ, AND SAPPHIRE,
Abstract
Contact angles of a variety of hydrophobic liquids were measured on clean surfaces of borosilicate glass, quartz, and sapphire at 20C with the RH at 0.6% and 95%. The adsorption of water molecules at 0.6% RH resulted in the formation of only a fraction of a monolayer; yet, this fraction converted each high-energy solid surface to one having a low critical surface tension of wetting, gamma sub c. The increased amount of water adsorbed at 95% RH to form a film comprising little more than a condensed monolayer further lowered gamma sub c to a value somewhat above that of bulk water. At each RH investigated the value of gamma sub c was the same for each of these three solids; hence, gamma sub c was dependent upon the surface concentration of adsorbed water but was independent of the chemical nature of the solid substrate. The somewhat different values of gamma sub c obtained on using several different homologous series of hydrophobic liquids are explained in terms of differences in the contribution from nondispersion interfacial forces acting between the water film and the contacting organic-liquid molecules. These results reveal clearly the important influence of only a monolayer of adsorbed water upon the spreading, adhesion, and contact angles of organic liquids resting upon high-energy, hydrophilic, solid surfaces. To illustrate the effect of the baking pretreatment temperature on the removal of physically adsorbed water, the three specimens were dried at three temperatures: 65C, 120C, and 215C. No significant differences were found on the specimens following baking treatment at the different temperatures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 06, 1968
- Accession Number
- AD0671180
Entities
People
- Marianne K. Bennett
- William A. Zisman
Organizations
- United States Naval Research Laboratory