Hydrogen-bonding liquids, wettability

The wettability of plasma deposited coatings can be compared with poly(tetrafluoroethylene) and poly(ethylene). When the cosine of contact angles obtained with non-hydrogen bonding liquids are plotted against their surface tension, extrapolation of the resulting straight line to cos 0=1 yields a term called the critical surface tension (CST) which is characteristic of that surface (ll). 

Some nine years ago, Ellison and Zisman [4] reported their study of the wettability of 6-6 nylon (polyhexamethylene adipamide) and compared their results to those previously obtained on polyethylene [7]. They found that the nylon was more easily wet than the polyethylene, especially by hydrogen-bonding liquids, and attributed these findings to the presence of amide groups in the nylon surface. 

It was expected that as the average nylon number increased, the contact angles exhibited by hydrogen-bonding liquids on the various surfaces would rise, approaching the wettability of polyethylene as an asymptotic limit (polyethylene might be regarded as nylon oo). Such... 

The intermolecular attraction between like molecules in the liquid state, such as the water-water attraction based on hydrogen bonds, is called cohesion. The attractive interaction between a liquid and a solid phase, such as water and the walls of a glass capillary (a cylindrical tube with a small internal diameter), is called adhesion. When the water-wall adhesion is appreciable compared with the water-water cohesion, the walls are said to be wettable, and water then rises in such a vertical capillary. At the opposite extreme, when the intermolecular cohesive forces within the liquid are substantially greater than is the adhesion between the liquid and the wall material, the upper level of the liquid in such a capillary is lower than the surface of the solution. Capillary depression occurs for liquid mercury in glass capillaries. For water in glass capillaries or in xylem vessels, the... 

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