Wettability, criteria

It becomes clear that the wettability criterion is not 750 5 since that quantity drops out. What does matter is the sign of S, If a > oll, S is positive and wettability is total. Hence the rule... 

Wettability. A comparison of contact angles for methylene iodide and pure water on natural films with the contact angles of the same liquids on known materials is shown in Table I. By the contact angle criterion, the natural films obviously resemble the two polar (but nonionic) polyamide materials much more closely than the high energy platinum or the non-polar polyethylene. There is a particularly close... 

The nature of the supporting membrane also plays an important role in the performance of supporting ILMs. In this context, de los Rios et al. [37] studied the performance of two polymeric membranes, nylon and mitex, as supporting membranes. Nylon membrane was a hydrophilic polyamide membrane with a pore size of 0.45 pm and a thickness of 170 pm. Mitex membrane was a hydrophobic polytetrafluo-roethylene membrane with a pore size of 10 pm and a thickness of 130 pm. It was observed that less IL was absorbed into the mitex membranes, which was explained by the different textural properties and the high hydrophobic character of these membranes, which probably restrict interaction with the hydrophilic ILs used. Simple determination of wettability has also been used as criterion in the selection of a suitable supporting membrane [86]. 

Polymer solvent interactions determine several properties, such as, solubility, solvent retention, plasticizer action, wettability, adsorption and adhesion. The solubility parameter is an important criterion for the choice of solvents. However, acid-basic characters of both solvent and polymer are also determinant parameters, which can affect the solution and final film properties. This part, devoted to the influence of acid-base interactions on the aggregation of poly(methyl methacrylate) will first present some recent concepts in acid-base interactions, followed by two practical examples based on experimental results obtained for PMMA/solvent systems. 

Zisman and co-workers showed [22,23] that contact angle measurements could be used to determine a criterion for wettability as well as surface tension of a solid. In their experiments, a series of testing liquids of known surface tension were used to measure contact angles against a solid. A linear or quasi-linear relationship was found between the cosine of the contact angle made by a liquid and the surface tension of the liquid. The linear relationship could be extrapolated to cos 0 = 1 (or 0 = 0). The intercept of the line at cos 0 = 1 is considered to be the critical surface tension (7c) of the solid, and the plot of cos 0 versus yiv is known as the Zisman plot. When cos 0 = 1 and yc = yiv. Equation (lb) can be rewritten as... 

The contact angle (0), another criterion for hydrophilicity and lipophilicity, is employed to evaluate the wettability of liquid to solid. Generally, the solid surface is considered to be wetted by liquid when 0 < 90° the solid surface is not considered to be wetted by liquid when 0 > 90° and the solid surface is wetted completely by liquid when 0 = 0°. As for inorganic whiskers, the bigger the contact angle between distilled water and whiskers, the better is the hydrophobicity of whiskers. 

Wettability is a critical factor when evaluating the performance of a solder-substrate system. In general, good wettability is a necessary but not sufficient requirement for good solderability, the latter requiring, as an additional criterion, good adhesion between the solder and the substrate subsequent to wetting. 

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