Wettability theory

Adhesives must effectively wet and completely contact the surfaces to assure a strong bond. The ability to wet a surface, wettability, is related to the ease with which a liquid spreads on a solid surface and is essential in maximizing coverage and minimizing voids in the bondlines.Pl Wettability is measured by the equilibrium contact angle, B, which is defined by balancing surface-tension forces in Young s equation (Fig. 2.3). 

Combining Eq. (2.2) with Young s equation yields the Young-Dupree equation. 

The spreading coefficient or work function (IF ) in Eq. (2.3) shows that good wetting (0 90°) is realized when is greater than zero. Good wetting 

6 increases from 90° to 180° and conditions go from partial wetting to nonwetting.t Based on this equation, conditions of wetting versus nonwetting are as follows  

0=0° Complete wetting liquid spreads spontaneously high surface attraction 

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Surface Energetics and Wettability Theory. The surface energetics and wettability theory of adhesion is concerned with the effect of intermolecular and interatomic forces on the surface energies of the adhesive and the adherend and the interfacial energy between the two. 

The wettability theory of adhesion is inextricably related to the study of contact angles of liquids on solid surf aces. A force balance at the point of contact between the liquid and the solid can be written (3)... 

Bascom, W.D. (1992) in Modern Approaches to Wettability Theory and Applications, M.E. Schrader and G. Loeb (eds) Plenum Press, New York, p. 73. 

Modem Approaches to Wettability Theory and Application. M.E. Schrader, G.I. Loeb, Eds. (Plenum, 1992). (Sixteen contributions on various aspects of wetting, honouring the memory of W.A. Zisman. Several of these chapters refer to applications.)... 

S Yariv. In Modem Approaches to Wettability—Theory and Applications (ME Schrader, GI Loeb, eds.). Plenum Press, New York, 1992, p. 279. 

Restrained Layer Theory Coefficient of Friction Theory Surface Wettability Theory... 

RJ Good, CJ van Oss. The modern theory of contact angles and the hydrogen bond components of surface energies. In ME Schrader, G Loeb, eds. Modern Approaches to Wettability Theory and Applications. New York Plenum Press, 1992, pp 1-27. 

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