Kinetics wetting

In many experimental situations, a contact angle that changes with time leads inevitably to the movement of the wetting line [29]. The result is a dynamic contact angle. This situation arises from non-equilibrium conditions and should be distinct from contact angle hysteresis. In dynamic contact angle measurements, some movement of the wetting line is unavoidable and this must cause a tempo- 

If the sorption-desorption processes or the accompanying transport processes to and from the various interfaces are slow compared with the rate of displacement, a non-equilibrium contact angle will result. If the external driving force is now removed, the contact angle will relax to its equilibrium value. If the relaxation processes are sufEciently slow relative to the experimental time scale, a nonequilibrium angle may persist in an apparently stable system. 

It is diflicult to distinguish the above situation from contact angle hysteresis. 

This behaviour may arise from the slow molecular orientation following the movement of the wetting line. If contact angle measurements are to be given equilibrium significance, great care must be taken to ensure that equilibrium has been reached. This is particularly the case with surfactant solutions, where there may be no ready mechanism by which a non-volatile solute (the surfactant molecules) can reach the solid/vapour interface, except by prior contact with the solution. 

Kinetic factors that may cause contact angle variation can also arise from penetration of the liquid into the solid surface. The penetration of non-polar surfaces by water has been commonly cited in the literature [29]. Zisman [18] reported a relationship between molecular size and the extent of contact angle hysteresis. 

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Blake TD (1993) Dynamic contact angles and wetting kinetics. In Berg JC (ed) Wettability. Dekker, New York, pp 251-309... 

Liquid Si dissolves little C at its melting point (the molar fraction of C in Si at saturation is less than 10 3) but reacts with C to form predominantly covalent SiC. This product is well wetted by molten Si, the contact angle of Si on (0001) basal planes of a-SiC being 30-40° (see Section 7.1.1). The wetting kinetics of Si on... 

Nieh, S.-Y, Ybarra, R. and Neogi, R, Wetting kinetics of polymer solutions. Experimental observations. Macromolecules, 29, 320, 1996. 

Depending on its affinity for tbe solid, a liquid placed on a substrate will show a tendency either to remain as a drop with a finite area of contact or to spread out and cover the solid surface available. In this article, it is assumed that equilibrium has been attained considerations of Wetting kinetics are given in a separate entry. 

Related articles are Contact angles and interfacial tension. Surface characterization by contact angles - polymers. Surface characterization by contact angles - metals. Surface energy and Wetting kinetics. 

Wetting kinetics M E R SHANAHAN Spreading on a solid surface capillary rise... 

The wetting kinetics of sized glass fibers by melt changed due to acid-base interactions and compatibility between the film former and surrounding bulk polymer matrix. The highest interfacial shear strength values corresponded to the... 

Here x and y are dimensions of the jump unit of flow and V is the displacement volume of the unit of flow. The values of x, y, and V for real systems are unknown. However, the dimensionality of xy/ V is a unit of reciprocal length which looks very similar to the shift factor used by Schonhorn et aV Although experiments to test the validity of the Cherry and Holmes expression will be difficult, the apparent agreement of their derivation with the results of Schonhorn et al is very satisfying in the conceptual sense. Cherry and El Muddarris have attempted to determine the effect of wetting kinetics on the strength of adhesive bonds, but the results were not conclusive. " ... 

R.R Rye, RG. Yost and J. Mann, Wetting kinetics in surface capfUciry grooves, Langmuir 12,4625-4627 (1996). 

EG. Yost, R.R. Rye and J. A. Mann, Solder wetting kinetics in narrow V-grooves, Acta Materialia 45,5337-5345 (1997). 

Troger, J., Lunkwitz, K., Grundke, K. and Burger, W., Determination of the surface tension of microporous membranes using wetting kinetics measurements. Colloids Surf., A, 134, 299-304 (1998). 

P G. Petrov and J. G. Petrov, A combined molecular-hydrodynamic approach to wetting kinetics, Langmuir, 8,1762 [1992]. 

Petrov J, Sedev R, Petrov P. (1992) Effect of geometry on steady wetting kinetics and critical velocity of film entrainment. Adv Colloid Interface Sci 38 229 269. 

In the high strain range, it can be assumed that the wetting kinetics is accelerated with respect to the oxide layer growth kinetics. This can probably be due to the presence of a high applied strain. 

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