Effect of Cross-Linking on the Dewetting of an Elastomeric Surface

It has been shown over the last few years how the wetting (or dewetting) of a soft, elastomeric substrate can be markedly affected by local deformation of the solid near the triple line, due to the component of liquid surface tension acting perpendicularly to the (undeformed) solid surface, i.e., the "wetting ridge." Since the degree of cross-linking of an elastomer affects its mechanical properties, we have undertaken a study of the influence of cross-linking on (de)wetting behavior. Using a silicone rubber in four states of cross-linking, we have observed that triple-line motion of tricresyl phosphate increases in speed with degree of cross-linking. Two principal factors influence this behavior, both being directly linked to average intercross-link molecular weight, M c . A decrease in M c increases elastic modulus and therefore decreases the importance of the wetting ridge, whilst also lowering the dissipative properties of the polymer. The combined effects lead, in the case studied, to a linear relationship between dewetting speed and elastomeric elastic modulus to the power 10/3.