Surface energy wetting

In an experiment on equal rubber surfaces under dry conditions, the black spot diameter was 1.37 mm, equivalent to a work of adhesion of71mJm , which is twice the surface energy of each individual surface. Thus the rubber surface energy was 35 mJ tn . But when the surfaces were immersed in water, the black spot fell to 0.63 mm in diameter, suggesting a work of adhesion reduced to corresponding to a wet surface energy of 3.4mJm . Thus the... 

J. A. Pask and A. P. Tomsia. Wetting, Surface Energies, Adhesion, and Interface Reaction Thermodynamics. In Ceramics and Glasses. Engineered Materials Handbook, Vol. 4. ASM International, 1991, pp. 482-492. 

Even when much effort was invested by the scientific community to understand wetting, surface energy and other apparently simple concepts, lots of questions stiU remain open in which we will discuss in this chapter. The exposition will be focused on some of those controversies with the hope to contribute to both the reader s knowledge acquisition and inquisition. 

We will not explain here why a given adhesive should stick to a given material, because this is explained in the chapter Theory of adhesion in Volume 2 in the light of wetting, surface energy, adsorption, work of adhesion, electrostatic, diffusion, covalent bonds and van der Waals forces, and it is also discussed in all the chapters dealing with the various chemical families of adhesives. 

When a surface-active agent is present in a liquid droplet, it can adsorb to the surface, lower the surface energy, and cause the liquid contact angle to increase. This phenomenon, known as autophobicity, was postulated by Zisman many years ago [78, 79]. Autophobicity is quite striking in wetting films on clean... 

Surfa.ce Energy. The surface energies of Parylenes N, C, and D were measured by observing the contact angles for several standard probe hquids. AH three have surface energies of approximately 45 mj/m (= dyn/cm), ie, all test Hquids having less than 45 mj/m surface tension completely wet the as-deposited parylene surfaces (43). 

Permanent Set. When an elastomer is stretched and then allowed to relax, it will not completely recover its original dimensions. This divergence from its original form is called its permanent set. It is principally affected by the affinity of the elastomer for the filler surface and is, therefore, primarily a function of the surface energy or wetting of the filler. 

Pressure-Sensitive Adhesives. SiHcoae PSAs are used primarily ia specialty tape appHcatioas that require the superior properties of siHcoaes, including resistance to harsh chemical environments and temperature extremes (398,399). SiHcone PSAs are also used ia appHcatioas requiring long service Hfe, electrical iasulatioa, and protection from moisture. Another distinctive advantage of siHcone PSAs is their abiHty to wet low surface energy tape substrates such as PTEE. 

The relationship between wetting and solid surface energy... 

The outer surfaces of these plasma polymers are terminated with hydroxyl groups and have high surface energies. They are readily wet by adhesives and form strong and durable adhesive bonds [51]. 

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