Interfadal phenomenon

Coatings are usually applied as multi-layered systems that are composed of primer and topcoat. However, in some cases - for example automotive coating systems -this may vary from four to six layers. Each coating layer is appHed to perform certain specific functions, though its activities are influenced by the other layers in the system. The interactions among different layers and the interfadal phenomenon play an important role in the overall performance of the multi-coat systems [5]. Different properties of coatings are typically associated with specific parts of a coating system (Fig. 1.1) [6]. 

It is possible to modify the interfaces between liquids with specific additives. This was discovered by andent and medieval investigators and applied in the form of soaps, and later in food technology and in the application of dyes. The mechanisms of these additives only came to be realized in about 1900. Such additives are generally molecules with hydrophobic and hydrophilic sedions that align along interfaces between the two liquid phases. They reduce interfadal tension and stabilize phase morphology to smaller dispersed phase sites. This phenomenon was realized by IG Farbenindustrie chemists who applied it in the late 1920s in emulsion polymerization that they used to produce synthetic rubber. 

In contrast to the case discussed above, an imposed gradient in the interfacial tension causes a viscous flow in the adjoining bulk phase(s), as shown in Figure 17.15. For instance, if the interfacial tension is locally lowered by applying an amphiphilic compound the monolayer moves away from that place to annihilate the interfadal tension gradient. This phenomenon is called the Marangoni effect. The ensuing shear rate in the bulk phase is such that Equation 17.22 is satisfied. 

Such definitive forecasts do not result from the theories of Leibler or Hong and Noolandi. However, the latter theory describes in detail the phase diagram for copolymer — homopolymer mixtures and is therefore pertinent to the X-ray work of Roe Similarly, Leibler s theory provides a detailed description of a microphase separation mechanism and thus is of value in the interpretation of experiments investigating this phenomenon. Small angle neutron scattering data reported to date has been maitily concerned with pure styrene-diene block copolymers which are fully microphase separated and thus examined D, dj, and interfadal layer thickness as a function of molecular weight and composition and therefore comparison has usually been made with the MIA theory of Helfand. 

Interfacial fracture is a failure mode usually associated with ENIG, and is also known as black-pad, brittle nickel, and black-line nickel (See Fig. 32.7). Technically, interfacial fracture simply refers to the location of physical separation when a solderjoint is tested to failure. Black-pad (black-line nickel) is a phenomenon of ENIG that, when sufficiently severe, results in interfadal fracture. Brittle nickel refers to the inherent weakness of solderjoints formed from nickel-tin intermetallics, regardless of the mechanism of failure. 

A general transport phenomenon in the intercalation electrode with a fractal surface under the constraint of diffusion mixed with interfadal charge transfer has been modelled by using the kinetic Monte Carlo method based upon random walk approach (Lee Pyim, 2005). Go and Pyun (Go Pyun, 2007) reviewed anomalous diffusion towards and from fractal interface. They have explained both the diffusion-controlled and non-diffusion-controlled transfer processes. For the diffusion coupled with facile charge-transfer reaction the... 

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