Interfacial mechanism chemical bonding theory

The mechanism of chemical adhesion is probably best studied and demonstrated by the use of silanes as adhesion promoters. However, it must be emphasized that the formation of chemical bonds may not be the sole mechanism leading to adhesion. Details of the chemical bonding theory along with other more complex theories that particularly apply to silanes have been reviewed [48,63]. These are the Deformable Layer Hypothesis where the interfacial region allows stress relaxation to occur, the Restrained Layer Hypothesis in which an interphase of intermediate modulus is required for stress transfer, the Reversible Hydrolytic Bonding mechanism which combines the chemical bonding concept with stress relaxation through reversible hydrolysis and condensation reactions. 

Adhesion refers to the state in which two dissimilar bodies are held together by intimate interfacial contact such that mechanical force or work can be transferred across the interface. There is unifying theory of adhesion that relates the physical-chemical properties of materials to the actual physical strength of an adhesive bond. The interfacial forces holding the two phases together may arise from van der Waals forces, chemical bonding, or electrostatic attraction. The mechanical strength of the system is determined not only by the interfacial forces, but also by the... 

Although the mechanisms of polyimide/metal adhesion remain to be fundamentally elucidated, it is generally accepted that the interfacial diffusion of metallic entities into the polyamic acid plays a key role at the interface [156-158]. Two main theories have been reported explaining the adhesion of the Pl/metal bond chemical and mechanical bonding [159]. Initial work emphasized mechanical bonding and most efforts were dedicated to the physical roughening of the substrate by different abrasive methods as well as chemical treatments in order to improve metal to polyimide adhesion by increasing the metal surface area [156,160-164]. 

There is very good agreement between the 0q values obtained directly from the mechanical debonding experiments and the calculated values obtained by surface chemical methods. This represents a powerful vindication of the GFM theory of adhesion, since for interfaces bonded only by secondary interatomic bonds 0q and are, by definition, the same quantity, namely, the energy required per unit area to break the interfacial atomic bonds. 

The second is developped from a chemiqal approach of the rupture according to the Tobolsky-Eyring theory [14, I5J. This model considers that the activation energy for the interfacial bond breaking reaction depends on the chemical and mechanical state of the interface. When this dependency is strong enough, two solutions... 

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