Mechanism of adhesion joint formation

To understand the properties of the adhesion joints one should consider the mechanism of their formation. The latter consists of several stages  

The emergence offerees of molecular interactions responsible for adhesion is possible only under conditions under which the molecular contact occurs at the adhesive-substrate interface. This process is dependent on the physical relief of the surface. The process of the formation of adhesive joints also depends on the kinetics of spreading, which, in turn, depends on the rheological properties of adhesive. As we have already noted, the state of true thermodynamic equilibrium in many cases cannot be achieved. 

There is a theory describing the kinetics of surface wetting due to the action of ca nllary forces in relation to the surface tension predicted by a Laplace equation. One can calculate the rate of liquid flow into a narrow or wedge-like slot, or a round hole. The theory takes into consideration the rheological properties of 

The molecular description of the formation of an adhesive layer does not take into account the polymeric structure of adhesives either. It is based on determination of the number of adhesion or molecular bonds, n, per unitary area of a true contact surface and the energy of a single bond between two surfaces. During the formation of such bonds the adhesion strength. A, can be expressed by a specific work spent on the destruction of the adhesive joint  

The appearance of the maximum number of bonds, determined by the surface relief and adhesive rheology, is one of the most essential conditions for the formation of contacts and increase in adhesion strength. Microrheological effects include adsorption interactions with the surface and are determined by the flexibility of chain and molecular mobility in the adsorption layer. 

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