Bulk properties compared with adhesive layer

When the water film is squeezed out, the thick water layer is removed and the surfaces are separated by lubricant film of only molecular dimensions. Under these conditions, which are referred to as BL conditions, the very thin film of water is bonded to the substrate by very strong molecular adhesion forces and it has obviously lost its bulk fluid properties. The bulk viscosity of the water plays little or no part in the frictional behavior, which is influenced by the nature of the underlying surface. By comparing with the friction force of an elastomer sliding on a rigid surface in a dry state, Moore was able to conclude that for an elastomer sliding on a rigid surface under BL conditions, one can expect ... 

In both the sterns, as a result of adsorption and adhesion interaction between the components at the interface, tte brnindary layers undergo changes, as compared with the rei ctive properties within the bulk. This brings about the appearance of additional levels of microheterogeneity (5). 

This current state has to do with the discovery that the action of fundamental adhesion forces is not restricted to the interface. They not only fix some layer of adhesive molecules on the surface of the adherend but they can exert strong influence on the formation of chemical and morphological structure as well as on molecular mobility in the adjacent region of the adhesive during solidification. Hence an interphase is formed. These interphases depend on the combination of adhesive and adherend surface and on the process of contact formation as well. Due to its distinct structure, the interphase possesses properties that can be much different from the behavior of the bulk adhesive. Compared to the complexity of the problem, we just start understanding what is behind interphases. 

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