This relation between and aI is clearly demonstrated, and several materials have been investigated. The adhesion energy G c at the interface between two materials can be measured in the so-called double cantilever beam test. A thin knife of thickness is introduced at the interface between two relatively thick films. The width of the gap a is is related to the adhesion energy. For practical applications also with respect to welding of two films, the relation between the interface width aI and the adhesion between the films expressed by the adhesion energy Gc has been investigated.
Adhesion is measured by a double cantilever beam test.
Three regimes can be distinguished, where with increasing interface width first adhesion is very low, then a direct correlation between aI and Gc is observed, and finally saturation close to the bulk adhesive energy is achieved. This behavior may be explained by a model, where the formation of mechanically effective entanglements between chains from both sides of the interface is assumed to be the important factor for the development of adhesive strength. In an attempt to understand the compatibalizing effect of copolymers, the copolymer distribution in a blend has been investigated. For a weakly incompatible blend system the situation turns out to be quite complex, and the copolymer may either be enriched at the interface or may be uniformly distributed in the phases. The behavior depends on concentration of the copolymer, molecular weights of components and temperature.