Interphase links, strength

The influence of wood includes a variety of topics. Wood bonding is often described as a chain of several links wood (substance), wood surface, interface between wood and adhesive, surface of the glue line (boundary layer), glue line itself. As with all chains, the weakest link determines the strength of the chain. In wood gluing, in most cases, the interphase is the weakest link. 

The surface potential (j)s depends on the concentration profiles of all ionic species present at the interphase, including ionic strength affecting the diffuse layer, specifically adsorbed ions, and surface ionizable groups. Thus, the surface itself possesses acid-base properties that are reflected in the response of the immobilized indicator dye but are not uniquely linked to the pH of the bulk of the solution. 

Figure 1. Chain-link diagram of well-formed (proper) wood-glue joint. The materials and conditions that were used have led to a joint with good bulk wood strength, a strong interphase with good adhesion, and a strong glue film. (Reproduced with permission from ref. 1. Copyright 1950 American Furniture Manufacturers Association.)...

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