How does interdiffusion create adhesion between an adhesive and a material surface?

Interdiffusion is one of several mechanisms that contribute to the formation of an adhesive bond. This process occurs when a liquid adhesive dissolves and subsequently diffuses into the material surface, known as the adherend.1

By penetrating the surface of the material, the adhesive creates a transitional zone at the interface called the interphase. This region is critical because its specific chemical and physical properties often control the overall strength and durability of the adhesive joint, as well as the efficiency with which loads are transferred between the joined components.1

While interdiffusion is a distinct mechanism, it is important to note that the formation of a stable bond typically involves a combination of multiple processes, such as adsorption, mechanical interlocking, and chemical reactions, depending on the specific nature of the adhesive and the surface being bonded. Synthetic adhesives, which are commonly composed of polymers, are specifically formulated to possess the necessary properties to spread and interact effectively with these surfaces.12