AbstractIn many engineering applications, elastomers are employed in multilayered and/or multicomponent composite structures. Rigid reinforcements are used to constrain the elastomer laterally, thus increasing the stiffness and load bearing capacity in the axial direction while retaining flexibility in other directions. Good, durable, adhesion is required between different elastomer layers and between elastomer and reinforcement to maintain these constraints. Owing to molecular characteristics, bonding processes for some elastomers can be spontaneous. Genuine spontaneity is exhibited in the phenomenon of tack when portions of the long elastomeric molecules interdiffuse across the interface between two contacting rubber surfaces. In addition,‘indirect spontaneity’can occur, e.g. when chemical bonding takes place between elastomer and brass plated steel wires at the same time as chemical crosslinks are formed between elastomer molecules during vulcanisation. Elastomers can be bonded to many substrates in various ways. Associated bonding mechanisms usually involve contributions from diffusion processes (of molecular portions, vulcanisation additives, adhesive or substrate constituents, etc.) and/or chemical reactions of widely varying form.MST/987