A Review on Natural Rubber/ Steel Composites: Rubber to Metal Bonding

In recent years, rubber- metal composite material has attracted much attention in automotive industry and structural rubber. To have the best mechanical properties and high performance composites, strong rubber to metal bonding is necessary. Among these, structural composites made from natural rubber and steel because of increasing use in various industries, has academic attraction. Natural rubber to steel bonding can be done through hot bonding of rubber compound (containing material, that naturally tend to bond to the metal; such as Ebonite) via vulcanization, or by using a cold bonding of adhesiveprimer system, to bond cured rubber to steel. The mechanism of rubber to metal bonding using an interlayer of bonding agent (adhesive) is discussed with respect to various physical and chemical events such as adsorption at the metal surface, chemical crosslinking within the adhesive and primer, inter diffusion, and formation of interpenetrating networks at the rubber–adhesive interface. In this review, the natural rubber to steel bonding, simultaneously or after the vulcanization, is studied. In this approach, the basic formulation and adhesion promoter additives, based on natural rubber are presented; and then different techniques of natural rubber to steel bonding are discussed. Finally, the most important test to evaluate rubber to metal bonding resistance is introduced.