Adhesion between Compounded Elastomers: A Critical Review

Rubber to rubber adhesion is very unique in a way that both joining substrates are flexible and of relatively low strength. Bonding of two different rubber compounds either through vulcanization or by using an adhesive compound bears significant importance from both scientific and technological points of view. This problem has significant implication especially in four areas of the rubber industry. The first is the adhesion between an unvulcanized rubber compound and an unvulcanized rubber compound which has direct relevance in the manufacturing process of tires and conveyor belts where different layers of unvulcanized rubbers are joined together and co-crosslinked. The second is the co-vulcanization between similar or dissimilar rubbers. The third is the adhesion between an unvulcanized rubber compound and a vulcanized rubber compound. This is generally practiced for repairing the damaged vulcanized rubber portions in a conveyor belt by pressing the unvulcanized rubber compounds against the damaged vulcanized rubber portions using heat and pressure. The fourth is the adhesion between a vulcanized rubber compound and a vulcanized rubber compound using a special bonding agent for retreading of tires. There are wide varieties of distinct variables affecting rubber to rubber bonding. The variables affecting the bonding between compounded rubber and compounded rubber have been identified and discussed in detail in this review. In addition, the precise nature of the interactions at interfaces of various rubber to rubber joints has been elaborated. The recent developments in the area of rubber to rubber bonding are collated and compared with old literature to present the current understanding of the subject.