Techniques for bonding rubber to metal

The difunctional zinc salts of acrylic and methacrylic acid are effective promotors for the creation of adhesive bond between metallic or fibrous substrates and peroxide crosslinked elastomer compounds. Commercially available additives on the basis of these salts additionally include scorch retarders to increase processing safety. They are either added to the rubber compounds as internal adhesives the way of common ingredients, or are applied to the substrate or compound as external adhesives in form of a paste, or alternatively they can be used as ingredients in an adhesive strip that is placed between the substrate and the compound surfaces. During vulcanization these adhesive systems form bonds not only between substrate and elastomer, but additional ionic crosslinks are also generated between adjacent rubber molecules, with positive effects on various mechanical cured rubber properties.