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Abstract
This study investigated the adhesive properties of some neoprene-phenolic adhesives for bonding different rubber and metal substrates. The metal substrates studied were titanium, stainless steel, aluminum and galvanized iron. Styrene butadiene rubber (SBR), natural rubber (NR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM) were the rubber substrates used. The phenolic resin was the product of condensation of a mixture of phenol and cardanol with formaldehyde. Cardanol, a meta-substituted phenol, is the main ingredient of cashew nut shell liquid (CNSL), a renewable resource. Cardanol-based resins were found to be effective for bonding metal substrates with the exception of galvanized iron. A high shear strength of the order of 12 000 kPa was obtained for stainless steel–stainless steel bonds. In the case of rubber-to-rubber bonding both high peel and shear strengths (10 kN/m and 1000 kPa, respectively) were found for SBR–SBR bonds. In general, it is possible to replace 20–40% phenol with cardanol for resin preparation without sacrificing the bond strength. The usefulness of cardanol as a starting material for formulating adhesive systems is amply demonstrated.