a method of bonding two substrates at least one of which is a rubbery polymeric material having carbon - carbon double bonds on the polymer backbone , the method comprising : a ) applying an aqueous polyurethane dispersion adhesive composition to at least one of the substrates , the adhesive compostion further comprising an epoxy resin ; b ) allowing the composition to dry ; and then c ) joining the substrates with heating to activate the adhesive . the substrates are suitably footwear materials such as a molded rubber outer sole which has been first primed with a chlorinating primer , and a foam midsole of a material such as a lightly crosslinked ethylene vinyl acetate . the process results in bonded assemblies having improved humidity resistance .