A study of the adsorption of selected organic molecules to model the adhesion of epoxy resins: thermal desorption of glycidyl and phenoxy compounds from gold, iron oxide and zinc oxide

Abstract

The adsorption of oligomeric model compounds of the bis-phenol A epoxy resin was studied on gold, zinc oxide and iron oxide by temperature programmed desorption (TPD) in order to elucidate the relative importance of the four possible adsorption sites. Glycidyl 2-methylphenyl ether and 2-phenoxy ethanol were selected as the model compounds. It was found that the interactions of the model compounds with gold was primarily via the benzene ring, and the heat of desorption was 100–110 kJ/mol. On iron oxide, the model compounds dissociated by C-O bond and O-H bond scission. The surface interactions were via the phenoxy and hydroxyl oxygens, and the heat of desorption was 130–140 kJ/mol. On zinc oxide, the heats of adsorption were somewhat less than on iron oxide. Glycidyl 2-methylphenyl ether interacted mainly via the benzene ring and partly via the epoxy ring while 2-phenoxy ethanol interacted via phenoxy and hydroxyl oxygens. Their heats of desorption were 70–100 and 120 kJ/mol, respectively. Based on these results, an adhesion mechanism of the epoxy resin was suggested.