Functional group efficiency in adhesion between polyethylene and aluminum
Abstract
The effect of different functional groups on the adhesion between polyethylene and aluminum has been studied. Poly(ethylene-co-butyl acrylate) (EBA) and poly(ethylene-co-vinyl acetate) (EVA) were used as such and provided polyethylene surfaces with two different kinds of ester groups, butyl ester and acetate, respectively. By alkaline hydrolysis in an organic solvent the surface functionality could be changed to carboxylate and hydroxyl, respectively. Finally, acid washing converted the carboxylate groups into carboxylic acid. The effect of the surface treatments were followed by reflection IR. T-peel tests of laminates made of the original, as well as the surface-treated polymers, and aluminum allowed an evaluation of the specific contribution to the adhesion for the groups in question. The peel strength increased linearily with the bulk concentration of comonomer in the original EBA and EVA samples. The values increased from about 100 N/m for polyethylene up to 2500 N/m in the case of 3.7 mol % of carboxylic acid. The efficiency of the investigated functional groups increased in the following order: H<OCOCH3 <COOC4H9 <COONa∼OH<COOH.
