| Abstract: | A number of vinyl monomers have been surface grafted onto a polyethylene sheet by the mutual irradiation in monomer vapor and by a trapped-radical technique. The surface composition of the grafted sheets has been determined by means of ATR infrared spectrophotometry and compared with the peel strength of the joints bonded with conventional structural adhesives. In the methyl acrylate grafts followed by a saponification treatment, only the surfaces having graft compositions of more than 80 mole-% methyl acrylate give a high peel strength. A similar relationship between peel strength and surface composition is found in the surface grafts of vinyl acetate, acrylic acid, acrylamide, and methylolacrylamide. It is concluded that the formation of a surface with such a high monomer content is a necessary condition for the strong adhesive bonding of grafted polyethylenes at bonding temperatures below the softening point. Moreover, the adhesive bondability of the highly modified surfaces with epoxy adhesives is significantly enhanced by the introduction of carboxy and carbamyl radicals. |
