Adhesion of Thin Plasma Polymer Films to Plastics

To date, no comprehensive study of the adhesion of plasma-polymerized films on plastics has been made. In the present work, 1400-Å films produced by the radio frequency discharge plasma polymerization of styrene and acrylonitrile were deposited on polyethylene, polystyrene, polypropylene, poly(ethyleneterephthalate) (Mylar), polytetrafluoroethylene (Teflon), polycarbonate (Lexan), polyimide (Kapton), poly(methyl methacrylate) (Lucite), polyamide (Nylon 6), poly(oxymethylene) (Delrin), and poly(vinyl fluoride) (Tedlar) substrates. Adherence of these films was then measured by applying a ½ by 2 in. (1.27 by 5 cm) piece of Scotch No. 810 tape to the film and then removing the tape in a 90-deg peel. This provides a lower limit of 190 g/in. for the adhesion of the polymer film to the substrate. It was found that both plasma polystyrene and plasma polyacrylonitrile were removed by this procedure from poly(oxymethylene), polypropylene, poly(methyl methacrylate), and polycarbonate. Both films remained adhered to the other seven plastics during this test. These results can be explained on the basis of molecular structure and can be correlated with literature data on bond strength results for activated gas-treated substrates. It was also concluded, considering the divergent properties of the two plasma polymers, that adhesion to any substrate is not dependent on the structure of the plasma polymer. Soaking films of plasma-deposited polyacrylonitrile on Mylar in solvents of varying polarity for long periods of time did not reduce the adhesion of the film to the substrate. It would seem that the film-substrate bond is either a physical one of a very high order or more likely a true chemical bond.