Surface lubrication of polymer films by photoinduced graft polymerization

Films of nylon 6, polypropylene, and ethylene–vinyl acetate copolymers were graft polymerized with acrylamide or dimethylacrylamide to render the hydrated surfaces slippery. Following UV irradiation in air, the films were placed in the aqueous monomer solution and then either heated to 50°C after degassing or UV-irradiated in the presence of a small amount of riboflavin without degassing to effect graft polymerization. The graft polymerization altered the films from the hydrophobic and nonlubricating to the hydrophilic and slippery surfaces. To evaluate the surface lubricity, the coefficient of friction (μ) against a glass plate in water was determined with the help of a tensile testing machine. The μ value for the films surface-grafted with acrylamide up to 30 μ g cm−2 was reduced to less than 0.05, regardless of the substrate polymers.