Atmospheric oxygen-helium plasma surface modification of medical plastics

This study examines the effect of atmospheric pressure plasma treatment on the surface energy and adhesive bond strength of three medical polymers: acetal copolymer (AC), polycarbonate (PC) and polyethylene terephthalate (PET). Surface treatments were applied with a two-inch plasma beam source and reactive oxygen-helium (~1-3 vol% O₂) plasma under 150 and 200 W RF power. Through contact angle measurements and surface energy calculations, the response of these polymers to the plasma was found to be unique. Surface activation was rapid, occurring within 5 to 10 seconds of exposure. The PC and PET surface energies approached ges 70 dyne/cm. The acetal copolymer initially jumped to 58 dyne/cm, then declined with further plasma exposure, possibly due to etching or chain scission of the polymer. Langmuir-Hinshelwood reaction kinetics provided an excellent fit to the surface energy versus time data. Subsequent adhesion tests with epoxy, urethane and acrylate glues revealed large increases in adhesive bond strength for the AC (+50-300%), PC (+20-60%) and PET (+100-350%) following exposure times of 0.25 to 40 s under the plasma beam. At the meeting, I will describe the mechanism for activation of the polymer chains with the atmospheric pressure oxygen plasma.