Soft plasma treatment of polymer surfaces

The effect of Ar, Ar/H 2 O and Ar/C 2 H 5 OH soft plasma treatments on the surface free energy of poly(methyl metacrylate) (PMMA) and polycarbonate (PC) has been studied. The plasma gas was excited by a 13.56 MHz radio frequency (RF) generator, in a GENUS 8720 plasma enhanced chemical vapour deposition facility. Changes in the surface free energy of the polymers were followed as a function of the plasma treatment time. Bickerman's method for precise measurements of contact angles of very small liquid sessile drops in contact with substrates was used to determinate the polar and dispersion components of the polymer free surface energy, on the basis of the theory of Owens, Wendt, Kaelble and Uy. It was found that all RF plasma treatments led to an increase in the polar component of PMMA and PC, mainly due to an increased hydrogen bonding ability. Short (1-5 min) Ar/C 2 H 5 OH and Ar/H 2 O plasma treatments exhibited the same effectiveness, greater than that of pure Ar treatment. It was observed that the introduction of ethanol in plasma gas resulted in more uniform, defect free and undamaged, polymer surfaces compared to those modified with pure Ar or Ar/water plasma gas.