Scanning force microscopy investigation of poly (ethylene terephthalate) modified by argon plasma treatment

Contact mode scanning force microscopy of plasma-treated poly(ethylene terephthalate) leads to poor resolution of surface features due to the disruption of delicate structures. However, non-contact mode imaging reveals important new insights into the development of the surface topography with plasma treatment. While the surface wettability reaches a steady state after only a few minutes, SFM reveals subtle topographical developments extending over a period of hours. Using a model polyester containing particulate surface additives, we demonstrate that the rate of erosion of the polymer during plasma treatment may be precisely quantified, and show that at 0.1 mbar Ar pressure, PET is eroded at 4 nm min(-1). This high erosion rate persists beyond the point at which the wettability of the polymer has reached a limiting value. Ultimately, the rate of erosion slows. At high treatment times the surface exhibits ridges that align perpendicular to the final draw direction of the film. We speculate that these arise from the preferential erosion of amorphous material.