Surface analysis of groundwood paper treated by diffuse coplanar surface barrier discharge (DCSBD) type atmospheric plasma in air and in nitrogen

Paper made of groundwood was surface treated by atmospheric plasma of the diffuse coplanar surface barrier discharge (DCSBD) type in air and in nitrogen. Changes in surface composition and chemical bonding of the constituent elements were studied by X-ray photoelectron spectroscopy (XPS), and alterations in wetting were examined by contact angle measurements. Air plasma treatment resulted in strong oxidation but no N incorporation, while the ratio of the area of the O1 component (binding energy 532.1 eV) to that of the O2 component (533.2 eV) decreased, reflecting an increase in the proportion of O in C-O type bonds. Nitrogen plasma treatment followed by exposure to the atmosphere resulted in a slight N incorporation (1.5 at.%) and oxidation even more intense than observed for air plasma treatment. The O1/O2 ratio slightly increased, implying more O in C=O type bonds. The time dependence of surface oxidation showed a local maximum at treatment time of approximately 2 s for both the air and nitrogen plasmas.