Atmospheric pressure DC glow discharge

The oxygen concentration in the polymer surface increases with the treatment time. At extended treatment times a saturation was found which is the result of two competing processes: binding of oxygen atoms to the surface and breaking up polymer chains resulting in the production of low molecular weight fragments. A washing procedure after the treatment reveals that the chains scission dominates at high treatment times so that a maximum oxygen concentration is reached at a treatment time of about 100 seconds. The measurement of water contact angle shows a similar behavior.

The dynamic treatments show that an increasing film velocity clearly results in a reduced oxygen concentration. Investigating the samples after washing in ethanol reveals an increasing oxygen concentration with the web speed. We believe that the treated samples contain long living radicals and functional groups which decompose in radicals (i.e. peroxides). In the presence of ethanol a chain reaction can occur which results in an increasing oxidation.

A sample treated in the static mode has been analyzed for its carbon functionalities. A XPS-spectrum of the C1s-region shows different binding states. For a detailed characterization, hydroxyl groups were labeled with trifluoroacetic anhydride, carbonyl groups with methylhydrazine, and trifluoroethanol in combination with thionylchloride reacted with carboxyl groups. The derivatization reactions were carried out in the vapor phase. The results of the curve fit and the derivatizations are listed in table.

Equipment: Atmospheric Pressure DC Glow Discharge