Application of microwave discharges for treatment of polymer surfaces
In this paper we analyze application of a simple microwave cavity discharge on the surface modification of polymers. Electrons and radicals from the low pressure plasma as well as the metastable excited oxygen species react intensively with many engineering plastic materials leading to the increased adhesion of polymers. This is of importance to achieve better bondability by gluing, painting, varnishing, stamping, printing or metalizing. The change of the wetting contact angle is discussed with respect to the treatment time and the polymer used. The creation of reactive functional groups of the hydroxyl and carboxyl acid type on the polymer surface is mainly responsible for the better adhesion. The lifetime of the bondability of polycarbonate, polymethyl methacrylate and polyether ketone was investigated. The surface modification of plastic materials may be performed in the vacuum chambers operated by low cost standar d microwave oven components or at a higher expense by rf generators at 13.6 MHz.
LETTER TO THE EDITOR: Wettability control of a plastic surface by Cf4-O2 plasma and its etching effect
Any desired surface wettability of a plastic surface can be produced by changing the concentration of the plasma gas, which here is a mixture of oxygen and a compound which includes fluorine. In the plasma treatment, the use of a third electrode consisting of a metal mesh for ion trapping can significantly decrease the etching effect. The plastic surface wettability, given by the contact angle of a water drop, does not have any direct relationship with the surface roughness due to etching in this experiment.
The Surface Fluorination of Graphite by Electric Discharge
The surface fluorination of graphite in some glow discharge plasmas was studied. The plasmas contained excited fluorine atoms, and were, generated by various discharges, Direct-current, RadioFrequency (13.56MHz) and Micro-Wave (2450MHz), with CF4 as source gas. The contact angles formed by water, dropped on the treated surfaces, were over 160°, and changes of mass indicated addition of the fluorine. But the effect of etching appeared as a decrease of mass under some conditions, and such effects were observed also by a scanning electron microscope. The ESCA results on the surfaces treated by plasma were similar to those which were measured on the surfaces treated by F2 gas at high temperature.