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.
Surface modification of plastics by plasma treatment and plasma polymerization and its effect on adhesion
The Adhesion between plasma-modified polyethylene (PE) and different polar polymers, as well as aluminium and steel, has been studied. The PE was modified by either oxygen plasma treatment or plasma polymerization of acrylic acid. The result show the importance of introducing polar groups on the surface of the non-polar PE in order to improve the adhesion to polar polymers as well as metals. Laminates made of plasma-modified PE ad polyamide 6 (PA-6) or poly(ethylene vinyl alcohol) (EVAL-G) showed failure in PA-6 or EVAL-G when delaminated. Poly(ethylene terephthalate) (PET), which is not as polar as PA-6 or EVAL-G, showed an adhesive failure when the PE was treated with either of the plasma methods. However, when both the PET and the PE were modified, the failure occurred in the PET upon delamination. Oxygen plasma treatment of PE resulted in an increased adhesion when laminated with cellophane, with no observed material failure. The laminates composed of plasma-modified PE and aluminium or steel showed cohesive failure in the PE.
Titration Method for Measuring Fluorine Atom Concentration in Microwave Plasma Etching
A titration method has seen developed to measure the concentration of fluorine (F) atom in microwave plasma etching. A rapid reaction of F atoms with H2 gas is used as a titration reaction to determine the absolute F atom concentration. Applying the present method to SF6 microwave discharge, the F atom concentration is measured under various discharge conditions. The F atom concentration is 2.9-4.0×1011 cm-3 at a typical operating pressure of 6.7×10-2 Pa and a microwave power of 200 W. It is confirmed that relative changes in the concentration agree well with those obtained with the optical spectroscopic method.