Jozef Ráhel

Atmospheric-pressure diffuse coplanar surface discharge for surface treatments

We report results from a plasma source; a diffuse coplanar surface discharge (DCSD), which is capable of generating macroscopically uniform thin layers of diffuse plasmas in air and other reactive gases at atmospheric pressure. DCSD is a type of dielectric barrier discharge generated on the surface of a dielectric barrier with embedded electrodes, which appears to be advantageous to surface treatment and deposition processes. Preliminary results on hydrophilization of polypropylene nonwoven fabric are also presented.

Atmospheric-pressure plasma treatment of polyester nonwoven fabrics for electroless plating

Abstract Atmospheric-pressure non-thermal plasmas have been increasingly promoted for polymer surface modifications. In this paper, atmospheric-pressure nitrogen plasma was used to render a polyester nonwoven fabric hydrophilic and facilitate absorption of a palladium catalyst in order to provide a catalytic surface for the deposition of electroless nickel. The plasma was produced in a surface barrier discharge generating a thin plasma layer in good contact with the fabric fibers. The optimum quality nickel coating was obtained for a 1 s treatment time. Treatment times in excess of 1 s resulted in a reduction of the nickel plating deposition rate, uniformity and adhesion values. The plasma-induced surface changes were characterized by liquid strike-through time measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy. Because of atmospheric-pressure operation, very short treatment times, and its robustness the method has the potential to be used in line with standard metal plating lines.

Hydrophilization of polypropylene nonwoven fabric using surface barrier discharge

Abstract Surface dielectric barrier discharges (SDBD), which find widespread industrial applications in ozone production, were used to hydrophilize light-weight polypropylene nonwoven fabric (PPNF) samples. The samples were treated in nitrogen plasma generated by SDBD at atmospheric pressure. The hydrophilicity of the samples was examined as a function of the storage time using a standard strike-through test. The surface chemical composition was characterized by X-ray photoelectron spectroscopy. Because of very short treatment times obtained (∼1 s) and its simplicity the method has the potential to be used in-line with standard high-speed PPNF production lines, laminating, printing and metal plating lines, etc.

Insulated surface discharge for metastables driven processing at atmospheric pressure

Abstract The insulated surface discharge (ISD) in helium under atmospheric pressure operated with voltage of 1–3 kV in frequency range from 1 to 10 kHz is investigated. The influence of the insulating film on the operation of ISD is discussed. The presence of poly-vinyl-chloride (PVC) foil or silicon polymer film on the surface of the discharge electrode prolongs the lifetime of metastable excited helium atoms up to 17 or 50 μs, respectively.

Wood Surface Modification in Diffuse Coplanar Surface Barrier Discharge for Creating Water Repellent Films from N2/HMDSO and N2/HMDS Mixtures.

Diffuse Coplanar Surface Barrier Discharge was successfully tested for creating a water-repellent surface from HMDSO and HMDS compounds on samples of spruce wood (Picea abies, Karst). The best results were achieved when the treated sample was in continuous motion during the course of film deposition. Best hydrophobic coating was achieved for 29% of total gas flow through the HMDSO and HMDS liquid. The surface free energy of modified surface was 30 mJ/m2 for HMDSO and 24 mJ/m2 for HMDS mixtures. The 50 μl water droplet required (180±30) min to penetrate into the modified spruce in HMDSO mixture and (213±30) min in HMDS mixture. This is more than 20 fold increase compared to the unmodified spruce. The chemical composition of deposited layer was analyzed by ATR-FTIR. The presence of Si-O-Si and Si(CH3) functional groups was confirmed.

Surface modification of polyester monofilaments by Atmospheric-Pressure Nitrogen Plasmas

Polyester monofilaments were treated by a pulsed surface electrical discharge in nitrogen at atmospheric pressure, to increase their adhesion to an epoxy resin matrix. The treatment resulted in an eight-fold increase in adhesive strength, without any change in mechanical properties of the monofilaments. It is concluded that polar group interactions, rather than increased surface area, are responsible for the improved adhesive strength.