Martin Šíra

Surface modification of polyethylene and polypropylene in atmospheric pressure glow discharge

An atmospheric pressure glow discharge (APGD) was used for surface modification of polyethylene (PE) and polypropylene (PP). The discharge was generated between two planar metal electrodes, with the top electrode covered by a glass and the bottom electrode covered by the treated polymer sample. The discharge burned in pure nitrogen or in nitrogen–hydrogen or nitrogen–ammonia mixtures. The surface properties of both treated and untreated polymers were characterized by scanning electron microscopy, atomic force microscopy, surface free energy measurements and x-ray photoelectron spectroscopy. The influence of treatment time and power input to the discharge on the surface properties of the polymers was studied. The ageing of the treated samples was investigated as well. The surface of polymers treated in an APGD was homogeneous and it had less roughness in comparison with polymer surfaces treated in a filamentary discharge. The surface free energy of treated PE obtained under optimum conditions was 54 mJ m−2 and the corresponding contact angle of water was 40°; the surface free energy of treated PP obtained under optimum conditions was 53 mJ m−2 and the contact angle of water 42°. The maximum decrease in the surface free energy during the ageing was about 10%.

Investigation of the coplanar barrier discharge in synthetic air at atmospheric pressure by cross-correlation spectroscopy

The barrier discharge in the coplanar arrangement operating in a single-filament mode was studied spectroscopically. The evolution of the discharge luminosity was measured by the technique of cross-correlation spectroscopy. The 1D-spatially and temporally resolved luminosities of the first negative (at 391.5 nm) and the second positive (at 337.1 nm) system of molecular nitrogen were recorded using the above-mentioned technique. A cathode-directed ionizing wave (IW) was clearly seen on the plot for radiation intensity at 337.1 nm. In addition to this, also observed was a wave of the enhanced electric field propagating over the anode. In this paper, the propagation of these waves is described and their velocities are determined. The discharge evolution is divided into three phases—the Townsend phase, the phase of the IWs propagation and the extinction phase. Since the above-mentioned luminosity distributions could be interpreted approximately as the electric field (for 391.5 nm) and the electron density (for 337.1 nm) distribution, the qualitative description of the discharge is made accordingly. All these parameters are compared with similar measurements of the volume discharge. Apart from this, an attempt to determine the reduced electric field is made according to the kinetic model. (Some figures in this article are in colour only in the electronic version)

Surface modification of polycarbonate in homogeneous atmospheric pressure discharge

A homogeneous atmospheric pressure dielectric barrier discharge was used for the surface modification of polycarbonate (PC). The discharge was generated between two planar metal electrodes, the top electrode was covered by glass and the bottom electrode was covered by a polymer sample. The discharge burned in pure nitrogen or in a mixture of nitrogen and hydrogen. The surface properties of both treated and untreated polymers were characterized by atomic force microscopy, surface free energy (SFE) measurements and x-ray photoelectron spectroscopy. The influence of the treatment time and power input to the discharge on the surface properties of polymers was studied. The ageing of treated samples was also investigated. The treatment of polymers in the homogeneous atmospheric pressure discharge was homogeneous and the polymer surfaces showed a smaller degree of roughness in comparison with the polymer surfaces treated in a filamentary discharge. The SFE of the treated PC obtained at optimum conditions was 53 mJ cm-2 and the corresponding contact angle of water was 38deg . The maximum decrease in the SFE during ageing was about 13%. The analysis of the chemical composition showed an increase in the nitrogen concentration in the surface layer, but almost a zero increase in the oxygen concentration. This result was discussed concerning the measured values of the SFE measurement.

On the analysis of surface free energy of DLC coatings deposited in low pressure RF discharge

The results of statistical study of acid-base approach to the determination of the surface free energy are presented. Plasma enhanced chemical vapour deposition (PECVD) in low pressure RF discharge was used to prepare diamond-like carbon (DLC) coatings. The plasma deposited films were investigated by means of contact angle technique in order to determine their surface free energy. Drops of various liquids were set on the film surface and the drop profiles were snapped with CCD camera. The obtained contact angle data using several testing liquids were analyzed by threeliquid acid-base method and the results retrieved on the basis of different liquid triplets used were compared.A multiple regression method for a determination of the surface energy from more than three liquids is suggested and its outputs are compared with the results obtained by standard three-liquid acid-base approach.

Deposition of teflon like coatings in surface barrier discharge

The plasma deposition at atmospheric pressure becomes a promising technology due to its economical and ecological advantages.The objective of the present work is to develop technique for deposition of thin films with desired surface energy, permeability and wear resistance on pulp board surface by means of discharge at atmospheric pressure.The deposition of thin films was carried out by surface discharge at atmospheric pressure. The films were deposited from the different mixtures of C4F8 with nitrogen. The properties of the thin film substrate systems were investigated by means of the contact angle measurement and industrial permeability tests. The mechanical properties were studied by means of the depth sensing indentation test. In the case of the mechanical tests glass plates were used as the substrate.

Activation of polyethylene and polypropylene in atmospheric pressure glow discharge

The atmospheric pressure glow discharge was used for activation of polymer materials. The discharge was generated between two plane metal electrodes covered by a glass dielectric barrier. The discharge was ignited in pure nitrogen or in mixtures of nitrogen with hydrogen or nitrogen with ammonia. Studied polymers were polyethylene and polypropylene. The surface energy of both activated and non-activated polymers was determined by means of contact angle measurements. The influence of treatment time on the surface free energy of polymers was studied.

HF-Plasma Pencil in Liquids

The plasma pencil in liquids is a new device for the treatment of archeological artifacts. Plasma jets out from the pencil so that it makes radical changes in the conductivity and reactivity of liquids. An artifact is immersed in liquid and the plasma has a local and rapid effect on materials.

Modification of Polymer Surfaces Using Atmospheric Pressure Barrier Discharges

Abstract The objective of the present work is the development of a technique for the deposition of thin films, by means of an atmospheric pressure discharge, onto a pulp board surface, with the desired surface energy, permeability and wear resistant surface. The deposition of thin films was carried out by a surface barrier discharge at the atmospheric pressure. The films were deposited from mixtures of C4F8 with nitrogen. The properties of the thin film substrate systems were investigated by means of contact angle measurement and industrial permeability tests. The chemical composition of the films was studied by means of a Fourier transform infrared spectroscopy. The mechanical properties of the films were studied by means of depth sensing indentation tests performed on samples deposited upon glass plate. The surface topographies of coated and uncoated samples were investigated using a scanning electron microscope.

Thermal stability of coatings prepared in atmospheric pressure glow discharge

In order to better understand the relations between the deposition conditions, the microstructure and hydrogen and/or nitrogen incorporation in polymeric films the thermal stability of coatings prepared in atmospheric pressure glow discharge was studied. The polymeric films were prepared from the mixture of hexamethyldisiloxane (HMDSO) or hexamethyldisilazane (HMDSZ) with nitrogen in atmospheric pressure glow discharge (APGD). The hydrogen and/or nitrogen evolved from polymeric films were studied by ther.