A corona apparatus comprising at least one roller electrode assembly, a supporting surface acting as a counter electrode, and a generator for generating an alternating current voltage for said electrode assembly characterized in that the roller electrode assembly comprises: a central shaft, an electrode, means for mounting said electrode to said shaft, a tube, means for mounting said tube for rotation about said shaft, said electrode contained within said tube, means for electrically connecting said electrode to said generator and means for supporting said shaft whereby said tube is positioned adjacent to said counter electrode.

A method for surface treatment of a substrate made of thermoplastic plastic is described, wherein the substrate is guided into the zone of a corona discharge flowing between two electrodes charged with high electrical voltage. The characterizing feature of the method comprises subjecting at least one surface of the substrate, simultaneously with corona treatment, to reactive ionized substances from the the liquid phase in the corona discharge zone.

In addition, a device for working the method recited hereinabove is described, comprising a support surface and a high-voltage electrode, said electrode being connected to a high-voltage generator via a high-voltage cable. The characterizing features of the device comprise the high-voltage electrode being a shaped electrode open toward the supporting surface, which is filled with a liquid.

Adhesion, whether the bonding of polymers or the adhesion of coatings to polymer surfaces, is a recurring and difficult problem for all industries that use these materials as key components in their products. Designers must often select specially formulated and expensive polymeric materials to ensure satisfactory adhesion (albeit even these materials often require surface preparation). In some cases, entire design concepts must be abandoned due to the prohibitive cost of the required polymer or the failure of crucial bonds. Historically, surface treatments to improve adhesion of coatings to plastics consisted of mechanical abrasion, solvent wiping, solvent swell that was followed by acid or caustic etching, flame treatment, or corona surface treatment. Each of these treatments has limitations, thus providing a strong driving force for the development of alternative surface preparation methods. Many of the common methods mentioned are accompanied by safety and environmental risks, increased risk of part damage, and expensive pollution and disposal problems.

Polystyrene films of 100 nm thickness were modified using plasma immersion ion implantation (PIII) with argon ions of energy 20 keV and fluences in the range 2 × 10 ¹⁴-2 × 10 ¹⁶ ions cm ^-2. The structure and properties of the films were determined by ellipsometry and FTIR spectroscopy, as well as AFM, wetting angle measurements, profilometry and optical microscopy. The effects of oxidation, carbonization, etching and gel-formation were observed. The etching rate was found to decrease with PIII fluence. The rates of degradation with increasing fluence of the aromatic and aliphatic parts of the polystyrene macromolecule were found to be similar. Oxidation of the polystyrene film ceases at fluences greater than 10 ¹⁵ ions cm ^-2. The surface morphology of the film did not change with PIII fluence. Washing with toluene produced surface wrinkling for low fluences up to 10 ¹⁵ ions cm ^-2 while at high fluences the modified films were stable.

The chemical and morphological influences of SF6 and Ar plasmas on bisphenol-A-polycarbonate (PC) and the influence of plasma treatments on Al metallisation were investigated. The treatment of the sample, X-ray photoelectron spectroscopic (XPS) and scanning force microscopic (SFM) analyses were made in an ultrahigh vacuum (UHV) chamber without breaking the vacuum. Using SF6 for the etching process, a significant inclusion of fluorine (C-F, C-F2) takes place. After argon plasma treatment of the PC surface a reduction in the carboxylic carbon was observed in the C1s spectrum. Both kinds of plasma treatments reduce the double and single bonded oxygen. During the metallisation process on an Ar-plasma treated PC surface aluminum couples via oxygen to the aromatic carbon. Al-metallisation on the SF6 pre-etched surface leads to the formation of an Al-F interlayer. With the SFM, the roughening effects on the nm scale after the two plasma treatments is observable. On the virgin PC, Al layers can be seen as slightly bound clusters. On both plasma pre-treated PC surfaces the Al grows as a film.

In this work, air dielectric barrier discharge (DBD) operating at the line frequency (60 Hz) or at frequency of 17 kHz was used to improve the wetting properties of polypropylene (PP). The changes in the surface hydrophilicity were investigated by contact angle measurements. The plasma-induced chemical modifications of PP surface were studied by X-ray photoelectron spectroscopy (XPS) and Fourier-transformed infrared spectroscopy (FTIR). The polymer surface morphology and roughness before and after the DBD treatment were analyzed by atomic force microscopy (AFM). To compare the plasma treatment effect at different frequencies the variation of the contact angle is presented as a function of the deposited energy density. The results show that both DBD treatments leaded to formation of water-soluble low molecular weight oxidized material (LMWOM), which agglomerated into small mounts on the surface producing a complex globular structure. However, the 60 Hz DBD process produced higher amount of LMWOM on the PP surface comparing to the 17 kHz plasma treatment with the same energy dose. The hydrophilic LMWOM is weakly bounded to the surface and can be easily removed by polar solvents. After washing the DBD-treated samples in de-ionized water their surface roughness and oxygen content were reduced and the PP partially recovered its original wetting characteristics. This suggested that oxidation also occurred at deeper and more permanent levels of the PP samples. Comparing both DBD processes the 17 kHz treatment was found to be more efficient in introducing oxygen moieties on the surface and also in improving the PP wetting properties.

Generally most plastic materials are intrinsically hydrophobic, low surface energy materials, and thus do not adhere well to other substances. Surface treatment of polymers by discharge plasmas is of great and increasing industrial application because it can uniformly modify the surface of sample without changing the material bulk properties and is environmentally friendly. The plasma processes that can be conducted under ambient pressure and temperature conditions have attracted special attention because of their easy implementation in industrial processing. Present work deals with surface modification of polycarbonate (PC) by a dielectric barrier discharge (DBD) at atmospheric pressure. The treatment was performed in a parallel plate reactor driven by a 60Hz power supply. The DBD plasmas at atmospheric pressure were generated in air and nitrogen. Material characterization was carried out by contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The surface energy of the polymer surface was calculated from contact angle data by Owens-Wendt method using distilled water and diiodomethane as test liquids. The plasma-induced chemical modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. Due to these surface modifications the DBD-treated polymers become more hydrophilic. Aging behavior of the treated samples revealed that the polymer surfaces were prone to hydrophobic recovery although they did not completely recover their original wetting properties.

An object of the invention is to present a corona discharge processing apparatus capable of performing uniform and excellent corona discharge processing, on work of any thickness or shape, with the constant processing effect regardless of a thickness and shape of the work. A corona discharge processing apparatus of the invention comprises an excitation electrode and a counter-electrode, and generates a corona discharge by applying a high voltage between them, thereby applying corona discharge processing on the work, wherein the excitation electrode and the counter-electrode are both disposed on the same surface of the work with an interval between them.

The theoretical analysis of electrostatic interactions and ion redistribution in the close vicinity of the three-phase contact line shows their important role in the Langmuir wetting process. To provide a sufficient rate for the ion transfer, which is intended to neutralize the interfacial charge, the concentration and potential distributions deviate from the equilibrium. As a consequence, during the deposition process the adhesion work, and hence the contact angle, are defined by the local ionic concentrations near the three-phase contact line. The concentration profiles and the electro-diffusion ion fluxes induced during the Langmuir wetting process are strongly dependent on the subphase composition and on the monolayer properties. The results of the analysis are in a good agreement with the experiments.

In this work, melt-spun polypropylene (PP) fibers were treated in an electric field of a corona discharge. The fibers were then characterized using the thermally stimulated current (TSC) spectroscopy. It has been shown that the electret state of corona-treated PP fibers is a result of the combination of Maxwell–Wagner polarization and charge trapping. Activation energies and relaxation times for these processes have been determined, and characteristics of trapping sites have been calculated. The electret state induced in PP fibers by the corona discharge treatment holds for a long time (several months). Our analysis of the effect of processing temperature and electric field intensity on the characteristics of the electret state in melt-spun PP fibers allows one to specify optimum technological regimes for industrial production of PP-based electret filter materials. © 2000 John Wiley & Sons, Inc. Adv Polym Techn 19: 312–316, 2000
https://onlinelibrary.wiley.com/doi/abs/10.1002/1098-2329%28200024%2919%3A4%3C312%3A%3AAID-ADV7%3E3.0.CO%3B2-X

A thermodynamic model is used to predict the adsorption of nonionic surfactants on latexes with different polarity. The model, which is based upon the Flory-Huggins theory of polymer solutions, predicts that the adsorption decreases as the polarity of the latex increases. It is predicted that adsorption should occur even when it is unfavorable to replace a surface-water contact with a surfacesurfactant contact. This is due to a lower number of unfavorable hydrocarbon-water contacts when the surfactant is adsorbed, compared to when it is free in solution. It is also predicted that it is in principle possible to determine the latex polarity or solubility parameter, from adsorption measurements, provided that a similar experiment is carried out on a latex with known polarity, or solubility parameter.

We present a new approach for the surface treatment of polymer films at atmospheric pressure. The DC glow discharge is generated by applying a high voltage between two electrodes which are placed in a channel with a high flux of air. The air flow removes charge carriers from the plasma zone which prevents the formation of sparks. In the almost homogeneous plasma a comparably high electrical power is converted forming a high concentration of active species. The flowing air transports them to the polymer surface. We report the results of the first experiments with this set-up. The influence of various process parameters on the discharge properties is shown. The resulting alterations in the surface structure of the polymers are characterised by XPS and contact angle geometry.

Corona treatment of films, mainly polypropylene (PP)-copolymers, was studied at commercial levels in a 2.7 kVA treater. The films were produced on a flat-film extruder with chill rolls. Degree of treatment was characterized by power of the generator divided by web speed and width of film (m Ws/cm²).

The effectiveness of the treatment was measured in terms of the polar and dispersion components of surface-energy, the peel adhesion of pressure sensitive tape (similar to ASTM Adhesion Ratio) and the peel adhesion of polyurethane adhesives.

The polar component of surface energy is a measure of the effectiveness of corona pretreatment. For a given degree of treatment, the polar surface energy component becomes greater as the film cooling rate increases (and the degree of crystallization falls).

A comparison of homopolymers and copolymers does, however, reveal that even where these have the same density or the same degree of crystallization one cannot count on them having equally-sized polar components.

Peel strengths of pressure-sensitive tapes and polyurethane-bonded patches confirm the influence of cooling conditions on wetting properties.

Many plastics have a poor tendency to bond to other materials because of their inherent inert chemical structure and thus require a pretreatment. Wet chemical methods are expensive because of the disposal of the waste liquids. In this study, the corona treatment (Ional process), the low-pressure plasma process, and the fluorination process were tested and compared with each other. The following plastics were tested: PP (polypropylene), PBT (polybutyleneterephthalate), PBT blends, and a high-temperature thermoplastic, PEEK (polyetheretherketone). In particular, the low-temperature plasma process results in excellent adhesion strength. In addition, we have shown that the stability of freshly plasma-treated surfaces could be maintained for time periods of at least several days.

Atomic-force microscopy was used to study structural chemical transformations on the surface of polyvinyl chloride films subjected to modification with compounds based on acrylic acid derivatives, with preliminary activation of the polymer surface with a corona discharge.

Described is a method of treating or coating homogeneously at least a portion of the surface of a material selected from metallic materials having a thickness of less than 100 mum and/or polymeric materials. The method of the present invention comprises exposing at least a portion of the surface of the material to an atmospheric plasma generated by an indirect plasmatron. In the method of the present invention, the surface of the material may undergo at least one of an increase in surface tension, a surface grafting, a surface cleaning and a surface sterilization.

Polymer surfaces can be covered with functional groups by exposure to a plasma. The species of the plasma gas are attached to surface carbon atoms forming functional groups of different compositions. To produce a modified polymer surface with a high density and homogeneity of functional groups several possibilities such as plasma grafting of intact monomers, selective plasma bromination, plasma oxidation followed by conversion to OH groups as well as introduction of spacers with functional groups were tested. Thus, to produce exclusively OH groups at the polymer surface, the O functional groups formed by an oxygen plasma were chemically reduced by diborane, Vitride™ (Na complex) or LiAlH4. Typical yields were 9 to 14 OH groups per 100 carbon atoms as detected by XPS. The segment lengths of the spacers were varied between 1 to 22 ethylene or ethylene oxide units. At the end of the different spacers OH, NH2, COOH, Br or C=C groups are bound. These specifically functionalized polymer surfaces are used in pharmacy and medicine. Especially C=C or OH group terminated spacers have been found to “preserve” the plasma activation of the polymer surface by converting the unstable radical sites into stable functional groups. On further processing these groups can react with polymer coatings by classic radical mechanisms (C=C) or by polyaddition (OH) with polyurethanes or other polymers forming pure covalent bonds.

Nitrogen-based plasma systems such as N₂, NH₃, Ar/NH₃, and O₂/NH₃ were used to modify microporous polyethersulfone membranes. Treatments were designed to alter the surface chemistry of the membranes to create permanently hydrophilic surfaces. Contact angle measurements taken initially, as well as 1 year post-treatment confirmed that treatments using O₂/NH₃ plasmas (with a 5:3 gas flow ratio) were successful in achieving our designed goals. Analyses by FT-IR and XPS established the incorporation of NH_x and OH species in the PES membranes. Moreover, the plasma penetrates the thickness of the membrane, thereby modifying the entire membrane cross-section. Optical emission spectroscopy studies of excited state species present in the modifying gases revealed the presence of OH^*, which was not present in a 100% ammonia plasma, suggesting OH^* must play a critical role in the membrane modification process. Investigations using bubble point analysis, differential scanning calorimetry, and scanning electron microscopy demonstrate there is no damage occurring under these specific treatment conditions. The usefulness of this treatment is revealed by increased water flux, reduced protein fouling, and greater flux recovery after gentle cleaning when compared to an untreated membrane.

Emission spectroscopy was applied to observe the reaction process of poly (ethylene terephthalate) (PET) in an oxygen (O2) plasma generated by a microwave discharge. As the PET was exposed in the O2 plasma flow, light emitted from the PET surface was monitored. In the diagnosis measurement, several emission peaks assigned to the Hα atomic line at 652 nm, Hβ at 486 nm, OH (2Σ→2Π) transition near 244–343 nm and CO (b3 Σ→a3 Σ) near 283–370 nm were observed and measured at various discharge times. These results indicated that after the plasma etching, the PET sample was decomposed by the oxygen plasma reaction, and then, hydrogen abstraction and carbon oxidation processes. We also observed the time profile of oxygen atom, as the atom-emission intensity at 777 nm was monitored. As Hβ atomic and OH molecule lines appeared in the presence of PET, the O atom intensity was significantly reduced. In the surface analysis on Fourier transform infrared and x-ray photoelectron spectroscopy measurements, it was found that for the PET surface treated by O2 plasma containing excited atomic oxygen species, ester bands were broken and carbonization formed on the PET surface.

Surface modification of polyethylene (PE), poly(vinylchloride) (PVC), and polystyrene (PS), was performed by thermal-ozone (O₃) treatment to improve their properties. Polymer films were exposed to dried O₃ gas with 3026 ppm at different temperatures. DRS-FT-IR and UV-Vis-NIR absorption methods were applied to observe the surface characteristics of polymers treated. Absorption band assigned to CO stretching appeared near 1720 cm^-1 in films treated with O₃ at 65°C, whereas O₃ treatment at 25°C showed no appearance of the CO band on the surface. In PS, the O3 oxidation proceeded regardless of temperature. Comparison between PE-O₃ and PS-O₃ systems showed that different processes of the surface modification occured. Furthermore, contact angle measurements indicated that the surface wettability of PE and PS was improved by the thermal-O₃ treatment.

Photomicrographs were taken of the organic drops formed on surfaces of vertical cylindrical fibers in water. The organic liquids used were 96% paraffin oil + 4% tetrabromoethane, paraffin oil, and 80% paraffin oil + 20% heptane. The fibers studied consised of plyester, a fluoroethylene-propylene copolymer (FEP), and nylon. The upper and lower contact angles, θ_t and θ_b, formed by the drops on the fiber surface were measured as a function of the dimensionless maximum drop radius, N, and length, $\text{L}$, from the projected images. As N increased so did θ_t, whereas θ_b only initially increased and then became more or less constant. Furthermore, θ_b decreased slightly close to the highest investigated values of N for systems involving FEP fiber. For a given system, the difference between the values of θ_t and θ_b increased as N increased, confirming that gravity forces affect the drop shape and contact angles. Good agreement is found between the measured values of θ_t and θ_b, and those obtained by using the theory for the shape of a drop on a vertical fiber [A. Kumar and S. Hartland, J. Colloid Interface Sci. 124, 67 (1988)].

The wettability and adhesion of the coating and printing films on the polymer substrates depend on the surface properties of the formulation ingredients and polymer surface. In addition, the transfer of ink from flexographic printing plates to substrates depends on the surface properties of the printing plate, water-based ink and polymer substrate. Among several surface properties such as surface composition, surface roughness, surface tension/surface energies and surface defects, the surface energies: polar, nonpolar and total energies of the dried coating films, flexographic printing plates and polymer substrates were determined by measuring contact angles of water and methylene iodide. These results were used to understand the ink transfer from printing plates to substrates during flexographic printing process, and ink spreading, wetting as well as ink adhesion behavior of the coatings and inks on the polymer substrates. The data indicates that for good ink transfer and adhesion to occur, the surface energy of the water-based ink should be lower than that of the printing plates and substrates.

The coating and printing of polymer films with water-based formulations are relatively difficult as compared to solvent-based formulations. The surface tension of water is higher than that of the solvents. In addition, the surface energy of polymer surfaces is in the range of 25–40 ergs/cm2. In order to understand the wetting and spreading behavior of coating materials, the polar and non-polar surface energies were evaluated by measuring contact angle of water and methylene iodide on various non-porous substrates. These results were utilized to explain the spreading, wettability and adhesion phenomena in order to understand the interactions between water-based coating/printing materials and non-porous substrates.

Surface charge decay on thick flat samples of high temperature vulcanized silicone rubber is studied prior and after ac and dc corona pre-treatments. It is found that the charge decay rate on the material exposed to ac corona becomes much higher and sensitive to moisture content in the surrounding air. These features are associated with an increased surface conductivity and formation of a silica-like layer on the polymeric surface, both resulting from ac corona treatment. In contrast, characteristics of the charge decay on the material exposed to dc corona are found to be similar to that measured on untreated samples.