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%.

There has been considerable interest in non-thermal atmospheric pressure discharges over the past decade due to the increased number of industrial applications. Diverse applications demand a solid physical and chemical understanding of the operational principals of such discharges. This paper focuses on the four most important and widely used varieties of non-thermal discharges: corona, dielectric barrier, gliding arc and spark discharge. The physics of these discharges is closely related to the breakdown phenomena. The main players in electrical breakdown of gases: avalanches and streamers are also discussed in this paper. Although non-thermal atmospheric pressure discharges have been intensively studied for the past century, a clear physical picture of these discharges is yet to be obtained.

This paper presents a review of the ST and SFE values expressed in dyn/cm for a number of polymers, minerals, oxides and clays. The review also deals with the calculation of ST based on parachor values and other polymer properties obtained from a DIPPR database accompanied and coupled with QSPR software entitled TSAR. Data are also given on the ST of clays. The three components of the ST, the apolar Lifshitz–van der Waals component and the two polar (electron-donor and electron-acceptor) components of the various clays are also presented, as calculated by the van Oss et al. equation. Substitution of the cations in the innerlayer of clays by other inorganic cations is reviewed. Data are given on the effect of introducing organic ammonium cations into the clays and how they affect MMT, laponite, and talc. The effect of temperature on the ST of small molecules and on polymers is discussed, and a formula for this effect is shown. The effect of surface crystallinity on ST is discussed. The effect of chemical composition, structure and molecular weight are discussed as well. Systems for the estimation of ITs are reviewed, in relation to the ST values of the components. Data on the ST of high-energy materials are presented. The changes in these values upon interaction with low-energy surfaces are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

Ink–cellulose interactions were evaluated using a new technique in which the adhesion properties between ink and cellulose were directly measured using a Micro-Adhesion Measurement Apparatus (MAMA). The adhesion properties determined with MAMA were used to estimate the total energy release upon separating ink from cellulose in water. The total energy release was calculated from interfacial energies determined via contact angle measurements and the Lifshitz–van der Waals/acid–base approach. Both methods indicated spontaneous ink release from model cellulose surfaces, although the absolute values differed because of differences in measuring techniques and different ways of evaluation. MAMA measured the dry adhesion between ink and cellulose, whereas the interfacial energies were determined for wet surfaces. The total energy release was linked to ink detachment from model cellulose surfaces, determined using the impinging jet cell. The influences of surface energy and surface roughness were also investigated. Increasing the surface roughness or decreasing the surface energy decreased the ink detachment due to differences in the molecular contact area and differences in the adhesiom properties.

Polymer surfaces typically have low surface tension and high chemical inertness and so they usually have poor wet-ting and adhesion properties. The surface properties can be altered by modifying the molecular structure using plasma immersion ion implantation (PIII). In this work, Nylon-6 was treated using oxygen/nitrogen PIII. The observed improvement in the wettability is due to the oxygenated and nitrogen (amine) functional groups created on the polymer surface by the plasma treatment. X-ray photoelectron spectroscopy (XPS) results show that nitrogen and oxygen plasma implantation result in C–C bond breaking to form the imine and amine groups as well as alcohol and/or car-bonyl groups on the surface. The water contact angle results reveal that the surface wetting properties depend on the functional groups, which can be adjusted by the ratio of oxygen–nitrogen mixtures.

The surface tension of a model, water-based, flexographic printing ink was measured at a range of surfactant concentrations along with the equilibrium contact angle formed with polymer substrates. The surface excess of surfactant at each concentration was calculated using the Gibbs adsorption isotherm and assumed equal to the concentration of surfactant at the interface. The change in the surface tension of the ink formulation was assumed to be determined entirely by the surface concentration of surfactant. This allowed the estimation of the surface tension at the solid–liquid and solid–vapour boundaries when in contact with substrate based on the values obtained for pendant drops. The associated polar and dispersive contributions to the surface tension were then calculated using the Young–Dupré equation. The values of the polar and dispersive surface tension components extracted in this manner were compared with those calculated using the approach of van Oss, Chaudhury and Good. The use of surface excess in estimating the contributions to surface tension was found to give far better agreement with experimental data than the van Oss approach which is intended for use with pure liquids.

In this paper, we present data on the physics and phenomenology of plasma reactors based on the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP^™) that are useful in optimizing the conditions for plasma formation, uniformity and surface treatment applications. It is shown that the real (as opposed to reactive) power delivered to a reactor is divided between dielectric heating of the insulating material and power delivered to the plasma available for ionization and active species production. A relationship is given for the dielectric heating power input as a function of the frequency and voltage at which the OAUGDP^™ discharge is operated.

Plasma, considered as the fourth state of matter, is playing a key role as a modern discipline. Plasma processing is drawing attention from various technology sectors such as microelectronics, automotive, and surface modifications of polymers. Some examples of additional new applications include functional coatings for architectural glass, mercury-free lamps, plasma-treated packaging for food, beverage and pharmaceutical industries, as well as nanomaterials. With the emergence of all new technological applications from basic research in academic, industrial, or government laboratories, plasma is set to have a brilliant future.

Interest has grown over the past few years in applying atmospheric pressure plasmas to plasma processing for the benefits this can offer to existing and potential new processes, because they do not require expensive vacuum systems and batch processing. There have been considerable efforts to efficiently generate large volumes of homogeneous atmospheric pressure non-thermal plasmas to develop environmentally friendly alternatives for surface treatment, thin film coating, sterilization, decontamination, etc.

Many interesting questions have arisen that are related to both fundamental and applied research in this field. Many concern the generation of a large volume discharge which remains stable and uniform at atmospheric pressure. At this pressure, depending on the experimental conditions, either streamer or Townsend breakdown may occur. They respectively lead to micro-discharges or to one large radius discharge, Townsend or glow. However, the complexity arises from the formation of large radius streamers due to avalanche coupling and from the constriction of the glow discharge due to too low a current. Another difficulty is to visually distinguish many micro-discharges from one large radius discharge. Other questions relate to key chemical reactions in the plasma and at the surface. Experimental characterization and modelling also need to be developed to answer these questions.

This cluster collects up-to-date research results related to the understanding of different discharges working at atmospheric pressure and the application to polymer surface activation and thin film coating. It presents different solutions for generating and sustaining diffuse discharges at atmospheric pressure. DC, low-frequency and radio-frequency excitations are considered in noble gases, nitrogen or air. Two specific methods developed to understand the transition from Townsend to streamer breakdown are also presented. They are based on the cross-correlation spectroscopy and an electrical model.

Coatings with polyethylene oxide (PEO)-like films deposited by RF (13.56 MHz) glow discharges and featuring a total cell-repulsive effect were deposited on polystyrene (PS) samples. Substrates containing tracks of PS of petri dishes surrounded by PEO-like domains have been prepared with a good spatial resolution by using a masking procedure. The behavior of the substrates after seeding NCTC2544 human keratinocytes and 3T3Murine fibroblasts has been studied. It has been found that also PS tracks are able to drive cells up to confluence, provided that a longer incubation time is provided. A phenomenological interpretation is suggested.

Different plasma treatments (NH3, O2) were carried out on polytetrafluoroethylene (PTFE) for grafting polar groups and obtaining a stable, permanent hydrophilic surface. Plasma pretreatments (H2 and Ar) were also utilized to limit the aging, including the hydrophobic recovery, of the treated surface with time. Dynamic water contact-angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS) analyses were performed to study in depth the chemical compositional changes as a function of ageing time. This paper illustrates mainly the remarkable effect of combining H2 plasma pretreatments with low-power NH3 plasma treatments for obtaining stable PTFE surfaces grafted with polar groups that exhibit permanent wettability. The results were expressed in terms of the fractions of mobile and immobile polar grafted groups.

The chemical modifications induced on PET by an excimer laser radiation or a lowpressure plasma were studied by XPS and Tof SIMS analyses. Both treatments induced surface oxidation but differences related to the type of oxidized groups and the level of degradation of the treated surface were evidenced. Both treatments can significantly enhance the adhesion but the surface change responsible for the improvement was different for each pretreatment.

An attempt to replace a wet-chemical surface modification of styrene-butadiene elastomers (SBS), improving their adhesion to polyurethane adhesives, with a clean low-pressure plasma technique has been undertaken. The plasma has been generated by an RF discharge (13.56 MHz, plate electrode reactor) in various reactive mixtures (eg CHCl3, CCl4, CO2, O2) to create chlorine (C–Cl) and oxygen (> C= O,–OH,–COOH) functionalities on the elastomer surfaces. T-peel tests, contact-angle measurements, and FTIR spectroscopy have been utilized to investigate the surfaces. It has been found that an important role in the plasma-improved adhesion is played by the chemical interaction between the modified SBS surfaces and polyurethanes. The peel strength for plasma-treated samples in many cases is much higher than that for the wetchemical modification. It clearly indicates that the plasma treatment is a very promising method of improving the adhesion properties of SBS

Thin polymer films were irradiated with boron ions with energies from 50 to 180 keV and irradiation doses between 1013 and 1016 B+/cm2. For comparison, plasma modification was performed in NH3 and N2O low-pressure gas discharges. A complex investigation of chemical changes in the surface regions was carried out using attenuated total reflection (ATR)-FTIR spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Optical properties were probed by spectroscopic ellipsometry. Hardness and elastic modulus profiles have been measured by a depth-sensing low-load indentation technique. Additionally, the surface and bulk conductivities of modified polymer films were determined. It could be shown that the increase of ion fluence leads to a partial destruction of the imide, aromatic and sulfone groups. The effective modification depth estimated from the hardness, Young’s modulus and refractive index depth profiles was 250–300 nm at an ion energy of 50 keV and 400–450 nm at an ion energy of 180 keV. In the case of low-pressure plasma treatment, the chemical modification of the polymer bulk extends only a few monolayers and is determined by the electronicprocess-related linear energy transfer (LET). The destruction of chemical bonds under ion bombardment leads to the formation of new amorphous and graphitelike structures, which increase the modified surface film conductivity, the optical absorption index, the density, and the sensitivity of these polymer films to moisture uptake, and decrease the refractive index anisotropy and the Freundlich’s coefficient of the moisture-uptake behavior.

In this study, an unvulcanized (thermoplastic) block styrene-butadiene-styrene rubber S0 was treated with argon, oxygen and carbon dioxide plasmas and the surface modifications produced were analyzed. The Ar, CO2 and O2 plasma treatments produced an increase in peel-strength values of S0 rubber/polyurethane adhesive joints due to improved wettability, chemical and morphological modifications. Ar plasma created polar moieties on the S0 rubber surface and a consequent increase of the polar component of the surface energy. On the other hand, CO2 and O2 plasma treatments produced ablation of the oxidized outermost S0 rubber surface. Short plasma treatment times are enough to produce adequate T-peel-strength values and a cohesive failure was obtained in the joint produced with S0 rubber treated with CO2 plasma for 1 min. The increase in the length of treatment or the treatment with the other plasmas did not affect the peelstrength values but different loci of failure in the adhesive joints were obtained.

Piezoelectric and nonpiezoelectric films of polyvinylidene fluoride (PVDF) have been treated in a microwave nitrogen and hydrogen plasma. Plasma parameters, eg ratio between N2 and H2, plasma power, gas flow rate, and the distance between the sample and the plasma have been varied in order to establish the treatment parameters that constitute a good compromise between an optimum functionalization and a minimum degradation. Under this treatment, the surface properties of PVDF have been modified in a controlled manner, allowing its metallization, necessary in a wide range of applications, without significantly changing its bulk properties.

Low-pressure plasma was selected as a surface treatment to improve the painting properties of elastomeric polyethylene (PE). Several experimental variables in the low-pressure synthetic air plasma treatment were considered: time of the treatment, plasma power and pressure inside the chamber. The durability of the treatment effects was also studied. Contact-angle measurements (water, 25 C) showed an increase in the wettability of elastomeric PE after treatment with plasma, which corresponds to an increase in the O/C ratio on the treated surface. In fact, different oxygen-containing groups were created on the PE surface. The more intense and longer the plasma treatment, the greater the degree of surface oxidation, up to a certain value. The painting properties of the material were evaluated by joints produced with as-received and treated elastomeric PE and an acrylic paint and using T-peel tests. Peel strength values increased after low-pressure plasma treatment, especially after the first 3 s of treatment with a power of 200 W; and an adhesion failure between the paint and the adhesive tape was obtained. This failure was maintained during four hours after the treatment. For longer treatment times the paint does not adhere to the material, the peel-strength values decrease and the contact angles increase, indicating that the effects of the surface modifications are not maintained.

The present work focuses on the deposition of fluorocarbon (FC) films on aluminum and SiO2 surfaces, and addresses the issue of selective deposition on Al versus SiO2 in order to obtain surfaces of distinctly different wettability. If this is achieved, hydrophobic/hydrophilic patterning of substrates would be feasible by means of a self-aligned and relatively simple method. The selectivity of the deposition is optimized through proper selection of the deposition conditions, mainly gas-mixture composition and deposition time, and is demonstrated by means of contact-angle measurements on Al and SiO2 surfaces. Chemical (XPS) analysis of the FC films deposited under various conditions is also performed and correlated with the wettability of the plasma-modified Al surfaces.

This study systematically characterises a matrix of water-based flexographic inks with respect to their rheology, surface tension and wetting of liquid packaging board, to provide a basis for interpretation and prediction of their printing performance. For all pigment and acrylate polymer vehicles and mixing proportions the inks were shown to be shear thinning and thixotropic, with plastic viscosity, yield stress and storage and loss moduli increasing strongly with content of solution polymer (at comparable solids contents). The solution polymer decreases the static surface tension of the inks, but generally leads to an increase in their equilibrium drop contact angle on the polyethylene- (PE-) coated board due to increase in the ink-board interfacial energy. The solution polymer also decreases the drop spreading rate, and a simple model is tested to express the spreading dynamics in terms of equilibrium contact angle and a rate parameter given by the effective ratio of surface tension to viscosity.

Non-thermal plasmas under atmospheric pressure are of great interest in polymer surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of Polyethylene terephthalate (PET) film surface for improving hydrophilicity using the non-thermal plasma generated by atmospheric pressure glow discharge (APGD) in air is conducted. The discharge characteristics of APGD are shown by measurement of their electrical discharge parameters and observation of light-emission phenomena, and the surface properties of PET before and after the APGD treatment are studied using contact angle measurement, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEh4). It is found that the APGD is homogeneous and stable in the whole gas gap, which differs from the commonly filamentary dielectric barrier discharge (DBD). -4 short time (several seconds) APGD treatment can modify the surface characteristics of PET film markedly and uniformly. After 10 s APGD treatment, the surface oxygen content of PET surface increases to 39%, and the water contact angle decreases to 19°, respectively.

Digital printing is increasingly being used for package printing. One of the major techniques of digital printing is dry-toner electrophotography. This paper evaluates the printability of three different extrusion coatings used for packaging boards: low-density polyethylene (PE-LD), ethylene methyl acrylate (E/MA) and polyethylene terephthalate (PET). Extrusion coatings in general have an impervious, chemically inert, nonporous surface with low surface energies that cause them to be non-receptive to bonding with toners. The most common methods used in improving the adhesion properties of polymer coatings are different surface treatments. These increase the surface energy and also provide the polar molecular groups necessary for good bonds between the toner and polymer molecules. The polymer coatings have been modified with electrical corona discharge treatment. The effects of corona on polymer surfaces and the correlation between surface modification and print quality have been evaluated. Results show that sufficiently high surface energy and surface-charge uniformity are necessary for even print quality and toner adhesion. E/MA and PET have the required surface-energy level without the corona treatment, but PE-LD needs surface modification in order to succeed in the electrophotographic process. E/MA also has exceptional surface-charge properties compared with PET and PE-LD. Polym. Eng. Sci. 44:2052–2060, 2004. © 2004 Society of Plastics Engineers.