In the broad spectrum of contamination control, a major concern is the presence of organic contamination on various inorganic surfaces. In order to control surface contamination of materials, a rapid-detection method is required that does not adversely affect the surface. Wettability measurements provide a convenient and rapid method for probing the outermost surface of a material. The technique is highly surface specific, generally exceeding the sensitivity of electron spectroscopies and is sensitive to a fraction of a monolayer. The most widely used quantitative measure of wettability is the contact angle. When a drop of a liquid with a sufficiently small size is placed on a smooth, flat, homogeneous solid substrate, the drop takes the shape of a spherical cap. The shape of the drop approximates that of a spherical cap when the forces other than the surface tension become negligible. Each solid and liquid (and vapor phase) combination gives rise to a specific degree of wettability. The parameter defining the wettability is the observed contact-angle; the lower the contact angle, the higher the wettability. This angle is measured between a tangent to the liquid surface where it meets the solid substrate and the plane of the solid substrate. It is found that any test of surface cleanliness involving wettability by water cannot be used on metal surfaces that have an indeterminate oxide layer. It is tempting to assume that any clean metal oxide surface would be hydrophilic, but even this rule may have some exceptions.

Non-thermal atmospheric pressure plasma jets/plumes are playing an increasingly important role in various plasma processing applications. This is because of their practical capability to provide plasmas that are not spatially bound or confined by electrodes. This capability is very desirable in many situations such as in biomedical applications. Various types of ‘cold’ plasma jets have, therefore, been developed to better suit specific uses. In this paper a review of the different cold plasma jets developed to date is presented. The jets are classified according to their power sources, which cover a wide frequency spectrum from DC to microwaves. Each jet is characterized by providing its operational parameters such as its electrodes system, plasma temperature, jet/plume geometrical size (length, radius), power consumption, and gas mixtures used. Applications of each jet are also briefly covered.

In the article the analysis of the main methods of calculations of interfacial free energy and surface free energy (SEP) values of solids, in which contact angle measurements' results play a key role, has been presented. The importance of Young's equation and Berthelot's hypothesis as the scientific basis of these methods has been indicated. Various methods of calculations of interfacial free energy values for solid-liquid systems, including calculations of this energy on the basis of state equations or SEP divide to independent components, (especially for polymers) were discussed. The most important methods of calculations of SEP values for polymeric materials on this basis were characterized. The methods of calculations of contact angle values for porous materials, granulated products, powders or fibers on the basis of Washburn equation, what is a base for calculations of SEP of these materials, were presented.

Extrusion coating, lamination and film lamination give rise to complex manufacturing techniques which allow a converter to make high-performance packaging films. The physical properties and the related performance characteristics of composites obtained by extrusion coating and lamination can be comparable to that produced by film lamination. This is not surprising since many of the major components involved by these techniques in the production of the final composites are also the same. The paper examines how the use of ozone combined with corona discharge compares to ozone combined with atmospheric plasma relative to seal strength for these composite film constructions, and suggests a direction for future improvements in seal strength.

The molecular parameters of poly(vinyl alcohol) have enormous effects on its physical and chemical properties. Therefore, the surface characteristics of poly(vinyl alcohol) films are also determined by the molecular parameters. In this study, the dependence of the surface free energy on the molecular weight, degree of saponification, and stereoregularity of poly(vinyl alcohol) films has been evaluated with contact-angle measurements. The surface free energy of poly(vinyl alcohol) films increases with decreases in the syndiotactic dyad content, molecular weight, and degree of saponification. The polar component of the surface energy is not affected by the deviation of the molecular weight and degree of saponification very much. However, it decreases with increases in the syndiotactic dyad content and ranges from 11.64 to 4.35 dyn/cm.
© 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 https://onlinelibrary.wiley.com/doi/abs/10.1002/app.26010

Atmospheric pressure plasma treatment has unique advantages over vacuum treatment for such industrial applications as surface energy ehancement of materials, cleaning, decontamination, and sterilization of surfaces, surface etching, plasma chemical vapor deposition (PCVD), and related tasks. The MOD VIII plasma reactor system has been developed to provide roll-to-roll surface treatment of fabrics and films using a One Atmosphere Uniform Glow Discharge Plasma (OAUGDP®) operating in air. Webs can be continuously and uniformly treated by proper control of gas flow; electrode configuration; plasma voltage, current, and frequency; fabric speed; and fabric tension.

In this paper, polyester (PET) and polypropylene (PP) films are modified by a dielectric barrier discharge in air, helium and argon at medium pressure (5.0 kPa). The plasma-modified surfaces are characterized by contact angle measurements and X-ray photoelectron spectroscopy (XPS) as a function of energy density. The polymer films, modified in air, helium and argon, show a remarkable increase in hydrophilicity due to the implantation of oxygen-containing groups, such as C–O, O–CO and CO. Atomic oxygen, OH radicals, UV photons and ions, present in the discharge, create radicals at the polymer surfaces, which are able to react with oxygen species, resulting in the formation of oxygen-containing functionalities on the polymer surfaces. It is shown that an air plasma is more efficient in implanting oxygen functionalities than an argon plasma, which is more efficient than a helium plasma. In an air plasma, most of the created radicals at the polymer surface will quickly react with an oxygen particle, resulting in an efficient implantation of oxygen functionalities. However, in an argon and helium plasma, the created radicals can react with an oxygen particle, but can also recombine with each other resulting in the formation of an oxidized cross-linked structure. This cross-linking process will inhibit the implantation of oxygen, resulting in a lower efficiency. In argon plasma, more ions are present to create radicals, therefore, more radicals are able to react with oxygen species. This can explain the higher efficiency of an argon plasma compared to a helium plasma.

The most important function of a packaging material is to shield the product inside the package. Extrusion coated paperboard is generally used in food, medical and cosmetic packages. Extrusion coatings give a barrier against water, water vapour, aroma, grease, oxygen, etc. In addition to barrier properties, heat sealability and printability are important properties in packaging applications. From point of view of printing, the dense and impervious structure of extrusion coatings is challenging: printing inks and toners do not penetrate into the coatings. The durability of the printed image is significant, because the image must withstand various converting operations when the package is constructed. The most common method for obtaining good ink adhesion is to oxidize the surface. Surface treatments are used to change the chemical composition, increase the surface energy, modify the crystalline morphology and surface topography, or remove the contaminants and weak boundary layers. Two widely used methods are electrical corona discharge treatment and flame treatment. These processes generally cause physical or chemical changes in a thin surface layer without affecting the bulk properties. Treatments will increase surface energy and also provide polar molecular groups necessary for good bonds between ink and polymer molecules. In addition to printability, surface treatments also affect the heat sealing properties of extrusion coatings. In this study, the surface chemistry of the extrusion coatings has been modified with corona and flame treatments. The effect of corona and flame treatment on surface energy has been evaluated with contact angle measurements. Surface energy has the habit of decreasing with time after treatment. In this work, the decay of surface energy and surface oxidation is followed for six months. ESCA and FTIR-ATR have been used to analyze oxidation and the surface chemical composition. Furthermore, the heat sealing and hot tack properties of the extrusion coatings are evaluated. The aim of this study is also to evaluate printability of extrusion coatings and to map out the role of surface modification in print quality formation. This study has concentrated on digital printing, particularly on dry toner-based electrophotographic printing process.

Surface modification of polystyrene derivatives by ozone (O3) was investigated by in situ FT-IR spectroscopy. Polystyrene (PS) and its derivatives, poly (4-methyl polystyrene)(P4MS) and poly (α-methyl polystyrene)(PαMS) were used to compare the surface modification by O3 at different temperatures. Polymer film of 5 µm thickness was exposed to 3026 ppm of gaseous O3 in the FT-IR cell heated in the range of 0–70◦ C. Then, in situ FT-IR spectra of these films were measured under O3 exposure. It was found that the IR band assigned to C= O stretching appeared in PS and P4MS with a weak dependence on temperature; but the appearance of the C= O band was strongly dependent on temperature in the case of PαMS. The O3 reactivity of PαMS was rather lower than that of polyethylene (PE). These results strongly suggested that thermally decomposed O3 species attacked the main chain of the PS and P4MS at high temperatures. Furthermore, we investigated the surface properties of these polymer films before and after the O3 modification by AFM and water contact angle. Evidence was shown that thermal ozonolysis process for PαMS having methyl group on the polymer main chain was depressed.

A novel atmospheric pressure plasma jet, that is operated with air, is used for the pretreatmet of different polymers. The resulting adhesive bond strengths and the corresponding changes of the polymer substrate surface are studied. The plasma treatment induces chemical and topographical changes on the polymer surface. It is likely that both types of surface modification contribute to the adhesion improvement. Results for poly (ethylene terephthalate) indicate that surface chemical composition is more influential in adhesion enhancement than surface roughness.

Plasma web treatment is a common practice for promoting adhesion, wettability and other surface or interfacial properties in the conversion industry. While the objective of creating new surface functional groups is conceptually simple, it can be difficult to choose the most appropriate kind and configuration of plasma source, the most appropriate feed gas composition and the most appropriate operating pressure for a given application. Such difficulties arise from the variety of species that can be formed in the plasma and the variety of possible plasma-surface interactions that can occur. A brief review of the importance of various plasma parameters (eg, specific energy, species concentrations, and energy distributions) and an example relating nitrogen uptake in poly (ethylene-2, 6-naphthalate) to plasma diagnostic data in a low-radiofrequency capacitivelycoupled nitrogen plasma are presented. The importance of driving frequency and treatment configuration is discussed in detail. Uptake kinetics for samples treated at floating potential at low radiofrequency is compared with that for samples treated in the cathode sheath. Analysis of the treatment kinetics is based on a simple model of surface saturation. This approach can be used not only to compare practical treatment results as a function of process conditions, but also to compare different treatment techniques in a practical manner.

The use of gas and/or liquid-phase carbon dioxide (CO2) with atmospheric plasma discharge surface pretreatment technology can remove micron and submicron particulates and hydrocarbon-based contaminations on plastics and metals. The cleaning process is based upon the expansion of either liquid or gaseous carbon dioxide through an orifice. The paper provides an understanding of the basic removal mechanism and provides experimental evidence of remarkable adhesion improvements relative to a broad range of applications in electrical, medical, and automotive manufacturing communities.

We report on the preparation of amphiphilic diblock copolymers containing a hydrophilic segment, poly(acrylic acid)(PAA), and a polystyrene hydrophobic part. We analysed, by means of contact-angle measurements, how the hydrophilic segments usually bury themselves under the hydrophobic when exposed to air to reduce the surface free energy of the system. In contrast, in contact with water, the hydrophilic blocks have a tendency to segregate to the interface. We first describe the parameters that control the surface reconstruction when the environmental conditions are inversed from dry air to water vapour. Then, annealing time, temperature, composition and size of the diblock copolymers, and size of the matrix that influenced the surface migration process are the main parameters also considered. Finally, the density of the carboxylic functions placed at the surface was determined using the methylene blue method.