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.

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.

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.

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.

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

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.

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.

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.

Single-type functionalizations with different types of functional groups at polypropylene (PP) and polytetrafluoroethylene (PTFE) surfaces were achieved using, instead of a simple plasma modification, either a combined plasmachemical–chemical process or the pulsed plasma-initiated homo-or copolymerization of monomers carrying functional groups. The combined process consists of O2 plasma pretreatment and wet-chemical reduction of O functional groups to OH groups using diborane, vitride (sodium bis (2-methoxyethoxy) aluminum hydride), or LiAlH4. The high degree of retained chemical structure and functional groups during the low-power pulsed plasma polymerization was found to be a prerequisite for producing well-defined, adhesion-promoting plasma polymer layers as model surfaces with high concentrations of exclusively or predominantly one type of functional group, such as OH, NH2, or COOH. The maximum concentrations of functional groups were found to be 31 OH, 21 NH2 or 25 COOH groups/100 C atoms using allyl alcohol, allylamine, or acrylic acid, respectively, as monomers in the plasma polymerization process and 14 OH groups/100 C atoms by applying the combined O2 plasma/diborane reduction process. To vary the density of functional groups, a so-called plasma-initiated gas-phase radical copolymerization with ethylene or styrene as a “chain-extending” comonomer, or butadiene as “chemical crosslinker” was employed. The peel strength of evaporated aluminum layers on unspecifically oxygen-plasma functionalized polypropylene (PP) and polyethylene (PE) shows in each case a maximum at 20 O per 100 C atoms. Initially the peel strength increased linearly with the concentration of functional groups when PP or polytetrafluoroethylene (PTFE) substrates were coated with plasma polymers or copolymers carrying a single type of adhesion-promoting functional groups. The ranking of the adhesion-promoting effect is CH2< NH2 (OH< COOH, and corresponds to the tendency to form chemical bonds between aluminum and the different functional groups.

Several techniques have been applied for the characterization of three PET films surfaces: homopolymer PET film, corona treated PET film and a poly(ethylene terephthalate‐co‐1,4‐cyclohexanedimethanol) film. The objective of this work is to investigate and to apply precise and mutually complementary techniques which give detailled information about theses surfaces, as there are few papers with global and conclusive results. The film surfaces were investigated to support the development of new products and envisage new apllications to the existent films. Scanning electron micrographs, attenuated total reflection Fourier transform infrared spectroscopy (FTIR‐ATR) and multiple internal reflection Fourier transform infrared spectroscopy (FTIR‐MIR) spectra show that the chemical composition, topography and surface roughness of the films are different. The corona‐treated PET film shows high surface tension value due to the major contribution on the polar groups and oxidation level acquired. The copolyester film is much less crystalline than the other films analyzed, as demonstrated by refractive index measurements and X‐ray photoelectron spectroscopy (XPS). The amorphous structures obtained and the high tension level of the corona‐treated films provide a better understanding of the adhesion phenomena. In view of results obtained, one can assume that corona treated films owing to its higher surface tension and films with CHDM owing to its surface amorphization should provide manufacturing industries better processing conditions than films without surface treatment and also higher levels of adhesion to paints and coatings.

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.

This chapter presents a comprehensive study on the thermodynamics of contact angles on general rough, heterogeneous surfaces. Conventionally, contact is defined as the angle formed between a liquid-vapor interface and a liquid-solid interface at the solid-liquid-vapor three-phase contact line. On an ideal solid surface, which is smooth, homogeneous, isotropic, and non-deformable, the contact angle is expressed by the Young equation. The concept of liquid front simplified the thermodynamic treatments of contact angles on rough, heterogeneous surfaces and thus made it possible to model real surfaces. Receding contact angles are poorly reproducible for hydrophilic surfaces but for extremely hydrophobic surfaces, advancing contact angles might have a poor reproducibility. An impurity might cause poor reproducibility for receding contact angles if it is the component with the smallest intrinsic contact angle, but it can make the advancing contact angle. An impurity might not affect contact angle hysteresis if it is the component with an intermediate intrinsic contact angle.

There is currently an interest in techniques to control surface and interfacial properties of polymeric materials, such as wettability, adhesion, biocompatibility, friction, and wear, for different applications and technologies and for the design of novel materials. The desired surface properties range from complete release toward all contacting gaseous, liquid or solid substances to irreversible covalent bonding to other substrates of interest. The macroscopic interfacial phenomena describing these properties are wetting, adhesion, and adsorption. They all share a common basis; they are dependent upon the intermolecular and surface forces and, on the molecular level, upon the chemical and physical details of the molecular structure of the surfaces, especially upon the availability of particular functional groups at the surface. This chapter focuses on the strategies to estimate the surface energetic from wetting and surface tension measurements. The fact that the surface chemistry of polymers might differ substantially from the average bulk chemistry is also caused by the structural features of macromolecules. Therefore, it has become a powerful tool to control the surface energetic of polymers by their chemical bulk structures.

Gas discharge plasma treatment can be used to modify the surface properties of biomaterials for a variety of biomedical applications. An established application is the use of oxygen and nitrogen plasmas to improve the hydrophilicity of surfaces, encouraging cell attachment and subsequent growth. The physical properties and surface chemistry of the biomaterial influences cell attachment and subsequent culture. In-situ cells are surrounded by a complex extracellular matrix (ECM) containing fibronectin, laminin, collagen types I-V, and proteoglycans. In this study, ammonia and sulphur dioxide gases have been chosen with the objective of incorporating carboxylic acid, sulphur and nitrogen containing groups on the surface.

Plasma diagnostic tools are an essential element towards the proper understanding and development of technological plasmas. Knowledge of the particle densities and energies in the bulk and at boundaries, the electrical potentials and the spatial and temporal evolution of these parameters allow technologists to operate plasmas in the most efficient way and allow the intrinsic plasma processes to be tailored to suit a particular application. There are many different diagnostic tools that can be used, depending on the type of plasma under investigation and the specific information that is required. Here, we have chosen to highlight four techniques frequently used in both academia and industrial settings. The first of these is the interpretation of the driving current and voltage waveforms. These measurements do not affect the plasma and can yield useful information on the major processes in the discharge. The second is electrical probing which, by their nature, are intrusive, since their presence affects the plasma under investigation. Their use is usually confined to low-pressure and low-temperature plasmas in which the heat flux will not destroy the integrity of the probe. The third area is mass spectrometry, which is most often performed at the substrate or plasma boundaries and may in many cases not affect the plasma unduly. The fourth diagnostic method discussed, optical emission spectroscopy, is non-perturbing; however, interpretation of spectral response is often difficult in low-pressure plasmas where the species are not in local thermodynamic equilibrium.

Although the power of plasma surface engineering across vast areas of industrial manufacturing, from microelectronics to medical and from optics to packaging, is demonstrated daily, plasma in the textile industry has been cynically described as the technology where anything can happen... but never does. Research into the application of plasmas to textiles goes back to the 1960s but, despite the reporting of novel and potentially commercial effects, it is only in recent years that plasma processing systems have begun to emerge into textile manufacturing in the production of specialty/high value fabrics. It is instructive to look at major criteria for the introduction of new technology into the textile market and to assess plasma processing against such criteria. They can be separated into qualifiers (must be satisfied by the new technology as a minimum) and winners (motivate take-up of the new technology by the industry). Here are ‘qualifier’criteria for new textile technologies:

Growing demands on the functionality of technical textiles as well as on the environmental friendliness of finishing processes increase the interest in physically induced techniques for surface modification and coating of textiles. In general, after the application of water-based finishing systems, the textile needs to be dried. The removing of water is energy intensive and therefore expensive. In contrast to conventional wet finishing processes, a plasma treatment is a dry process. The textile stays dry and, accordingly, drying processes can be avoided and no waste water occurs. Plasma treatments represent, therefore, energy efficient and economic alternatives to classical textile finishing processes. Within plasma processes, a high reactive gaseous phase interacts with the surface of a substrate. In principle, all polymeric and natural fibres can be plasma treated. For many years, mainly low-pressure plasma processes have been developed for textile plasma treatment. However, the integration of these processes, which typically run at pressures between 0.1 and 1 mbar, into continuously and often fast-running textile production and finishing lines is complex or even impossible. In addition, due to the need for vacuum technology, low-pressure processes are expensive. The reasons why plasma processes at atmospheric pressure are advantageous for the textile industry are in detail: • The typical working width of textile machines is between 1.5 and 10 meters. Textile-suited plasma modules need to be scalable up to these dimensions, which is easier for atmospheric-pressure techniques.• Textiles have large specific surfaces compared to foils, piece goods or bulk solids. Even with strong pumps, the reduced pressure which is necessary for low pressure plasma will only be reached slowly due to the desorption of adsorbed gases.

This chapter provides a general summary of the current state of knowledge of plasma modification of various natural cellulosic fibres. Much of the information reported here is taken from the references cited at the end of the chapter, which should be consulted for a more in-depth treatment. Several aspects of plasma modification of various natural cellulose fibres are thoroughly treated in a number of excellent works. [1, 2]