Flock coating is a widely used process to create a textile-like texture on substrates of various shapes and materials. In the process, flock fibers—short fibers typically 1–3 mm long—are oriented and accelerated towards the substrate by means of an electric field. Impacting fibers are stuck to the substrate surface by an appropriate adhesive. Primary quality criteria are adhesion of the flock fibers to the adhesive, and also the so-called flock density, ie number of fibers per unit area, and evenness. The influential physical and chemical factors refer to interfacial adhesion, but also charging effects by the impacting fibers. The system presently under investigation is based on aliphatic polyamides as material for a molded car component, hot-melt adhesive, and flock fibers. Experiments reported here refer to the application of an air plasma pretreatment of the polyamide (PA) substrate, mainly in order to increase the adhesion of the hot-melt layer. It was found that the plasma treatment affects the polar energy of the PA surface with a related increase in wettability due to a reduction of C–C and C–H bonds and an increase of carboxylic groups. Surface carbonization occurred at higher plasma doses. The effect on hot-melt adhesion was rather small, however two types of failures were observed in these experiments, either due to insufficient adhesion of the hot-melt or due to a break of one of the PA plates with the bond still intact. The characterization of flock coatings on these samples showed no effect on flock fiber adhesion in pull-out as well as on abrasion resistance, but an increased flock density was observed. This is assumed to be due to enhanced dissipation of charges by the conductive water layer adsorbed on the substrate surface.

Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.

A summary is given of different elementary processes influencing the thermal balance and energetic conditions of substrate surfaces during plasma processing. The discussed mechanisms include heat radiation, kinetic and potential energy of charged particles and neutrals as well as enthalpy of involved chemical surface reactions. The energy and momentum of particles originating from the plasma or electrodes, respectively, influence via energy flux density (energetic aspect) and substrate temperature (thermal aspect) the surface properties of the treated substrates. The various contributions to the energy balance are given in a modular mathematical framework form and examples for an estimation of heat fluxes and numerical values of relevant coefficients for energy transfer, etc. are given. For a few examples as titanium film deposition by hollow cathode arc evaporation, silicon etching in CF4 glow discharge, plasma cleaning of contaminated metal surfaces, and magnetron sputtering of aluminum the energetic balance of substrates during plasma processing will be presented. Furthermore, the influence of the resulting substrate temperature on characteristic quantities as etching or deposition rates, layer density, microstructure, etc. will be illustrated for some examples, too.

Polytetrafluorethylene (PTFE) was treated with N⁺ , O⁺ and C⁺ ion beams with energies of 20 and 30 keV at 5 mA/cm² current density in the pulse regime. Structural changes were studied by IR ATR, XPS, IR diffuse reflectance spectra and wetting methods. After treatment the PTFE surface became chemically active to isocyanate, acrylamide and epoxy reagents, which caused a change of interface interaction with active adhesives. The durability of the PTFE adhesion joint to an epoxy adhesive increases by more than 100 times. The ion beam treatment can be used to increase adhesion joint durability of PTFE.

In the last few decades there has been an intense development in non-equilibrium (“cold”) plasma surface processing systems at atmospheric pressure. This new trend is stimulated mainly to decrease equipment costs by avoiding expensive pumping systems of conventional low-pressure plasma devices. This work summarizes physical and practical limitations where atmospheric plasmas cannot compete with low-pressure plasma and vice-versa. As the processing conditions for atmospheric plasma are rather different from reduced pressure systems in many cases these conditions may increase final equipment costs substantially. In this work we briefly review the main principles, advantages and drawbacks of atmospheric plasma for a better understanding of the capabilities and limitations of the atmospheric plasma processing technology compared with conventional low-pressure plasma processing.

We present a study on ageing of polymethyl methacrylate (PMMA) polymer treated with oxygen plasma. Oxygen plasma was created with an RF generator operating at a frequency of 27.12 MHz and a power of 200 W. The oxygen pressure was 75 Pa. The samples were treated for different time from 5 s to 60 s. The chemical modifications of the surface after plasma treatment were monitored by XPS (X-ray photoelectron spectroscopy), while the wettability and ageing effects were studied by WCA (water contact angle measurements). The samples were aged in dry air or in water. In the case of dry air, the least pronounced ageing was observed for the sample treated for 60 s. For samples aged in water, however, the lowest ageing rate was observed for the sample treated for 5 s. The samples were ageing slightly faster in water than in air. We also investigated the temperature effect on ageing of plasma treated samples. A set of samples was stored in a refrigerator at 5 °C and the other set was placed into an oven at 50 °C. The ageing rate of the samples stored at 5 °C was significantly lower than for the samples stored at 50 °C, so cooling the samples help keeping the required surface properties.An atmospheric pressure plasma syste

RFID research and development requires technical expertise of ink and adhesive manufacturers, surface treatment and printing equipment manufacturers, package printers, and electronics firms. In this framework, a strong enhancement in production and quality can be obtained with surface substrate treatments. Here we will discuss the state-of-art in RFID production and the advantages that a plasma treatment of the substrate can give to RFID label printing.

Different methods used to determine the surface energy of solids from the contact angles of different liquids were compared considering their theoretical background, and multicomponent approaches were applied to polymers and surface-treated polymers containing only C, H, O and N. These methods involve different approximations and give different results regarding surface energy, supporting the view that none of them provides absolute values having the accuracy expected for thermodynamic parameters and their use in computing quantities such as the work of adhesion and interfacial energy. Nevertheless they ranked the surface polarity in the same order, which was also the order simply provided by the water contact angle. A multivariate analysis of works of adhesion deduced from measured contact angles for a set of liquids on different solids may be a relevant alternative to deterministic approaches for ranking surfaces and deciphering the factors which govern their behavior. As the acid-base interactions are involved in surface energy and are due to specific chemical functions, the relationship between the water contact angle and the surface composition was examined, using surface-oxidized polypropylene as a model case. The cosine of the water contact angle was found to correlate with the “surface” oxygen concentration determined by XPS. However, this correlation may be misleading. Actually the surfaces showing the highest oxidation and the highest apparent hydrophilicity should be regarded as covered with a layer of adsorbed compounds, rather than belonging to a defined solid phase.

The wet adhesion of water borne acrylic dispersions is a crucial factor on the performance of outdoor coatings on wood. Pine sapwood was treated with several methods for surface activation to increase the wet adhesion of water borne acrylic dispersions. The wet adhesion was measured by pull-off tests as well as with a modified cross-cut test. Atmospheric plasma, corona treatment and fluorination increased the wet adhesion of the coating which is attributed to the increasing polar portion of the surface free energy. Other ways of improving the wet adhesion are the addition of promotors, the use of primers and organisational improvements.

The first part of the contribution deals with the interfacial tension, σ, of phase‐separated polymer solutions in single or mixed solvents and of binary polymer blends as a function of the relative distance to the critical temperature of the system, special attention being paid to the possibilities of theoretical prediction. Two methods are discussed in more detail. One is based on a realistic description of the Gibbs energy of mixing as a function of composition, the second correlates σ with the length of the measured tie line. The second part is devoted to another aspect, namely the effects of additives on the interfacial tension between the coexisting phases of demixed polymer solutions and between highly incompatible polymers. In the former case, it is demonstrated that an addition of a thermodynamically good solvent is normally associated with a reduction in σ; however, adding a high‐molecular‐weight compound which is incompatible with the dissolved polymer leads to an increase in σ. The interfacial tension between incompatible homopolymers is efficiently reduced by block copolymers consisting of monomeric units which are either identical with or different from those of the homopolymers; in contrast to theoretical expectation, the molecular architecture of the additives seems to be of minor importance only. Random copolymers which are insoluble in the homopolymers can also efficiently reduce the interfacial tension.

A brief review of the surface tension of polymer liquids is presented. A strong emphasis is placed on recent measurements of surface tensions of homologous liquid series up to high-molecular-weight polymers, and the thermodynamic liquid properties of these same homologous series obtained from sources such as pressure-volume-temperature (PVT) data. The accuracy and limitations of the thermodynamic information which are used as input to many of the theories applied to the surface properties of polymer molecules are discussed. By scaling the surface tension data using a true measure of the cohesive energy density of the liquid state, we can clearly observe the entropic contribution to the surface tension caused by the conformational restriction of a large molecule at the liquid-vapor interface. The scaling implies the existence of a corresponding states principle for both polymer liquids and for low-molecular-weight liquids. The ramifications of the existence of a corresponding states principle for the surface tension of polymer melts are discussed. One consequence of the corresponding states principle is that it allows us to use surface tension measurements to compute the cohesive energy density of polymer melts using PVT data.

Polycarbonate (PC) and poly(vinylidene fluoride) (PVDF) are two immiscible polymers which form two‐phase blends with weak interfacial adhesion and high interfacial tension. This situation may be changed by the addition of poly(methyl methacrylate) (PMMA), which concentrates preferably in the PVDF‐rich phase, but also at the PVDF/PC interface. The interfacial activity of PMMA was estimated by the measurement of the interfacial adhesion and interfacial tension in relation to the PMMA content in the PVDF/PC blends. The interfacial adhesion between PC and homogeneous PVDF/PMMA blends of various compositions was measured by the dual cantilever beam technique. The imbedded fiber retraction method was used for the measurement of the interfacial tension. A very beneficial effect was observed when PVDF was premixed with PMMA amounts increasing up to ca. 35 wt.‐%. Beyond that content, the improvement tends to level off.

Scanning force microscopy has been used to characterize the surface structure and properties of poly(ethylene terephthalate) (PET) films. Two types of biaxially oriented film have been studied: one (Melinex O) is free of additives while the other (Mylar D) contains particulate additives at the surface. Contact mode characterization of both materials provide clear images of the polymer surface and (in the case of Mylar D) the additives. Phase images reveal substantial nanoscale morphological detail, including small features thought to be crystallites. To model the adhesive properties of polymer surfaces, mixed self-assembled monolayers containing polar and methyl terminated adsorbates were studied using chemical force microscopy. It was found that the strength of the tip-sample adhesion increased with the fraction of polar terminated adsorbates at the surface when a carboxylic acid terminated tip was employed, while the trend was reversed when a methyl terminated tip was used. Adhesion forces measured for plasma treated PET increased with treatment time, and linearly with the cosine of the water contact angle, illustrating the chemical selectivity of chemical force microscopy. However, friction forces were found to vary in a non-linear fashion, indicating that changes to the polymer surface mechanical properties following treatment were important.

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.

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.