Oxygen plasma-treated quenched and annealed polypropylene (PP) films with different crystallinities were investigated to characterize the surface rearrangement behavior during aging using contact-angle measurements and X-ray photoelectron spectroscopy. Optimum plasma conditions were examined by varying the power, time and pressure. Less crystalline quenched PP showed a larger increase in water contact angle and a larger decrease of oxygen atomic concentration during aging than the more crystalline annealed PP, since the oxygen species, such as hydroxyl groups, introduced by oxygen plasma treatment, oriented towards or diffused faster into the bulk with lower crystallinity. The degree of crosslinking on the surface was enhanced after plasma treatment and, in addition to increased crystallinity, the crosslinked structure induced by plasma treatment restricted chain mobility and lowered the aging rate of the PP surface.

Several methods for the determination of both the surface free energy of polymer materials and the conditions necessary to perform contact angle measurements are discussed. The effects of the corona-treatment energy on the surface free energy and on the adhesion of acrylic adhesive were studied using a biaxially-oriented polypropylene film. The surface free energy was determined by the Owens-Wendt, and van Oss-Chaudhury-Good approaches, as well as with the wettability method, using different liquids. The presented results confirm that the surface free energy value depended on both the method used and the nature of probe liquids. Thus, it cannot be considered as a parameter characterizing unambiguously the surface layer of a corona-treated film. The values of the surface free energy for different film samples can be compared with one another only if determined using the same method and the same liquids. The variations of particular components of the surface free energy with the corona-treatment energy depend on e.g. the nature of probe liquids, which makes interpretation of the observed effects difficult.

The results of an X-ray photoelectron spectroscopic investigation of the oxidation of surface layers of low-density polyethylene (LDPE) and biaxially oriented polypropylene (BOPP) films are presented. The analysis was performed using different take-off angles, namely 10°, 30°, and 90°; thus, the depths of the examined layers were 0.6, 1.9, and 3.7 nm, respectively. It was found that the course of the oxidation process in the surface layers was similar for both polymer films. However, for treatment energies lower than 5 kJ/m², the extent of the oxidation was higher for the LDPE film, whereas for energies above this value, the BOPP film was more oxidized. As detected by X-ray photoelectron spectroscopy (XPS), desorption of oxygen from the film surface occurs for both polymers during the treatment.

The surface of a polyimide [poly(biphenyl 3,3′,4,4′-dianhydride-p-phenylene diamine)] film was modified with an O₂ glow plasma and subsequent treatment with polyethyleneimine (PEI) and poly(maleic anhydride-co-vinyl methyl ether) (PMAVM). The density of peroxide groups formed on the surface after O₂ plasma exposure was determined with 1,1-diphenyl-2-picrylhydrazyl and was found to level off to 1.2 nmol/cm² within the plasma exposure time of 20-60 s. The peroxide groups formed were utilized to immobilize PEI covalently onto the plasma-treated polymer film. After that, PMAVM was immobilized on the surface through the formation of amide bonds between the amino groups of PEI and the anhydride groups of PMAVM. The water contact angle on the modified films showed that the hydrophilic durability of the PMAVM-PEI-modified polyimide film was superior to that of the polyimide film treated by O₂ plasma alone.

X-ray photoelectron spectroscopy (XPS) has been used to study the chemical effects of both inert (argon) and reactive (oxygen, nitrogen, and mixed gas) plasma treatments done in situ on a variety of polymer surfaces. Inert gas plasma treatments introduce no new detectable chemical species onto the polymer surface but can induce degradation and rearrangement of the polymer surface. However, plasma treatments with reactive gases create new chemical species which drastically alter the chemical reactivity of the polymer surface. These studies have also shown that the surface population of chemical species formed after plasma treatment is dependent on both the chemical structure of the polymer and the plasma gas. The effects of direct and radiative energy-transfer processes in a plasma have also been studied. Polymers containing certain functional groups were found to be more susceptible to damage via radiative energy transfer. Ageing studies of plasma-modified polymer surfaces exposed to the atmosphere have shown that the ageing process consists of two distinct phases. The initial phase, which occurs rapidly, involves adsorption of atmospheric contaminants and, in some cases, specific chemical reactions. The second phase, which occurs slowly, is due to surface reorganization.

The inconsistencies in contact angle data presented in the literature can be attributed to a number of factors. The awareness of these factors would allow novice researchers to make meaningful contact angle measurements and interpretations. In this survey the effects of surface roughness and heterogeneity, surface preparation and the presence of contaminants, the vapor environment, pressure and temperature, drop size, electrical charge, and heat transfer on the wettability of polymer surfaces were examined.

Contact angles of binary liquid mixtures on Teflon FEP were measured. It was found that the equation of state for interfacial tensions, γ_SL = f (γ_LV, γ_sv), cannot be used to determine solid surface tensions from these contact angles of binary liquid mixtures. These findings are explained in terms of the thermodynamic phase rule.

In order to investigate the effect of atmospheric pressure plasmas on adhesion between aramid fibers and epoxy, aramid fibers were treated with atmospheric pressure helium/air for 15, 30 and 60 s on a capacitively-coupled device at a frequency of 5.0 kHz and He outlet pressure of 3.43 kPa. SEM analysis at 10 000× magnification showed no significant surface morphological change resulted from the plasma treatments. XPS analysis showed a decrease in carbon content and an increase in oxygen content. Deconvolution analysis of C1s, N1s and O1s peaks showed an increase in surface hydroxyl groups that can interact with epoxy resin. The microbond test showed that the plasma treatment for 60 s increased interfacial shear strength by 109% over that of the control (untreated). The atmospheric pressure plasma increased single fiber tensile strength by 16-26%.

The effects of atmospheric air-plasma treatments on woven and non-woven polyester (PET) textile structures were studied by surface analysis methods: wettability and capillarity methods, as well as atomic force microscopy/lateral force microscopy (AFM/LFM). The water contact angle on plasma-treated PET decreased from 80° to 50–40°, indicating an increase in the surface energy of PET fibres due to a change in the fiber surface chemical nature, which was confirmed by a higher fiber friction force measured by the LFM. The extent of water contact angle decrease, as well as the wash fastness of the treatment varied with the structure of the textile. Indeed the more porous the textile structure is (such as a non-woven), the fewer are the chain scissions of the PET at the fiber surface, during the plasma treatment. Thus, the level of surface oxidation and the weak boundary layers formation depend not only on plasma treatment parameters but also on the textile structure.

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) surfaces were exposed to vacuum UV (VUV) photo-oxidation downstream from Ar microwave plasma. The modified surfaces showed the following: (1) an improvement in wettability as observed by water contact angle measurements; (2) surface roughening; (3) defluorination of the surface; and (4) incorporation of oxygen as CF—O—CF₂, CF₂—O—CF₂ and CF—O—CF₃ moieties. With long treatment times, a cohesive failure of copper sputter-coated onto the modified surface occurred within the modified FEP and not at the Cu–FEP interface.

Adhesion of evaporated Cu to Teflon PFA (polytetrafluoroethylene-co-perfluoroalkoxy vinyl ether) was greatly enhanced by plasma pretreatment. The efficiency of the treatment decreased in the following order: N₂ > O₂ > (N₂ + H₂) > (O₂ + H₂) > H₂. X-ray photoelectron spectroscopy (XPS) showed the loss of fluorine and the incorporation of oxygen and nitrogen at the polymer surface. Among the gases, H₂ was found to be the most efficient for fluorine elimination, and (N₂ + H₂) for surface functionalization. Based on this investigation, it is proposed that Cu reacts with both oxygen and nitrogen to form, respectively, Cu-O and Cu-N bonds at the interface but no reaction occurs with carbon and fluorine. While greater enhancement in polymer surface wettability and stronger interfacial reactions can account for the higher performance of N₂ over O₂ in improving adhesion, these effects cannot explain the lower efficiency of H₂. Several possibilities are discussed, including surface cleaning, oxygen incorporation and the formation of weak boundary layers.

Treatment of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) in ammonia plasmas produced surfaces with very high wettability by water, but on storage in air at ambient temperature, the air/water contact angles increased markedly. The evolution of the surface composition and topography was studied by angle-dependent X-ray photoelectron spectroscopy (XPS), derivatization of amine groups with fluorescein isothiocyanate, scanning tunelling microscopy (STM), and atomic force microscopy (AFM). XPS demonstrated a continuous increase in the oxygen content over periods of weeks; this was assigned to oxidation of trapped radicals and subsequent secondary reactions. In addition, the fluorine content also changed markedly on storage; the XPS fluorine signal suggested that there was a substantial amount of fluoride in the freshly treated surfaces, and this component disappeared rapidly on storage. STM and AFM showed no changes in topography with aging but suggested surface hardening on plasma treatment. The events following treatment of FEP and PTFE in ammonia plasmas are not adequately described by a model involving plasma-induced, instantaneous chemical modification followed by surface restructuring; the surface and sub-surface compositions evolve over a period of several weeks due to the occurrence of oxidative reactions, and these chemical changes interact with the physical process of surface restructuring.

Quantitative correlations among surface chemical composition, acid-base thermodynamics, adhesion strength, and locus-of-failure are demonstrated. Four types of functional Teflon surfaces were prepared: two acidic (containing hydroxyl and carboxyl groups), and two basic (containing acetyl and dinitrobenzoate groups). X-Ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared (ATR-IR) spectroscopy were used to characterize the molecular structure of the surface region. Contact angle adsorption isotherms were determined using phenol as an acidic probe and tetrahydrofuran (THF) as a basic probe. The carboxylated surface had a higher molar ▵H^ab with basic THF than the hydroxylated surface, and neither surface had any interaction with the acidic phenol probe. The acetylated surface behaved as a base, interacting with phenol but not with THF, while the dinitrobenzoyl surface had both acidic and basic character. Adhesion tests were carried out in the 180° peel mode using post-chlorinated poly(vinyl chloride) as a model acidic adhesive between pairs of each type of film. The two surfaces with basic character had significant peel strengths, while the two acidic surfaces had very low peel strengths. Scanning electron microscopy (SEM) of the basic failure surfaces showed significant plastic deformation of the Teflon polymer, while the acidic failure surfaces showed no deformation. XPS analysis of the failure surfaces confirmed interfacial failure for the acid-acid pairs, and bulk FEP failure for the acid-base pairs. These results demonstrate directly and quantitatively the enhancement of adhesive bond strength through acid-base interactions.

Surface modification of poly(tetrafluor oethylene) (PTFE) by NH₃-plasma treatment was investigated by means of contact angle measurement, XPS, and ATR FT/IR spectroscopy. The modified surfaces were adhesively bonded to nitril rubber. The NH₃-plasma irradiation made PTFE surfaces hydrophilic. The contact angle of water on the modified PTFE surface was 16 deg, and the surface energy was 62-63 mJ/m². The NH₃-plasma irradiation improved adhesion between PTFE and nitril rubber using a phenol-type adhesive. The peel strength of the joints reached 8.1 × 10³ N/m. Carbonyl and amido groups were created on PTFE surfaces by the NH₃-plasma irradiation. The mechanism of the improvement of adhesion by the NH₃-plasma irradiation is discussed.

Poly(phenylene sulfide) (PPS) films were modified by Ar, O₂, N₂ and NH₃ plasmas in order to improve their adhesion to copper metal. All four plasmas modified the PPS film surfaces, but the NH₃ plasma modification was the most effective in improving adhesion. The NH₃ plasma modification brought about large changes in the surface topography and chemical composition of the PPS film surfaces. The peel strength for the Cu/plasma-modified PPS film systems increased linearly with increasing surface roughness, R_a or R_rms, of the PPS film. The plasma modification also led to considerable changes in the chemical composition of the PPS film surfaces. A large fraction of phenylene units and a small fraction of sulfide groups in the PPS film surfaces were oxidized during the plasma modification process. Nitrogen functional groups also were formed on the PPS film surfaces. The NH₃ plasma modification formed S—H groups on the PPS film surfaces by reduction of S—C groups in the PPS film. Not only the mechanical interlocking effect but also the interaction of the S—H groups with the copper metal may contribute to the adhesion of the Cu/PPS film systems.

A cross-web non-uniformity ('laning') in the flame surface modification of polypropylene (PP) film was investigated using flame temperature measurements and Wilhelmy plate force measurements. To associate the cross-web non-uniformity in the flame treatment with specific features of the flame supported on an industrial 4-port ribbon burner, the temperature and force measurements were registered to a specific burner port. The Wilhelmy force measurements show that the upstream pair of ribbon-burner ports causes a slightly greater treatment of the PP surface than the corresponding downstream pair of ports. The average temperature experienced by the PP as the film traverses through the flame is noticeably higher along the down-web line of the upstream burner ports as compared with a line passing through the downstream pair. This greater average temperature correlates to an exposure to a greater concentration of the active species, such as OH radicals, that cause the surface oxidation of the PP.

The influence of corona treatment on the near-surface structures of treated ultra-high-molecular-weight polyethylene (UHMWPE) fibers was studied first by atomic force microscopy (AFM). AFM pictures showed that the pits on the corona-treated PE fiber surfaces had different change characteristics in depth compared with in length and breadth with variations of corona power. Then the UHMWPE fibers were subjected to chemical modification following the corona treatment, named the two-stage treatment. Surface morphologies and chemical properties of the treated fibers were analyzed by scanning electron microscopy (SEM), FT-IR–ATR spectroscopy and Raman spectroscopy. The results obtained suggested that some carbon–carbon double bonds had been introduced on the surfaces of the PE fibers after the two-stage treatment. These unsaturated groups could participate in free-radical curing of vinylester resin (VER), and this resulted in improvement of interfacial adhesion strength in the PE fiber/VER composites. In addition, the mechanical properties of the UHMWPE fibers reduced after corona treatment did not reduce further after subsequent chemical treatment with increase of corona power. In short, the two-stage treatment proved to be effective in improving the interfacial adhesion of the composites and maintaining the high mechanical properties of the PE fibers, as this treatment method did not destroy the bulk structure of the UHMWPE fibers.

A droplet of liquid placed on a flat high-energy solid surface spreads to give a thin film so that no macroscopic droplet shape exists. On a chemically identical solid surface with only the geometry changed to a cylinder, the same droplet can have an equilibrium conformation. When the equilibrium conformation is of a barrel type, the profile of the droplet changes rapidly in curvature as the three-phase contact line is approached and the direct measurement of the contact angle is difficult. This work considers the theoretical profile for barrel-type droplets on cylinders and discusses how the inflection angle in the profile depends on droplet parameters. Experimental results are reported for poly(dimethylsiloxane) oils on a range of fiber surfaces and these are used to estimate the equilibrium contact angle from the inflection angle. The drop radius and volume dependence of the inflection angle is confirmed.

One of the major disadvantages of low density polyethylene (LDPE) films is their poor adhesive properties. Therefore, LDPE films have been treated with atmospheric pressure air plasma in order to improve their surface properties. So as to simulate the possible conditions in an industrial process, the samples have been treated with two different sample distances (6 and 10 mm), and treatment rates between 100 and 1000 mm s⁻¹. The different sample distances are the distance of the sample from the plasma source. The variation of the surface properties and adhesion characteristics of the films were investigated for different aging times after plasma exposure (up to 21 days) using contact angle measurement, atomic force microscopy, weight loss measurements and shear test. Results show that the treatment increases the polar component and these changes improve adhesive properties of the material. After the twenty-first day, the ageing process causes a decrease of wettability and adhesive properties of the LDPE films (up to 60%).

Since the earliest systematic research during the 1960s, the field of materials surface modification by 'cold', low-pressure plasma treatment has undergone an enormous expansion. Much of this expansion has taken place in recent years, particularly in the surface modification of polymeric materials, for which there now exist numerous industrial applications (enhancement of paint adhesion, improved bonding in polymer matrix composites, etc.). In this paper, we provide a critical review of the development and trends in this field; reference is also made to other surface modification techniques, particularly to corona treatment, and comparisons are made wherever appropriate. We begin with a brief overview of adhesion theory, and of the physics and chemistry of 'cold' plasmas. Next, interaction mechanisms between a plasma and a polymer surface are examined; these include physical bombardment by energetic particles and by ultraviolet photons, and chemical reactions at or near the surface. The resulting four main effects, namely cleaning, ablation, crosslinking, and surface chemical modification, occur together in a complex synergy, which depends on many parameters controlled by the operator. In spite of this complexity, for there are still many unanswered questions, it is nevertheless possible to optimize the main set of parameters governing a given process, and then to reliably reproduce the process outcome. Three industrially important systems, for which many research results exist, are then separately examined, namely: (i) polymer-polymer bonding, (ii) polymer-matrix composites, and (iii) metal-polymer bonding. Finally, we present a brief overview of commercial plasma reactors for industrial (non-semiconductor) purposes, and of process considerations for efficient use of such equipment. We foresee that the use of plasma processes will continue to expand, because they have unique capabilities, are economically attractive, and are 'friendly' towards the environment.

The growing realization of the importance of intermolecular acid-base interactions in promoting the solubility, adsorption, and adhesion of polymers to other materials has caused a demand for the quantitative characterization of the acid-base properties of the commonly used solvents, polymers, and inorganic fillers and substrates. There have been several recent advances in the measurement techniques for such determinations, especially in the fields of inverse gas chromatography, microcalorimetry, ellipsometry, FTIR, NMR, and XPS spectroscopy, all leading to the capability of determining the Drago E and C constants or the Gutmann acceptor numbers (AN) or donor numbers (DN) for the acidic or basic sites of solvents, polymers, or inorganic surfaces. In the last year, new studies have also allowed the characterization of the specific acid-base cohesive interactions in solvents and polymers, and the determination, from contact angle measurements on polymers, of the surface concentration and strength of acidic and basic surface sites. All of these techniques are discussed in this paper and it is expected that they will soon become standard laboratory practices.

It is now generally recognized that the principal forces contributing to the work of adhesion between two phases, W_A, are the Lifshitz-van der Waals forces (which include a small contribution from permanent and induced dipoles) and acid-base interactions, taken in the most general 'Lewis' sense. One may thus write W_A = W^LW_A + w^ab_A = 2√σ^LWSσ^LWL + fN(-ΔH^ab), where W^LW_A and W^ab_A are the Lifshitz-van der Waals and acid-base contributions to the work of adhesion, and σ^LW_S and σ^LW_L are the Lifshitz-van der Waals contributions to the surface free energies of the solid and the liquid, respectively; ΔH^ab is the enthalpy (per mol) of the acid-base adduct formation between the acid or base functional groups on the adherend and in the adhesive; N is the number (moles) of accessible functional groups per unit area of the adherend; and f is an enthalpy-to-free energy correction factor (which has normally been assumed to be ~1). The present work seeks to evaluate W^ab_A for several systems using wetting measurements and, for at least one system, to obtain a quantitative check of the above equation using independently measured values of f, N, and (ΔH^ab). The total work of adhesion is determined from the measured surface tension of the liquid, σ_L' and its contact angle, 0, against the solid: W_A= σ_L(1 + cos ). σ^LW_S and σ^LW_L are determined using probe liquids, N is determined from conductometric titrations of the solid in finely divided form, and ΔH^ab is determined by flow microcalorimetry. f is determined from a Gibbs-Helmholtz analysis of surface tension and contact angle data obtained over a range of temperatures. Conclusions reached are that the f factor is significantly below unity in most cases and that even including this effect, the above equation is still not verified quantitatively when the terms are measured independently.

—ESCA, wettability measurements, SEM, weight-loss determinations, and an ink adhesion test were used to characterize low-molecular-weight oxidized materials (LMWOM) formed during the corona-discharge treatment of polypropylene film. Water-soluble LMWOM is readily formed by scission processes occurring during corona treatment. The presence of water-soluble LMWOM complicates the interpretation of wettability-based measurements of corona effectiveness. Surface roughening on corona-treated polypropylene is caused by the interaction of LMWOM and water in a high-relative-humidity environment. LMWOM does not necessarily form a weak boundary layer that hinders subsequent adhesion of ink to the corona-treated film.

ETFE film surfaces were modified by CO₂, O₂ and Ar plasmas in order to form carboxylic groups on their surfaces, and the possibility that carboxylic groups could be predominantly introduced into the CH₂–CH₂ component rather than the CF₂–CF₂ component in the ETFE polymer chains was investigated from the viewpoint of chemical composition analyzed by XPS. The CO₂ plasma modification was more effective in the selectivity of the CH₂CH₂ component for the introduction of carboxylic groups, as well as in the concentration of the carboxylic groups formed on the film surfaces than O₂ plasma modification. The concentration of carboxylic groups formed on the ETFE film surfaces by the CO₂ plasma modification was 1.40–1.50 groups per 100 carbons. Topographical changes on the ETFE film surfaces by the plasma modification were also investigated by scanning probe microscopy.

The wetting behavior of a series of polymer-coated papers has been studied. Different ways of determining the acid–base properties of the polymers are presented. The well-known van Oss–Chaudhury–Good (vOCG) bi–bi polar model is compared with more simplified mono–bi polar and mono–mono polar models. The effect of surface roughness on the wetting was also studied with atomic force microscopy. The overall wetting of each probe liquid was evaluated by calculating the work of adhesion to the polymer surfaces. It is shown that ethylene glycol and water may be considered as mono polar liquids, which simplifies the original vOCG-model. It is also shown that in most cases the surface energy values are in the same range when using both the complex bi–bi polar approach and the simpler mono–mono polar approach. The different polymers used are found to be of a predominating basic character.

Four ethylene vinyl acetate (EVA) co-polymers with different vinyl acetate (VA) contents (9–20 wt%) were treated with corona discharge to improve their adhesion to polychloroprene (PCP) adhesive. The thermal properties of the EVAs decreased as their VA content increased, caused by a decrease in crystallinity. The elastic and viscous moduli of the EVAs decreased and the temperature and modulus at the cross-over between these moduli decreased with increasing VA content. Contact-angle measurements (water), infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyse the surface modifications produced in the corona-discharge-treated EVAs. The corona discharge treatment produced improved wettability and created roughness and oxygen moieties on the EVA surfaces. The higher the VA content and the higher the corona energy, the more significant modifications were produced on the EVA surface. The VA content also affected the T-peel strength values of treated EVA/polychloroprene + isocyanate adhesive joints, as the values increased with increasing VA content. Mixed failure modes (interfacial + cohesive failure in the EVA) were obtained in the adhesive joints produced with corona discharge treated EVAs containing more than 9 wt% VA. The accelerated ageing of the joints did not affect the T-peel strength values, but the locus of failure in most cases became fully cohesive in the EVA, likely due to the higher extent of curing of the adhesive.

The influence of different surface treatments on the physical and chemical surface properties of poly(etheretherketone) (PEEK), poly(phenylenesulfide) (PPS) and a liquid crystal polymer (LCP) was studied. For all the three polymers, the adhesion strength of an adhesively-bonded copper foil could be increased significantly by a chemical etching process using chromic sulphuric acid or a low pressure air-plasma treatment. However, for LCP the enhancement of adhesion by the surface treatments was lower than for the other polymers. Peel tests were employed for determining the adhesion strength of the copper foil. The physical surface properties were investigated by laser scanning microscopy (LSM). Contact-angle measurements and X-ray photoelectron spectroscopy (XPS) provided detailed information on the chemical surface properties. The detailed XPS analyses revealed different chemical mechanisms of the surface treatments depending on the polymer investigated. In all cases an incorporation of oxygen containing groups by the surface treatments was found to be responsible for a better adhesion of the copper foil on the treated polymer films compared to the untreated.

The surface of polypropylene (PP) film was oxidized by exposure to a flame fueled by isotopically labeled methane (CD4). The isotopic sensitivity of static secondary ion mass spectrometry (SIMS) was then used to gain new insights into the mechanism of flame treatment. SIMS analysis indicated that much of the oxidation of PP occurring in fuel-lean flames is not deuterated, while for PP treated in fuel-rich flames, some of the affixed oxygen is deuterated. These observations imply that O₂ is the primary source of affixed surface oxygen in fuel-lean flame treatments, but that OH may be a significant source of affixed oxygen in fuel-rich flame treatments. Hydroxyl radicals are primarily responsible for hydrogen abstraction in fuel-lean flames, while H is the primary active gasphase species in fuel-rich flames. SIMS also detected trace quantities of oxidized nitrogen groups affixed to the flame-treated PP.

In this study the effect of low temperature plasma (LTP) treatment of cotton fabric for ink-jet printing was investigated. Owing to the specific printing and conductivity requirements for ink-jet printing, none of the conventional printing chemicals used for cotton fabric can be directly incorporated into the ink formulation. As a result, the cotton fabric requires treatment with the printing chemicals prior to the stage of ink-jet printing. The printing chemicals as a treatment to cotton fabric are applied by the coating method. The aim of this study was to investigate the possibility and effectiveness of applying LTP pre-treatment to enhance the performance of treatment paste containing sodium alginate, to improve the properties of the ink-jet printed cotton fabric. Experimental results revealed that the LTP pre-treatment in conjunction with the ink-jet printing technique could improve the final properties of printed cotton fabric.

The aging effects of atmospheric pressure plasma treated fiber surfaces are important for storage and processing of the fibers. One of the high-performance fibers, ultrahigh modulus polyethylene (UHMPE) fiber, was chosen as a model system to investigate the aging process of atmospheric pressure plasma jet (APPJ) treated fibers surfaces 0, 7, 15 and 30 days after initial plasma treatment. The fiber was first plasma-treated and then stored at temperatures varying from −80 to 80°C on the same relative humidity (RH, 0%) and on RH of 0%, 65% and 100% at the same temperature of 20°C. Immediately after the plasma treatment, scanning electron microscope (SEM) showed the roughened fiber surface. X-ray photoelectron spectroscopy analysis showed changed surface chemical compositions. Contact-angle measurement showed increased surface wettability and microbond test showed an increase in IFSS. With increasing relative humidity or decreasing temperature, the IFSS value decreased and the contact angle increased more slowly. However, after 30 days, the IFSS values and contact angles reached a similar level for all groups. Moisture showed no effect on the single fiber tensile strengths during aging. The reasons for the observed aging behavior could be that decreasing temperature or increasing relative humidity hindered the surface rearrangement of polymer chains after plasma treatment.

The effect of the addition of clay and TiO₂ pigments on the surface energy and surface chemistry of films made from polymers used in paper coating formulations was evaluated. The polymers were carboxymethyl cellulose, polyvinyl alcohol and a protein-based polymer - all water-soluble - and two styrene-butadiene latexes of different carboxylation levels. The morphology of the surfaces was characterized by SEM examination, gloss measurement and stylus profilometry. Chemical composition was determined by EDS and XPS techniques. Surface energy and its Lifshitz-van der Waals and acid-base components were obtained from contact angle measurements using the van Oss et al. approach. Even though the addition of pigment increasingly upset the planar surface of the films, their surface chemistry and surface energy were only slightly affected over the pigmentation range studied (up to 40% by volume) and were dominated by the characteristics of the binder polymer.

The apolar and the polar (electron-acceptor and electron-donor, or Lewis acid-base) surface tension components and parameters of solid surfaces can be determined by contact angle measurements using at least three different liquids, of which two must be polar. With swelling clay minerals (e.g. smectite clay minerals), smooth contiguous membranes can be fabricated, upon which contact angles can be measured directly. With non-swelling clay minerals (e.g. talc), contact angles can be determined by wicking, i.e. by the measurement of the rate of capillary rise of the liquids in question through thin layers of clay powder adhering to glass plates. The apolar and polar (acid-base) surface tension components and parameters thus found for various untreated and quaternary ammonium base-treated clays allowed the determination of the net interfacial free energy of adhesion of human serum albumin onto the various clay particle surfaces immersed in water. The free energies of adhesion, thus found, correlate well with the experimentally observed degree of adsorption of human serum albumin.

Numerous relationships have been proposed in the literature to interpret wettability in terms of solid and liquid surface free energies. In the classical approach based on surface free energy components, the energy of interactions between the liquid and the solid is obtained from the geometric mean of the dispersion and polar contributions of the liquid and solid surface free energies. In this work, it is shown that the surface polarity of polar liquids can be modeled by the interaction of aligned permanent dipoles. A good agreement is found between the surface polarity characterized by polar component of the surface free energy of polar liquids (water, formamide and ethylene glycol) and the dipolar energy of interactions calculated from their dipole moment. At the liquid/polymer interfaces, polar interactions are better described by a simple relationship of proportionality with the polar component of the liquid surface free energy. This observation leads us to evaluate the hypothesis of induced polar interactions at liquid/polymer interfaces, the surface polarity of the solid being induced by the polar liquid in contact with the solid surface. Thus, the variation of the contact angle of a series of polar and non-polar liquids on various polymer substrates appears to be in better agreement when compared to the classical description of permanent polar interactions, so that a surface polarizability is defined for polymers. Using the surface polarizability approach rather than the polar component for the solid surface, we find also that the dispersion (non-polar) component of the polymer surface free energy is obtained with a better confidence, especially by taking into account the contact angles of both non-polar and polar liquid probes, or even by considering only polar liquid probes.

Webs of Kapton 200-H and Upilex-S polyimide films were treated using oxygen plasma prior to sequential sputter deposition of chromium and copper in a roll metallization system. Two plasma system configurations were employed for treatment. In one configuration, the sample traveled downstream from a microwave plasma; in the other, the web moved through a DC-generated glow discharge. For the DC-glow treatment, the potential difference between the plasma and the web, Φ_f, and relative ion densities, n+, were measured at various values of chamber pressure and DC power using a Langmuir probe. Although samples treated downstream from the microwave plasma were not subjected to bombardment by energetic ions, Φ_f for the DC-glow operating conditions was between 5 and 13 eV. For both films, advancing DI water contact angles of less than 20° were achieved using both modes of treatment. Contact angles for untreated films were greater than 60°. However, 90° peel tests yielded values of 15 to 20 g/mm for microwave plasma treatments and 40 to 60 g/mm for DC-glow treatment. Peel values for untreated Kapton and Upilex films were about 25 g/mm. High-resolution X-ray photoelectron spectroscopy in the C1s region for Kapton film surfaces treated downstream from the microwave plasma showed increases in carbonyl groups, with concentrations inversely proportional to web speed. In contrast, DC-glow modification was due mainly to formation of carboxylates with a small increase in carbonyl component. It is proposed that treatment downstream from the microwave plasma results in formation of a weak boundary layer at the polyimide surface. Ion bombardment occurring in the DC-plasma configuration results in relatively more crosslinking at the polymer surface. Furthermore, adhesion between the sputter-deposited chromium and the DC-glow modified polyimide improved with increasing values of Φ_fn+.

X-Ray photoelectron spectroscopy (XPS) was used to determine plasma induced chemical species on the surface of polyethylene (PE). Argon plasmas were found to have no detectable chemical effect on the PE surface, whereas oxygen and nitrogen plasmas created new chemical species which altered the chemical reactivity of the PE surface. Oxygen plasmas were found to react more rapidly with the PE surface than nitrogen plasmas. The degree of incorporation of new chemical species in the near surface region is approximately 20 at. % at the saturation level for both oxygen and nitrogen plasmas. Core level spectra for oxygen and nitrogen plasma treated PE suggest the formation of primarily C-O-C species in the former and C-N species in the latter. Angle-resolved XPS measurements indicate that the depth of incorporation of new chemical species is confined to the top 25 A.

The van Oss–Chaudhury–Good theory (vOCGT) was checked for a small artificial set of the work of adhesion input data calculated for 9 solids and 7 liquids. Taking from the literature the data for Lifshitz–van der Waals (LW) component and acid and base (A and B) parameters for 7 liquids and the values of the component and the parameters for 9 solids (close to those in the literature), the work of adhesion was calculated and its value was assumed to be free of error. Next, new values of the work of adhesion were obtained by adding a random error of normal distribution belonging to 11 distributions of a mean value equal to the errorless work of adhesion value and standard deviations from 0.1 to 60% of the mean value. The LW components and A and B parameters for these solids were back-calculated for each solid and the error level by solving 20 3-equation systems. These 9 solids were grouped in 3 sets of 3 solids in each, and for each of the solid sets the over determined system of equations (of matrix 7 × 3) for these 7 liquids was solved. The root mean square errors (RMSEs) of the LW component and A and B parameters were linear functions of RMSE of the vector (matrix) of the work of adhesion in both solution methods of a set of equations. It was found that a solution of the 3-equation set of the vOCGT was always exact for all liquid triplets. Erroneous LW components and acid and base parameters are obtained because quite a different set of equations (caused by an existing error in the data) is solved than in the case of error-free data. There is a linear transformation from the input error in the work of adhesion vector (matrix) space into the output error in the solution vector (matrix) space, and the inverse (or pseudoinverse) of the matrix A is the transformation matrix. In the case of a 3-equation set there is a linear relationship between the total RMSE of the solution and the condition number of the matrix A. The higher the input error in the work of adhesion data the higher is the influence of the condition number on the error in the solution. The RMSE value of the solution of an over determined system of equations was about 10-times lower than the mean value of RMSE calculated for the same liquids used as separate triplets.

The occurrence of negative square roots of the Lifshitz–van der Waals (LW) component and acid and base (A and B) parameters calculated from the van Oss–Chaudhury–Good theory was checked for a small artificial set of the work of adhesion input data calculated for 9 solids and 7 liquids. Taking from the literature the data for the LW component and A and B parameters for 7 liquids and the values of such component and parameters for 9 solids (close to those in the literature), the work of adhesion was calculated and its value was assumed to be error-free (un-biased). Next, new values of the work of adhesion were obtained by adding a random error having normal distribution belonging to 8 distributions of a mean value equal to the error-free work of adhesion value and standard deviations of 1, 5, 7, 10, 20, 25, 30 and 40% of the mean value. The LW components and A and B parameters for the nine solids were back-calculated for each solid and the error (bias) level by solving the overdetermined system of equations (of matrix 7 × 3) for 7 liquids. These 9 solids were grouped in 3 sets of 3 solids in each. It was found that an experimental error caused the work of adhesion data for real systems to be biased. This bias caused the solution of the equation system also to be biased and both biases were linearly dependent. This paper confirms that the appearance of negative roots of A and B parameters is caused by a specific bias in the components of the work of adhesion matrix. If the work of adhesion matrix is negatively biased there is a greater possibility of obtaining a negative value of the square root of γ⁺, and the smaller the value of this parameter the greater is the possibility of obtaining a negative square root for it. Both the negative and positive biases in the work of adhesion matrix almost equally influence the bias in γ⁻. The smaller this parameter the greater is its bias and greater the possibility of obtaining its negative square root.

Wetting of hydrophobic polymer surfaces commonly employed in electronic coatings and their interaction with surfactant-laden liquids and aqueous polymer solutions are analyzed using a contact angle hysteresis (CAH) approach developed by Chibowski and co-workers. In addition, a number of low surface tension acrylic monomer liquids, as well as common probe liquids are used to estimate solid surface energy of the coatings in order to facilitate a thorough analysis of surfactant effects in adhesion. Extensive literature data on contact angle hysteresis of surfactant-laden liquids on polymeric surfaces are available and are used here to estimate solid surface energy for further understanding and comparisons with the present experimental data. In certain cases, adhesion tension plots are utilized to interpret wetting of surfaces by surfactant and polymer solutions. Wetting of an ultra-hydrophobic surface with surfactant-laden liquids is also analyzed using the contact angle hysteresis method. Finally, a detailed analysis of the effect of probe liquid molecular structure on contact angle hysteresis is given using the detailed experiments of Timmons and Zisman on a hydrophobic self-assembled monolayer (SAM) surface. Hydrophobic surfaces used in the present experiments include an acetal resin [poly(oxymethylene), POM] surface, and silane, siloxane and fluoro-acrylic coatings. Model surfaces relevant to the literature data include paraffin wax, poly(methyl methacrylate) and a nano-textured surface. Based on the results, it is suggested that for practical coating applications in which surfactant-laden and acrylic formulations are considered, a preliminary evaluation and analysis of solid surface energy can be made using surfactant-laden probe liquids to tailor and ascertain the quality of the final coating.