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%).

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.

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.

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.

Multilayer films were prepared from poly(tetrafluoroethylene) (PTFE) and poly(ethylene terephthalate) (PET) films together with using an adhesion promoting layer (tie-layer) consisting of ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer and low density polyethylene (LDPE) blend. Na/naphthalene treatment and subsequent acrylic acid grafting were applied on the surfaces of PTFE for chemical modification. FT-IR spectroscopy, XPS analysis and surface energy measurements were performed to characterize the modified PTFE films. The analyses showed defluorination and oxidation of PTFE surface, and supported the acrylic acid grafting. The surface energy of modified surfaces enhanced with respect to unmodified one, which promoted adhesion. The multilayers were subjected to T-peel tests to measure the adhesion strength between PET and modified PTFE. Peel strength between the films increased with increasing E-MA-GMA amount in the tie-layer. A proportional dependence of peel strength on Na/naphthalene treatment time was observed for multilayers containing acrylic acid grafted or ungrafted PTFE. From SEM analysis, it was observed that the texture of the PTFE surface after modifications became rougher when compared to untreated PTFE. The peeled surfaces were also analyzed by SEM. The micrographs evidence that the energy absorbing mechanism is the plastic deformation of the tie-layer, which is responsible for obtaining high peel strengths.

One of the main differences between low-pressure and atmospheric-pressure plasma treatments is that there is little moisture involved in the low-pressure plasma treatment, although moisture could exist at the wall of the vacuum chamber or react with the substrate after plasma treatment, while in the atmospheric-pressure plasma treatment moisture exists not only in the environment but also in any hygroscopic substrate. In order to investigate the influence of environmental moisture on the effect of atmospheric pressure plasma treatment, ultra-high-modulus polyethylene (UHMPE) fibers were treated using an atmospheric-pressure plasma jet (APPJ) with 10 l/min helium gas-flow rate, treatment nozzle temperature of 100°C and 5 W output power. The plasma treatments were carried out at three different relative humidity levels, namely 5, 59 and 100%. After the plasma treatments, the surface roughness increased while the water-contact angle decreased with increasing relative humidity. The number of oxygen containing groups increased as the environmental moisture content increased. The interfacial shear strength of the UHMPE fiber/epoxy system was significantly increased after the plasma treatments, but the moisture level in the APPJ environment did not have a significant influence on the adhesion properties. In addition, no significant difference in single fiber tensile strength was observed after the plasma treatments at all moisture levels. Therefore, it was concluded that the environmental moisture did not significantly influence the effect of atmospheric-pressure plasma treatment in improving interfacial bonding between the fiber and epoxy. The improvement of the interfacial shear strength for the plasma-treated samples at all moisture levels was mainly due to the increased surface roughness and increased surface oxygen and nitrogen contents due to the plasma etching and surface modification effect.

In this paper, we present a simple, yet novel, method, utilizing scraping to obtain continuous rough microstructures over large areas, leading to a tunable wettability conversion from hydrophilicity to superhydrophobicity on polymer surfaces. A series of polymers ranging from hydrophobic to hydrophilic were used, and we found that the wettability of these polymer surfaces could be modified by the scraping process, irrespective of their hydrophobicity or hydrophilicity. More importantly, those polymers with contact angle ranging from 65° to 90° on their smooth surfaces also exhibit enhanced hydrophobicity after scraping. Our results indicate that 65° is the critical value which is more suitable to define hydrophobicity and hydrophilicity for polymer materials.

Measurements of the surface tension (γ_LV) and advancing contact angle () on poly(tetrafluoroethylene) (PTFE) were carried out for aqueous solutions of cetyltrimethylammonium bromide (CTAB), cetylpyridynium bromide (CPyB), sodium decylsulfate (SDS), sodium dodecylsulfate (SDDS), p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycol)s, Triton X-100 (TX100) and Triton X-165 (TX165) and their mixtures. The results obtained indicate that the values of the surface tension and wettability of PTFE depend on the concentration and composition of the surfactants mixture. In contrast to Zisman finding, there was no linear dependence between cos and the surface tension of aqueous solutions of surfactants and their mixtures for all studied systems, but a linear dependence existed between the adhesional tension and solution surface tension for PTFE in the whole concentration range, the slope of which was –1, indicating that the surface excess concentration of surfactant at the PTFE–solution interface was the same as that at the solution–air interface for a given bulk concentration. It was also found that the work of adhesion of aqueous solutions of surfactants and their mixtures to PTFE surface did not depend on the type of surfactant, its concentration and composition of the mixture. This means that for the studied systems the interaction across PTFE–solution interface was constant, and it was largely of Lifshitz–van der Waals type. On the basis of the surface tension of PTFE and the Young equation and thermodynamic analysis of the work of adhesion of aqueous solutions of surfactants to the polymer surface it was found that in the case of PTFE the changes of the contact angle as a function of the total mixture concentration in the bulk phase resulted only from changes of the polar component of the solution surface tension.

Surface modification by corona discharge plasma is one of the most interesting industrial applications for surface modification compared with other techniques which require vacuum conditions. In this work, we have used the corona discharge plasma technique to modify the wettability properties of low density polyethylene (LDPE) film. The effects of this treatment on the surface of LDPE film have been quantified by contact angle measurements, Fourier-transform Infrared Spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. With these methods, we have determined how the treatment modifies, activates and functionalizes the surface of LDPE film, increasing its hydrophilic behavior, and how the process parameters influence the uniformity and homogeneity of the treated surface. The results obtained show good treatment homogeneity and an improvement of adhesion properties by the functionalization and etching of the film surface.

A superhydrophobic polyurethane-based film is described, on which the water advancing and receding contact angles are 150° and 82°, respectively. The film was prepared from surface-fluorinated polyurethane (PU), obtained from a well-defined fluorinated isocyanate, with silica particles incorporated within the film. In the absence of the silica particles, smooth fluorinated PU films with about 2 wt% fluorine demonstrate water advancing and receding contact angles of 110° and 63°, respectively. A major cause for the large contact angle hysteresis, similar to the so-called 'sticky' superhydrophobic behavior, on the roughened PU films is believed to originate from the surface reorganization of the fluorinated PU upon contact with water, which is characteristic for the partially fluorinated PU film. When a similar poly(dimethylsiloxane) (PDMS)-based roughened film was made, the water contact angle hysteresis could be reduced significantly, since the long PDMS chain can effectively suppress the surface reorganization upon contact with water.

SBS rubbers containing different loadings of calcium carbonate and/or silica fillers were surface treated with UV-ozone to improve their adhesion to polyurethane adhesive. The surface modifications produced on the treated filled SBS rubbers have been analyzed by contact angle measurements, ATR-IR spectroscopy, XPS and SEM. The adhesion properties have been evaluated by T-peel strength tests on treated filled SBS rubber/polyurethane adhesive/leather joints. The UV-ozone treatment improved the wettability of all rubber surfaces, and chemical (oxidation) and morphological modifications (roughness, ablation, surface melting) were produced. The increase in the time of UV-ozone treatment to 30 min led to surface cleaning (removal of silicon-based moieties) due to ablation and/or melting of rubber layers and also incorporation of more oxidized moieties was produced. Although chemical modifications were produced earlier in an unfilled rubber for short time of treatment with UV-ozone, they were more noticeable in filled rubbers for extended length of treatment, mainly for S6S and S6T rubbers containing silica filler. The oxidation process seemed to be inhibited for S6C and S6T rubbers (containing calcium carbonate filler). On the other hand, the S6S rubber containing silica filler and the lowest filler loading showed the higher extent of modification as a consequence of the UV-ozone treatment. The UV-ozone increased the joint strength in all joints, more noticeably in the rubbers containing silica filler, in agreement with the greater extents of chemical and morphological modifications produced by the treatment in these rubbers. Finally, the nature and content of fillers determined the extent of surface modification and adhesion of SBS rubber treated with UV-ozone.

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