In moist environments biaxially-oriented corona-treated polyethylene terephthalate (BOPET) film undergoes a decay in surface energy with time. This decay is a significant and well-known problem and it considerably restricts the industrial application of BOPET film. In the present study the decay effect and the dynamics of corona-treated BOPET film in an aqueous environment have been studied using water contact angle and variable angle X-ray photoelectron spectroscopy (XPS) measurements. In addition the surface decay mechanism of the corona-treated BOPET film in aqueous environments was analyzed and a molecular moving model for the decay mechanism is proposed.

Plasma treatment is often used to modify the surface properties of polymer films, since it offers numerous advantages over the conventional surface modification techniques. However, plasma-treated polymer films have a tendency to revert back to the untreated state (aging process). Therefore, the stability of plasma-induced changes on polymer surfaces over a desired period of time is a very important issue. The objective of this study is to examine the effect of storage conditions (relative humidity and temperature) on the aging behavior in air of plasma-treated low density polyethylene (LDPE) films. Plasma treatment is performed using a dielectric barrier discharge (DBD) operating in different argon/water vapor mixtures at medium pressure (5.0 kPa). Results show that the aging process can be suppressed by storing the plasma-modified LDPE films at low temperature and by decreasing the relative humidity of the surrounding air. Adding water vapor in the plasma discharge has a positive influence on the aging process: lower plateau WCA values are found for plasmas containing a higher water vapor concentration and it takes a longer time to reach these plateau values. In this paper, it is also shown that storage first at a lower temperature and then aging at a higher temperature is not able to slow down the aging effect.

An atmospheric-pressure plasma jet (APPJ)-based surface treatment process was investigated for the structural (τB > 15 MPa) adhesive bonding of polyamide 6 (PA6) composites. The treated surfaces were examined by contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). Additionally, the shear strengths of single lap specimens were determined as a function of different plasma intensities and polyurethane adhesives. Our results show that APPJ leads to an increase of the surface free energy, oxygen concentration, and number of functional groups. Furthermore, the topography of the surface was significantly modified by exposure to APPJ. AFM measurements show that special attention has to be paid to the intensity of the plasma treatment to avoid melting and flattening of the PA6 surface on the nanometer scale. With optimized multiple APPJ treatments, lap shear strength of 20 MPa was achieved for the first time for this material system, allowing the material system to be employed in future automobile applications.

Advancing and receding contact angle measurements on polymer surfaces can be performed using a number of different methods. Ballistic deposition is a new method for both rapidly and accurately measuring the receding contact angle of water. In the ballistic deposition method, a pulsed stream of 0.15-μL water droplets is impinged upon a surface. The water spreads across the surface and then coalesces into a single 1.8-μL drop. High-speed video imaging shows that, on most surfaces, the water retracts from previously wetted material, thereby forming receding contact angles that agree with the receding angles measured by the Wilhelmy plate technique. The ballistic deposition method measures the receding angle within one second after the water first contacts the surface. This rapid measurement enables the investigation of polymer surface properties that are not easily probed by other wettability measurement methods. For example, meaningful contact angles of water can be obtained on the water-soluble low-molecular-weight oxidized materials (LMWOM) formed by the corona and flame treatment of polypropylene (PP) films. Use of the ballistic deposition method allows for a characterization of the wetting properties and an estimation of the surface energy components of LMWOM itself. Both corona- and flame-generated LMWOM have significant contact angle hysteresis, almost all of which is accounted for by the non-dispersive (polar) component of the surface rather than by the dispersive component. Surface heterogeneity is thus associated primarily with the oxidized functionalities added to the PP by the corona and flame treatments.

The measurements of the contact angle of the aqueous solutions of TX-100 and TX-165 mixture with propanol on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) were carried out. On the basis of the obtained results, the dependence between the cosine of contact angle and surface tension as well as between the adhesion and surface tension of the solutions in the light of the work of adhesion of the solutions to the PTFE and PMMA surface was discussed. The dependence between the adhesion and surface tension for PMMA was correlated to the surface concentration of propanol as well as TX-100 and TX-165 mixture concentration determined from the Frumkin equation at the PMMA-air, PMMA-solution and solution–air interfaces. For this purpose, the surface tension of PMMA covered by a surface active agent film was determined using the Neumann et al. equation and next the PMMA–solution interface tension was evaluated from the Young equation. The values of the surface tension of PMMA covered by propanol and surfactants mixture layer were applied to describe the changes of the adhesion work of solutions to PMMA surface as a function of propanol and surfactants mixture concentration. The adhesion work of the aqueous solutions of TX-100 and TX-165 mixture with propanol to the PTFE and PMMA surfaces was discussed in the light of the adhesion work of particular components of the solutions. On the basis of the results obtained from the contact angle measurements, the standard Gibbs free energy of adsorption of particular components of solution was also considered.

A wide variety of plasma treatments was performed on polyethylene surfaces, resulting in a wide range of total surface energies. The linear correlation of with cos θ was discussed in light of the Young–Dupré equation. Hundred percent of the surface energy variation was accounted for by the polar component of surface energy; the dispersive component was not affected by surface treatment. These data show that for this polymer the contact angle of a single polar liquid can be used as a robust quantitative indicator of treatment level, and because of its excellent linear correlation with total surface energy for this system, can be used as a quantitative measure of total surface energy.

In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO₂ photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO₂ crystal forms, TiO₂ particle sizes, and TiO₂ content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO₂ with a particle size of 5 nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4° to 19.8°, and the surface roughness of the PET film increased from 36 to 117 nm. The adhesion strength between the PET film and the electroless copper film reached 0.89 KN m⁻¹. X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO₂ photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.

Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films were treated with an atmospheric-pressure plasma (APP) jet and a 172-nm ultraviolet (UV) excimer light in air. The advancing and receding water contact angles on both films decreased after the treatments, especially after APP treatment. After the treatments, the hydrophobic recovery was observed and almost diminished within a week. The dispersive component of the surface free energy of the two polyester films did not change due to the APP and UV exposure, whereas the acid–base component drastically increased after the treatments. The X-ray photoelectron spectroscopy results showed that the polyester film surfaces were oxidized by the treatments. From the AFM images, the topographical change on the film surfaces due to the treatments was clearly observed. It was found that the APP treatment of the PET film prevented the deposition of particulate soils in air due to the decrease in the contact area between the film and the soil particle. Furthermore, the soil release in the aqueous solutions was promoted as a result of the hydrophilization of the polyester films due to the APP treatment.

This paper reports on a special pilot coating and industrial printing trial designed to gain fundamental knowledge on ink adhesion failure on coated papers. We found that ink adhesion failure resulted in white spots without ink on the paper, referred to as uncovered areas and these spots gave print mottle problems. The white spots were due to two fundamentally different types of ink adhesion failure. One is the well-known ink rejection, which simply means that ink is not transferred to the surface. The other is a new type of ink adhesion failure, confirming a previous hypothesis suggested from laboratory observations. We refer to this as ink-lift-off adhesion failure, meaning that ink initially deposited on the paper surface becomes lifted off from the surface in a subsequent print unit. Adhesion failure by this mechanism was seen to occur more frequently than failure due to the well-known ink rejection.

In the case of the peeling of adhesive tapes from soft adherends, the contributions of the compressive force at the adhered portion as well as the larger deformation of adherend have essential roles in determining the peeling properties. In this paper, the peel force of an adhesive tape from a soft adherend has been measured to understand the peeling mechanism, which is greatly affected by the peel angle. A commercially available pressure-sensitive adhesive was used as the tape, and a cross-linked polydimethylsiloxane (PDMS) was used as the soft adherend. The purpose of this study is to clarify the effects of the peel angle on the peel behavior of this system at room temperature under different material specifications and different experimental conditions. The factors that affect the peel force of the PDMS adherend included the degree of cross-linking in PDMS, the thickness of PDMS, peel angle, and peel velocity. Two characteristic peel patterns were observed, which depended on the material specifications and different experimental conditions. The peel mechanism was discussed in terms of the deformation of the adherend.

Polystyrene (PS) was treated with vacuum UV (VUV) (λ = 104.8 and 106.7 nm) photo-oxidation and X-ray photoelectron spectroscopy detected a controlled increase in the atomic percentage of oxygen up to a saturation level of ca. 20 at% O. Initially, C–O and carbonyl groups are observed due to the formation of alcohols, ethers, esters, and ketones. Water contact angle measurements showed ca. 25% increase in hydrophilicity of the surface with oxidation. Atomic Force Microscopy observed little changes in surface roughness with treatment time. The super water absorbent polymer poly(acrylic acid) was thinly grafted to the modified PS surface.

The uncertainty in contact angles from sessile drops measured by the tangent method was estimated using a standard error propagation technique involving partial derivatives. If contact angles are <60°, then uncertainty of the tangent method appears to be quite small,≤ ± 2°. However, as θ values approach 90°, uncertainty increases asymptotically and can exceed  ±5°.

The effect of atmospheric pressure plasma treatment on the adhesion between a protective coating and AA1100 alloy was investigated. Two plasma sources were used for surface modifications: atmospheric pressure plasma jet and dielectric barrier discharge. The surface roughness and water contact angle measurements were conducted in order to evaluate the changes on the aluminium surface after plasma processing. The paint coating was tested using the adhesion tape test (ASTM D3359). A significant improvement of surface wettability and adhesion was obtained after plasma treatments.

The uncertainty in contact angles from the Wilhelmy tensiometer was analyzed using standard error propagation techniques involving partial derivatives across the full range of wettability, from completely wetting to non-wetting surfaces. Uncertainties in force, sample perimeter, and liquid surface tension of 1% were shown to yield uncertainty in contact angles of a few degrees over the middle range of wettability, but exceeded 10° at the extremes.