A novel method combining corona treatment and Bristow’s wheel has been developed to study the effect of corona charging on immediate liquid-substrate interactions. The assembly makes it possible to study the effects of in-line corona treatment, where the delay between the charging and the application of ink is very short but is adjustable from milliseconds to hours or days. The short delay between these process phases is a prerequisite when studying and interpreting liquid wetting and sorption phenomena on substrates, because polar species and polarization effects formed during corona treatment may be both short-and long-lived and the influence of short-lived effects on immediate liquid-substrate interactions can be significant. The study focuses on evaluating the effects of direct current corona treatment on inkjet ink absorption mechanisms and printability. The substrates were fine papers surface-treated with cationic polydiallyldimethyl ammonium chloride, anionic sodium carboxymethyl cellulose and anionic fumed silica-based formulations. Both positive and negative direct current corona treatments were studied and it was found that corona treatment increased the optical density of the ink layer and reduced the mottling of ink tracks, indicating a change in the ink setting process. As expected, contact time was an important variable affecting the ink absorption behavior and the visual quality of the ink track. The absorption-normalized density values revvealed significant differences between the substrates.

Cellulose is a biodegradable, renewable, flexible, inexpensive biopolymer that is abundant in nature. However, due to its hydrophilicity, applications of cellulose (paper) in the handling of liquids are severely limited. Appropriate plasma-or glow discharge-assisted processing sequences can be used to modify the surface of cellulose/paper so that the interaction of liquids with these surfaces can be altered. In particular, nanostructures associated with crystalline regions of cellulose fibers can be uncovered by plasma-enhanced etching; subsequent plasma-enhanced fluorocarbon film deposition (~ 100 nm) converts the surface into a superhydrophobic (static water contact angle> 150o; receding contact angle< 8o) state. Similar results can be obtained by depositing diamond-like carbon films on the plasmaetched surface, in spite of the inherently hydrophilic nature of diamond-like carbon itself. In addition, droplet adhesion and mobility can be controlled; depending on the etch cycle parameters, the paper surface can be rendered ‘roll-off’or ‘sticky’superhydrophobic. Use of a commercial printer to generate hydrophobic ink patterns on superhydrophobic paper surfaces allows controlled movement, transfer and storage of water or other aqueous liquids on the paper surface. These basic functionalities can be combined to design simple two-dimensional lab-on-paper (LOP) devices. Finally, by controlling both the cellulose fiber size and spacing, and depositing a fluorocarbon film, paper surfaces can be rendered superomniphobic, repelling both polar and apolar liquids.

An atmospheric-pressure plasma jet (APPJ) is used to increase the wettability of polypropylene (PP) polymer films. Reduction in contact angle from 95 to 50 degrees was measured for treatment times of 1 - 10 seconds. Contact angle reductions of PP as a function of distance between APPJ and PP surface, and oxygen gas admixture, suggest that the surface reaction mechanism is related to the atomic oxygen density produced in the APPJ.

This study aims to verify the effectiveness of a biodegradable PLA coating on biaxially oriented poly ethylene terephthalate (BOPET) films substrates in order to develop a biodegradable sealant layer for improving the functional properties of polyester films. In particular, this work focuses on the evaluation of different surface treated BOPET films to understand the effect of typical polyester substrate treatments on the adhesion of the PLA coating. At this purpose the film’s surface properties and topography have been characterized respectively by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and by atomic force microscopy (AFM); while their surface tension has been analyzed by contact angle tests. Furthermore, the PLA coating adhesion to different BOPET webs has been assessed by delamination tests and dynamical mechanical analysis. In addition, to evaluate the optical properties haze and transparency measures have been performed. It was found that corona treatment proves to be more effective in increasing surface energy and roughness of substrate with respect to a chemical treatment. The coating adhesion to corona treated BOPET was higher compared to the neat and the chemical treated BOPET films. Improvement in adhesion of PLA on corona treated BOPET was interpreted on the basis of surface oxidation due to the electrical discharge as showed by AFM and ATR-FTIR analyses. Indeed the increase of both contact surface and functional groups able to form hydrogen bonds and other molecular interactions, allow to a better interface interaction between the two layers.

Enhancement of the surface wettability and surface free energy of thermoplastic materials is an effective way of improving their adhesion and consequently the adhesive joint strength. A nanosecond pulsed Nd:YAG laser was selected in this work to provide energetic treatment of PEEK surfaces, in order to investigate its effectiveness in increasing the performance of lap shear adhesive joints. The laser was used to irradiate the PEEK, by rastering a spot of ca. 1 mm diameter across a large area. The resulting surfaces were characterised using single lap shear testing, confocal laser scanning microscopy, contact angle analysis, FT-IR, XPS and ToF-SIMS. Single lap shear testing of PEEK joints showed that the strength of adhesively bonded joints is greatly improved by laser treatment, up to 13 times that of untreated PEEK. Confocal laser scanning microscopy showed that the higher laser power intensities (≥107 W mm−2) disrupted the surface of the PEEK more than the lower laser power intensities (<107 W mm−2), but also showed that, as expected, only some of the surface is treated by the laser. Contact angle analysis showed a decrease in water contact angle with increasing laser power intensity, and the derived surface free energy increased accordingly. FT-IR in the specular reflectance mode showed no discernible change but XPS and ToF-SIMS did, suggesting that laser treatment only affects the near surface at the extremity of the 1–2 μm sampling depth. XPS showed a decrease in the carbon/oxygen ratio of PEEK on treatment, indicating that oxygen-containing functional groups were being created at the surface. XPS also suggested a cleaning mechanism at a laser intensity of 7.83×106 W mm−2, progressing to surface modification from a laser intensity of 107 W mm−2 and above. ToF-SIMS confirmed that laser treatment cleans the surface of PEEK of extraneous material.

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.

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.

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.

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.

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.

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.

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.

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.

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.

An overview of surface modification and coating techniques for plastics is presented for changing the surface properties to meet the performance requirements in a variety of applications. Surface modification and coatings are utilized for purposes of adhesion, wettability, biocompatibility, scratch and abrasion resistance, chemical resistance, barrier properties, and more. Methods for modification include physical processes, such as surface roughening and abrading; liquid chemical processes, such as acid etching; and reactive gas chemical processes. The reactive gas chemical processes covered include corona, flame, and low-temperature plasma. Surface degradation from reactive gas exposure is presented with respect to the sources, chemical mechanisms, and methods for characterization. Coatings for plastics, including paints, functional coatings, and metallization, are summarized.