Polyethylene (PE) is often used in several industrial applications including the building, packaging and transport industries. Aluminum (Al) is widely used in different applications in the automotive, railway, aeronautic, and naval industries because of its excellent mechanical and chemical properties. Laminates prepared from Al and PE lead to an enhancement in physical and mechanical properties. These materials play a main role in the packaging and building sectors, such as in TetraPak containers and aluminum composite panels. The main problem observed is associated with the adhesion between polymers and metals. This research focused on investigating the enhancement in the adhesion of the PE/Al laminate using the corona discharge. The corona treatment of the surfaces led to a significant increase in the adhesion of the PE/Al laminate as a result of improved surface properties confirmed by peel test measurements. Moreover, the positive effect of the corona treatment in combination with a primer on the improvement of adhesion characteristics was observed too. Different analytical techniques were employed to characterize the effect of the corona treatment on the improvement in adhesion of PE/Al. A significant increase in wettability was confirmed by the measurement of contact angles. Changes in the surface morphology of the PE and Al surface, after the corona treatments at different operating conditions, were observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In addition, x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to analyze changes in chemical composition after the corona discharge effect on PE and Al surfaces.

Polymers/metal laminates are often used to improve physical and mechanical properties, especially those required in building applications. A flat aluminum composite panel (ACP) consisted mainly of two thin metal sheets usually made of aluminum (Al) and a non-metal core, such as polyethylene (PE). The lack of adhesion associated with the low wettability of PE is a serious problem. An eco-friendly, dry, non-destructive corona treatment technique can be applied to solve this problem. In this work, the use of a corona treatment to enhance the adhesion properties of linear low-density polyethylene (LLDPE) was studied. The changes in surface and adhesion properties were thoroughly analyzed using various analytical techniques and methods to obtain the optimal parameters for corona discharge using contact angle measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). AFM force adhesion measurements were used to analyze the effect of the corona treatment on the adhesion enhancement of LLDPE, and the peel tests confirmed a significant increase in peel resistance in the LLDPE/Al laminate. A synergy effect from using the corona treatment in combination with an ethylene acrylic acid dispersion primer was observed.

Pigment-coated, surface-sized, and surface-sized copy papers were treated with conventional corona, experimental pilot-scale plasma and laboratory-scale plasma. All the treatments increased the surface energy and oxidized the surface. The changes in the surface chemistry depended on treatment time and composition of the substrate surface. It seems that plasma especially oxidizes the long polymer chains, such as surfactants and other paper chemicals, on the surface of the paper. The ToF-SIMS distribution maps indicated that the pilot-scale treatment led to an uneven CO⁺ group distribution, whereas laboratory scale treatment gave a more even distribution of CO⁺ groups. In addition to chemical changes, topographical changes due to plasma treatment were detected. The RMS roughness increased for pigment-coated paper, whereas plasma treatment induced small nodules between the paper pigment particles with pigmented and surface-sized paper. The increase in roughness was also found to increase the wettability. This serves as a demonstration of roughness-induced increase of surface energy of the samples.

The objective of this paper was to understand the effects of plasma activation, and thus influence of the surface energy and chemistry changes on offset print quality. Pigment coated and surface sized papers were treated with corona and atmospheric plasma in pilot and laboratory scales. The surface energy and surface chemistry changes were evaluated by contact angle and X-ray photoelectron spectroscopy (XPS). Offset printing was performed in laboratory scale with an IGT unit with predampening and in a pilot scale sheet-fed offset printing press. In addition, the ink setting rate was measured using an ink on paper tack tester. Plasma activation increased the surface energy of the papers. Furthermore, the polarity of the paper surface increased due to formed polar oxygen containing molecular groups. Due to differences in treatment times laboratory scale plasma treatment formed mainly carboxyl and ester groups, whereas pilot scale treatment induced mainly alcohol, ethers, aldehydes and/or ketones on paper surfaces. Printing evaluation showed that plasma activation influences both ink and water absorption properties. According to print tack results plasma activation led to faster ink-setting. With hydrophobic surface-sized paper plasma activation influenced the ink transfer, print gloss and density by changing dampening water absorption properties. The difference in surface chemistry with laboratory scale plasma treated samples was also reflected in the print quality properties. SEM imaging showed that too intense plasma activation can cause topography changes in addition to of the surface chemistry changes.

This work concerns the ageing effect of the atmospheric plasma and corona treatments when used to treat paper substrates. Pigment coated and surface sized papers were modified using two types of atmospheric plasma equipment; one at the pilot scale and one at the laboratory scale. In addition, the plasma treatments were compared to conventional corona treatment. Surface energy was estimated by contact angle measurements and surface chemistry by X-ray photoelectron spectroscopy (XPS) as a function of the time during three months. The treatments increased surface energy and oxidation level of surface for both papers. The ageing effect could be detected only in the surface energy, whereas the oxidation level remained stable during the twelve weeks. The decay in surface energy was faster during the first weeks of storage and subsequently leveled off leading to a permanent change. The permanent change was explained as a contribution of oxygen containing polar molecular groups, which were detected by XPS. The ageing effect was suggested to originate from already existing polar molecular groups, which have rotated on the surface by plasma-related process and then rotate back into the material in time. A part of the decay was also explained by the plasma cleaning model, in which the ageing effect occurred through re-contamination. Paper is a multicomponent system, where the constituents that have the lowest surface energy were suggested to migrate to paper surfaces.

The objective of this paper was to understand the effects of plasma activation, and thus influence of the surface energy and chemistry changes on offset print quality. Pigment coated and surface sized papers were treated with corona and atmospheric plasma in pilot and laboratory scales. The surface energy and surface chemistry changes were evaluated by contact angle and X-ray photoelectron spectroscopy (XPS). Offset printing was performed in laboratory scale with an IGT unit with predampening and in a pilot scale sheet-fed offset printing press. In addition, the ink setting rate was measured using an ink on paper tack tester. Plasma activation increased the surface energy of the papers. Furthermore, the polarity of the paper surface increased due to formed polar oxygen containing molecular groups. Due to differences in treatment times laboratory scale plasma treatment formed mainly carboxyl and ester groups, whereas pilot scale treatment induced mainly alcohol, ethers, aldehydes and/or ketones on paper surfaces. Printing evaluation showed that plasma activation influences both ink and water absorption properties. According to print tack results plasma activation led to faster ink-setting. With hydrophobic surface-sized paper plasma activation influenced the ink transfer, print gloss and density by changing dampening water absorption properties. The difference in surface chemistry with laboratory scale plasma treated samples was also reflected in the print quality properties. SEM imaging showed that too intense plasma

We discuss in this review how the roughness of a solid impacts its wettability. We see in particular that both the apparent contact angle and the contact angle hysteresis can be dramatically affected by the presence of roughness. Owing to the development of refined methods for setting very well-controlled micro- or nanotextures on a solid, these effects are being exploited to induce novel wetting properties, such as spontaneous filmification, superhydrophobicity, superoleophobicity, and interfacial slip, that could not be achieved without roughness.