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

It is recognized that the non-dispersive components, γ^ab, of the surface free energies, γ, play an important role in the interactions of a polymer with other substrates. Because of the difficulty in measuring the surface free energy of a solid polymer surface, many methods to estimate γ have been developed. The purpose here is to examine how to characterize a high energy polymer surface using our recently proposed model and the modified two-liquid contact angle technique. First, the dispersion component, γ^d, of surface free energy of polystyrene (PS) is obtained by measuring the contact angles of water on PS surface in a series of n-alkanes. Its γ^ab is then calculated by our three-parameter semi-empirical model using the contact angle data of several key non-alkane liquids on the surface. Given the surface thermodynamic parameters, our model also enables us to calculate the interfacial free energies, γ_SL, between PS and other liquids. An attempt to relate γ_SL to the equilibrium concentrations of crazing solvents in PS is presented.

Ultrahigh-modulus polyethylene fibers were treated with atmospheric pressure He plasma on a capacitively coupled device at a frequency of 7.5 kHz and a He partial vapor pressure of 3.43 × 10³ Pa. The fibers were treated for 0, 1, and 2 min. Microscopic analysis showed that the surfaces of the fibers treated with He plasma were etched and that the 2-min He plasma-treated group had rougher surfaces than the 1-min He plasma-treated group. XPS analysis showed a 200% increase in the oxygen content and a 200% increase in the concentration of CO bonds (from 11.4% to 31%) and the appearance of CO bonds (from 0% to 7.6%) on the surface of plasma-treated fibers for the 2-min He plasma-treated group. In the microbond test, the 2-min He plasma-treated group had a 100% increase of interfacial shear strength over that of the control group, while the 1-min He plasma-treated group did not show a significant difference from the control group. The 2-min He plasma-treated group also showed a 14% higher single-fiber tensile strength than the control group.

Ultrahigh modulus polyethylene fibers were treated with atmospheric pressure helium + oxygen plasma in a capacitively coupled device at a frequency of 7.5 kHz. The fibers were treated for 0, 0.5, 1, 1.5, and 2 min. The surfaces of the fibers treated with He + O₂ plasma were etched and micro-cracks were formed. XPS analysis showed a 65—213% increase in oxygen content on the surfaces of all plasma-treated fibers, except for the 1.5 min group. An increase in the concentration of CO and the appearance of CO bonds on the surfaces of plasma-treated fibers were observed. In the micro-bond test, He + O2 plasma-treated groups had a 65–104% increase in interfacial shear strength over that of the control. The tensile strength of the fibers was either unchanged or decreased by 10–13% by the plasma treatments.

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.

Total surface free energy, γ_S ^TOT, for several solids (glass, PMMA, duralumin, steel and cadmium) was calculated from the surface free energy components: apolar Lifshitz–van der Waals, γ_S ^LW, and acid–base electron–donor, γ_S ^-, and electron–acceptor, γ_S ⁺. Using van Oss and coworkers' approach (Lifshitz–van der Waals/acid–base (LWAB) approach), the components were determined from advancing contact angles of the following probe liquids: water, glycerol, formamide, diiodomethane, ethylene glycol, 1-bromonaphthalene and dimethyl sulfoxide. Moreover, receding contact angles were also measured for the probe liquids, and then applying the contact angle hysteresis (CAH) approach very recently proposed by Chibowski, the total surface free energy for these solids was calculated. Although the thus determined total surface free energy for a particular solid was expected to depend on the combination of three probe liquids used (LWAB approach), as well as on the kind of the liquid used (CAH approach), surprisingly the average values of the surface free energy from the two approaches agreed very well. The results obtained indicate that both approaches can deliver some useful information about the surface free energy of a solid.

The idea of the treatment of textiles with plasma is a few decennia old. There is no consensus about who was “the first,” but it is clear that the treatment of textiles is historically linked to the plasma treatment of polymers in general. As one of the most promising alternatives in many fields, the importance of plasma treatments results from the exceptional advantages it offers. It does have specific action only at the surface, keeping the bulk properties unaffected. The future of plasma is closely linked to the fact that this technique gives the treated surface some properties that cannot be obtained by conventional techniques, and this is without the need to use water as a reaction medium. At the level of textiles, this means changing an almost inert surface into a reactive one, and in this way, it becomes a surface engineering tool. The transfer of research results into the technological field would lead to nonpolluting and very promising operating conditions. In the prospect of chemical finishing using plasma, two main methods can be considered: grafting of a compound on the fiber or surface modification by means of discharges.

Polyester monofilaments were treated by a pulsed surface electrical discharge in nitrogen at atmospheric pressure, to increase their adhesion to an epoxy resin matrix. The treatment resulted in an eight-fold increase in adhesive strength, without any change in mechanical properties of the monofilaments. It is concluded that polar group interactions, rather than increased surface area, are responsible for the improved adhesive strength.

The surface free-energies of the polyethers, polyethylene glycol, polypropylene glycol, polyepichlorohydrin, and polybutylene glycol, their mixtures and their random and block copolymers were determined by means of the pendant drop method. In all cases, except that of random copolymers, surface excesses of the low surface-energy component have been found. In the mixtures of homopolymers the behavior of surface excess isotherms depends on the molecular weight of the two components, while in block copolymers it depends on the degree of polymerization of the base unit. The Belton and Evans Equation for perfect solutions and the Prigogine equation for r-mer solutions have been applied to the experimental data.

The surface tension and surface entropies of different molecular weight polyethylene glycols and polypropylene glycols have been measured. The surface entropy of a mixture of polyethylene glycol and polypropylene glycol and that of block copolymers have also been determined. In the case of homopolymers, there is no effect of molecular weight on surface free energy and the increase in free energy on passing from the interior to the surface is due mainly to the heat content with the entropic contribution being very small.

In the case of a mixture of homopolymers and block copolymers, a minimum is observed when surface entropy is plotted against composition. At any particular composition, the surface entropy of a mixture is higher than that of a block copolymer of the same composition.

Presently, it is desirable that one type of ink be suitable for printing on various substrates with different properties. Hence, the emphasis on new models and methods of printability prediction is necessary. The main objective of this work was to study and find correlation between physical properties of printing ink and substrate and finally how these properties can affect printability. For this purpose, contact angle measurement, surface tension measurement, rheology, and various methods for surface characterization of substrates were used.

The effect and interrelationship between primary (segmental backbone) and secondary (side chain) molecular motions on thrombogenesis, independent of morphological order/disorder, crystallinity, and/or associated water is elucidated using an amorphous hydrophobic polymer of poly-[(trifluoroethoxy) (fluoroalkoxy)phosphazene], PNF. The results indicate that thrombogenesis for an amorphous hydrophobic polymer is sensitive and dependent on the degrees and types of primary and secondary molecular motions at the polymer interface.

The chemical species created in a low-pressure electrical discharge in oxygen attack the polymer at the surface, converting it to gaseous products. This process is interesting because: 1) the chemical changes on the resulting surface facilitate the formation of strong adhesive bonds and provide sites for the chemical attachment of other molecules, 2) significant morphological features lying below the surface may be revealed, 3) polymer can be cleanly removed from surfaces which are resistant to oxidation, and 4) dielectric breakdown frequently is preceded by the attack on the polymer of chemical species created in a corona discharge. Atomic oxygen is an important chemical species created in such a discharge. It reacts with organic substances rapidly at room temperature, but lives long enough in the low-pressure gas that it can be separated from many other reactive species created in the discharge. “Titration” with NO₂ provides a straightforward chemiluminescent means for determining the concentration of atomic oxygen to which the sample is exposed. This paper characterizes the attack of atomic oxygen, perhaps in the presence of long lived but less reactive species such as excited O₂molecules, on polymer surfaces, using electron microscopic observations of known morphological features of polyethylene to observe the changes produced by atomic oxygen. Lamellar polyethylene crystals were attacked both at the edges and the fold surfaces. Layers many microns thick were removed from spherulitic samples and replicas obtained from the surfaces thus exposed. Thick samples were thinned to the point at which they were transparent to an electron beam and interior morphological features were directly observed.

This study systematically characterises a matrix of water-based flexographic inks with respect to their rheology, surface tension and wetting of liquid packaging board, to provide a basis for interpretation and prediction of their printing performance. For all pigment and acrylate polymer vehicles and mixing proportions the inks were shown to be shear thinning and thixotropic, with plastic viscosity, yield stress and storage and loss moduli increasing strongly with content of solution polymer (at comparable solids contents). The solution polymer decreases the static surface tension of the inks, but generally leads to an increase in their equilibrium drop contact angle on the polyethylene- (PE-) coated board due to increase in the ink-board interfacial energy. The solution polymer also decreases the drop spreading rate, and a simple model is tested to express the spreading dynamics in terms of equilibrium contact angle and a rate parameter given by the effective ratio of surface tension to viscosity.

The performance of water-based acrylic flexographic inks laboratory printed on three different polymer-coated boards, namely coated with LDPE, OPP and PP, have been analysed and interpreted. The print quality and resistance properties obtained were related to varying ink formulation, in particular choice of emulsion polymer and presence of silicone additive in the vehicle, as well as varying levels of corona pretreatment. Print mottle and adhesion were worst on PP, while wet (water) rub and scratch resistance were worst on OPP and PE, respectively. However, these properties could be greatly influenced by the ink formulation, more so than corona level. In general addition of silicone improved scratch resistance, due to reduction in polar energy component of the print surface, but at the expense of worsened wet rub resistance. The emulsion polymer giving best resistance performance was generally found to give poorest optical properties, presumably due to more limited resolubility on press.