Polystyrene films of 100 nm thickness were modified using plasma immersion ion implantation (PIII) with argon ions of energy 20 keV and fluences in the range 2 × 10 ¹⁴-2 × 10 ¹⁶ ions cm ^-2. The structure and properties of the films were determined by ellipsometry and FTIR spectroscopy, as well as AFM, wetting angle measurements, profilometry and optical microscopy. The effects of oxidation, carbonization, etching and gel-formation were observed. The etching rate was found to decrease with PIII fluence. The rates of degradation with increasing fluence of the aromatic and aliphatic parts of the polystyrene macromolecule were found to be similar. Oxidation of the polystyrene film ceases at fluences greater than 10 ¹⁵ ions cm ^-2. The surface morphology of the film did not change with PIII fluence. Washing with toluene produced surface wrinkling for low fluences up to 10 ¹⁵ ions cm ^-2 while at high fluences the modified films were stable.

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 surfaces of polyester (PET) fabrics and foils were modified by low-pressure RF plasmas with air, CO₂, water vapor as well as Ar/O₂ and He/O₂ mixtures. To increase the wettability of the fabrics, the plasma processing parameters were optimized by means of a suction test with water. It was found that low pressure (10–16 Pa) and medium power (10–16 W) yielded a good penetration of plasma species in the textile structure for all oxygen-containing gases and gaseous mixtures used. While the wettability of the PET fabric was increased in all cases, the Ar/O₂ plasma revealed the best hydrophilization effect with respect to water suction and aging. The hydrophilization of PET fabrics was closely related to the surface oxidation and was characterized by XPS analysis. Static and advancing contact angles were determined from the capillary rise with water. Both wetting and aging demonstrated a good comparability between plasma-treated PET fabrics and foils, thus indicating a uniform treatment. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1452–1458, 2006
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.24308

The influence of corona treatment on the near-surface structures of treated ultra-high-molecular-weight polyethylene (UHMWPE) fibers was studied first by atomic force microscopy (AFM). AFM pictures showed that the pits on the corona-treated PE fiber surfaces had different change characteristics in depth compared with in length and breadth with variations of corona power. Then the UHMWPE fibers were subjected to chemical modification following the corona treatment, named the two-stage treatment. Surface morphologies and chemical properties of the treated fibers were analyzed by scanning electron microscopy (SEM), FT-IR–ATR spectroscopy and Raman spectroscopy. The results obtained suggested that some carbon–carbon double bonds had been introduced on the surfaces of the PE fibers after the two-stage treatment. These unsaturated groups could participate in free-radical curing of vinylester resin (VER), and this resulted in improvement of interfacial adhesion strength in the PE fiber/VER composites. In addition, the mechanical properties of the UHMWPE fibers reduced after corona treatment did not reduce further after subsequent chemical treatment with increase of corona power. In short, the two-stage treatment proved to be effective in improving the interfacial adhesion of the composites and maintaining the high mechanical properties of the PE fibers, as this treatment method did not destroy the bulk structure of the UHMWPE fibers.

A cross-web non-uniformity ('laning') in the flame surface modification of polypropylene (PP) film was investigated using flame temperature measurements and Wilhelmy plate force measurements. To associate the cross-web non-uniformity in the flame treatment with specific features of the flame supported on an industrial 4-port ribbon burner, the temperature and force measurements were registered to a specific burner port. The Wilhelmy force measurements show that the upstream pair of ribbon-burner ports causes a slightly greater treatment of the PP surface than the corresponding downstream pair of ports. The average temperature experienced by the PP as the film traverses through the flame is noticeably higher along the down-web line of the upstream burner ports as compared with a line passing through the downstream pair. This greater average temperature correlates to an exposure to a greater concentration of the active species, such as OH radicals, that cause the surface oxidation of the PP.

Poly(phenylene sulfide) (PPS) films were modified by Ar, O₂, N₂ and NH₃ plasmas in order to improve their adhesion to copper metal. All four plasmas modified the PPS film surfaces, but the NH₃ plasma modification was the most effective in improving adhesion. The NH₃ plasma modification brought about large changes in the surface topography and chemical composition of the PPS film surfaces. The peel strength for the Cu/plasma-modified PPS film systems increased linearly with increasing surface roughness, R_a or R_rms, of the PPS film. The plasma modification also led to considerable changes in the chemical composition of the PPS film surfaces. A large fraction of phenylene units and a small fraction of sulfide groups in the PPS film surfaces were oxidized during the plasma modification process. Nitrogen functional groups also were formed on the PPS film surfaces. The NH₃ plasma modification formed S—H groups on the PPS film surfaces by reduction of S—C groups in the PPS film. Not only the mechanical interlocking effect but also the interaction of the S—H groups with the copper metal may contribute to the adhesion of the Cu/PPS film systems.

The effects of atmospheric air-plasma treatments on woven and non-woven polyester (PET) textile structures were studied by surface analysis methods: wettability and capillarity methods, as well as atomic force microscopy/lateral force microscopy (AFM/LFM). The water contact angle on plasma-treated PET decreased from 80° to 50–40°, indicating an increase in the surface energy of PET fibres due to a change in the fiber surface chemical nature, which was confirmed by a higher fiber friction force measured by the LFM. The extent of water contact angle decrease, as well as the wash fastness of the treatment varied with the structure of the textile. Indeed the more porous the textile structure is (such as a non-woven), the fewer are the chain scissions of the PET at the fiber surface, during the plasma treatment. Thus, the level of surface oxidation and the weak boundary layers formation depend not only on plasma treatment parameters but also on the textile structure.

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N{2 } plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.

Single-type functionalizations with different types of functional groups at polypropylene (PP) and polytetrafluoroethylene (PTFE) surfaces were achieved using, instead of a simple plasma modification, either a combined plasmachemical–chemical process or the pulsed plasma-initiated homo-or copolymerization of monomers carrying functional groups. The combined process consists of O2 plasma pretreatment and wet-chemical reduction of O functional groups to OH groups using diborane, vitride (sodium bis (2-methoxyethoxy) aluminum hydride), or LiAlH4. The high degree of retained chemical structure and functional groups during the low-power pulsed plasma polymerization was found to be a prerequisite for producing well-defined, adhesion-promoting plasma polymer layers as model surfaces with high concentrations of exclusively or predominantly one type of functional group, such as OH, NH2, or COOH. The maximum concentrations of functional groups were found to be 31 OH, 21 NH2 or 25 COOH groups/100 C atoms using allyl alcohol, allylamine, or acrylic acid, respectively, as monomers in the plasma polymerization process and 14 OH groups/100 C atoms by applying the combined O2 plasma/diborane reduction process. To vary the density of functional groups, a so-called plasma-initiated gas-phase radical copolymerization with ethylene or styrene as a “chain-extending” comonomer, or butadiene as “chemical crosslinker” was employed. The peel strength of evaporated aluminum layers on unspecifically oxygen-plasma functionalized polypropylene (PP) and polyethylene (PE) shows in each case a maximum at 20 O per 100 C atoms. Initially the peel strength increased linearly with the concentration of functional groups when PP or polytetrafluoroethylene (PTFE) substrates were coated with plasma polymers or copolymers carrying a single type of adhesion-promoting functional groups. The ranking of the adhesion-promoting effect is CH2< NH2 (OH< COOH, and corresponds to the tendency to form chemical bonds between aluminum and the different functional groups.

Gas discharge plasma treatment can be used to modify the surface properties of biomaterials for a variety of biomedical applications. An established application is the use of oxygen and nitrogen plasmas to improve the hydrophilicity of surfaces, encouraging cell attachment and subsequent growth. The physical properties and surface chemistry of the biomaterial influences cell attachment and subsequent culture. In-situ cells are surrounded by a complex extracellular matrix (ECM) containing fibronectin, laminin, collagen types I-V, and proteoglycans. In this study, ammonia and sulphur dioxide gases have been chosen with the objective of incorporating carboxylic acid, sulphur and nitrogen containing groups on the surface.

Paperboard was coated on a pilot scale using aqueous dispersions of styrene–butadiene (SB) copolymers in order to improve its surface characteristics (including printability) and barrier properties with regard to the transmission of water vapour. Coating the paperboard with the dispersion in two steps gave a smoother surface with a remarkable increase in gloss. The printing properties of the smoother double-coated surface were slightly better than those of the single-coated surface. Paraffin wax added to the latex dispersion reduced the water vapour transmission rate (WVTR) but had a negative effect on the printability of the board.

The effect of two commonly used surface treatment techniques (corona and plasma at atmospheric pressure) on the printing and barrier properties of dispersion-coated (containing wax) paperboard was evaluated. A fairly intense corona treatment led to an undesirable increase in the WVTR-value. A less intense corona treatment preserved the WVTR-value to a great extent, but the printability remained at an unsatisfactory level. With plasma treatment, the water vapour barrier was not impaired, and the printability of the plasma-treated dispersion-coated (wax-containing) substrate was good. It is suggested that a better result using corona treatment may be obtained by optimising the power and controlling the time between the treatment and the printing, although this was not investigated here.

This work reports a methodology to improve the adhesion between poly(ethylene terephthalate) (PET) fibers and poly(hydroxyethyl methacrylate) (pHEMA) hydrogels by treating PET with ozone. The surface chemistry of PET was examined by water contact angle measurements, X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS) and attenuated total reflectance infrared spectroscopy (ATR-IR) yielding information about the chemical functionalities at depths upon 0.6 μm. Ozone treatment introduces several polar groups in the surface of PET through oxidation and chain scission resulting in increased wettability. These groups include mostly carboxylic and anhydride groups and in small extent hydroxyl groups. Atomic force microscopy (AFM) analysis shows that the surface of ozone-treated PET films is fully covered with spherical particles that are removed after washing the film with water. During the washing step carboxylic functionalities were removed preferentially, as demonstrated by XPS and IR analysis. According to pull-out tests, PET monofilaments and bundles treated by ozone had a higher adhesion to pHEMA hydrogels than untreated ones. The apparent interfacial shear strength is 65% higher on pHEMA hydrogel containing an ozonated than an untreated PET monofilament. In addition, the force to pull-out an ozone-treated PET bundle from pHEMA hydrogel is ca. 81% higher than the one observed for the untreated bundle.

This chapter discusses the physicochemical principles of surface phenomena, and provides an overview of the research regarding surface properties of biopolymers used for the manufacturing of biodegradable films. Surface properties of food packaging polymers, such as wettability, scalability, printability, dye uptake, resistance to glazing, and adhesion to food surfaces or other polymers are of central importance to food packaging designers and engineers with respect to product shelf-life, appearance, and quality control. The most commonly used food packaging polymers are low-density polyethylene, high-density polyethylene, polypropylene, polytetrafluoroethylene, and nylon. In recent years, environmental concerns have increased the interest in preparing biodegradable packaging materials. Proteins and polysaccharides are the biopolymers of prime interest, since they can be used effectively to make edible and biodegradable films to replace short shelf-life plastics. Surface properties of biopolymers provide a supplementary understanding of film behavior, leading to an enhanced design of packaging materials for specific applications.

The peel strength of aluminium to polypropylene and poly(tetrafluoroethylene) was determined in dependence on the type and the concentration of functional groups on the polymer surface. For this purpose the polymer surface was equipped with monotype functional groups. The first method to produce monotype functionalized surfaces was an introduction of O functional groups using an oxygen plasma treatment and converting these groups to OH groups applying a wet chemical reduction. In result of this two-step treatment the hydroxyl group concentration at the polymer surface could be increased from 3–4 to 10–14 OH groups/100 C atoms. The second method consists in the deposition of a 150 nm adhesion-promoting layer of plasmapolymers or copolymers onto the polymer surface using the pulsed plasma technique. For that purpose functional groups carrying monomers as allyl alcohol, allylamine and acrylic acid were used. Applying the plasma-initiated copolymerization and using neutral “monomers” like ethylene or butadiene the concentration of the functional groups was varied.

A correlation of peel strength with the ability of forming chemical interactions between Al atoms and functional groups was found: COOH > OH >> NH₂ > H(CH₂–CH₂).

The effect of Ar, Ar/C2H5OH, O2 and Ar/O2 RF (13.56 MHz) plasma treatments on surface free energy and morphology, optical properties and adhesion of polycarbonate (PC) substrates has been studied. Changes in the surface properties were followed as a function of the plasma treatment time. The polar and dispersion components of the polymer free surface energy were determined on the basis of the theory of Owens, Wendt, Kaelble and Uy. It was found that all RF plasma treatments led to an increase in the polar component of PC, mainly due to an increased hydrogen bonding ability. The increase in surface free energy reached its maximum at short plasma treatment with 3:1 gas mixture of Ar/O2. This treatment also led to pronounced improvement of the adhesion of thin SiO2 films plasma deposited on modified PC substrates, while the treatments with pure oxygen or Ar/ethanol plasma had negative effect on the adhesion.

Poly(tetrafluoroethylene) and a fluoroethylene copolymer were surface treated with a 2.45-GHz microwave plasma to enhance their adhesion to a vinylester thermoset. The plasmas were generated with an inert gas (Ar) and with reactive gases (H₂, O₂, and N₂). The lap-joint shear stress was measured on fluoropolymer samples glued with the vinylester. In general, the stress at failure increased with increasing plasma-energy dose. The H₂ plasma yielded the best adhesion, and X-ray photoelectron spectroscopy revealed that it yielded the highest degree of defluorination of the fluoropolymer surface. The defluorination efficiency declined in the order H₂, Ar, O₂, and N₂. Contact angle measurements and scanning electron microscopy revealed that the surface roughness of the fluoropolymer depended on the rate of achieving the target energy dose. High power led to a smoother surface, probably because of a greater increase in temperature and partial melting. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 838–842, 2005
https://onlinelibrary.wiley.com/doi/abs/10.1002/app.22174

This paper describes theoretical and experimental investigations of the effect of an electrode coating on the onset voltage of a corona on negatively stressed electrodes. Dielectric-coated hemispherically-capped rod-to-plane gaps positioned in air are investigated. The onset voltage is calculated based on the self-recurring single electron avalanche developed in the investigated gap. Accurate calculation of the electric field in the vicinity of a coated rod and its correlation to the field values near a bare rod of the same radius are obtained using the charge simulation method. The calculated field values are utilized in evaluating the onset voltage of the corona. Also, laboratory measurements of the onset voltage on bare and coated electrodes are carried out. The effects of varying the field nonuniformity, the coating thickness and its permittivity on the onset voltage values are investigated. The results show that coating the electrodes with a dielectric material is effective in increasing the onset voltage of the corona on its surface. The calculated onset voltage values for coated and bare electrodes agree satisfactorily with those measured experimentally.