We have subjected polycarbonate (PC), low density polyethylene (LDPE), polystyrene (PS), polypropylene (PP), and Hytrel^® (HY, a thermoplastic elastomer) to atmospheric pressure oxygen plasma treatment for varying amounts of time. Effects of the treatment have been evaluated in terms of the water wetting angle, dynamic friction, scratch resistance, and sliding wear. Although PS, PP, and HY do not undergo significant tribological changes as a result of the interaction with plasma, PC and LDPE show more pronounced and useful effects, such as a lowering of dynamic friction in PC and wear reduction in LDPE. These results can be explained in terms of the changes in chemical structures and increase of hydrophilicity. Based on the effects of oxygen plasma treatment on PC and LDPE, these two polymers have been subjected to longer oxygen plasma treatments and to argon, nitrogen, and air plasmas. Resulting effects on friction and scratch resistance are compared to determine the mechanisms responsible for the various surface behaviors. Chemical surface modification—as represented by changing contact angles—contributes to the tribological responses. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Underwater plasma and glow discharge electrolysis are interesting new methods for polymer surface functionalization. The achievable content of O-containing functional groups exceeds that of oxygen glow discharge gas plasmas by a factor of two (up to ca. 56 O/100 C). The percentage of OH groups among all O-containing groups can reach 25 to 40%, whereas it is about 10% in the gas plasmas. Addition of hydrogen peroxide increases the fraction of OH groups to at most 70% (27 OH/100 C). The liquid plasma systems are also able to polymerize acrylic acid and deposit the polymer as very thin film on substrate surfaces or membranes, thereby retaining about 80% of all COOH functional groups (27 COOH/100 C).

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.

A study of the durability of corona discharge plasma effects on a polymer surface was investigated in this work. We used the corona discharge plasma technique to modify the wettability properties of low density polyethylene (LDPE) film and evaluated the influence of relative humidity and temperature on the aging process with three different storage conditions. The effects of the aging process on the plasma-treated surface of LDPE film were quantified by contact angle measurements, Fourier-transformed infrared spectroscopy, and X-ray photoelectron spectroscopy. The results obtained with these techniques have allowed us to determine how the aging process promotes changes in the plasma-treated surface by decreasing its wettability and taking place a remarkable hydrophobic recovery process.

Low contact angle hysteresis is an important characteristic of superhydrophobic surfaces for nonstick applications involving the exposure of these surfaces to water or dust particles. In this article, a relationship is derived between the surface work of adhesion and the dynamic contact angle hysteresis, and the resulting predictions are compared with experimental data. Superhydrophobic surfaces with different contact angles and contact angle hysteresis were prepared by generating silicon pillars with varying pillar size and pitch. Surfaces were subsequently treated with fluoroalkyl silanes to modify further the hydrophobicity. The three-phase contact line established for such systems was related to the Laplace pressure needed to maintain a stable superhydrophobic state.

Parallel plates dielectric barrier discharge (DBD) at atmospheric pressure has been investigated to modify and functionalize the surface of different polymer substrates, e.g. polyolefins, poly(ethylene terephtalate), polyamide, in order to enhance their hydrophilic properties. Surface properties have been altered to meet the requirements of specific applications by introducing the appropriate functionalities through the use of either acetic acid or ethyl acetate. The coatings have been characterized through wettability measurements, labeling coupled with X-Ray photoelectron spectroscopy, and IR spectroscopy.

The effect of forced air-plasma pre-treatment, Lectro-treat (TM), on polypropylene has been investigated using X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (AR-XPS), and atomic force microscopy (AFM). The pre-treatment process is found to induce both surface chemistry changes and topographical changes. The parameters of the pre-treatment process can be optimised from these observations. The Lectro-treat pre-treatment process has been used for adhesive bonding of a demonstrator component: a bumper assembly. The adhesively bonded bumpers performed successfully in standard automotive tests.

The effects of the electron radiation dose and of compatibilizers on the contact angle and surface free energy (SFE) of the composites made of low-density polyethylene (PE-LD), high-density polyethylene (PE-HD), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) were studied. Use of the high-energy electron radiation with doses up to 300kGy and of compatibilizers was done to reach better mechanical and adhesion properties of the composites studied and, at the same time, to investigate the possibility of applying of this technique in the processes of polymeric materials recycling. The compatibilizers were the styrene-ethylene/butylene-styrene elastomer grafted with maleic anhydride (SEBS-g-MA), added at the amounts of 5, 10 or 15 wt.%, and trimethylol propane trimethylacrylate (TMPTA), added at the amounts of 1, 2 or 3 wt.%. The effects, discussed in the present article, are: enhancement of wettability and increase in SFE of the composites studied. It was found that the contact angle steadily decreased and SFE of the composites increased with the rising dose of the electron radiation and that TMPTA intensified these tendencies.

Atmospheric plasmas have traditionally been used as a non-chemical etching process for polymers, but the characteristics of these plasmas could very well be exploited for metals for purposes more than surface cleaning that is presently employed. This paper focuses on how the corona discharge process modifies aluminium AA 1050 surface, the oxide growth and resulting corrosion properties. The corona treatment is carried out in atmospheric air. Treated surfaces are characterized using XPS, SEM/EDS, and FIB-FESEM and results suggest that an oxide layer is grown, consisting of mixture of oxide and hydroxide. The thickness of the oxide layer extends to 150–300 nm after prolonged treatment. Potentiodynamic polarization experiments show that the corona treatment reduces anodic reactivity of the surface significantly and a moderate reduction of the cathodic reactivity.

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.

A study on surface modification of extended PTFE (polytetrafluoroethylene) foil after treatment in oxygen and nitrogen plasma is presented. PTFE was exposed to a weakly ionized, highly dissociated RF plasma with a high density of neutral atoms. The gas pressure was 75 Pa and the discharge power was 200 W. The appearance of the functional groups on the sample surface was determined by using high-resolution XPS. The results showed that oxygen plasma treatment did not cause any noticeable changes in the surface composition, while after nitrogen plasma treatment new functional groups were detected on the surface. Copyright © 2008 John Wiley & Sons, Ltd.

The surface chemistry and surface energies of materials are important to performance of many products and processes—sometimes in as yet unrecognized ways. This article has been written for the researchers who wish to calculate solid surface energy (SE) from contact angle data. In this article, we describe various methods of calculations and their assumptions. The theoretical and experimental approaches for understanding the solid surface free energy using various methods are discussed in this article. Researchers concerned with many fields such as printing, dyeing, coating, adhesion, pharmaceuticals, composite materials, textiles, polymers, and ceramics should have interest in this topic. SE calculated by various methods for polyethylene surface treated in air plasma is discussed. Using contact angle data, the values of surface roughness using Wenzels equation, have been obtained and correlated to surface roughness calculated from AFM data.
© 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 https://onlinelibrary.wiley.com/doi/abs/10.1002/app.27446

The influence of pigment shapes and pigment blends on the surface energy was investigated and compared with the surface chemistry of pigmented latex coatings. The coatings were made of different volume ratios of two pigments: plate-like kaolin clay pigment and prismatic precipitated calcium carbonate (PCC) pigment. These were mixed together with carboxylated styrene–butadiene–acrylonitrile latex (SBA), and applied over nonabsorbent substrates as well as absorbent substrates. The composition of the surface of the coatings was investigated by X-ray photoelectron spectroscopy (XPS). Two approaches were used to estimate the total surface energy and the components of the coatings: a conventional approach—“the Kaelble approach”—and a more modern approach—“the van Oss approach.” Pigment blends with different shapes and increments caused a change in the surface chemistry and the surface energy of the latex coatings. As the prismatic PCC pigment particles increased in the kaolin/SBA coating system, the SBA latex content at the coating surface increased and the total surface energy of the coating decreased. This is valid for both nonabsorbent as well as absorbent substrates. It was found that there was a strong correlation between the surface energy and the surface composition. The surface energy of the coatings estimated by the Van Oss approach was always lower than that estimated by the Kaelble approach. Colloidal interactions between pigment–pigment and/or pigment–binder were thought to play an essential role in determining the final coating surface energy and its components. Changes in the surface latex content and the surface energy due to the different pigment blends investigated were found to fit straight-line equations.

Poly(tetrafluoroethylene) (PTFE) surfaces are modified with remote and direct Ar plasma, and the effects of the modification on the hydrophilicity of PTFE are investigated. The surface microstructures and compositions of the PTFE film were characterized with the goniometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Results show that the remote and direct plasma treatments modify the PTFE surface in morphology and composition, and both modifications cause surface oxidation of PTFE films, in the forming of some polar functional groups enhancing polymer wettability. When the remote and direct Ar plasma treats PTFE film, the contact angles decrease from the untreated 108–58° and 65.2°, respectively. The effect of the remote Ar plasma is more noticeable. The role of all kinds of active species, e.g. electrons, ions and free radicals involved in plasma surface modification is further evaluated. This shows that remote Ar plasma can restrain the ion and electron etching reaction and enhance radical reaction.