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656. Vargo, T.G., and J.A. Gardella Jr., “Modification of surfaces designed for cell growth studies,” in Polymer - Solid Interfaces, Pireaux, J.J., P. Bertrand, and J.L. Bredas, eds., 485-494, Institute of Physics Publishing, 1991.

587. Varughese, K.T., P.P. De, and S.K. Sanyal, “Contact angle behavior of poly(vinyl chloride)/epoxidized natural rubber miscible blends,” J. Adhesion Science and Technology, 3, 541-550, (1989).

Contact angle studies of miscible poly(vinyl chloride)/epoxidized natural rubber (PVC/ ENR) blends were carried out in air using water and methylene iodide. The solid surface free energy was calculated from harmonic mean equations. Blending of PVC and ENR decreased their contact angle or increased their solid surface free energy due to the improved chain mobility, and the accumulation of excess polar sites at the surface through conformational alterations resulting from the specific interaction of PVC and ENR. The work of adhesion, interfacial free energy, spreading coefficient, and Girifalco-Good's interaction parameter changed markedly with the blend composition. In blends, PVC and ENR improved hydrophilicity, and wettability with polar and non-polar liquids. The presence of a plasticizer in PVC, in general, further improved the wettability and hydrophilicity in blends.

588. Vavruch, I., “On the determination of the factor between cohesive energy density and surface tension,” J. Colloid and Interface Science, 63, 600+, (1978).

589. Vavruch, I., “On the relation between surface energy, internal pressure and molar volume in pure fluids,” Colloids and Surfaces, 30, 405+, (1988).

2531. Vesel, A., I. Junkar, U. Cvelbar, J. Kovac, and M. Mozetic, “Surface modification of polyester by oxygen- and nitrogen-plasma treatment,” Surface and Interface Analysis, 40, 1444-1453, (Nov 2008).

In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 1015 m−3, and the neutral atom density was about 4 × 1021 m−3 for oxygen and 1 × 1021 m−3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen-plasma-treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen-plasma-treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma-treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.

2532. Vesel, A., M. Mozetic, A. Hladnik, J. Dolenc, J. Zule, S. Milosevic, et al, “Modification of ink-jet paper by oxygen-plasma treatment,” J. Physics D: Applied Physics, 40, 3689-3696, (2007).

A study on oxygen-plasma treatment of ink-jet paper is presented. Paper was exposed to a weakly ionized, highly dissociated oxygen plasma with an electron temperature of 5 eV, a positive-ion density of 8 × 1015 m−3 and a density of neutral oxygen atoms of 5 × 1021 m−3. Optical emission spectroscopy (OES) was applied as a method for detection of the reaction products during the plasma treatment of the paper. OES spectra between 250 and 1000 nm were measured continuously during the plasma treatment. The wettability of the samples before and after the plasma treatment was determined by measuring the contact angle of a water drop. The appearance of the surface-functional groups was determined by using high-resolution x-ray photoelectron spectroscopy (XPS), while changes in the surface morphology were monitored with scanning electron microscopy (SEM). Already after 1 s of the plasma treatment the surface, which was originally hydrophobic, changed to hydrophilic, as indicated by a high absorption rate of a water drop into the paper. The OES showed a rapid increase of the CO and OH bands for the first few seconds of the plasma treatment, followed by a slow decrease during the next 40 s. The intensity of the O atom line showed reversed behaviour. The XPS analyses showed a gradual increase of oxygen-rich functional groups on the surface, while SEM analyses did not show significant modification of the morphology during the first 10 s of the plasma treatment. The results were explained by degradation of the alkyl ketene dimer sizing agent during the first few seconds of the oxygen-plasma treatment.

2533. Vesel, A., M. Mozetic, and A. Zalar, “XPS characterization of PTFE after treatment with RF oxygen and nitrogen plasma,” Surface and Interface Analysis, 40, 661-663, (Apr 2008).

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.

2985. Vesel, A., and M. Mozetic, “Surface modification and ageing of PMMA polymer by oxygen plasma treatment,” Vacuum, 86, 634-637, (Jan 2012).

We present a study on ageing of polymethyl methacrylate (PMMA) polymer treated with oxygen plasma. Oxygen plasma was created with an RF generator operating at a frequency of 27.12 MHz and a power of 200 W. The oxygen pressure was 75 Pa. The samples were treated for different time from 5 s to 60 s. The chemical modifications of the surface after plasma treatment were monitored by XPS (X-ray photoelectron spectroscopy), while the wettability and ageing effects were studied by WCA (water contact angle measurements). The samples were aged in dry air or in water. In the case of dry air, the least pronounced ageing was observed for the sample treated for 60 s. For samples aged in water, however, the lowest ageing rate was observed for the sample treated for 5 s. The samples were ageing slightly faster in water than in air. We also investigated the temperature effect on ageing of plasma treated samples. A set of samples was stored in a refrigerator at 5 °C and the other set was placed into an oven at 50 °C. The ageing rate of the samples stored at 5 °C was significantly lower than for the samples stored at 50 °C, so cooling the samples help keeping the required surface properties.An atmospheric pressure plasma syste

887. Veselovsky, R.A., and V.N. Kestelman, Adhesion of Polymers, McGraw-Hill, Dec 2001.

590. Vetelino, K.A., et al, “A novel microsensor technique for polymer surface characterization,” in ANTEC 95, Society of Plastics Engineers, 1995.

1751. Vieira de Vasconcelos Villaca Pinto, G., et al, “Effect of the corona treatment and of the 1,4-cyclohexanedimethanol on the surface characteristics of the poly(ethylene terepthalate) film,” in Polymer Characterization (Macromolecular Symposia 148), W. Brostow, N.A. D'Souza, V.M.C. Menesses, and M. Hess, eds., 333-343, Wiley-VCH, Jan 1999.

Several techniques have been applied for the characterization of three PET films surfaces: homopolymer PET film, corona treated PET film and a poly(ethylene terephthalate‐co‐1,4‐cyclohexanedimethanol) film. The objective of this work is to investigate and to apply precise and mutually complementary techniques which give detailled information about theses surfaces, as there are few papers with global and conclusive results. The film surfaces were investigated to support the development of new products and envisage new apllications to the existent films. Scanning electron micrographs, attenuated total reflection Fourier transform infrared spectroscopy (FTIR‐ATR) and multiple internal reflection Fourier transform infrared spectroscopy (FTIR‐MIR) spectra show that the chemical composition, topography and surface roughness of the films are different. The corona‐treated PET film shows high surface tension value due to the major contribution on the polar groups and oxidation level acquired. The copolyester film is much less crystalline than the other films analyzed, as demonstrated by refractive index measurements and X‐ray photoelectron spectroscopy (XPS). The amorphous structures obtained and the high tension level of the corona‐treated films provide a better understanding of the adhesion phenomena. In view of results obtained, one can assume that corona treated films owing to its higher surface tension and films with CHDM owing to its surface amorphization should provide manufacturing industries better processing conditions than films without surface treatment and also higher levels of adhesion to paints and coatings.

2419. Villermet, A., F. Coeuret, and J. Delumeau, “Device for the zonal surface treatment of an article by dielectric barrier discharge,” U.S. Patent 7699022, Apr 2010.

2562. Villermet, A., P. Cocolius, G. Rames-Langlade, F. Coeuret, et al, “ALDYNE surface treatment by atmospheric plasma for plastic films converting industry,” Surface and Coatings Technology, 174-175, 899-901, (Oct 2003).

Based on the Corona process and a substitution of air with specific gaseous mixtures into the discharge area, the newly developed surface treatment ALDYNE™ offers both high level improvement and high flexibility to film converters. By grafting nitrogen-based chemical functions, it confers to the treated surface excellent properties such as high surface energy and high adhesion of coatings.

2706. Vitchuli, N., Q. Shi, J. Nowak, R. Nawalakhe, M. Sieber, M. Bourham, X. Zhang, and M. McCord, “Atmospheric plasma application to improve adhesion of electrospun nanofibers onto protective fabric,” J. Adhesion Science and Technology, 27, 924-938, (2013).

Nylon 6 electrospun nanofibers were deposited on plasma-pretreated woven fabric substrates with the objective of improving adhesion between them. The prepared samples were evaluated for adhesion strength and durability of nanofiber mats by carrying out peel strength, flex resistance, and abrasion resistance tests. The test results showed significant improvement in the adhesion of nanofiber mats on woven fabric substrates due to atmospheric plasma pretreatment. The samples also exhibited good flex and abrasion resistance characteristics. X-ray photoelectron spectroscopy and water contact angle analyses indicate that plasma pretreatment introduces radicals, increases the oxygen content on the substrate surface, and leads to formation of active chemical sites that may be responsible for enhanced cross-linking between the substrate fabric and the electrospun nanofibers, which in turn increases the adhesion properties. The work demonstrates that the plasma treatment of the substrate fabric prior to deposition of electrospun nanofiber mats is a promising method to prepare durable functional materials.

703. Voelkel, A., E. Andrzejewska, R. Maga, and M. Andrzejewski, “Dispersive and acid-base properties of poly(dimethacrylate)s surfaces,” Presented at First International Congress on Adhesion Science and Technology, Oct 1995.

591. Vogel, S.L., and H. Schonhorn, “Adhesion of evaporated films onto polyethylene and poly(tetrafluorethylene): importance of surface crosslinking,” J. Applied Polymer Science, 23, 495+, (1979).

Ni, Fe, Ti, Al, Au, and Cu were each evaporated and deposited onto both sides of polyethylene and poly(tetrafluoroethylene) (PTFE) films. Adhesive joint strengths of the different metal–polymer–metal composites were compared and subsequent surface modifications due to metalization were investigated. Studies show no change in wettability of polyethylene or PTFE after a metal layer was deposited onto their surfaces and subsequently removed. There was also no evidence of oxidation or unsaturation of the surface. Gel fractions of polyethylene show a definite correlation between joint strength and crosslink at the surfaces of the different metal–polymer composites. Metals forming the strongest joints with polyethylene yield the greatest amount of crosslinking. Conversely, metals forming the weakest joints result in the least amount of crosslinking.

620. Vogler, E.A., “On the origins of water wetting terminology,” in Water in Biomaterials Surface Science, Morra, M., ed., 149-182, John Wiley & Sons, Sep 2001.

2342. Von der Heide, J.C., “Guide to corona film treatment,” Plastics Engineering, 17, 199-205, (May 1961).

1600. Vrbanac, M.D., and J.C. Berg, “The use of wetting measurements in the assessment of acid-base interactions at solid-liquid interfaces,” J. Adhesion Science and Technology, 4, 255+, (1990) (also in Acid-Base Interactions: Relevance to Adhesion Science and Technology, K.L. Mittal and H.R. Anderson Jr., eds., p. 67-78, VSP, Nov 1991).

It is now generally recognized that the principal forces contributing to the work of adhesion between two phases, WA, are the Lifshitz-van der Waals forces (which include a small contribution from permanent and induced dipoles) and acid-base interactions, taken in the most general 'Lewis' sense. One may thus write WA = WLWA + wabA = 2√σLWLWL + fN(-ΔHab), where WLWA and WabA are the Lifshitz-van der Waals and acid-base contributions to the work of adhesion, and σLWS and σLWL are the Lifshitz-van der Waals contributions to the surface free energies of the solid and the liquid, respectively; ΔHab is the enthalpy (per mol) of the acid-base adduct formation between the acid or base functional groups on the adherend and in the adhesive; N is the number (moles) of accessible functional groups per unit area of the adherend; and f is an enthalpy-to-free energy correction factor (which has normally been assumed to be ~1). The present work seeks to evaluate WabA for several systems using wetting measurements and, for at least one system, to obtain a quantitative check of the above equation using independently measured values of f, N, and (ΔHab). The total work of adhesion is determined from the measured surface tension of the liquid, σL' and its contact angle, 0, against the solid: WA= σL(1 + cos ). σLWS and σLWL are determined using probe liquids, N is determined from conductometric titrations of the solid in finely divided form, and ΔHab is determined by flow microcalorimetry. f is determined from a Gibbs-Helmholtz analysis of surface tension and contact angle data obtained over a range of temperatures. Conclusions reached are that the f factor is significantly below unity in most cases and that even including this effect, the above equation is still not verified quantitatively when the terms are measured independently.

2075. W. Keiko, A. Shin'ya, M. Shuichi, T. Kiyoshi, and F. Akio, “Application of flame treatment for degreasing aluminum foil,” Keikinzoku Gakkai Taikai Koen Gaiyo, 93, 263-264, (1997).

592. Waddington, S., and D. Briggs, “Adhesion mechanisms between polymer coatings and polypropylene studied by X-ray photoelectron spectroscopy and secondary ion mass spectrometry,” Polymer Communications, 32, 506-508, (1991).

1438. Wade, G.A., W.J. Cantwell, and R.C. Pond, “Plasma surface modification of glass fibre-reinforced nylon-6,6 thermoplastic composites for improved adhesive bonding,” Interface Science, 8, 363-373, (Oct 2000).

The surface modification and adhesive bonding of a unidirectional GFRP Nylon-6,6 thermoplastic composite has been investigated. Wettability studies of plasma-treated specimens showed a significant reduction in the advancing and receding contact angles in water, relative to untreated material. The most effective treatment used oxygen plasma. The increases in wettability observed were determined to be the result of (a) an increase in the concentration of oxygen- and nitrogen-containing functional groups on the surface of the polymer and, (b) removal of fluoropolymer contamination, the source of which was identified as the PTFE mould release agent. This was established by SSIMS analysis. The surface modification resulted in significantly improved adhesion between the composite and an applied toughened epoxy adhesive; a considerable increase in the Mode II critical strain energy release rate, GIIc, was observed following plasma treatment. Specimens treated in an oxygen plasma showed the greatest improvement in GIIc, failing cohesively at a value of 1.6 kJ·m−2 after only 15 seconds exposure. Without plasma treatment the specimens failed in an adhesive mode at very low values of GIIc. Adhesion was further optimised by moulding the GFRP Nylon-6,6 against steel plates instead of PTFE.

2398. Wadsworth, L.C., and P.P. Tsai, “Method and apparatus for the electrostatic charging of web or film,” U.S. Patent 5686050, Nov 1997.

375. Wagner, H.D., “Spreading of liquid droplets on cylindrical surfaces: accurate determination of contact angle,” J. Applied Physics, 67, 1352-1355, (1990).

The wetting of cylindrical monofilaments by liquid polymers is a problem of much scientific and technological importance. In particular, the characterization of the physicochemical nature of interfaces is a key problem in the field of advanced fibrous composites. The macroscopic regime contact angle, which reflects the energetics of wetting at the solid-liquid interface, is difficult to measure by usual methods in the case of very thin cylindrical fibers.

In the present article a numerical method is proposed for the calculation of macroscopic regime contact angles from the shape of a liquid droplet spread onto a cylindrical monofilament. This method, which builds on earlier theoretical treatments by Yamaki and Katayama [1], and Carroll [2], very much improve the accuracy of the contact angle obtained. Experimental results with high-strength carbon, para-aramid, and glass fibers, are presented to demonstrate the high degree of accuracy of the method proposed.

1386. Wagner, H.E., R. Brandenburg, K.V. Kozlov, A. Sonnenfeld, P. Michel, J.F. Behnke, “The barrier discharge: Basic properties and applications to surface treatment,” Vacuum, 3, 417-436, (May 2003).

Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.

776. Wallace, E. Jr., B.B. Sauer, and G.S. Blackman, “Surface analysis of polyester film modified by flame and corona surface treatments,” in Polymer Surfaces and Interfaces: Characterization, Modification and Application, K.L. Mittal and K.-W. Lee, eds., 91-100, VSP, Jun 1997.

Modified surfaces of polyethylene terephthalate)(Mylar® or PET film) have been studied by surface energetics, ESCA, atomic force microscopy (AFM), and optical profilometry. For the surface energetics studies, receding contact angle titrations were used to evaluate the surface functional groups in the outer few angstroms of the surface. This sensitive method of determining the contact angle with buffer solutions of different pHs allows one to investigate the nature of the chemical species introduced by the various energetic treatments. The data are consistent with a surface that is covered by a low density of carboxylic acid moieties in the case of corona and flame treatments, applied in a high-speed commercial type of a process at low doses. The high contact angle hysteresis indicates that the coverage is moderately heterogeneous but on a very small length scale, less than a few micrometers. ESCA qualitatively supported this, although this technique is not optimum for the low degrees of surface modification. A comparison is made of the two surface treatments in terms of depth of penetration, roughness, and surface density of chemical moieties introduced. UV laser-treated surfaces showed no indication of surface chemical modification.

593. Wallace, E. Jr., et al, “Contact angle titration and ESCA analysis of polyester surfaces modified by flame and corona treatment,” in ANTEC 95, Society of Plastics Engineers, 1995.

1056. Walsh, P.J., and A.J. Lesser, “Measuring small contact angles of sessile drops on low energy substrates by refraction,” in PMSE Reprints, American Chemical Society, Mar 2004.

1045. Walzak, M.J., J.M. Hill, C. Huctwith, M.L Wagter, and D.H. Hunter, “AFM and FTIR-ATR in study of UV/ozone modified surfaces of polyethyleneterephthalate and polypropylene,” in 20th Annual Anniversary Meeting, 505-508, Adhesion Society, 1997.

1897. Walzak, M.J., S. Flynn, R. Foerch, et al, “UV and ozone treatment of polypropylene and poly(ethylene terephthalate),” J. Adhesion Science and Technology, 9, 1229-1248, (1995) (also in Polymer Surface Modification: Relevance to Adhesion, K.L. Mittal, ed., p. 253-272, VSP, May 1996).

The effects of exposure to ultraviolet (UV) light and ozone, separately and in combination, were investigated with respect to polypropylene (PP) and poly(ethylene terephthalate) (PET) surfaces. Three combinations of UV light and ozone were studied: ozone only, UV light in air (producing ozone), and UV light in air (producing ozone) supplemented by additional ozone in the incoming air. The effect of the exposure time of the PP and PET to each treatment was studied. The samples were analyzed by X-ray photoelectron spectroscopy (XPS) to determine the surface composition, and by dynamic contact angle to determine the water wettability. The results showed that the effect of the treament was dependent on the properties of the exposed polymer, with PET being more sensitive to the UV light and PP being more sensitive to the reactive species in the gas. The exposure times studied ranged from 1 to 90 min. By monitoring the oxygen uptake levels, we were able to determine that surface modification occurred within minutes. The possible reactive species and mechanisms are discussed.

594. Walzak, M.J., et al, “Characterization of PP and PET surfaces after exposure to UV light and/or ozone,” in ANTEC 95, Society of Plastics Engineers, 1995.

1644. Wang, C., “Polypropylene surface modification model in atmospheric pressure dielectric barrier discharge,” Surface and Coatings Technology, 201, 3377-3384, (Dec 2006).

o optimize the effects of some discharge parameters on the surface wettability of polypropylene (PP) in atmospheric pressure dielectric barrier discharge, a surface modification model is created based on statistical theory and orthogonal experimental design method. Contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) are used to study the changes in the surface wettability, surface topology and chemical compositions of the samples. The results show that surface wettability has been improved due to roughness increasing and the introduction of oxygen-containing functional groups. High-resolution XPS of C1s peak deconvolution indicates that the types and contents of oxidized functional groups are different in different discharge conditions or plasma energy. Moreover, the model analysis reveals that it has better predictive ability, and different discharge parameters has selective influence on water contact angle and surface O atom percentage.

2563. Wang, C., J.-R. Chen, and R. Li, “Studies on surface modification of poly(tetrafluoroethylene) film by remote and direct Ar plasma,” Applied Surface Science, 254, 2882-2888, (Feb 2008).

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.

1677. Wang, C., X. Lv, Y. Liu, L. Ge, Y. Ren, and Y. Qiu, “Influence of temperature and relative humidity on aging of atmospheric plasma jet treatment effect on ultrahigh-modulus polyethylene fibers,” J. Adhesion Science and Technology, 21, 1513-1527, (2007).

The aging effects of atmospheric pressure plasma treated fiber surfaces are important for storage and processing of the fibers. One of the high-performance fibers, ultrahigh modulus polyethylene (UHMPE) fiber, was chosen as a model system to investigate the aging process of atmospheric pressure plasma jet (APPJ) treated fibers surfaces 0, 7, 15 and 30 days after initial plasma treatment. The fiber was first plasma-treated and then stored at temperatures varying from −80 to 80°C on the same relative humidity (RH, 0%) and on RH of 0%, 65% and 100% at the same temperature of 20°C. Immediately after the plasma treatment, scanning electron microscope (SEM) showed the roughened fiber surface. X-ray photoelectron spectroscopy analysis showed changed surface chemical compositions. Contact-angle measurement showed increased surface wettability and microbond test showed an increase in IFSS. With increasing relative humidity or decreasing temperature, the IFSS value decreased and the contact angle increased more slowly. However, after 30 days, the IFSS values and contact angles reached a similar level for all groups. Moisture showed no effect on the single fiber tensile strengths during aging. The reasons for the observed aging behavior could be that decreasing temperature or increasing relative humidity hindered the surface rearrangement of polymer chains after plasma treatment.

1645. Wang, K., W. Wang, D. Yang, Y. Huo, and D. Wang, “Surface modification of polypropylene non-woven fabric using atmospheric nitrogen dielectric barrier discharge plasma,” Applied Surface Science, 256, 6859-6864, (Sep 2010).

In this paper, a dielectric barrier discharge operating in nitrogen at atmospheric pressure has been used to improve the surface hydrophilic property of polypropylene (PP) non-woven fabric. The changes in the hydrophilic property of the modified PP samples are investigated by the contact angle measurements and the variation of water contact angle is obtained as a function of the energy density; micrographs of the PP before and after plasma treatment are observed by scanning electron microscopy (SEM) and the chemical composition of the PP surface before and after plasma treatment is also analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the surface hydrophilic property of the PP samples is greatly improved with plasma treatment for a few seconds, as evidenced by the fact that the contact angle of the treated PP samples significantly decreases after plasma treatment. The analysis of SEM shows that the surface roughness of the treated PP samples increases due to bonding and etching in plasma processing. The analyses of FTIR and the C1s peak in the high-resolution XPS indicate that oxygen-containing and nitrogen-containing polar functional groups are introduced into PP surface in plasma processing. It can be concluded that the surface hydrophilic property of the modified PP samples has been obviously improved due to the introduction of oxygen-containing and nitrogen-containing polar groups and the increase of the surface roughness on the PP surface.

376. Wang, L.-H., and R.S. Porter, “The surface orientation of polystyrene measured by liquid contact angle,” J. Applied Polymer Science, 28, 1439-1445, (1983).

The surface contact angle of glycerol and of water on polystyrene (PS) films has been found to depend on the extent of uniaxial draw for atactic PS. The contact angle depends on direction for the smooth films of PS drawn by solid state coextrusion. Results as a function of draw ratio to values over 4 on these noncrystalline PS samples, Mw = 6 × 105, have also been interrelated with other measures of orientation such as the anisotropy of surface and bulk properties measured, respectively, by dichroic reflectance infrared spectroscopy and by birefringence.

2093. Wang, M.-J., Y.-I. Chang, and F. Poncin-Epaillard, “Effects of the addition of hydrogen in the nitrogen cold plasma: The surface modification of polystyrene,” Langmuir, 19, 8325-8330, (2003).

Polystyrene, a polymer extensively used in the biomedical field, causes a problem for some applications because of its surface hydrophobicity. Nitrogen plasma could transform this shortage through polar group attachment. To understand the role of hydrogen during surface functionalization in the nitrogen cold plasma, the effects of the nitrogen and the mixture of N2/H2 plasma are investigated by both the examinations of the densities of attached amine groups and the in-situ diagnostic analyses such as optical emission spectroscopy and mass spectrometry. An increase of functionalization has been proved to be controlled by the gaseous NH radical formation when H2 is added.

2534. Wang, M.-J., Y.-I. Chang, and F. Poncin-Epaillard, “Acid and base functionalities of nitrogen and carbon dioxide plasma-treated polystyrene,” Surface and Interface Analysis, 37, 348-355, (Mar 2005).

The choice of plasma gas can determine the interaction between material and plasma and therefore the applications of the treated materials. Nitrogen plasma can integrate functional groups such as primary amines and carbon dioxide plasma can incorporate carboxylic groups on the surface of polymers. For specific adhesion such as bio-adhesion, polar groups must be attached to the surface to enhance bio-film formation but the acidic or basic character also controls the adhesion mechanism.

Nitrogen and carbon dioxide plasmas are chosen to treat the surface of polystyrene and to show the effects of different functionalizations, i.e. attachment of acid or basic groups and degradation are compared in the present work.

Nitrogen-containing plasma induces mainly weak degradation at a rate of ∼0.13 µg cm−2s−1. The roughness of the treated surface remains mostly unchanged. Functionalization leads to amino group attachment at a concentration of 1.2 sites nm−2. We found that carbon dioxide plasma treatment shows more drastic degradation with a rate three times higher than that of nitrogen plasma and can create more functional groups (4.5 sites nm−2) at mild plasma treatment. However, the roughness of the surface is altered. In both cases the aromatic groups are degraded through the plasma treatment (again this is more evident with the CO2 plasma) and the induced functionalization was shown to be quick (the upper monolayer of polystyrene film can be functionalized rapidly). Copyright © 2005 John Wiley & Sons, Ltd.

2704. Wang, X.-S., S.-W. Cui, L. Zhou, S.-H. Xu, Z.-W. Sun, and R.-Z. Zhu, “A generalized Young's equation for contact angles of droplets on homogeneous and rough substrates,” J. Adhesion Science and Technology, 28, 161-170, (2014).

Using Gibbs’ method of dividing surfaces, the contact angle of a drop on a flat homogeneous rough non-deformable solid substrate is investigated. For this system, a new generalized Young’s equation for the contact angle, including the influences of line tension and which valid for any dividing surface between liquid phase and vapor phase is derived. Under some assumptions, this generalized Young’s equation reduces to the Wenzel’s equation or Rosanov’s equation valid for the surface of tension.

848. Wang, Y., and S. Rak, “Surface modification of polyphenylene sulfide plastics to improve their adhesion to a dielectric adhesive,” in Adhesion Aspects of Polymeric Coatings, Vol. 2, K.L. Mittal, ed., 121-136, VSP, Jun 2003.

The adhesion strength of a perfluorinated dielectric adhesive to polyphenylene sulfide (PPS) was investigated. The effect of different fillers in the PPS as a function of plasma treatment conditions was evaluated. The change in adhesion as a result of thermal baking was also addressed. The surface composition and surface energy were monitored and systematically quantified by X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements, respectively. The correlations between the presence of certain functional groups, change in surface energy and polarity, and variation in adhesion properties indicate that the adhesion mechanism is mainly due to van der Waals forces. Enhanced wetting at the adhesive/substrate interface and a deeper interfacial diffusion zone are found to be necessary conditions to achieve the optimal adhesion.


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