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744. Sprycha, R. and R. Krishnan, “Application of surfactants in liquid printing inks,” in Interfacial Dynamics, N. Kallay, ed., 699-736, Marcel Dekker, Feb 2000.

Most printing inks used in major printing processes such as lithography, gravure, and flexography contain organic solvents. Some of these solvents, e.g., toluene, are toxic and can be harmful to humans. Both environmental and workplace safety considerations exert growing pressure on the printing industry to limit the use of toxic organic solvents. Due to this pressure, the share of water-based liquid printing inks in packaging printing (including corrugated) has achieved a respectable level of about 50%. In newspaper printing the share is estimated at about 10 to 15% of the total. To prepare for a possible ban on the use of toxic organic solvents, the printing industry is exploring the viability of water-based technology.

352. Stobbe, B.D., “Corona discharge treatment for medical surface preparation,” Medical Device and Diagnostic Industry, (Feb 2000).

3017. Rulison, C., “Two-component surface energy characterization as a predictor of wettabiltiy and dispersability,” Kruss Application Report AR213e, Jan 2000.

2947. Palmers, J., “Surface modification using low-pressure plasma technology,” Medical Device & Diagnostic Industry, (Jan 2000).

1514. Kabza, K., J.E. Gestwicki, and J.L. McGrath, “Contact angle goniometry as a tool for surface tension measurements of solids, using Zisman plot method: A physical chemistry experiment,” J. Chemical Education, 77, 63-65, (Jan 2000).

The paper describes a physical chemistry experiment for measurement of surface tension of solids. It includes description of the Zisman-plot method for obtaining the surface tensions of solids as well as a detailed experimental procedure for surface tension measurements using contact angle goniometry. Four surfaces were analyzed and the critical surface tension (gc) for each of them was obtained. Excellent reproducibility was achieved despite measurement of less accurate Young's contact angles. The experiment includes an extensive data analysis section combined with graphical interpretation of the results. It can be included in an undergraduate physical chemistry laboratory sequence on its own or combined with existing experiments pertaining to surface phenomena.

2686. Shimizu, R.N., and N.R. Demarquette, “Evaluation of surface energy of solid polymers using different methods,” J. Applied Polymer Science, 76, 1831-1845, (2000).

In the present work, contact angles formed by drops of diethylene glycol, ethylene glycol, formamide, diiodomethane, water, and mercury on a film of polypropylene (PP), on plates of polystyrene (PS), and on plates of a liquid crystalline polymer (LCP) were measured at 20°C. Then the surface energies of those polymers were evaluated using the following three different methods: harmonic mean equation and geometric mean equation, using the values of the different pairs of contact angles obtained here; and Neumann's equation, using the different values of contact angles obtained here. It was shown that the values of surface energy generated by these three methods depend on the choice of liquids used for contact angle measurements, except when a pair of any liquid with diiodomethane was used. Most likely, this is due to the difference of polarity between diiodomethane and the other liquids at the temperature of 20°C. The critical surface tensions of those polymers were also evaluated at room temperature according to the methods of Zisman and Saito using the values of contact angles obtained here. The values of critical surface tension for each polymer obtained according to the method of Zisman and Saito corroborated the results of surface energy found using the geometric mean and Neumann's equations. The values of surface energy of polystyrene obtained at 20°C were also used to evaluate the surface tension of the same material at higher temperatures and compared to the experimental values obtained with a pendant drop apparatus. The calculated values of surface tension corroborated the experimental ones only if the pair of liquids used to evaluate the surface energy of the polymers at room temperature contained diiodomethane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1831–1845, 2000;2-Q

2094. Zhang, D., S.M. Dougal, and M.S. Yeganeh, “Effects of UV radiation and plasma treatment on a polystyrene surface studied by IR-visible sum frequency generation spectroscopy,” Langmuir, 16, 4528-4532, (2000).

IR−visible sum frequency generation (SFG) spectroscopy was used to study surface modification of polystyrene by its exposure to a UV light source or plasma. It was found that the polystyrene surface underwent dramatic changes after exposure to these treatments, as evidenced by marked changes in the surface SFG spectra. Before the treatments, the surface spectrum showed a pronounced peak at 3068 cm-1 which is characteristic of the symmetric stretch of the aromatic C−H of polystyrene. This peak decreased markedly, and other vibrational bands associated with the CH2 and CH3 groups appeared after the treatments. The observed spectral changes provided direct evidence of surface reactions involving the aromatic ring. In addition, our data showed that the degrees of oxidation of the polystyrene surface were different with the two processes. The oxidation to a higher oxidation state, resulting in the formation of carbonyl/carboxyl species, was observed with plasma treatment but not with UV irradiation. This difference was also reflected in contact angle measurements. Before the treatments, the contact angle was 95 ± 4°. It decreased to 45 ± 4° and to less than 10° with UV irradiation and plasma treatment, respectively. The different pathways for the two treatments are discussed. In addition, the kinetics of photooxidation of the polystyrene surface was measured in situ, yielding a half-life of 15 min, which is much shorter than that of the bulk.

2028. Hautojarvi, J., and S. Laaksonen, “On-line surface modification of polypropylene fibers by corona treatment during melt-spinning,” Textile Research J., 70, 391-396, (2000).

On-line corona treatment of polypropylene (PP) fibers during melt-spinning is studied. After extrusion of pp filaments, collected fiber tow is subjected to corona treatment prior to drawing, crimping, and cutting into staple fibers, and wettability, antistatic, and friction properties of treated fibers are characterized. Corona treatment results in an average decrease of 5-10° in the advancing contact angle and of 10-25° in the receding contact angle for water on fibers. With amounts of spin finish lower than 0.2% by weight of fiber, treated fibers have considerably better antistatic properties than untreated fibers. Treated fibers have an order of magnitude lower electrical resistance and about 50% less static charge build-up during carding than untreated fibers. In addition, there is a sharp change in wetting and friction properties of fibers with corona treatment when the amount of spin finish is between 0.12 and 0.13 wt %. These effects are attributed to improved wetting of the treated fibers by spin finishes, leading to a more uniform spreading of finish agents on the fiber surface.

1799. Grundke, K., and A. Augsburg, “On the determination of the surface energetics of porous polymer materials,” J. Adhesion Science and Technology, 14, 765-775, (2000).

The solid surface tension γsv of hydrophobic polymer powders has been determined using the capillary penetration technique. By plotting Kγlv cos ζ, where K is a geometric factor, versus the liquid surface tension γlv, the following values of γsv were directly derived from the curves: poly(tetrafluoroethylene) γsv = 20.4 mJ/m2, polypropylene γsv = 30.2 mJ/m2, polyethylene γsv = 34.4 mJ/m2, and polystyrene γsv = 27.5 mJ/m2. These values are in good agreement with the γsv values obtained from contact angle measurements on flat and smooth solid surfaces of the same materials. If the contact angles were first calculated from the capillary penetration experiments, which is the usual procedure applied in the literature, distinctly higher contact angles were obtained. Obviously these angles are affected by the powder morphology and are therefore meaningless contact angles in terms of a surface energetic interpretation.

1717. Grosse, W., “Process and device for Opto-Dynamic Surface Tension (or surface energy) measurement - ODSTM-1 - for running plastic films or other substrates,” Germany Patent Application DE 195.42.289 A 1, 2000.

1685. Klomp, A.J.A., et al, “Treatment of PET nonwoven with a water vapor or carbon dioxide plasma,” J. Applied Polymer Science, 75, 480-494, (2000).

Gas plasma treatment of poly(ethylene terephthalate) nonwoven (NW–PET) was used to increase the hydrophilicity of single- and multilayer NW–PET. NW–PET was treated with a pulsatile CO2 or with a pulsatile H2O glow discharge. X-ray photoelectron spectroscopy (XPS) showed significantly more oxygen with CO2 glow-discharge-treated NW–PET than with H2O glow-discharge-treated-NW–PET surfaces. Moreover, the introduction rate of oxygen at a single layer of NW–PET was higher for a CO2 than for a H2O glow-discharge treatment. Titration data revealed significantly higher surface concentrations of carboxylic groups for CO2 glow-discharge NW–PET than for H2O glow-discharge-treated NW–PET. Mass spectrometry analysis revealed that the entire internal surface of a single layer of NW–PET was modified. XPS and contact measurements confirmed the modification of the internal surface of multilayers of NW–PET. H2O and CO2 glow-discharge-treated substrates consisting of six layers of NW–PET had a nonuniform surface concentration of carboxylic acid groups as determined with titration experiments. The outside layers of the substrate contained a higher surface concentration of carboxylic acid groups than did the inside layers. XPS analysis and titration data showed that the rinsing of H2O and CO2 glow-discharge-treated NW–PET with water changed the surface composition considerably. Part of the carboxylic acid group-containing species were washed off. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 480–494, 2000;2-9

1668. Roth, J.R., Z. Chen, D.M. Sherman, F. Karakaya, and P. P.-Y. Tsai, “Plasma treatment of nonwovens and films for improved wettability and printability,” in 10th Annual International TANDEC Nonwovens Conference Proceedings, TANDEC, 2000.

1413. Bardos, L., and H. Barankova, “Radio frequency hollow cathode source for large area cold atmospheric plasma applications,” in Proceedings of the International Conference on Metallurgical Coatings and Thin Films, American Vacuum Society, 2000 (also in Surface and Coatings Technology, Nov 2000, Vol. 133, p. 522-527).

A new type of radio frequency (rf) large area non equilibrium (‘cold’) plasma source operating at atmospheric gas pressures in an open reactor was presented. The source was based on a specially designed rf electrode with the gas flowing through an inner microstructure integrated in the electrode. A cylindrical source of 35 mm in diameter with approximately 900 hollow cathodes forming an integrated open structure and a rectangular 120×20 mm2 source of this type were tested. A typical rf power for the source operation is only several tens of watts. Experiments show that the performance of both sources at atmospheric pressure was substantially better in comparison with single cylindrical rf hollow cathodes of 400 μm in diameter. The argon and neon plasmas generated in the space between the main electrode and the substrate holder were uniform and very stable. The optical emission spectroscopy study, the rf current, voltage and impedance measurements, as well as the substrate temperature tests reveal three different power dependent regimes of these plasma sources. Effects of plasma treatment of surfaces were studied on both temperature sensitive samples (plastic webs) and metals (aluminum, steel). An effective cleaning of Al samples was observed after 5 min treatment in the neon plasma in an open reactor. After 1 s treatment of the Polyethylene web the surface tension increases from values<34 mN/m to values ⩾56 mN/m. Design of sources allows their direct scaling up and may bring a number of interesting applications in large area cold atmospheric plasma processing.

1326. Wulf, M., K. Grundke, D.Y. Kwok, and A.W. Neumann, “Influence of different alkyl side chains on solid surface tension of polymethacrylates,” J. Applied Polymer Science, 77, 2493-2504, (2000).

Low-rate dynamic contact angles on poly(t-butyl methacrylate) (PtBMA) were measured by an automated axisymmetric drop shape analysis profile (ADSA-P). The solid surface tension of PtBMA is calculated to be 18.1 mJ/m2, with a 95% confidence limit of ±0.6 mJ/m2. This value was compared to previous results with different homopolymeric polymethacrylates [poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(n-butyl methacrylate) (PnBMA)] and with copolymeric polymethacrylates {poly(methyl methacrylate/ethyl methacrylate, 30/70) [P(MMA/EMA, 30/70)] and poly(methyl methacrylate/n-butyl methacrylate) [P(MMA/nBMA)]}. It was found that increasing length and size of the alkyl side chain decrease the solid surface tension, as expected. Comparison with pure alkyl surfaces suggests that the surface tension of PtBMA is dominated by the very hydrophobic t-butyl group. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2493–2504, 2000

1325. Kwok, D.Y., and A.W. Neumann, “Contact angle interpretation in terms of solid surface tension,” Colloids and Surfaces A: Physicochemical and Engineering Aspects, 161, 31-48, (2000).

Recent experimental (low-rate) dynamic contact angles for 14 solid surfaces are interpreted in terms of their solid surface tensions. Universality of these experimental contact angle patterns is illustrated; other reasons that can cause data to deviate from the patterns are discussed. It is found that surface tension component approaches do not reflect physical reality. Assuming solid surface tension is constant for one and the same solid surface, experimental contact angle patterns are employed to deduce a functional relationship to be used in conjunction with the Young equation to determine solid surface tensions. The explicit form of such a relation is obtained by modifying Berthelot’s rule together with experimental data; essentially constant solid surface tension values are obtained, independent of liquid surface tension and molecular structure. A new combining rule is also derived based on an expression similar to one used in molecular theory; such a combining rule should allow a better understanding of the molecular interactions between unlike solid–liquid pairs.

1295. Laurens, P., M. Ould Bouali, F. Meducin, and B. Sadras, “Characterization of modifications of polymer surfaces after excimer laser treatments below the ablation threshold,” Applied Surface Science, 154-155, 211-216, (2000).

The modifications induced by excimer laser radiation on different types of polymer surfaces (polyether-etherketone (PEEK), polycarbonate (PC) and epoxy resin) performed at laser fluences below the material ablation threshold have been investigated. Particular attention was given to the role of laser irradiation wavelength (193 or 248 nm) on the nature and properties of the treated surfaces. Results indicate that a much stronger reactivity was obtained after treatments at 193 nm for all the investigated polymers. At this wavelength, the original polymer surfaces are strongly modified by UV photons; surface reorganization occurs and polar groups induce an increase in the surface wettability.

1264. Zhu, B., H. Iwata, I. Hirata, and Y. Ikada, “Hydrophilic modification of a polyimide film surface,” J. Adhesion Science and Technology, 14, 351-361, (2000).

The surface of a polyimide [poly(biphenyl 3,3′,4,4′-dianhydride-p-phenylene diamine)] film was modified with an O2 glow plasma and subsequent treatment with polyethyleneimine (PEI) and poly(maleic anhydride-co-vinyl methyl ether) (PMAVM). The density of peroxide groups formed on the surface after O2 plasma exposure was determined with 1,1-diphenyl-2-picrylhydrazyl and was found to level off to 1.2 nmol/cm2 within the plasma exposure time of 20-60 s. The peroxide groups formed were utilized to immobilize PEI covalently onto the plasma-treated polymer film. After that, PMAVM was immobilized on the surface through the formation of amide bonds between the amino groups of PEI and the anhydride groups of PMAVM. The water contact angle on the modified films showed that the hydrophilic durability of the PMAVM-PEI-modified polyimide film was superior to that of the polyimide film treated by O2 plasma alone.

1255. Strobel, M., N. Sullivan, M.C. Branch, J. Park, M. Ulsh, R.S. Kapaun, B. Leys, “Surface modification of polypropylene films using N2O-containing flames,” J. Adhesion Science and Technology, 14, 1243-1264, (2000).

Contact-angle measurements and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize polypropylene (PP) films that were exposed to laminar premixed air: natural gas flames containing small quantities of nitrous oxide. During combustion, the nitrous oxide generates gas-phase nitrogen oxides that lead to the affixation of nitrogen-containing functional groups to the PP surfaces. Treatment of PP in nitrous oxide-containing flames also leads to an increase in surface oxidation and markedly improves wettability when compared with standard flame treatments. The chemical form of the nitrogen affixed to the PP surface is strongly dependent on the flame equivalence ratio. Fuel-lean flames tend to affix highly oxidized forms of nitrogen such as nitrate and nitro groups, while fuel-rich flames tend to affix less-oxidized nitrogen groups such as nitroso, oxime, amide, and amine. A computational model, SPIN, was used to elucidate the chemistry of the flame as it impinges upon the cooled PP surface. The SPIN modeling indicates that the principal reactive gas-phase species at or near the PP surface are O2, OH, H, NO, NO2, HNO, and N2O. A number of possible reactions between these species and the PP can account for the formation of the various nitrogen functional groups observed.

1252. Shi, M.K., G. Dunham, M.E. Gross, G.L. Graff, and P.M. Martin, “Plasma treatment of PET and acrylic coating surfaces, I. In-situ XPS measurements,” J. Adhesion Science and Technology, 14, 1485-1498, (2000).

The surface modification of poly(ethylene terephthalate) (PET) and UV-cured tripropyleneglycol diacrylate (acrylic) films induced by remote N2 and Ar microwave plasmas (2.45 GHz) was compared by in-situ XPS measurements. Both N2 and Ar plasma treatments led to destruction of the initial oxygen-containing groups. The destruction of ester groups was much faster for the acrylic than for the PET film, and the destruction of ether groups was much faster than that of ester groups within the acrylic film. Among the plasma gases, N2 was more effective than Ar in the case of PET, but their difference was negligible in the case of the acrylic film. The higher stability of the PET surface was attributed to the presence of a rigid aromatic backbone, which protected the ester groups from plasma UV irradiation and stabilized the free radicals. The lower stability of the acrylic film was associated with the presence of weak ether groups. New functional groups were created, attributed to carbonyl in the case of Ar, and carbonyl/amide and amine in the case of N2 plasma treatments. The formation of these new functional groups was very small compared with the loss of ether and ester groups, suggesting that the destruction of these oxygen-containing groups proceeded mainly through elimination of the entire groups.

1241. Osterberg, M., and P.M. Claesson, “Interactions between cellulose surfaces: Effect of solution pH,” J. Adhesion Science and Technology, 14, 603-618, (2000).

The forces acting between cellulose surfaces have been studied using the interferometric surface force apparatus. The cellulose surfaces were prepared by Langmuir-Blodgett deposition of trimethylsilyl cellulose (TMSC) onto hydrophobized mica. Prior to measurements, the surfaces were desilylated to obtain pure cellulose. The degree of silylation and the molecular weight of the TMSC both affect the structure of the deposited layer. This was observed from the surface pressure-area isotherm, force versus distance curves, and atomic force microscopy images. The forces between the cellulose surfaces were found to depend on the pH of the solution. In dilute electrolyte solutions, the cellulose film was uncharged and rather compact when the pH of the solution was 6.0. However, when the pH was increased to 7.3, the cellulose film swelled considerably and a long-range steric force was measured. The swelling of the film is interpreted as being due to the dissociation of a few carboxylic acid groups present along the cellulose chain. The forces measured were, however, dominated by steric interactions. The repulsion does not increase substantially when the pH is increased from 7.3 to 9.5. Our results suggest that the pKa of the acid groups present within the cellulose film is larger than it would be in the bulk aqueous solution.

1232. Matsunaga, M., and P.J. Whitney, “Surface changes brought about by corona discharge treatment of polyethylene film and the effect on subsequent microbial colonisation,” Polymer Degradation and Stability, 70, 325-332, (2000).

Microbial colonisation of synthetic plastic films is normally slow, which affects the total period of biodegradation. Correlation between the modified surface condition and the ability for microorganisms to colonise low-density polyethylene (LDPE) film was studied. Corona discharge treatment was applied to obtain enriched and activated surface condition of LDPE film. It was found from water contact angle and FTIR spectrum evaluations that surface energy was significantly increased due to production of free radicals. Stabilised oxidised LDPE surface was also obtained by further exposure to the corona which gave more suitable condition for subsequent colonisation. Results were compared with UV irradiated (photo-oxidised) LDPE films. Colonisation of corona discharged and UV treated LDPE films were tested in the laboratory environment using known fungal isolates and in a natural compost environment. More active microbial colonisation was observed in all cases for corona discharged and UV treated LDPE films. Far longer UV exposure was required to have the same physicochemical and biological effect as the corona discharge treatment.

1229. Lee, L.-H., “The gap between the measured and calculated liquid-liquid interfacial tensions derived from contact angles,” J. Adhesion Science and Technology, 14, 167-185, (2000).

We present our new findings about the causes of discrepancies between the measured and calculated liquid-liquid interfacial tensions derived from contact angles. The calculated ones are based on either the equation developed by Fowkes or that by van Oss, Chaudhury and Good (VCG), while the measured ones are based on the sessile drop, weight-volume by Jańzuk et al. and the axisymmetric drop shape analysis (ADSA) by Kwok and Neumann. Indeed, there are deviations between the calculated and measured results. For an immiscible liquid-liquid or liquid-solid interface, we prefer to employ Harkins spreading model, which requires the interfacial tension to be constant. However, for the initially immiscible liquid-liquid pairs, we propose an adsorption model, and our model requires the interfacial tension to be varying and the surface tensions of bulk liquids at a distance from the interface to remain unchanged. Thus, the difference between the initial and final interfacial spreading coefficients (Si) equals the equilibrium interfacial film pressure (πi)e. According to our findings, the calculated interfacial tension represents the initial value (γ12)o, which differs from the equilibrium value (γ12)e obtained experimentally after some time delay. This expected gap at a reasonable time frame is chiefly caused by the equilibrium interfacial film pressure between the two liquids. The initial (or calculated) interfacial tension can be positive or negative, while the equilibrium (or measured) one can reach zero. In fact, the former is shown to have more predictive value than the latter. A negative initial interfacial tension is described to favor miscibility or spontaneous emulsification but it tends to revert to zero instantaneously. Thus, a miscible liquid mixture should have zero interfacial tension. In response to recent papers by Kwok et al., we show that the disagreements between the calculated and measured interfacial tensions are definitely not caused by the failure of the VCG approach. Correct interfacial tensions are calculated for liquid pairs containing formamide or dimethyl sulfoxide (DMSO) by using the dispersion components cited in Fowkes et al.'s later publication. With the corrected surface tension components, the equilibrium interfacial film pressures (πi)e's for at least 34 initially immiscible liquid pairs have been calculated. These values are generally lower than the corresponding spreading pressures πe's obtained by others using the Harkins model. Recently, we established a relationship between these two film pressures with the Laplace equation and found a new criterion for miscibility to be (πi)e = πe.

1226. Kwok, D.Y., and A.W. Neumann, “Contact angle measurements and interpretation: Wetting behavior and solid surface tension for poly(alkyl methacrylate) polymers,” J. Adhesion Science and Technology, 14, 719-743, (2000).

Low-rate dynamic contact angles of a large number of liquids were measured on a poly(ethyl methacrylate) (PEMA) polymer using an automated axisymmetric drop shape analysis profile (ADSA-P). The results suggested that not all experimental contact angles can be used for the interpretation in terms of solid surface tensions: eight liquids yielded non-constant contact angles and/or dissolved the polymer on contact. From the experimental contact angles of the remaining four liquids, we found that the liquid-vapor surface tension times the cosine of the contact angle changes smoothly with the liquid-vapor surface tension, i.e. γlv cos ζ depends only on γlv for a given solid surface (or solid surface tension). This contact angle pattern is again in harmony with those from other methacrylate polymer surfaces of different compositions and side-chains. The solid-vapor surface tension of PEMA calculated from the equation-of-state approach for solid-liquid interfacial tensions was found to be 33.6 ± 0.5 mJ/m2 from the experimental contact angles of the four liquids. The experimental results also suggested that surface tension component approaches do not reflect physical reality. In particular, experimental contact angles of polar and nonpolar liquids on polar methacrylate polymers were employed to determine solid surface tension and solid surface tension components. Contrary to the results obtained from the equation-of-state approach, we obtained inconsistent values from the Lifshitz-van der Waals/acid-base (van Oss and Good) approach using the same sets of experimental contact angles.

1211. Drelich, J., J. Nalaskowski, A. Gosiewska, E. Beach, and J.D. Miller, “Long-range attractive forces and energy barriers in de-inking flotation: AFM studies of interactions between polyethylene and toner,” J. Adhesion Science and Technology, 14, 1829-1843, (2000).

The interfacial forces between a polyethylene particle and a toner substrate in alkaline aqueous solutions were studied using an atomic force microscope colloidal probe technique. Measurements were taken at pH 9 in water and solutions of 5 × 10-4 M CaCl2, 1 × 10-4 M Na oleate, and 1 × 10-4 M Na oleate plus 5 × 10-4 M CaCl2 in order to mimic the conditions present during de-inking flotation. A polyethylene particle was used to represent the air bubble. The observed interaction forces were described by the extended DLVO theory. An energetic barrier caused by electrical double-layer repulsion was observed in water and Na oleate solutions but was greatly diminished in CaCl2 solution. A long-range attractive force was found to be present in these systems and was described using a simple exponential function. The long-range attractive force was virtually the same in water and CaCl2 solution but decreased significantly in Na oleate solution because of the reduced hydrophobicity of the interacting surfaces caused by the adsorbed carboxylate layer. However, in the presence of oleate and calcium ions the observed attraction was even stronger and of longer range than in water and CaCl2 solutions. Moreover, no energetic barrier was observed. These results can be attributed to the presence of precipitated calcium oleates on the interacting surfaces.

1209. Dilsiz, N., “Plasma surface modification of carbon fibers: A review,” J. Adhesion Science and Technology, 14, 975-987, (2000).

The properties of the fiber/matrix interface in carbon fiber-reinforced composites play a dominant role in governing the overall performance of the composite materials. Understanding the surface characteristics of carbon fibers is a requirement for optimizing the fiber-matrix interfacial bond and for modifying fiber surfaces properly. Therefore, a variety of techniques for the surface treatment of carbon fibers have been developed to improve fiber-matrix adhesion as well as to enhance the processability and handling of these fibers. Many research groups have studied the effects of plasma treatments, correlating changes in surface chemistry with the interfacial shear strength. This article reviews the recent developments relative to the plasma surface modification of carbon fibers.

1206. Della Volpe, C., and S. Siboni, “Acid-base surface free energies of solids and the definition of scales in the Good-van Oss-Chaudhury theory,” J. Adhesion Science and Technology, 14, 235-272, (2000) (also in Apparent and Microscopic Contact Angles, J. Drelich, J.S. Laskoski, and KL. Mittal, eds., p. 171-208, VSP, Jun 2000).

The overwhelming basicity of all analysed surfaces strongly dependent on the choice of liquid triplet used for contact angle measurements and the negative values sometimes obtained for the square roots of the acid-base parameters can be summarized as the main problems arising from the application of the Good-van Oss-Chaudhury (GvOC) theory to the calculation of Lewis acid-base properties of polymer surfaces from contact angle data. This paper tries to account for these problems, namely: (1) the Lewis base, or electron donor component, is much greater than the Lewis acid or electron-acceptor component because of the reference values for water chosen in the original GvOC theory. A direct comparison of the acidic component with the basic one of the same materials has no meaning. A new reference scale for water which is able to overcome this problem is suggested. For the calculation of acid-base components, a best-fit approach is proposed which does not require any starting information about the liquids or polymers and can yield estimates of the acid-base parameters for both the liquids and the polymers involved; (2) the strong dependence of the value of the acid-base components on the three liquids employed is due to ill-conditioning of the related set of equations, an intrinsic and purely mathematical feature which cannot be completely cured by any realistic improvement in experimental accuracy. To reduce or eliminate the effect, one only needs a proper set of liquids, representative of all kinds of different solvents; (3) the negative coefficients appear as a simple consequence of measurement uncertainty, combined with the possible ill-conditioning of the equation set. We cannot exclude, however, that in some cases they could have a different origin.

1042. Zeiler, T., S. Kellermann, and H. Muenstedt, “Different surface treatments to improve the adhesion of polypropylene,” J. Adhesion Science and Technology, 14, 619-634, (2000).

Injection-molded samples of polypropylene were exposed to oxygen plasma and SACO (SAndblasting and COating) treatments. The pretreated surfaces were successively adhesively bonded or lacquered. The adhesion strength and failure mode of these specimens were examined. The surfaces obtained after treatments were characterized by electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and scanning electron microscopy (SEM). Both microroughness and chemical modification of the surface led to an increase in adhesion by up to a factor of 10. The stability of the surface changes generated during the plasma and SACO pretreatments was observed by different kinds of aging experiments in air and water. The aging of SACO-treated surfaces led to no significant change on the surface. In the case of plasma-treated surfaces, hydrophobic recovery during aging in air reduced the polarity of the surface layer. During aging in water, no hydrophobic recovery on the surface was observed.

1026. Chou, S., and S. Chen, “Effect of plasma polymerisation of monomers on glass fibre surfaces on adhesion to polypropylene,” Polymers & Polymer Composites, 8, 267-279, (2000).

New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.

1010. Zenkiewicz, M., “Flame modification of the surface layer of plastics products,” Polimery, 45, 81-88, (2000).

A review covering the general objectives of surface modification of plastics articles with particular reference to the flame modification technique. Hydrocarbon combustion conditions and flame modification parameters are described. Flame modification effects exercised on various, mostly polyolefinic, products are synthetically analyzed. The flame technique is shown to be advantageous and complementary to the corona-discharge technique. The effects of the polypropylene modification conditions on the oxygen content, the wetting angle for water, the free surface energy and the resistance of adhesion bonds are described.

964. Cho, C.K., B.K. Kim, and C.E. Park, “The aging effects of repeated oxygen plasma treatment on the surface rearrangement and adhesion of LDPE to aluminum,” J. Adhesion Science and Technology, 14, 1071-1083, (2000).

The effects of aging temperature and time on the adhesion properties of oxygen plasmatreated low-density polyethylene (LDPE) were investigated. As the aging temperature and time increased, surface rearrangement and the migration of molecules containing polar functional groups into the bulk were accelerated to the surface to form a hydrophobic surface. The adhesion strength of oxygen plasma-treated LDPE/aluminum joints was measured using a 90° peel test by varying the plasma treatment time and aging temperature. The adhesion strength was constant, regardless of the plasma treatment time. As the aging temperature increased, the adhesion strength of the LDPE/aluminum joints decreased and the locus of failure changed from cohesive to interfacial failure. It was also found that the polar functional groups buried in the bulk could be reoriented to the surface in a polar environment. This study also investigated whether repeated oxygen plasma treatment would increase the concentration of polar functional groups at the surface and reduce the surface rearrangement and the migration of molecules containing polar functional groups during aging. Contact angle measurements and X-ray photoelectron spectroscopy (XPS) showed that repeated oxygen plasma treatments increased the concentration of polar functional groups at the surface. However, the aging time between plasma treatments had a negligible effect on the concentration of polar functional groups at the surface.

961. Zenkiewicz, M., and J. Dzwonkowski, “Experimental evaluation of the process of decohesion of adhesive joints with polymer films,” Polimery, 45, 802-807, (2000).

Acrylic adhesive/PE film joints were prepared by using PE films preactivated by corona discharges. The tear-off work, a measure of strength of the joint, is the sum of several terms; the major terms include the work of adhesion and the work of deformation (here: stretching of film) involved in the tear-off process. The tear-off work (P-o, Fig.5) and the stretching work (P-r, Fig. 6) were determined for films that varied from 50 to 150 mum in thickness, in relation to specific treatment energies (E-j) ranging up to 7.5 kJ/m2. Within the interval 0 < E-j < 3 kJ/m2, P-r rises in an approximately linear way. As E-j is increased, evaluation of the unit adhesion work from tear-off tests becomes more and more burdened with error. Within the range of E-j adopted in technical preparation of upper layers of PE films (E-j = 2 kJ/m2), the error is kept within 9% and is only slightly related to film thickness.

772. Shi, S.Q., and D.J. Gardner, “A new model to determine contact angles on swelling polymer particles by the column wicking method,” J. Adhesion Science and Technology, 301-314, (2000) (also in Apparent and Microscopic Contact Angles, J. Drelich, J.S. Laskowski, and K.L. Mittal, eds., p.431-444, VSP, Jun 2000).

73. Decker, W., S. Pirzada, M. Michael, and A. Yializis, “Long lasting surface activation of polymer webs,” in 43rd Annual Technical Conference Proceedings, Society of Vacuum Coaters, 2000.

Surface activation of polymer films to modify surface properties is widely practiced to enhance wettability, printability and adhesion properties of these films. Sigma Technologies has been actively pursuing the area of longlasting activation of polymer films using various techniques including plasma technology. Atmospheric glow discharge plasma technology has been a recent addition towardsthese efforts. Plasma activation using a variety of precursors has been investigated for long lasting functionilization of various substrates. Latest developments in the area of surface activation of polymer films will be presented.

1240. Morvova, M., “The influence of water vapour and temperature on depletion of carbon monoxide in d.c. corona discharge,” Czechoslovak J. Physics, 49, 1703-1719, (Dec 1999).

The plasmochemical and/or electrocatalytical reactions of carbon monoxide with water vapour were studied. Dc corona discharge of both polarities at room temperature and temperatures enhanced up to 70°C was applied at pressures close to atmospheric.

The reaction products were analysed by IR absorption spectrometry. The main products in the gas phase were CO2 and CH4. The reactions are influenced by the formation of a catalytically active surface layer on electrodes. The composition of this layer depends on the polarity of electrode.

1012. Stefecka, M., J. Rahel, M. Cernak, I. Hudec, M. Mikula, and M. Mazur, “Atmospheric-pressure plasma treatment of ultrahigh molecular weight polyethylene fibres,” J. Materials Science Letters, 18, 2007-2008, (Dec 1999).

Ultrahigh molecular weight polyethylene fibres have been treated in nitrogen plasma at atmospheric pressure. The plasma was generated by a pulsed electric discharge on the fibre surface. Fibre/rubber matrix interfacial adhesion was improved substantially by the plasma treatment. Zeta-potential measurements indicate an increase in hydrophilicity and basic groups density on the treated fibre surface. EPR spectrometry study reveals creation of peroxy type radicals by the plasma treatment.

276. Opad, J.S., “Choosing the correct dielectric in corona treating,” Converting, 17, 88-90, (Dec 1999).

17. Bentley, D.J., “Excessive treating can be too much of a good thing,” Paper Film & Foil Converter, 73, 22, (Dec 1999).

2808. Mount, E.M. III, and J.R. Wagner Jr., “Enhanced barrier vacuum metallized films,” U.S. Patent 5981079, Nov 1999.

966. Suezer, S., A. Argun, O. Vatansever, and O. Aral, “XPS and water contact angle measurements on aged and corona treated PP,” J. Applied Polymer Science, 74, 1846-1850, (Nov 1999).

Effects of corona treatment and aging on commercially produced corona discharged polypropylene (PP) films were followed via surface sensitive roughness analysis by atomic force microscopy (AFM), water contact angle (WCA), and X-ray photoelectron spectroscopic (XPS) measurements. Roughness analysis by AFM gave similar results for both untreated and corona-treated samples. The measured water contact angle decreased after corona treatment but increased with aging. XPS findings revealed that corona treatment caused an increase in the O-containing species on the surface of the films, but the measured O/C atomic ratio decreased with aging. The angle dependence of the observed XPS O/C atomic ratio further revealed that surface modifications by the corona treatment were buried into the polymer away from the surface as a function of aging. This is attributed to a surface rearrangement of the macromolecules in agreement with the findings of Garbassi et al. on oxygen–plasma-treated polypropylene. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1846–1850, 1999

297. Podhajny, R.M., “Common causes of blocking in flexo and gravure printing,” Paper Film & Foil Converter, 73, 26, (Nov 1999).


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