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1292. Yetka-Fard, M., and A.B. Ponter, “Factors affecting the wettability of polymer surfaces,” J. Adhesion Science and Technology, 6, 253-277, (1992).

The inconsistencies in contact angle data presented in the literature can be attributed to a number of factors. The awareness of these factors would allow novice researchers to make meaningful contact angle measurements and interpretations. In this survey the effects of surface roughness and heterogeneity, surface preparation and the presence of contaminants, the vapor environment, pressure and temperature, drop size, electrical charge, and heat transfer on the wettability of polymer surfaces were examined.

1299. Li, D., and A.W. Neumann, “Equation of state for interfacial tensions of solid-liquid systems,” Advances in Colloid and Interface Science, 39, 299-345, (1992).

1300. Moy, E., and D. Li, “Solid/fluid interfacial tensions of solid-liquid systems: Corroboration by independent approaches,” Advances in Colloid and Interface Science, 39, 257-297, (1992).

1301. Li, D., and A.W. Neumann, “Contact angles on hydrophobic solid surfaces and their interpretation,” J. Colloid and Interface Science, 148, 190-200, (1992).

Contact angles of 17 liquids on 3 hydrophobic solid surfaces, FC721, fluorinated ethylene propylene, and polyethylene terephthalate, were measured by using the Axisymmetric Drop Shape Analysis-Profile (ADSA-P) technique. Details of the surface preparation and the experiments are presented. The accuracy of these contact angle data is better than 0.2° in most cases. These data were used to calibrate an equation of state for interfacial tensions of solid—liquid systems. The end results of the analysis is an equation of state for interfacial tensions with a single parameter β = 0.0001247 (m2/mJ)2, cf., Eqs. [22]–[24]. Within the experimental limitations, there is no evidence for the notion that β might change from system to system.

1302. Li, D., and A.W. Neumann, “Surface heterogeneity and contact angle hysteresis,” Colloid and Polymer Science, 270, 495-504, (1992).

The effect of surface heterogeneity on contact angle hysteresis is studied by using the model of Neumann and Good of a vertical plate with horizontal heterogeneous strips. The results of this study explain well known, but not understood patterns of contact angle behaviour: On the one hand, the advancing contact angle on a carefully prepared solid surface is generally reproducible; on the other hand, even a very small amount of surface heterogeneity may cause the receding contact angle to be less reproducible and to depend on several non-thermodynamic factors.

1303. Li, D., C. Ng, and A.W. Neumann, “Contact angles of binary liquids and their interpretation,” J. Adhesion Science and Technology, 6, 601-610, (1992).

Contact angles of binary liquid mixtures on Teflon FEP were measured. It was found that the equation of state for interfacial tensions, γSL = f (γLV, γsv), cannot be used to determine solid surface tensions from these contact angles of binary liquid mixtures. These findings are explained in terms of the thermodynamic phase rule.

1344. Brewis, D.M., “Surface modification of fluoropolymers for adhesion,” Presented at Fluoropolymers Conference, 1992.

1594. Li, D., P. Cheng, and A.W. Neumann, “Contact angle measurement by axisymmetric drop shape analysis (ADSA),” Advances in Colloid and Interface Science, 39, 347+, (1992).

1642. Shanahan, M.E.R., “Effects of surface flaws on the wettability of solids,” J. Adhesion Science and Technology, 6, 489-501, (1992) (also in Contact Angle, Wettability and Adhesion: Festschrift in Honor of Professor Robert J. Good, K.L. Mittal, ed., p. 159-171, VSP, Nov 1993).

1643. Hazlett, R.D., “On surface roughness effects in wetting phenomena,” J. Adhesion Science and Technology, 6, 625-633, (1992) (also in Contact Angle, Wettability and Adhesion: Festschrift in Honor of Professor Robert J. Good, K.L. Mittal, ed., p. 173-181, VSP, Nov 1993).

1886. Strohmeier, B.R., “Improving the wettability of aluminum foil with oxygen plasma treatments,” J. Adhesion Science and Technology, 6, 703-718, (1992) (also in Contact Angle, Wettability and Adhesion: Festschrift in Honor of Professor Robert J. Good, K.L. Mittal, ed., p. 453-468, VSP, Nov 1993).

The wettability of aluminum foil is an important concern in many industrial converting processes. X-ray photoelectron spectroscopy (XPS or ESCA) and water contact angle results indicated that relatively mild (i.e. 250 W, 15 s) oxygen plasma treatments efficiently removed residual carbon contamination from cold-rolled foil surfaces. This resulted in a significant improvement in the foil wettability. It was also found that the wettability of plasma-treated foils degraded with time, apparently due to the adsorption of hydrophobic, airborne carbon species and other contaminants. Furthermore, oxygen plasma treatments caused additional aluminum oxide to grow on the metal surface. The composition of this additional oxide was found to be similar to that of the native passivation oxide. The thickness of the aluminum oxide layer increased with both the plasma RF power and the plasma exposure time.

1887. Inagaki, N., S. Tasaka, and H. Kawai, “Surface modification of Kevlar fiber by a combination of plasma treatment and coupling agent treatment for silicone rubber composite,” J. Adhesion Science and Technology, 6, 279-291, (1992).

To improve the adhesion between poly(p-phenylene terephthalamide), PPTA, fiber and silicone rubber, the surface modification of PPTA was investigated. Combining plasma treatment and coupling agent treatment with the silicone adhesive was found to be effective in improving adhesion. The combination process made the pull-out force of the PPTA yarn/silicone rubber composite 2.5 times higher, compared with the plasma treatment or the coupling agent treatment alone. The plasma treatment led to the elimination of carbonized layer from the PPTA yarn surface and the formation of oxygen functionalities including CSingle BondO and CDouble BondO groups. The elimination of the carbonaceous deposits from the PPTA surface and the interaction between the silicone adhesive and the oxygen functionalities created by the plasma treatment contribute to the improvement of adhesion with silicone rubber.

1913. Padday, J.F., “Spreading, wetting, and contact angles,” J. Adhesion Science and Technology, 6, 1347-1358, (1992) (also in Contact Angle, Wettability and Adhesion: Festschrift in Honor of Professor Robert J. Good, K.L. Mittal, ed., p. 97-108, VSP, Nov 1993).

The thermodynamic energies associated with conventional wetting, spreading, adhesion, cohesion, and disjoining pressure, as defined in classical equations, are re-examined for their significance in a force field. They are then converted into dimensionless form such that the equilibrium properties of both wetting and spreading all fall on the same line when the dimcnsionless spreading coefficient is plotted as a function of the dimensionless work of adhesion. The effects of a force field such as gravity are examined and it is further shown that spreading is always thickness-dependent, whether in a force field or in a gravity-free field. Non-equilibrium processes such as autophobicity are shown on the same dimensionless plot and indicate clearly that the speed with which the process approaches equilibrium depends on the difference between the initial and equilibrium spreading coefficients. All these processes are expressed in terms of a dimensionless group Pn, the reduced wetting energy, which, when lying between the values of + 1 and -1, equals the cosine of the contact angle, . The implication of this approach to non-equilibrium processes is discussed.

1914. Xie, X., T.R. Gengenbach, and H.J. Griesser, “Changes in wettability with time of plasma-modified perfluorinated polymers,” J. Adhesion Science and Technology, 6, 1411-1431, (1992) (also in Contact Angle, Wettability and Adhesion: Festschrift in Honor of Professor Robert J. Good, K.L. Mittal, ed., p. 509-529, VSP, Nov 1993).

Treatment of fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) by plasmas established in water vapour or ammonia gas enabled the rapid and facile modification of their surface chemistries. Under comparable plasma conditions, ammonia plasma exposures produced considerably lower air/water contact angles than water vapour plasmas. On storage of samples in air at ambient temperature, contact angles increased markedly within a few days on ammonia plasma-treated samples but remained constant over many weeks on water plasma-treated surfaces. Angle-dependent X-ray photoelectron spectroscopy (XPS) demonstrated a very low depth of modification in the case of ammonia plasma exposure, whereas the oxygen content of water plasma-treated samples was invariant with depth within the XPS analysis region. The long-term stability of water plasma-treated fluorocarbon polymer surfaces is believed to be due to this deep modification which prevents polymer chain reorientation, whereas the shallow modification in ammonia plasmas allows the rapid partial burial of the newly attached chemical groups inside the polymer. When ammonia plasma-treated samples stored in air were immersed in water, the contact angles remained constant, suggesting that the buried groups could not resurface. Contact angle measurements provided a simple and sensitive method for studying the time-dependent reduction in plasma treatment effects and the segmental mobility of modified fluorocarbon polymer surfaces; very shallow reorientation movements can be detected.

2775. Kano, Y., and S. Akiyama, “Critical surface tension of poly(vinylidene fluoride-co-hexafluoroacetone) by the contact angle method,” Polymer, 33, 1690-1695, (1992).

The contact angles θ of dispersion (D), polar (P) and hydrogen bonding (H) liquids on poly(vinylidene fluoride-co-hexafluoroacetone) (P(VDF-HFA); HFA content 6.5, 8.3 and 10.4 mol%) were measured. The critical surface tensions γc of P(VDF-HFA) were evaluated by the Zisman plot (cos θ versusγL), Young-Dupre-Good-Girifalco plot (1 + cos θ versus 1γ0.5L) and the log(1 + cos θ) versus log (γL) plot. The following results were obtained: the γc values of P(VDF-HFA) evaluated for the P liquids were larger than those for the D and H liquids; the γc values estimated by the Zisman plot were smaller than those obtained by the other plots; the surface tension γs values of P(VDF-HFA) revealed a minimum at the HFA content of 8.3 mol%. It was expected that P(VDF-HFA) with HFA = 8.3 mol% induced surface segregation most easily.

2921. Glasmacher-Seiler, B., S. Voigt, and H. Reul, “Determination of surface energetic properties by contact angle measurements,” in The Reference Materials of the European Communities, W. Lemm, ed., 85-94, Springer, 1992.

The surfaces of five EUROBIOMAT standard biomaterials are characterized by contact angle measurements applying the sessile drop method using a goniometer. The advancing angles of ten liquids composed of formamide and ethyl CellosolveR according to ASTM D 2578-84 and aqua bidest. are measured. From these data, surface characteristics such as critical surface tension, surface free energy and dispersive surface tension are determined.

371. van Ness, K.E., “Surface tension and surface entropy for polymer liquids,” Polymer Engineering and Science, 32, 122-129, (Jan 1992).

A cell theory for the prediction of the surface tension of polymer liquids is modified to include an entropic effect due to molecular asymmetry. Also considered is the extent of the effect of the preservation of connectivity in the vicinity of the surface upon the potential energy zero term due to missing nearest neighbors of orders greater than one. Theory and experiment are in good agreement without an adjustable surface parameter.

651. Raleigh, P., “Surface treatment: styles and options,” Plastics & Rubber Weekly, 1468, 12+, (Jan 1992).

85. Domingue, J., “A dynamic approach to surface energy and wettability phenomena in flexography,” in Surface Phenomena and Additives in Water-Based Coatings and Printing Technology, Sharma, M.K., ed., 163-170, Plenum Press, Feb 1992.

Dynamic Contact Angle Technique offers a unique, non-optical alternative to solid surface energy analysis. The technique provides advancing and receding hysteresis profile scans of a surface recorded in real time as the liquid meniscus traverses the solid surface. Changes in the wetting hysteresis scan can be used to characterize the qualitative effects of surface roughness, surface homogeneity, and surface polarity, as well as measure the quantitative surface energy of the solid. Applications in flexography in which wettability plays a critical role are numerous, and the switch from solvent-based inks to water-based inks gives impetus for future study.

192. Kigle-Boeckler, G., “Surface tension measurement (ring method) and characterization of coating materials,” in Surface Phenomena and Additives in Water-Based Coatings and Printing Technology, Sharma, M.H., ed., 269-282, Plenum Press, Feb 1992.

A detail discussion of the theoretical aspects of surface tension measurements by ring method is provided with special emphasis on the sources of error. The accuracy of the measured data is mainly limited by the correction factor “f”, which compensates for the non-symmetrical shape of the surface. Based on the experimental findings, it is suggested to include the correction factor during the evaluation of the surface tension, especially if an accuracy of less than 0.1mN/m is required. The effect of meniscus shape and size on the surface tension is discussed. In addition to the surface tension measurements, several other physical properties of the coating systems such as settling behavior and hardness of the settlement can be measured by using the dynometer from BYK-Gardner as a measuring device. The results on different coating systems are presented to study the settling and hardness of the settled material.

203. Kumar, D., “Surface characterization of polymer substrates, flexographic printing plates, and dried ink films printed with water-based ink systems,” in Surface Phenomena and Additives in Water-Based Coatings and Printing Technology, Sharma, M.S., ed., 151-162, Plenum Press, Feb 1992.

The wettability and adhesion of the coating and printing films on the polymer substrates depend on the surface properties of the formulation ingredients and polymer surface. In addition, the transfer of ink from flexographic printing plates to substrates depends on the surface properties of the printing plate, water-based ink and polymer substrate. Among several surface properties such as surface composition, surface roughness, surface tension/surface energies and surface defects, the surface energies: polar, nonpolar and total energies of the dried coating films, flexographic printing plates and polymer substrates were determined by measuring contact angles of water and methylene iodide. These results were used to understand the ink transfer from printing plates to substrates during flexographic printing process, and ink spreading, wetting as well as ink adhesion behavior of the coatings and inks on the polymer substrates. The data indicates that for good ink transfer and adhesion to occur, the surface energy of the water-based ink should be lower than that of the printing plates and substrates.

331. Sharma, M.K., ed., Surface Phenomena and Additives in Water-Based Coatings and Printing Technology, Plenum Press, Feb 1992.

615. no author cited, “Non-flaming: a good way to treat apolar surfaces,” Plastics and Rubber International, 1421, 6, (Feb 1992).

1955. Brewis, D.M., “Pretreatments of hydrocarbon and fluorocarbon polymers,” J. Adhesion, 37, 97-107, (Feb 1992).

Pretreatments of polyolefins and fluoropolymers are usually necessary to achieve satisfactory adhesion for bonding and related technologies. In this paper results for various pretreatments of these polymers are presented. These are the treatment of polyolefins with aqueous reagents, dilute fluorine and a natural gas flame, the treatment of PTFE with sodium naphthalenide and the treatment of ECTFE with sodium naphthalenide and a flame. X-ray photoelectron spectroscopy was used to investigate the chemical changes caused by the treatment and the adhesion levels were discussed in relation to wetting, interactions across interfaces and weak boundary layers.

1956. Schreiber, H.P., “Specific interactions and contact angle measurements on polymer solids,” J. Adhesion, 37, 51-61, (Feb 1992).

The present work examined the susceptibility of contact angle data to specific interactions taking place between solids and contacting liquids. The polymers involved were polystyrene, polyvinyl chloride and polyethylene, representing respectively basic, acidic and neutral substrates. Contacting fluids also were chosen to represent acid and base interaction categories.

Significant time-dependent changes in contact angles were observed when acid/base pairs were involved in the experimental sequence. In specific cases it was possible to identify initial (zero contact time) contact angles, as well as equilibrium values, attained after prolongued contact times. Local solvation, or plasticization, of the polymer by the wetting fluid was postulated as the operative mechanism. The differences between initial and final values of the contact angles were correlated with parameters of specific interaction, calculated from the acceptor/donor numbers for the pertinent materials as measured by inverse gas chromatography. In contrast, when acid/acid or base/base combinations of polymer and wetting fluid were studied, equilibrium values of the contact angle were established rapidly. Since accurate information on acid/base properties of polymers and wetting fluids is not always available, it seems prudent to record contact angles as a function of contact time, and by extrapolation to determine the initial (true) value for further use in surface characterizations of polymers.

55. Chaudhury, M.K., and G.M. Whitesides, “Correlation between surface free energy and surface constitution,” Science, 255, 1230-1232, (Mar 1992).

Self-assembled monolayers (SAMs) of alkylsiloxanes on elastomeric PDMS (polydimethylsiloxane) were used as model systems to study interactions between surfaces. Surface free energies (γsv) of these chemically modified surfaces were estimated by measuring the deformations that resulted from the contact between small semispherical lenses and flat sheets of the elastomer under controlled loads. The measured surface free energies correlated with the surface chemical compositions of the SAMs and were commensurate with the values estimated from the measurements of contact angles. This study provides direct experimental evidence for the validity of estimates of the surface free energies of low-energy solids obtained from contact angles.

452. Dobreva, E.D., M.A. Encheva, and A.T. Trandafilov, “The effect of preliminary treatment with surfactants in the metallization of dielectrics,” Metal Finishing, 90, 29-32, (Mar 1992).

815. Kloubek, J., “Development of methods for surface free energy determination using contact angles of liquids on solids,” Advances in Colloid and Interface Science, 38, 99-142, (Mar 1992).

Methods for the surface free energy determination of solids based on wetting by liquids are reviewed. Some critical remarks and new ideas are included.

2104. Zelez, J., “Surface modification of plastic substrates,” U.S. Patent 5098618, Mar 1992.

224. Lindsay, K.F., “Process surface-treats PP parts in line, opening market opportunities,” Modern Plastics, 69, 47-48, (Apr 1992).

336. Sherman, P.B., “Technological advancements improve corona treatment,” Flexo, 17, 74-78, (May 1992).

49. Caimi, R.J., L.K. Derr, T.J. Dunn, and D. Ruff, “Precision of the surface energy test,” Converting, 10, 62-64, (Jun 1992).

1715. Smith, R.E., “Personal communication re Converting Magazine article ‘Precision of the surface energy test’,” Diversified Enterprises, Jun 1992.

2386. Uchiyama, H., S. Okazaki, and M. Kogoma, “Atmospheric pressure plasma surface treatment process,” U.S. Patent 5124173, Jun 1992.

598. Wightman, J.P., T.D. Lin, and H.F. Webster, “Surface chemical aspects of polymer/metal adhesion,” Intl. J. Adhesion and Adhesives, 12, 133-137, (Jul 1992).

This paper reports on a three-part study: (1) to determine the effect of surface pretreatment of BDS, a siloxane/polyimide copolymer, on adhesion; (2) to determine the extent of segregation of components of BDS against metal substrates; and (3) to determine the properties of ultrathin polymer films against metal substrates.

Surface pretreatment of bds films with aqueous NaOH etched away the top siloxane layer, roughening the polymer surface and producing surface functional groups. These changes resulted in increased wettability and peel strength. Siloxane segregation when bds films were formed against metal surfaces was in the order: Al > Ti > Zn. The relative acidity of the metal oxides as measured by polyvinyl chloride adsorption was in the same order. Reflection-absorption measurements using Fourier transform infra-red spectroscopy were found to be useful in studying the crystallinity of thin polyphenylene sulphide (pps) films. X-ray photoelectron spectroscopy was used to show that failure occurred through a thin layer of residual pps polymer close to the copper oxide substrate.

1451. Botwell, M., “Meeting focuses on adhesion and surface analysis,” Adhesives Age, 35, 51-52, (Jul 1992).

235. Maust, M.J., “Low VOC inks: correlation of two-parameter surface energies to printability on plastic films,” in 1992 Polymers, Laminations and Coatings Conference Proceedings, 391-396, TAPPI Press, Aug 1992.

337. Sherman, P.B., S. Greig, and M.P. Garrard, “Corona generated ozone - its in-house destruction,” in 1992 Polymers, Laminations and Coatings Conference Proceedings, 325-334, TAPPI Press, Aug 1992.

538. Morris, B., “Factors influencing adhesion in coextruded structures,” TAPPI J., 75, 107-111, (Aug 1992).

230. Markgraf, D.A., “Understanding causes can deter backside treatment,” Paper Film & Foil Converter, 66, 145-146, (Sep 1992).

 

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