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492. Johnson, B.A., “Studies of advancing and receding contact angles (MS thesis),” Univ. of Wisconsin, Madison, 1982.

467. Gregory, B.H., D. Michiels, and W.D. McIntyre, “Adhesion improvement by ozone treatment,” in 1982 Paper Synthetics Conference Proceedings, 167-172, TAPPI Press, 1982.

428. Briggs, D., “XPS studies of polymer surface modifications and adhesion mechanisms,” J. Adhesion, 13, 287, (1982).

XPS has been used to elucidate the mechanisms of surface modification of low density polyethylene by electrical (“corona”) discharge treatment and by chromic acid treatment. The use of derivatisation techniques for improving the precision of functional group analysis is described. These techniques also allow the role of specific interactions in adhesion to discharge treated surfaces to be investigated. The role of residual Cr on the adhesion of deposited metal to polymer surfaces is discussed.

394. Yagi, T., A.E. Pavlath, and A.G. Pittman, “Grafting fluorocarbons to polyethylene in glow discharge,” J. Applied Polymer Science, 27, 4019-4028, (1982).

A systematic surface fluorination of high-density polyethylene was carried out using CF4, CF3H, CF3Cl, and CF3Br, in a radio-frequency glow discharge. Based on ESCA and wettability measurements, all of these compounds provided a fluorocarbon layer on high-density polyethylene surface, but the fluorine to carbon ratio and extractability of the films were strongly dependent on the starting materials and the location of the sample specimen in the reactor chamber as well as the duration of the reaction. The results with vertically held, CF3H-treated samples showed a high level of nonextractable surface fluorination and very little change in wetting properties before and after extraction with CF2ClCFCl2.

67. Corbin, G.A., R.E. Cohen, and R.F. Baddour, “Kinetics of polymer surface fluorination: elemental and plasma-enhanced reactions,” Polymer, 23, 1546-1548, (1982).

E.s.c.a. spectra of surface fluorinated polyethylene, poly(vinyl fluoride), and poly(vinylidene fluoride) are reported. Two reaction environments were used in this study: exposure to elemental fluorine and immersion in a glow discharge plasma. The systematic variation of fluorine composition in the polymer phase is shown to have a dramatic effect on the kinetics of the elemental reaction and little effect in the plasma reaction.

66. Coopes, I.H., and K.J. Gifkins, “Gas plasma treatment of polymer surfaces,” J. Macromolecular Science, A17, 217-226, (1982).

The modification of polymer surfaces by gas plasma treatment is reviewed. The two regimes of major interest are radio-frequency at low pressure (about 1 torr) and corona discharge at atmospheric pressure. The reactions produced by plasmas at polymer surfaces are due to both radiation and chemically active species created by electron bombardment. The major changes produced are in wettability, molecular weight, chemical composition, and surface morphology. The mechanisms of plasma polymerization and the properties of polymers produced by this technique are described. Finally, a brief outline is given of the industrial applications of plasma techniques.

2369. Hood, J.L., “Method and apparatus for the corona discharge treatment of webs, and webs treated therewith,” U.S. Patent 4298440, Nov 1981.

1991. Matsunaga, T.J., and Y. Ikada, “Dispersive component of surface free energy of hydrophilic polymers,” J. Colloid and Interface Science, 84, 8-13, (Nov 1981).

The London dispersive component of surface free energy γsd and the nondispersive interactions with polar liquids W Iswn were determined for hydrophilic polymers S, that is, cellulose, poly(vinyl alcohol) (PVA), and poly(methylmethacrylate) (PMMA). On applying the geometric-mean relation 2(γsdγwd)12 to the dispersive interaction with W Iswd, the γsd values were found to be 30, 29, and 37 erg·cm−2 for cellulose, PVA, and PMMA, respectively. Each of them is completely independent of the nature of the testing liquids W, indicating that the geometric-mean equation is appropriate for representing the dispersive interaction. On the contrary, such a geometricmean expression is shown to be inapplicable to the nondispersive interactions. It is suggested that Fowkes' approach, in which intermolecular forces are regarded to be dominated by dispersion force interactions and electron donor-acceptor interactions, is more reasonable than the popular approach.

408. no author cited, “Surface treatment improves polyethylene barrier properties,” Package Engineering, 26, 64-66, (Nov 1981).

2370. Deguchi, Y., H. Yamagishi, and S. Kirimura, “Surface treatment of plastic material,” U.S. Patent 4297187, Oct 1981.

1809. Penn, L.S., and E.R. Bowler, “A new approach to surface energy characterization for adhesive performance prediction,” Surface and Interface Analysis, 3, 161-164, (Aug 1981).

A new approach to qualitatively predicting adhesion at a solid/solid interface is described. It is based on thermodynamic compatibility of the two adhering surfaces, but it overcomes the weaknesses of existing methods by using a full set of contact angle data and by assembling the data to reveal the main features of the set without loss of information. Adhesive performance data to support this approach are presented.

1967. Carter, A.R., “Adhesion to polyolefins with flexible adhesives,” J. Adhesion, 12, 37-49, (May 1981).

Compounds based on polyolefins may find further use in the footwear industry as solings. However, a significant problem is the poor adhesion obtained with the urethane adhesives currently used. SATRA has recently attempted to develop practical bonding systems for commercial olefinic compounds. The use of flame treatments for polyethylene appeared to be a possible method of improving compatibility between the adhesive and substrate if an isocyanate is present at the interface. Polypropylene does not respond to the flame treatment but reasonable bonds have been obtained after surface oxidation or by using a sensitiser in conjunction with UV irradiation. The use of dual compound moulding is described as a possible alternative means of obtaining adequate adhesion to difficult surfaces.

1811. Omenyi, S.N., A.W. Neumann, and C.J. can Oss, “Attraction and repulsion of solid particles by solidification fronts I: Thermodynamic effects,” J. Applied Physics, 52, 789, (Feb 1981).

This paper presents and discusses particle behavior at solidification fronts from a thermodynamic point of view. Engulfing or rejection of particles embedded in a melt by solidification fronts depends on whether such quantities as the free energy of adhesion or of engulfing are positive or negative. As the relevant energy balances contain solid‐liquid interfacial tensions which are difficult to determine, these studies may also be viewed as tests for the validity of such data and the underlying theories used to determine them. In this paper, solid‐liquid interfacial tensions are derived from contact angle data and the equation of state approach for interfacial tensions [Neumann et al., J. Colloid Interface Sci. 49, 291 (1974)]. The thermodynamic predictions obtained in this way for approximately 60 systems agree very well with microscopic observations with particles in the range of 10–200 mm in diameter.

546. Podhajny, R.M., “Surface tension and water-based flexo inks,” Flexo, 6, (Jan 1981).

1762. Hitchcock, S.J., N.T. Carroll, and M.G. Nicholas, “Some effects of substrate roughness on wettability,” J. Materials Science, 16, 714, (1981).

The influence of substrate roughness on wettability has been investigated at room and high temperatures using sixteen material combinations, mostly liquid metals and solid ceramics but also water, glycerol and solid nickel. The contact angles assumed by both wetting and non-wetting drops of all but two material combinations increased linearly with the relative steepness of the surface features, the effect being less for experiments conducted at high temperatures. In contrast, the contact angles of good wetting drops of glycerol and exceptionally good wetting drops of Easy-flo decreased when their silica and nickel substrates were roughened. Similarly, contact angles of both wetting and non-wetting drops were decreased by ultrasonic vibration. The experimental data can best be interpreted in terms of the metastable equilibrium configuration models in which an advancing liquid front has to overcome energy barriers associated with surface features. This occurs more readily if these barriers are small relative to the energy of the liquid which our data suggest can be equated with the enthalpy of the liquid. This interpretation enables the effects of substrate roughness at one temperature or with one liquid to be used to predict behaviour at other temperatures and with other liquids.

1718. Jaycock, M.J., and G.D. Parfitt, “The study of liquid interfaces,” in Chemistry of Interfaces, John Wiley & Sons, 1981.

1400. Collins, W.M., “Recent technological advances in corona treating,” in 1981 Paper Synthetics Conference Proceedings, 129, TAPPI Press, 1981.

1196. Brewis, D.M., and D. Briggs, “Adhesion to polyethylene and polypropylene,” Polymer, 22, 7-16, (1981).

Adhesion to polyethylene and polypropylene is a complex subject requiring understanding of (a) the poor adhesive characteristics of these polymers; (b) the superior performance following certain pretreatments and (c) the nature of the changes brought about by these pretreatments and the mechanisms involved. This review discusses work on these topics and examines the impact of recent data resulting from the application of surface analytical techniques. The roles of ‘weak boundary layers’, surface energy and wettability and specific interactions are discussed in some detail.

637. Good, R.J., “Semantic physics of adhesion,” in Treatise on Adhesion and Adhesives, Vol. 5, Patrick, R., ed., 293-312, Marcel Dekker, 1981.

566. Seffins, W., “A model treatment of solid/liquid interfacial energies for non-zero contact angle systems (MS thesis),” Univ. of Texas, El Paso, 1981.

494. Joos, P., and E. Rillaerts, “Theory on the determination of the dynamic surface tension with the drop volume and maximum bubble pressure methods,” J. Colloid and Interface Science, 79, 96-100, (1981).

The paper presents a theory on determining the dynamic surface tension using two methods: the drop volume method and the maximum bubble pressure method.

485. Huntsberger, J.R., “Surface energy, wetting, and adhesion,” J. Adhesion, 12, 3+, (1981).

Surface energies of solids can be estimated using contact angles of liquids of known surface tension and susceptibilities for polar or acid-base interactions. Interfacial tensions and work of adhesion can be calculated using these estimated energies. There are three circumstances in which performance or bond strengths are related directly to surface energies: when separation occurs interfacially, when interfaces are not completely wetted, and when third phases are present at the interface.

445. Cramm, R.H., and D.V. Bibee, “Theory and practice of corona treatment for improvement of adhesion,” in 1981 Paper Synthetics Conference Proceedings, 1-11, TAPPI Press, 1981 (also in TAPPI J., V. 65, p. 75-78, Aug 1982).

430. Burkstrand, J.M., “Metal-polymer interfaces: Adhesion and x-ray photoemission studies,” J. Applied Physics, 52, 4795-4800, (1981).

The interfaces formed by evaporating copper, nickel, and chromium layers on polystyrene, polyvinyl alcohol, polyethylene oxide, polyvinyl methyl ether, polyvinyl acetate, and polymethyl methacrylate have been studied with x‐ray photoemission spectroscopy (XPS). The adhesion strengths of the metal films to the polymers were measured by a tensile‐pull test. At submonolayer coverages of the metals, the peak positions and widths of the metallic electron core levels measured with XPS vary significantly from one polymer substrate to another. Most of these variations can be accounted for in terms of changes in the atomic and extra‐atomic relaxation energies during the photoemission process. Much of this change is brought about when the metal atom deposited on an oxygen‐containing polymer interacts with the substrate oxygen and forms a metal‐oxygen‐polymer complex. The presence of this complex is verified by changes in the photoemission lineshapes of the substrate carbon and oxygen atoms. The XPS signatures of these various complexes are quite similar and suggest that they are chelate‐like complexes. The adhesion strength of any metal on an oxygen‐containing polymer is greater than on the oxygen‐free polystyrene. In general, the increased adhesion strength correlates with the presence of the metal‐oxygen chelate complexes.

397. Yasuda, H.K., A.K. Sharma, and T. Yasuda, “Effect of orientation and mobility of polymer molecules at surfaces on contact angle and its hysteresis,” J. Polymer Science Part B: Polymer Physics, 19, 1285-1291, (1981).

The contact angle of a water droplet on the surface of a solid polymer or hydrogel (water-swollen three-dimensional network) depends on whether a hydrophilic moiety of the polymer molecule is oriented towards the air interface or towards the bulk of the solid, but not on the hydrophilicity of the molecule. Therefore, the short-range rotational mobility of a polymer molecule has a major influence on the apparent hydrophilicity of a polymer surface as measured by the contact angle of water. By the came principle, the abnormally large hysteresis effect observed in advancing and receding contact angles of water on some polymer surfaces can be attributed to the reorientation of hydrophilic moieties of polymer molecules at the surface. These factors are demonstrated by selected polymer surfaces with different degrees of mobility at the polymer-air interface.

268. Ohsawa, T., and T. Ozaki, “New method for determination of surface tension of liquids,” Review of Scientific Instrumentation, 52, 590-593, (1981).

A new method of quickly and precisely measuring the surface tension of liquids and solutions is described. Utilizing the fact that the size of the bubbles formed from a gas flowing out of a nozzle is dependent on the nozzle diameter and the surface tension of the liquid used, the surface tension of a liquid can be determined by simply counting the number of bubbles formed from a gas flowing out at a constant flow rate or by measuring the period of bubble formation. The expected accuracy of the method is below 0.1% of variance. An evident correlation between the period of bubble formation and the surface tension was shown with several kinds of liquids which differ in surface tension. Changes in surface tension with varied degree of neutralization were determined in an aqueous solution of polyacrylic acid (PAA), 20-30 points of measurement with an accuracy of about 0.1% could be easily obtained within one hour.

227. Lunkenheimer, K., and K.D. Wandtke, “Determination of the surface tension of surfactant solutions applying the method of Lecomte de Nouy (ring tensiometer),” Colloid and Polymer Science, 259, 354-366, (1981).

Starting from a comparative assessment of the outstanding works on the ring method (du Noüy) for the determination of the surface tension of liquids and its solutions it is shown that the application of this method to surfactant solutions can lead to substantial errors if one follows conventional conditions. These errors are mainly connected with so far unknown phenomena occurring during the raising of the ring and concerning the influence of the hydrophilic vessel wall above the solution level and the stretching of the solution surface. This is demonstrated quantitatively with surfactant solutions of different kind and concentration. These effects can be explained theoretically very simply by introducing certain assumptions on the behaviour of a surfactant adsorption layer on the inner vessel wall. Conditions leading to the elimination of these errors are given, thus enabling the application of the ring method to the determination of the surface tension of surfactant solutions.

197. Ko, Y.C., D.B. Ratner, and A.S. Hoffman, “Characterization of hydrophilic-hydrophobic polymeric surfaces by contact angle measurements,” J. Colloid and Interface Science, 82, 25-37, (1981).

Polymeric solid surfaces were prepared by a radiation-induced graft copolymerization technique using various mixtures of 2-hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA). Low-density polyethylene (PE) films were used as graft substrates. Contact angles on these polymeric surfaces were determined in air and under water. The critical surface tension (γc) of each polymeric surface in air was estimated by the Zisman method. Geometric mean and harmonic mean approximation methods were utilized to estimate the dispersion force contribution (γsd) and the polar contribution (γsp) to the total surface free energy (γs) from contact angle data in air. The geometric mean approximation was also used to estimate γsd′ and γsp′ from contact angles under water. The calculated values of γsd, γsp are strongly dependent on the pair of liquids chosen for the calculation regardless of the approximation adopted. The values of γs, calculated as the sum of γsd and γsp, are close to the γc values and are less dependent on the pair of liquids used. A comparison of the ratio γsd/γsp for the same surface in air and under water suggests that major polymer chain conformational changes occur, particularly with respect to the hydroxyl side chain, when such surfaces are immersed in water.

166. Huntsberger, J.R., “Interfacial energies, contact angles, and adhesion,” in Treatise on Adhesion and Adhesives, Vol. 5, 1-20, Marcel Dekker, 1981.

61. Cherry, B.W., Polymer Surfaces, Cambridge University Press, 1981.

46. Busscher, H.J., and J. Arends, “Determination of the surface forces from contact angle measurements on polymers and dental enamel,” J. Colloid and Interface Science, 81, 75-79, (1981).

13. Banerji, B.K., “Physical significance of contact angles,” Colloid and Polymer Science, 259, 391-394, (1981).

The physical significance of contact angles has been interpreted on the basis of a model derived from known surface energy relationships. The degrees of non-spreading and spreading have been expressed in terms of the magnitude of contact angles. On the basis of the physical picture, hysteresis of contact angle has been calculated from the experimental values of equilibrium contact angle and surface tension of the liquid. It has been suggested that it is not necessary to assume that hysteresis of contact angles is due to surface roughness of solids. The picture also explains why apparent contact angle on a non-flat solid surface is more than that on a flat solid.

2305. Kolbe, A., and P. Dinter, “Device for the surface treatment of film webs by means of electrical corona discharge,” U.S. Patent 4239973, Dec 1980.

2281. Penn., L.S., and B. Miller, “A study of the primary causes of contact angle hysteresis on some polymeric solids,” J. Colloid and Interface Science, 78, 238-241, (Nov 1980).

2046. Schreiber, H.P., and M.D. Croucher, “Surface characteristics of solvent-cast polymers,” J. Applied Polymer Science, 25, 1961-1968, (Sep 1980).

Films of poly(methyl methacrylate) (PMMA), polystyrene, and a styrene/acrylic terpolymer have been cast from solutions of varying thermodynamic quality and the film properties studied by inverse gas chromatography and by critical surface tension measurements. Surface properties of the non-polar polystyrene were independent of solvent medium, but significant variations in these properties were observed in the case of PMMA and the terpolymer. Solvent balance also appeared to affect the bulk properties of the latter films, as judged by the penetration rates of interacting liquids. The observations indicate the feasibility of controlling film properties of the solid by the appropriate selection of solution media; a time-dependent variation in solid properties is to be expected, however, as the film structure attains an equilibrium state.

2309. Lundell, E.O., and W.H. Smarook, “Method of selectively treating a plastic surface to prevent blocking,” U.S. Patent 4216254, Aug 1980.

1992. Schwartz, A.M., “Contact angle hysteresis: A molecular interpretation,” J. Colloid and Interface Science, 75, 404-408, (Jun 1980).

“Intrinsic contact angle hysteresis” is defined as hysteresis that cannot be ascribed to roughness, heterogeneity, or penetrability of the solid surface. It can be explained if we postulate that the layer of liquid immediately adjacent to the solid surface has an ordered structure similar to that of a liquid monocrystal. This structure is fluid (zero yield point in shear) in the plane of the solid surface and presents no obstacle to an increase of the solid—liquid interfacial area (advancing of the three-phase boundary line). In planes normal to the solid surface the structure has a positive yield point in shear, which prevents decrease of the solid—liquid interfacial area (receding of the three-phase line) until the yield point is exceeded by the surface pressure πSL. Mechanical stability of the system at all values of the contact angle between the “advancing” and “receding” angles θA and θR is ascribed to a continuously changing value of πSL and of the corresponding specific interfacial free energy γSL in this interval. This change reflects the elastic response in shear of the solid—liquid interfacial film in planes normal to the solid surface in this interval.

1812. Omenyi, S.N., R.P. Smith, and A.W. Neumann, “Determination of solid/melt interfacial tensions and of contact angles of small particles from the critical velocity of engulfing,” J. Colloid and Interface Science, 75, 117-125, (May 1980).

The critical velocity of engulfing Vc of acetal, nylon-6,6, and nylon-12 particles when encountered by the solidification front of salol is reported as a function of particle size. Using the dimensional analysis derived previously, the free energy of adhesion ΔFadh for the attachment of these particles to the salol solid/melt interface is determined. These values of ΔFadh, together with the known surface tension values γPV of the particles, are used to determine the salol solid/melt interfacial tension γSL to be γSL = 0.0053 ± 0.0025 erg/cm2. Similarly, the free energies of adhesion ΔFadh for PMMA particles to the solid/melt interfaces of naphthalene, biphenyl, and salol are determined. As all the γSL values for these systems are known—in the case of naphthalene and biphenyl from the temperature dependence of contact angles—γPV for the PMMA particles is determined. Using the equation of state for interfaces, the contact angle for the system PMMA/water is predicted. This value is in excellent agreement with the contact angle of water on a film of PMMA obtained by solvent casting. It is concluded that measurement of the critical velocity of engulfing represents a unique method for contact angle determinations on small particles.

1517. Holland, L., “Glow discharge excitation and surface treatment in low-pressure plasmas,” in Low Energy Ion Beams (Conference Series No. 54), L.H. Wilson and K.G. Stephens, eds., 220-228, Institute of Physics, Apr 1980.

Advances in glow discharge excitation for sputtering and surface treatment are reviewed. Conditions for the production of the glow discharges either by using a DC supply with a cold cathode or using an RF supply capacitively coupled to an electrode are discussed. Examples are given of surface treatment processes at present under study including RF magnetron sputtering of silica, a-C film growth in hydrocarbon plasmas and plasma nitriding.

1279. Carley, J.F., and P.T. Kitze, “Corona-discharge treatment of polymeric films, II. Chemical studies,” Polymer Engineering and Science, 20, 330-338, (Mar 1980).

Polymeric films, chiefly polyethylenes, were subjected to corona-discharge treatment in a continuous treater at commercial rates in a program covering wide ranges of the main processing factors (2). Electron-spin-resonance measurements on freshly treated films found no free radicals. Reactions of the treated surfaces with a free-radical compound, diphenyl picryl hydrazyl (DPPH) were studied, focusing mainly on the rate effects. The evidence indicates that corona treatment produces fairly stable peroxide structures of the forms RO2R and RO3R on polyethylene surfaces. RO3R reacts rapidly with DPPH alone, while RO2R undergoes a slower reaction after addition of the catalyst, triethylene diamine. DPPH is capable of detecting as few as 1013 peroxide groups per square centimeter. Activation energies were 12 kcal/mole for the uncatalyzed reaction and 16 kcal/mole for the amine-catalyzed reaction. As with the physical effects reported earlier (2), the production of peroxides is most strongly dependent on the energy delivered to the film during treatment. This energy is proportional to the quotient of corona current and web speed, I/S, Regression analysis showed that air-gap thickness, relative humidity, and number of electrodes used also were significant factors, while dielectric thickness and corona frequency were not. We found that-γ, the polar component of surface energy of the treated film, which is nearly zero for untreated polyethylenes, is exponentially related to the concentrations of both RO2R and RO3R with a correlation coefficient for 92 specimens tested of 0.88. We believe this is the first strong evidence linking treatment factors, at commercial levels of treatment, to chemistry of the treated surface and linking both of those to changes in physical behavior of the surface.

 

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