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557. Savolainen, A., J. Kuusipalo, and H. Karhuketo, “Optimization of corona and flame pretreatment in multilayer coating,” in 1991 Extrusion Coating Short Course (Dusselfdorf), 333-340, TAPPI Press, 1991.

312. Sayka, A., and J.G. Eberhart, “The effect of plasma treatment on the wettability of substrate materials,” Solid State Technology, 32, 69-70, (May 1989).

2718. Schafer, J., T. Hofmann, J. Holtmannspotter, M. Frauenhofer, J. von Czarnecki, and H.-J. Gudladt, “Atmospheric-pressure plasma treatment of polyamide 6 composites for bonding with polyurethane,” J. Adhesion Science and Technology, 29, 1807-1819, (2015).

An atmospheric-pressure plasma jet (APPJ)-based surface treatment process was investigated for the structural (τB > 15 MPa) adhesive bonding of polyamide 6 (PA6) composites. The treated surfaces were examined by contact angle measurement, X-ray photoelectron spectroscopy, and atomic force microscopy (AFM). Additionally, the shear strengths of single lap specimens were determined as a function of different plasma intensities and polyurethane adhesives. Our results show that APPJ leads to an increase of the surface free energy, oxygen concentration, and number of functional groups. Furthermore, the topography of the surface was significantly modified by exposure to APPJ. AFM measurements show that special attention has to be paid to the intensity of the plasma treatment to avoid melting and flattening of the PA6 surface on the nanometer scale. With optimized multiple APPJ treatments, lap shear strength of 20 MPa was achieved for the first time for this material system, allowing the material system to be employed in future automobile applications.

1281. Schleising, E., “Corona discharge treatment,” FlexoTech, 13, 26, (1997).

314. Schmidt, J.J., J.A. Gardella Jr., J.H. Magill, and R.L. Chin, “Surface spectroscopic studies of polymer surfaces and interfaces, II. Poly(tetramethyl-P-silphenylenesiloxane/poly(dimethylsiloxane) block copolymers,” Polymer, 28, 1462-1466, (1987).

The surface region of a series of poly(tetramethyl-p-silphenylenesiloxane)poly(dimethylsiloxane) block copolymers was investigated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infra-red spectroscopy. Analysis of the results shows the surface region to be equivalent to the bulk composition for all but one sample. This indicates that for all but the most crystalline samples the surface region comprises a relatively thick layer of non-crystalline amorphous domains.

313. Schmidt, J.J., J.A. Gardella, Jr., and L. Salvati Jr., “Surface studies of polymer blends, II. An ESCA and IR study of poly(methylmethacrylate)/poly(vinyl chloride) homopolymer blends,” Macromolecules, 22, 4489-4495, (1989).

Angle-dependent ESCA and ATR-FTIR results are presented for homopolymer blends of poly(Methyl methacrylate) and poly(vinyl chloride}. Blends over the entire composition range were cut from tetrahydrofuran (THF) and methyl ethyl ketone (MEK). Surfacee enrichment of PMMA was present at all compositions of blends cast from THF, while blends cast from MEK exhibited surface compositions that were within error limits equivalent to the bulk compositions in the blends.

619. Schmitt, M., M. Schmitt, M. Schmitt, and F. Heib, “A more appropriate procedure to measure and analyse contact angles/drop shape behaviours,” in Advances in Contact Angle, Wettability and Adhesion (Vol. 3), K.L. Mittal, ed., 1-57, Scrivener, Feb 2018.

Surface science, which comprises the preparation, development and analysis of surfaces, is of utmost importance in both fundamental and applied sciences as well as in engineering and industrial research. During our research in the field of coatings/surfaces and coating materials, the analyses of wetting of coating materials and the coatings themselves led us to the field of dynamically performed drop shape analysis. We focussed our research efforts on the main problem of the surface science community, which is to determine the correct and valid definition and measurement of contact angles. So we developed the high-precision drop shape analysis (HPDSA) and three statistical contact angle determination procedures. HPDSA involves complex transformation of images from dynamic sessile drop experiments to x-y-coordinates and opens up the possibility of a physically meaningful calculation of curvature radii. This calculation of radii is the first step to an “assumption-free” link to the Laplace equation, which can deepen the understanding of the interface between the liquid and the vapour in relation to different properties and conditions (temperature, experimental technique, surface, etc.). The additional benefit of a tangent-free calculation of contact angles is presented in our 2014 and 2016 published papers. To fulfil the dire need for a reproducible contact angle determination/definition, we developed three procedures, namely, overall, global, and individual statistical analyses, which are based on, but not restricted to, HPDSA . . .

315. Schoff, C.K., “Wettability phenomena of coatings,” in Modern Approaches to Wettability: Theory and Applications, Schrader, M.E., and G.I. Loeb, eds., 375-395, Plenum Press, Oct 1992.

1116. Schoff, C.K., “Coatings clinic: Wetting and wettability,” JCT CoatingsTech, 1, 108, (Oct 2004).

1167. Schoff, C.K., “Coatings clinic: Surface tension and surface energy,” JCT CoatingsTech, 3, 72, (Feb 2006).

2154. Schoff, C.K., “Coatings clinic: Interfaces and migration,” JCT CoatingsTech, 6, 48, (May 2009).

2646. Schoff, C.K., “Application defects,” CoatingsTech, 13, 32-39, (Apr 2016).

1916. Scholberg, H.M., R.A. Guenther, and R.I. Coon, “Surface chemistry of fluorocarbons and their derivatives,” J. Physical Chemistry, 57, 923-925, (1953).

Data are given for the free surface energy of a number of fluorocarbons. These data show that fluorocarbons as a class have lower surfaceenergies than all other compounds. Curves for the lowering of surface tension as a function of concentration are given for a series ofcompletely fluorinated acids. These surface active compounds cause a greater lowering of the surface tension of water than has ever been found before. Fluorocarbon surface active compounds are shown to lower the surface tension of organic substances very materially. Some measurements of interfacial tensions between fluorocarbons and water and between fluorocarbons and organic solvents are presented. An attempt is made to show some correlation between the above effects in the formation of emulsions and in the wetting of fluorocarbon surfaces.

316. Schonhorn, H., “Theoretical relationship between surface tension and cohesive energy density,” J. Chemical Physics, 43, 2041-2043, (1965).

The rigid‐sphere theory of liquids is shown to yield an expression for the surface tension of a one‐component liquid which is essentially identical to an expression previously derived by the author employing a qualitative approach. Such a correlation suggests that the rigid‐sphere theory of liquids approach is applicable to a wide variety of nonpolar polymeric liquids.

321. Schonhorn, H., “Heterogeneous nucleation of polymer melts on high-energy substrates, II. Effect of substrate on morphology and wettability,” Macromolecules, 1, 145-151, (1968).

Heterogeneous nucleation and crystallization of polymer melts against high-energy surfaces (eg, metals, metal oxides, and alkali halide crystals) have been found to result in markedchanges in both thesurface region morphology and wettability of these polymers even though the chemical constitution of the polymer is un-changed. The critical surface tensions (7c) of a variety of polymers nucleated against gold are considerably in excess of the commonly accepted values. Employing a modified Fowkes-Young equation can account for these sizable differences if the surface layer of these crystallizable polymers generated against high-energy surfaces is essentially crystalline.

917. Schonhorn, H., “Surface modification of polymers for adhesive bonding,” in Polymer Surfaces, Clark, D.T., and W.J. Feast, eds., 213-233, John Wiley & Sons, 1978.

1835. Schonhorn, H., “Dependence of contact angles on temperature: Polar liquids vs. polypropylene,” J. Physical Chemistry, 70, 4086-4087, (Dec 1966).

1841. Schonhorn, H., “Dependence of contact angles on temperature: Polar liquids on polyethylene,” Nature, 210, 896-897, (1966).

685. Schonhorn, H., F.W. Ryan, and R.H. Hansen, “Surface treatment of polypropylene for adhesive bonding,” J. Adhesion, 2, 93-99, (Apr 1970).

The CASING (crosslinking by activated species of inert gases) treatment of polypropylene film in both oxygen and nitrous oxide is shown to be an effective surface treatment for conventional adhesive bonding. A crosslinked surface extending to a depth of about 300 Å, apparently independent of exposure time, is produced in both excited oxygen and nitrous oxide.

320. Schonhorn, H., and F.W. Ryan, “Effects of morphology in the surface region of polymers on adhesion and adhesive joint strength,” J. Polymer Science Part B: Polymer Physics, 6, 231-240, (1968).

The morphological character of the surface region of polyethylene has been considered with respect to adhesion and adhesive joint strength. By melting polyethylene onto a high-energy surface (e.g., aluminum) we have provided for extensive nucleation and the formation of a transcrystalline region in the polymer. Dissolution of the metal rather than peeling the metal from the polymer leaves the surface region of the polymer intact. The polymer sheet is now amenable to conventional adhesive bonding and forms a strong adhesive joint. We conclude from this study that the occurrence of the normal weak boundary layer is a consequence of the morphology of the surface region of the material and is, therefore, influenced by the method of preparation.

323. Schonhorn, H., and F.W. Ryan, “Effect of polymer surface morphology on adhesion and adhesive joint strength, II. FEP Teflon and nylon 6,” J. Polymer Science Part B: Polymer Physics, 7, 105-111, (1969).

Heterogeneous nucleation and crystallization of FEP Teflon and nylon 6 melts against high energy surfaces (i.e., gold) produce an interfacial region, in these polymers, of high mechanical strength. Dissolution of the metal substrate rather than removal by mechanical means results in a polymer surface which is amenable to conventional structural adhesive bonding. Nucleation and crystallization of the polymer melts in contact with phases of low surface energy (e.g., vapor) result in the generation of weak boundary layers.

324. Schonhorn, H., and F.W. Ryan, “Surface crosslinking of polyethylene and adhesive joint strength,” J. Applied Polymer Science, 18, 235-243, (1974).

Exposure of polyethylene film to UV radiation at wavelengths of ≤2537 Å is sufficient to induce surface crosslinking and to facilitate the formation of strong adhesive joints to these surfaces with conventional adhesives. Reduction of the vapor pressure in the reaction vessel to about 1 torr apparently maximizes the efficiency of the crosslinking process. Examination of the treated films which have been exposed for times necessary to form strong adhesive joints has revealed an absence of surface oxidation. It appears that crosslinking to improve the mechanical strength of the surface region of the polyethylene is sufficient to allow the formation of strong adhesive joints.

1836. Schonhorn, H., and F.W. Ryan, “Wettability of polyethylene single crystal aggregates,” J. Physical Chemistry, 70, 3811-3815, (Dec 1966).

317. Schonhorn, H., and L.H. Sharpe, “Surface energetics, adhesion, and adhesive joints, III. Surface tension of molten polyethylene,” J. Polymer Science, 3, Part A, 569-573, (1965).

The surface tension of polyethylene has been measured by the ring method over the temperature range 125–193°C. Because of problems with the viscousness of the liquid polyethylene, it was found convenient to use an Instron testing apparatus instead of the usual du Nouy torsion balance. The surface tension of the polyethylene decreased from a value of 28.5 dynes/cm. at 125°C. to 23.3 dynes/cm. at 193°C. with an average temperature coefficient of −0.076 dynes/cm./°C.

318. Schonhorn, H., and L.H. Sharpe, “Surface energetics, adhesion, and adhesive joints, IV. Joints between epoxy adhesives and chlorotrifluoroethylene copolymer and terpolymer (Aclar),” J. Polymer Science, 3, Part A, 3087-3097, (1965).

It is shown that structural joints can be formed between conventional epoxy adhesives and copolymer and terpolymer of chlorotrifluoroethylene, at temperatures well below the softening points of these polymers, without their prior surface treatment. An explanation of this low temperature behavior is given in terms of the surface tension of the adhesive, surface roughness, and the micro-Brownian motion of the polymers associated with the glass transition.

1840. Schonhorn, H., and L.H. Sharpe, “Surface tension of molten polypropylene,” J. Polymer Science Part B: Polymer Letters, 3, 235-237, (1965).

Data for the surface tension of molten polymers are scarce and relatively incomplete (1, 2). Schonhorn and Sharpe (3) have recently reported the surface tension of a molten polyethylene over a wide temperature range as measured with a strain gage type testing apparatus (4). In the present communication, we report the surface tension of a molten polypropylene as a function of temperature using techniques described previously (3). For this study we chose a completely atactic low molecular weight (in= 3,000) polypropylene, Epolene D-10, supplied by Eastman Chemical Products, Incorporated, Kingsport, Tennessee. This material was purified further by dissolving the polypropylene in xylene and then precipitating it with isopropyl alcohol. This process was repeated twice. The final product was colorless and probably had a higher in since low molecular weight fractions would tend to remain in the eluent. The details of the experimental procedures and standardization of the modified du Nouy technique are described elsewhere (3). The ring employed in this study was calibrated with a variety of low viscosity liquids. The manually operated du Nouy tensiometer was found to be inadequate because of the high viscosity of the liquid polymer and the sluggish response of the film under load. At the low crosshead speed of 0.02 in./min., no decay in force was noted when the crosshead was stopped. At higher crosshead speeds (> 0.05 in./min.) there was an increasingly large decay in the force as a function of time. By employing atactic polypropylene we were able to operate at lower temperatures. Dry preheated nitrogen was continually passed through the oven chamber to preclude oxidation of the molten polypropylene. Samples aged at 199OC. for an hour showed no change of surface tension with time. One hour is considerably longer than the time necessary for a determination. Measurements were repeated a minimum of three times for each recorded temperature.

319. Schonhorn, H., and R.H. Hansen, “Surface treatment of polymers for adhesive bonding,” J. Applied Polymer Science, 11, 1461-1473, (1967).

Further studies of a new and highly effective method for the surface treatment of low surface energy polymers for adhesive bonding are reported. Mechanisms are suggested for the increase in the cohesive strength in the surface region of polyethylene when it is exposed to activated species of inert gases. The technique is unique because, in contrast with results obtained with other methods, bulk properties of the polymer such as color or tensile strength and elongation are unaffected and surface properties such as wettability and dielectric properties such as surface conductivity are essentially unchanged.

322. Schonhorn, H., and R.H. Hansen, “Surface treatment of polymers, II. Effectiveness of fluorination as a surface treatment for polyethylene,” J. Applied Polymer Science, 12, 1231-1237, (1968).

An effective surface treatment for adhesive bonding of polyethylene has been developed. It involves exposing the polymer to an environment of elemental fluorine or fluorine diluted in argon. By this treatment, extensive fluorination of the surface region is effected. The fluorinated surface permits formation of strong adhesive joints by conventional adhesive bonding techniques even though the wettability of the new surface is similar to polytetrafluoroethylene. We believe that treatment of the polymer with elemental fluorine effectively eliminates the weak boundary layer associated with polyethylene by either crosslinking or by increasing the molecular weight in the surface region.

1518. Schonhorn, H., et al, “Surface modification of polymers and practical adhesion,” Polymer Engineering and Science, 17, 440-449, (1977).

The, nature of polymer surfaces has received increasing attention as the use of these materials, in a variety of forms, increases yearly. Modifications of polymer surfaces for adhesion, friction, and diffusion oriented appiications have necessitated a careful analysis of the surfade region morphology (surface physics) and chemical properties of the surface layer (surface chemistry). The behavior of composite structures has involved the discipline of classical fracture mechanics. The orientation of polymeric species or additives which migrate to the interface may modify the wetting characteristics and, most certainly, the frictional properties in addition to the diffusion of penetrant species beyond the boundary layer. The above topics are discussed within the framework of recent analytical and theoretical developments in surface science. The findings of these recent studies have facilitated many exciting technological advances.

1098. Schrader, M.E., “Effect of adsorbed vapor on liquid-solid adhesion,” in Contact Angle, Wettability and Adhesion, Vol. 3, K.L. Mittal, ed., 67-94, VSP, Nov 2003.

An overview is presented of a series of papers published during the last decade which show that the conventional thermodynamic approach to liquid—solid adhesion requires some fundamental changes. It is pointed out that it has been a long-neglected fact that adsorption, as generally measured in adsorption isotherms, is actually surface excess, so that it can, in principle, be negative as well as positive. As a result, the free energy of adsorption, AF, can be positive as well as negative. Small amounts of water vapor adsorbing onto previously evacuated poly (tetrafluoroethylene) could, in principle, therefore be increasing the free energy of the low-energy polymer surface. It is further pointed out that from the strictly thermodynamic point of view, changing the free energy of a surface by adsorption of the vapor of a liquid does not necessarily change the contact angle. Resulting changes in contact angle can, however, theoretically occur from changes in the intermolecular force interaction term (proposed work of adhesion), such as those terms proposed by Good and Girifalco, Fowkes and others, where such changes would be speculative. In addition, it is pointed out that an accurate thermodynamic representation of liquid-solid adhesion should take into account the shape of the drop to be deposited (or drop that has been detached), as well as the resulting contact angle. An equation is presented for the free energy of adhesion of a spherical drop.

325. Schrader, M.E., and G.I. Loeb, eds., Modern Approaches to Wettability: Theory and Applications, Plenum Press, Oct 1992.

878. Schramm, L.L., Dictionary of Colloid and Interface Science, Wiley-Interscience, Jan 2001.

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.

1970. Schreiber, H.P., M.D. Croucher, and C. Prairie, “On multi-valued surface properties of PMMA films,” J. Adhesion, 11, 107-112, (1980).

An apparent link between the surface properties of polar group-containing polymers, such as PMMA and Styrene/Acrylic copolymers, and the thermodynamic quality of solvents used in solutions from which the polymers were cast, was described in earlier papers.1,2 In these polymers, significant variations have been observed in critical surface tensions(γc), and in the thermodynamic interaction parameters for selected vapor-polymer pairs, when the configuration of the polymer in solution was varied through the suitable selection of solvents of differing thermodynamic quality. The “solvent history” effect on surface properties of solid film was not detected however for non-polar polymers such as polystyrene (PS).1,2 Apparently the distinct chain configurations adopted in solution by PMMA are carried over into the solid and result in different proportions of non-polar (backbone) and polar (side chain) moieties being located in the surface layer of the solid. Since only one surface state can correspond to a thermodynamic equilibrium, it may be expected that the film surface properties will change with time, as the thermodynamically preferred state is attained. As a consequence, use properties of these films should also display (initially) the “solvent history” effect, and should vary similarly with time. The present communication is concerned with these points.

558. Schreiber, H.P., and F. Ewane-Ebele, “On the surface tension and its temperature variation in film-forming polymers,” J. Adhesion, 9, 175+, (1978).

A thermal gradient bar has been used for convenient measurements of γc and dγc/dT in complex polymers used as film-formers. The technique yields both γc and its temperature variation in one experimental sequence well suited for rapid, routine applications. Surface tension data have been obtained for a styrene-acrylic terpolymer, and these have also been used to characterize the compatibility of external plasticizers for the polymer. The surface tension approach has shown that glyceryl dibenzoate, though compatible with the polymer at temperatures above ∼70°C becomes incompatible at use temperatures, and exudes to the polymer film surface. Measurements of moisture sensitivity in plasticized polymer samples have confirmed the incompatibility and illustrated one of the applications to which the gradient bar and its data generation potential may be put.

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.

559. Schreiber, H.P., et al, “Inverse gas chromatography (IGC): a versatile tool for polymer surface characterization,” in ANTEC 95, Society of Plastics Engineers, Apr 1995.

2101. Schroder, K., A. Meyer-Plath, D. Keller, W. Besch, G. Babucke, and A. Ohi, “Plasma-induced surface functionalization of polymeric biomaterials in ammonia plasma,” Contributions to Plasma Physics, 41, 562-572, (2001).

Plasma-chemical modification is frequently used to improve the adaption of polymer surfaces to biological environments. In this regard amino functional groups play a key role. They provide an excellent basis for subsequent modifications with specific biomolecules. It would be of great value to get an amino functionalization independent of the specific material in use. The paper reports on an investigation concerning the feasibility of such an universal plasma functionalization procedure. Two different downstream microwave plasma sources were taken to apply a procedure, which was developed for high-grade modification of polystyrene (PS), to a number of other polymers including polyetheretherketone (PEEK), polyethyleneterephthalate (PET), polyethylenenaphthalate (PEN), polycarbonate (PC), polyethylene (PE), polymethylmethacrylate (PMMA) and fluorinated polymers. In many cases, very similar results were obtained. At maximum 5% of the surface were covered by nitrogen functional groups. In some cases, about 50% of total nitrogen functional groups were amino groups. The results suggest that a downstream ammonia plasma treatment indeed is a fairly universal method for high performance amino functionalization of polymeric biomaterials.

694. Schubert, G., “Adhesion of coatings to aluminum foil - a sticky issue,” in 2002 PLACE Conference Proceedings, TAPPI Press, Sep 2002.

2571. Schubert, G., “Adhesion to foil: More than just a one-sided story,” in 2008 PLACE Conference Proceedings, 1123-1152, TAPPI Press, Sep 2008.

 

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