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1383. Lindland, T., and A. Peach, “Substrate preparation through direct flame,” in 1985 TAPPI Polymers, Laminations and Coatings Conference Proceedings, TAPPI Press, Aug 1985.

545. Pochan, M., et al, “XPS and contact angle investigation of corona treatment,” in 1985 Polymers, Laminations and Coatings Conference Proceedings, 109+, TAPPI Press, Aug 1985.

524. Markgraf, D.A., “Ozone decomposition in corona treatment,” in 1985 Polymers, Laminations and Coatings Conference Proceedings, 227+, TAPPI Press, Aug 1985.

2375. Priz, E., and B. Kluss, “Apparatus for the electric pretreatment of non-conductive foils,” U.S. Patent 4527969, Jul 1985.

1461. Rose, P.W., and E. Liston, “Gas plasma technology and surface treatment of polymers prior to adhesive bonding,” in Antec '85, 685-688, Society of Plastics Engineers, May 1985.

2374. Andrade, J.D., P.M. Triolo, L.M. Smith, and F.J. Miller, “Process for treating polymer surfaces to reduce their friction resistance characteristics when in contact with non-polar liquid, and resulting products,” U.S. Patent 4508606, Apr 1985.

928. Markgraf, D.A., “Practical aspects of determining the intensity of corona treatment,” TAPPI J., 68, (Feb 1985).

377. Ward, T.L., and R.R. Benerito, “Testing based on wettability to differentiate washed and unwashed cotton fibers,” Textile Research J., 55, 40-45, (Jan 1985).

Cotton fibers from four varieties were washed with water using two procedures that included several combinations of temperatures and water volumes. Wettability of unwashed and washed fibers was determined by contact angle measurement and by a sink-float technique. The sink-float technique could be used to sort washed and unwashed cotton fibers.

2067. Goldman, M., A. Goldman, and R.S. Sigmond, “The corona discharge, its properties and specific uses,” Pure and Applied Chemistry, 57, 1353-1362, (1985).

The main properties of corona discharges are reviewed, with emphasis on the features which make them unique for use as non-equilibrium chemical reactors : Their stability andease of operation over a wide range of gasesand pressures, including atmospheric : their sharply confined ionization regions where hot electrons interact with cold gas, inducing reactions without back reactions ; and their extended low field drift regions which act as gaseous electrolytes, inducing electrochemical reactions on surfaces. Present and future applications are discussed : Synthesis of ozone and ammonia, promotion of flames and combustion, surface treatment, and electrical insulation improvement.

1964. Yetka-Fard, M., and A.B. Ponter, “Surface treatment and its influence on contact angles of water drops residing on teflon and copper,” J. Adhesion, 18, 197-205, (1985).

The variation of contact angle of liquid sessile drops on solids has been attributed to roughness (Wenzel2), the static charge effect (Holly,3 Ponter and Yekta-Fard3) and contamination at the solid surface or in the liquid and gaseous phases.

1802. Lelah, M.D., T.G. Grasel, J.A. Pierce, and S.L. Cooper, “The measurement of contact angles on circular tubing surfaces using the captive bubble technique,” J. Biomedical Materials Research, 19, 1011-1015, (1985).

Circular tubings are used extensively in biomedical implants and devices. It is desirable to determine contact angles on the inner or outer surfaces of such tubing in its final fabricated form. In this study, a technique for the measurement of contact angles on tubing surfaces in an aqueous environment is reported. This has particular applications to biomaterials research, where polymer tubings contact the biologic environment. In this technique, air or octane captive bubble dimensions can be measured, and an underwater contact angle calculated from these dimensions. The validity of the technique was experimentally confirmed using Solution Grade Biomer and NIH standard polyethylene surfaces.

1634. Hsieh, Y.-L., and E.Y. Chen, “Improvement of hydrophilicity of poly(ethylene terephthalate) by non-polymer forming gaseous glow discharge,” Industrial & Engineering Chemistry Product Research and Development, 24, 246, (1985).

1490. Allain, C., D. Ausserre, and F. Rondelez, “A new method for contact angle measurement of sessile drops,” J. Colloid and Interface Science, 107, 5-13, (1985).

A new method to measure the contact angle θ of sessile drops deposited onto solid substrates is presented. The crux of the method is to use the drop as a convex mirror for large, collimated, incident laser beams. The reflected light is intercepted on a screen in the far field. It appears as a bright circular spot, the diameter of which is simply related to the beam angular divergence 4θ. Overall measuring accuracies can be made better than 0.1° for θ angles less than 45θ. Reproducibility is also excellent because of the natural averaging over the entire three-phase line boundary of the drop. It is estimated to be ±0.25°. An extension of the method, valid for all angles less than 90°, is to use the drop as a plano-convex lens. This is of course applicable only if the solid substrate is optically clear. The refracted light is then intercepted on a screen and analyzed to yield the contact angle through simple geometrical optics considerations. These two methods are demonstrated on a series of short-chain alkanes (hexane to hexadecane) in contact with hydrophobic glass slides and/or polytetrafluoroethylene plates.

1404. Sherman, P.B., “Corona treat - mechanical not electrical problem,” in 1985 Film Extrusion Conference Proceedings, 45, TAPPI Press, 1985.

603. Yasuda, H.K., Plasma Polymerization, Academic Press, 1985.

553. Ruckenstein, E., and S.V. Gourisankar, “Environmentally induced restructuring of polymer surfaces and its influence on their wetting characteristics in an aqueous environment,” J. Colloid and Interface Science, 107, 488-502, (1985).

In the conventional methods of estimating the wetting characteristics of solids from contact angle experiments, the surface energetic properties of the solid are assumed to be identical in the environments of both the surrounding medium and probe fluids. While this assumption is suitable for solids which possess rigid surface structures (such as glasses, ceramics, and metals for example), it is generally inapplicable to polymeric solids, since the surfaces of the latter are relatively mobile so as to be able to adopt considerably different configurations in different environments. Based on a recognition of this feature of polymeric surfaces, a sequence of contact angle experiments is suggested to estimate: (a) the instantaneous as well as equilibrium surface energetic properties of a polymeric solid in an aqueous environment and (b) the time required for the polymeric surface to attain its equilibrium wetting characteristics in the aqueous environment. In order to illustrate the applicability of the suggested contact angle procedure, it is necessary to prepare model polymeric surfaces, which are smooth in surface texture, nonporous, and also chemically homogeneous. Such model surfaces were prepared in this study, by radio frequency sputter deposition of thin solid films of oxidized fluorocarbon compounds (from a Teflon FEP target) onto the smooth surfaces of highly polished, single crystal silicon substrates. The estimation of the wetting characteristics of the sputtered polymer films in an aqueous environment was then carried out by the suggested contact angle procedure. The results of the contact angle experiments indicate that the solid-water interfacial free energy of the sputtered polymer film which was initially equilibrated in an octane environment, decreases from an instantaneous value of 50.88 dyn/cm to an equilibrium value of 26.59 dyn/cm, over a duration of about 24 h. Such a change in the solid-water interfacial free energy of these model polymeric surfaces can arise due to a time-dependent reorientation of the buried polar groups of the solid from its bulk to its surface, when it is placed in contact with a strongly polar liquid like water. This interpretation was found to be consistent with the results of ESCA characterization, which indicated that the outer surface layers of the sputtered polymeric specimen contained a fair amount of the polar oxygen atoms that are capable of reorienting themselves from either the interior of the solid to its surface or vice versa, depending on their surrounding environment.

536. Mier, M.A., and C.G. Seefried, “Surface characterization of corona treated polyethylene films,” in ANTEC 85, Society of Plastics Engineers, 1985.

484. Hoy, K.L., “Tables of Solubility Parameters,” Union Carbide Corp., Chemicals and Plastics Research and Development Dept., 1985.

460. Fulcher, M.R., “An evaluation of the measurement of wettability (MS thesis),” Univ. of Notre Dame, 1985.

415. Barton, A.F.M., “Applications of solubility parameters and other cohesion parameters in polymer science and technology,” Pure and Applied Chemistry, 57, 905-912, (1985).

Cohesion parameters (solubility parameters) provide one of the simplest methods of correlating and predicting the cohesive and adhesive properties of polymers and solvents from a knowledge of the properties of the individual components alone. It is therefore not surprising that there are severe limitations on their precision. Whether or not any correlation or prediction is ‘satisfactory’ depends on the precision that is expected or needed. When one is looking for relatively minor differences in behaviour, such as solubility differences between isomeric liquids or between polymers with different degrees of cross-linking, cohesion parameters may not be appropriate. The most important situation where caution is required in using Hildebrand parameters or Hansen parameters is where the extent of donor-acceptor (Lewis acid-Lewis base) interactions(particularly hydrogen bonding) within a component is very different from that between components.

387. Winters, H.F., R.P.H. Chang, C.J. Mogab, J. Evans, J.A. Thornton, and H. Yasuda, “Coatings and surface modification using low pressure non-equilibrium plasmas,” Materials Science and Engineering, 70, 53-77, (1985).

356. Strobel, M., S. Corn, C.S. Lyons, and G.A. Korba, “Surface modification of polypropylene with CF4, CF3H, CF3Cl, and CF3Br plasmas,” J. Polymer Science Part A: Polymer Chemistry, 23, 1125-1135, (1985).

ESCA and contact angle measurements were used to characterize the surfaces of polypropylene and glass substrates exposed to CF4, CF3H, CF3Cl, and CF3Br plasmas. The use of both organic and inorganic substrates allowed clear distinction between treatments which led to plasma polymerization and treatments which caused grafting of functional groups directly to the substrate surfaces. CF4 plasmas were the only treatments studied which fluorinated polypropylene surfaces directly, without the deposition of a thin, plasma-polymerized film. CF3H polymerized in a plasma, while CF3Cl and CF3Br plasmas caused chlorination and bromination of polypropylene surfaces, respectively. Correlations were made between the active species present in the plasmas and the surface chemistry observed on the treated polypropylene substrates.

267. Ogita, T., A.N. Ponomarev, S. Nishimoto, and T. Kagiya, “Surface structure of low-density polyethylene film exposed to air plasma,” J. Macromolecular Science, A22, 1135-1150, (1985).

The surface structures of low-density polyethylene (LDPE) film exposed to plasma or γ-ray in air were characterized by ESCA, IR, and EMS. The formation of trans C[dbnd]C bond on the LDPE film surface was observed by the exposure to ac air plasma (2 × 10−2 torr, 19 W plasma power). Large amounts of O and N atoms as an amide structure were incorporated into the polymer surface by the plasma treatment. These plasma reactions occurred mainly in the amorphous region, and the polymer surface became rough enough to have a microdomain structure upon increasing the plasma treatment time up to 3 h. γ-Irradiation of LDPE in air only brought about O-atom incorporation as ketone and ether linkages. The polymer surface did not undergo etching under γ-irradiation as it did in plasma treatment.

210. Lavielle, L., and J. Schultz, “Surface properties of graft polyethylene in contact with water, I. Orientation phenomena,” J. Colloid and Interface Science, 106, 438-445, (1985).

The reorganization of the surface of a polyethylene grafted with 1% acrylic acid during contact with water has been studied using contact-angle measurements, a color test, esterification, inverse gas chromatography and ESCA spectroscopy. The evolution of the surface properties of the polymer in contact with water is explained by movements of the macromolecular chains followed by the orientation at the surface of the acrylic grafts, initially buried in the bulk of the polymer. The concept of “potential” surface energy of a polymer is proposed.

126. Gerenser, L.J., J.F. Elman, M.G. Mason, and J.M. Pochan, “ESCA studies of corona-discharge-treated polyethylene surfaces by use of gas-phase derivatization,” Polymer, 26, 1162-1166, (1985).

Chemically specific gas-phase reactions have been used to tag corona-discharge-induced chemical species on the surface of polyethylene. These tag reactions provide distinct moieties that can be detected via e.s.c.a. to provide a surface count of induced species. Hydroxyl, epoxy, hydroperoxy, carboxylic acid and carbonyl populations are discussed as a function of corona energy input, time after treatment and water washings.

74. de Gennes, P.-G., “Wetting: statics and dynamics,” Review of Modern Physics, 57(3), P1, 827-863, (1985).

The wetting of solids by liquids is connected to physical chemistry (wettability), to statistical physics (pinning of the contact line, wetting transitions, etc.), to long-range forces (van der Waals, double layers), and to fluid dynamics. The present review represents an attempt towards a unified picture with special emphasis on certain features of “dry spreading”: (a) the final state of a spreading droplet need not be a monomolecular film; (b) the spreading drop is surrounded by a precursor film, where most of the available free energy is spent; and (c) polymer melts may slip on the solid and belong to a separate dynamical class, conceptually related to the spreading of superfluids.

1285. Ikezaki, K., T. Ishii, and T. Miura, “Thermal influence of vacuum deposition on metallic electrodes on TSC from positively corona-charged polyethylene films,” Physica Status Solidi, 85, 615-618, (Oct 1984).

Thermally stimulated currents (TSC) are studied in the temperature range between 30 and 130°C on positively corona-charged high-density polyethylene films. TSC spectra from these charged films strongly depend on the order of the processes: heat-treatment of the sample films prior to charging and vacuum deposition of metallic electrodes. They also depend on the electrode materials. Observed TSC behaviors are explained in terms of the thermal influence of the vacuum deposition of metallic electrodes. Charge stability of these charged films is also studied for samples with Al and Bi electrodes.

595. Watson, W.M., “Adhesion to polyethylene with water-based inks,” American Ink Maker, 62, 38-106, (Oct 1984).

414. Aspler, J.S., and M.B. Lyne, “The dynamic wettability of paper: influence of surfactant type on improved wettability of newsprint,” TAPPI J., 67, 96-99, (Oct 1984).

1986. Ponter, A.B., and M. Yetka-fard, “Contact angle variation on polymer surfaces,” J. Colloid and Interface Science, 101, 282-284, (Sep 1984).

It is demonstrated that extraneous electric charge can produce a large variation in contact angle for water drops on polytetrafluoroethylene surfaces.

1801. Li, S.K., R.P. Smith, and A.W. Neumann, “Wilhelmy technique and solidification front technique to study the wettability of fibres,” J. Adhesion, 17, 105-122, (Aug 1984).

The strength of fibre-reinforced materials depends heavily on the adhesion between the fibre and the resin. To predict the bond strength of the adhesion, it is desirable for the surface tension of the fibre to be known. Two independent methods, the Wilhelmy balance method and the solidification front method, were investigated. The fibres used for this investigation included a carbon fibre, Thornel 300®, and an aromatic poiyamide fibre, Kevlar.

In the Wilhelmy experiments three liquids, ethylene glycol, glycerol and distilled water were employed to measure the surface tensions of the test fibres. They were found to be 42.4 mJ/m2 and 43.7 mJ/m2 for the carbon fibre and Kevlar, respectively. These values agreed very well with the results obtained from the solidification front method, from which the carbon fibre was found to have a surface tension value of 41.8 mJ/m2 while that for Kevlar was 46.4 mJ/m2. Furthermore, error analysis has shown that the error limits of the experiments are within 5% of the resulting values. The reproducibility and accuracy of these two techniques indicate that they are viable for determining the surface tension of small diameter fibres.

1407. Schuelke, G.W., “Modern trends in corona treating,” in 1984 Polymers, Laminations and Coatings Conference Proceedings, 249+, TAPPI Press, Aug 1984.

1406. Markgraf, D.A., “Practical aspects of determining level of corona treatment,” in 1984 Polymers, Laminations and Coatings Conference Proceedings, 507+, TAPPI Press, Aug 1984 (also in 1985 Film Extrusion Conference Proceedings, p. 65+, TAPPI Press, 1985).

2115. Busscher, H.J., A.W.J. van Pelt, P. de Boer, H.P. de Long, and J. Arends, “The effect of surface roughening of polymers on measured contact angles of liquids,” Colloids and Surfaces, 9, 319-331, (May 1984).

Equilibrium, advancing and receding contact angles for five different liquids have been determined on twelve commercial polymers after various surface roughening procedures. It was found that influences of surface roughening on contact angles disappear if the stylus surface roughness RA is < 0.1 μm. Surface roughening tends to increase observed contact angles, if the contact angle on the smooth surface is above 86°, whereas contact angles decrease if the contact angle on the smooth surface is below 60°. For contact angles on the smooth surface between 60° and 86°, surface roughening was found not to influence measured contact angles. These results show a broad similarity in the trend, predicted by the early Wenzel equation, describing the influence of surface roughness on contact angles, although of course the stylus surface roughness RA is not identical to the theoretical r-parameter in the Wenzel equation.

1267. Steinhauser, H., and G. Ellinghorst, “Corona treatment of isotactic polypropylene in nitrogen and carbon dioxide,” Angewandte Makromolekulare Chemie, 120, 177-191, (Feb 1984).

Corona discharge treatment of isotactic polypropylene surfaces in N2 and CO2 was investigated by contact angle measurements and ESCA. The electrical characteristics of the discharges as well as the influence of indirect parameters (moment of air contact and ageing time) and direct parameters (applied charge, electrical field strength and film temperature) on the surface modification were determined. These investigations showed that electrons, emitted by photo effect are the dominant charge carriers and the main cause of surface activation. The active species in the surfaces (presumably radicals) can either perform crosslinking and H-abstraction or react with the discharge gas. In the N2-discharge the polymer radicals can only react with atomic or excited nitrogen whereas in CO2 they also react with ground state molecules. If the samples are brought into air contact after discharge leftover radicals are oxidized by atmospheric oxygen. In addition a UV-radiation causing activation in a surface layer was found. The bulk of the polymer is not influenced by corona discharge.

2110. Bottin, M.F., H.P. Schreiber, J. Klemberg-Sapieha, and M.R. Wertheimer, “Modification of paper surface properties by microwave plasmas,” J. Applied Polymer Science, 38, 193-200, (1984).

A large-volume microwave plasma (LMP) apparatus has been used to polymerize organosilicone and styrene vapors onto paper substrates. Polymerization rates were established in the active glow of the plasma and in the dark, downstream volume of the reactor. Rates decrease from about 70 Ä/s in the former to about 1 Ä/s in the latter space. Surface modifications of paper substrates were studied by measurements of contact angles, of resistivity, and of charge retention properties. Plasmapolymer layers increased water contact angles from about 45 for control paper samples to> 110 for plasma-treated specimens. Resistivity was increased by up to four orders of magnitude, and the charge retention of coated papers was increased significantly. Controlled variations of the environment into which materials were placed immediately after plasma polymerization led to changes in the property balance of paper, confirming that plasma-polymer surfaces remain in active states for some time following quenching of the plasma.

2109. Matsuzawa, Y., and H. Yasuda, “Semicontinuous plasma polymerization coating onto the inside surface of plastic tubing,” J. Applied Polymer Science, 38, 65-74, (1984).

A semicontinuous, if capacitively coupled plasma polymerization apparatus was designed and constructed to coat the internal surface of a small-diameter plastic tubing. The glow zone was restricted to a small area to obtain a uniform coating of plasma polymer over the entire length of tubing (13 m long). It was found that a uniform coating can be achieved by maintaining the glow discharge parameters and velocity of moving substrate. In such a reactor, it was found that the deposition rates obtained for plasma polymers of tetrafluoroethylene, hexafluoroethane, and hexafluoroethane/hydrogen were very high compared with those polymerized in a conventional plasma polymerization apparatus. Special attention was needed to avoid deposition of an excessively thick coating, which was found to damage the barrier characteristics of the coating

2108. Yasuda, T., M. Gazicki, and H. Yasuda, “Effects of glow discharges on fibers and fabrics,” J. Applied Polymer Science, 38, 201-214, (1984).

1485. Joanny, J.F., and P.G. de Gennes, “A model for contact-angle hysteresis,” J. Chemical Physics, 81, 552-562, (1984).

We discuss the behavior of a liquid partially wetting a solid surface, when the contact angle at equilibrium θ0 is small, but finite. The solid is assumed to be either flat, but chemically heterogeneous (this in turn modulating the interfacial tensions), or rough. For weak heterogeneities, we expect no hysteresis, but the contact line becomes wiggly. For stronger heterogeneities, we first discuss the behavior of the contact line in the presence of a single, localized defect, and show that there may exist two stable positions for the line, obtained by a simple graphic construction. Hysteresis shows up when the strength of the defect is above a certain threshold. Extending this to a dilute system of defects, we obtain formulas for the “advancing” and “receding” contact angles θa, θr, in terms of the distribution of defect strength and defect sharpness. These formulas might be tested by controlled contamination of a solid surface.

461. Gagnon, D.R., and T.J. McCarthy, “Polymer surface reconstruction by diffusion of organic functional groups from and to the surface,” J. Applied Polymer Science, 29, 4335-4340, (1984).

Three nonpolar organic polymers containing small amounts of polar functionality were studied with regard to their surface characteristics. Two of the materials, potassium chlorate/sulfuric acid-oxidized polyethylene and poly(ethylene-co-acrylic acid) display variable surface polarities which can be reversibly accessed by heating films of the polymers in air or aqueous sodium hydroxide. Sodium-reduced Teflon–FEP did not exhibit this characteristic. A combination of contact angle, ESCA, and ATR IR data are used to display that the surface changes are caused by migration of functional groups within the outer few tens of angstroms of the surface.

 

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