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108. Fowkes, F.M., “Comments on 'The calculation of cohesive and adhesive energies', by J.F. Padday and N.D. Uffindell (letter),” J. Physical Chemistry, 72, 1407, (1968).

Sir: Padday and Uffindell produced a well organized and readable article, but unfortunately their mathematics is incorrect (by nearly one order of magnitude) because intermolecular potentials were integrated over molecular distances, breaking a fundamental principle of integral calculus.

2865. Newman, S., “The effect of composition on the critical surface tension of polyvinyl butyral,” J. Colloid and Interface Science, 25, 341-345, (Nov 1967).

The critical surface tension γc of polyvinyl butyral has been measured with polyhydric alcohols and halogenated hydrocarbons. Despite variations in polymer composition (residual OH content) and modes of preparation, γc is found to be 24–25 dynes/cm. with the former class of liquids. The —CH3 groups appears to predominate over —CH2, ether oxygen, and OH groups present. Steric effect may account for this biasing of the γc values toward the lowest surface energy group present. Fowkes' relation based on dispersion force interactions only is found to fit the data reasonably well. Comparative data on polyethylene are also presented.

1850. Newman, S., “The effect of composition on the critical surface tension of polyvinyl butyral,” J. Colloid and Interface Science, 25, 341-345, (Nov 1967).

The critical surface tension γc of polyvinyl butyral has been measured with polyhydric alcohols and halogenated hydrocarbons. Despite variations in polymer composition (residual OH content) and modes of preparation, γc is found to be 24–25 dynes/cm. with the former class of liquids. The —CH3 groups appears to predominate over —CH2, ether oxygen, and OH groups present. Steric effect may account for this biasing of the γc values toward the lowest surface energy group present. Fowkes' relation based on dispersion force interactions only is found to fit the data reasonably well. Comparative data on polyethylene are also presented.

2867. Bright, K., and B.A.W. Simmons, “Testing the level of pretreatment of polyethylene film using critical surface tension measurements,” European Polymer J., 3, 219-222, (May 1967).

A method is described for measuring the level of pretreatment of polyethylene films in terms of critical surface tensions. Drops of water-dioxan mixtures of various surface tensions are placed upon the pretreated films and their critical surface tensions assessed from the spreading behaviour of the liquids.

A suggestion is made for using this method as a process control test.

2308. Sullivan, M.W., “Process and apparatus for treating plastics,” U.S. Patent 3308045, Mar 1967.

1792. Dettre, R.H., and R.E. Johnson, Jr., “Concerning the surface tension, critical surface tension, and temperature coefficient of surface tension of poly(tetrafluoroethylene),” J. Physical Chemistry, 71, 1529-1531, (Apr 1967).

2354. Mantell, R.M., “Method of treating synthetic resinous material to increase the wettability thereof,” U.S. Patent 3309299, Mar 1967.

2780. Jones, W.C., and M.C. Porter, “A method for measuring contact angles on fibres,” J. Colloid and Interface Science, 24, 1+, (1967).

A technique has been developed for rapid and extremely accurate measurements of contract angles formed by liquids on the surface of small-diameter filaments. The light beam reflection technique first de- scribed by Langmuir and Sehaeffer (1) and recently by Fort and Patterson (2) for liquid drops on flat plates has been refined for use with filaments and microscope equipment.

2773. Shafrin, E.G., and W.A. Zisman, “Critical surface tension for spreading on a liquid substrate,” J. Physical Chemistry, 71, 1309-1316, (1967).

A plot of the initial spreading pressures F sub ba or initial spreading coefficients S sub ba against the surface tensions of a homologous series of organic liquids b can be used to determine the critical surface tension for spreading on a second substrate liquid phase a. Straight-line relations are found for various homologous series. The intercept of that line with the axis of abscissas F sub ba 0, or S sub ba 0 defines a value of spreading for that series. This method is advantageous because it eliminates the need for measuring or calculating the contact angle of lens b floating on liquid a, it can be applied to any liquid substrate, and it is applicable even when spreading does not lie within the range of surface tensions of the members of the homologous series of liquids b. The value of spreading for the waterair interface was determined in this way using several homologous series of pure hydrocarbon liquids. The lowest value found was 21.7 dynescm at 20 deg C for the n-alkane series. Higher spreading values were obtained using olefins or aromatic hydrocarbons as the result of interaction between the unsaturated bond and the water surface. Since the results are analogous to those reported earlier for solid surfaces, it is concluded that the clean surface of water behaves as a low-energy surface with respect to low-polarity liquids. This result is to be expected if only dispersion forces are operative between each alkane liquid and water.

1335. Hellwig, G.E.H., and A.W. Neumann, “Contact angles and wetting energies pertinent to pigment behaviour,” Farbe und Lack, 73, 823-829, (1967).

1322. Neumann, A.W., and P.J. Sell, “Estimation of surface tensions of polymers from contact angle data without neglecting the equilibrium spreading pressure,” Kunststoffe, 57, 829-834, (1967).

938. Iyengar, Y., and D.E. Erickson, “Role of adhesive-substrate compatability in adhesion,” J. Applied Polymer Science, 11, 2311-2324, (1967).

For substrates such as polyesters having limited capacity for hydrogen bonding or other specific interactions, thermodynamic compatibility of the substrate and adhesive is shown to be a key factor in promoting bondability to the substrate. Such compatibility occurs, as shown by Abere, when the cohesive energy densities (CED) or solubility parameters (δ = √CED) of substrate and adhesive are matched. Investigations with polyester film-adhesive-film model systems with the use of a variety of nonpolar (hydrocarbon) and polar (chlorinated compounds, ethers, esters) adhesives illustrate how compatibility promotes bondability to poly(ethylene terephthalate). The poor adhesion of polyester fibers to resorcinol–formaldehyde–latex (RFL) adhesives is attributed to the incompatibility of resorcinol (δ = 16.0) with the polyester (δ = 10.3). Adhesion to RFL was improved by substituting the more compatible n-hexyl resorcinol (δ = 12.5) for resorcinol in RFL adhesives. Currently, the best adhesive systems for polyester tire yarns are those (e.g., isocyanate–epoxy) involving formation of urethane polymers having matching δ values with poly(ethylene terephthalate).

472. Hansen, C.M., “The three dimensional solubility parameter - key to paint component affinities, III. Independent calculation of the parameter components,” J. Paint Technology, 39, 511+, (1967).

471. Hansen, C.M., “The three dimensional solubility parameter - key to paint component affinities, II. Dyes, emulsifiers, mutual solubility and compatability, and pigments,” J. Paint Technololgy, 39, 505-510, (1967).

The concept that the solubility parameter is a vector composed of hydrogen bonding, polar, and dispersion components is proposed and applied with success to prediction of the solubility of 33 poylmers and resins in 90 solvents and 10 plasticizers. The application of the solubility parameter concept is described. The three dimensional solubility parameter system based on the homomorph concept has been developed on the basis of polymer solubility. The same system has been applied to the characterization of dyes, nonionic emulsifiers, and pigments. The system is also useful for selecting solvents when protective coatings are formulated with more than one polymeric solute.

470. Hansen, C.M., “The three dimensional solubility parameter - key to paint component affinities, I. Solvents, plasticizers, polymers, and resins,” J. Paint Technology, 39, 104+, (1967).

The concept that the solubility parameter is a vector composed of hydrogen bonding, polar, and dispersion components is proposed and applied with success to prediction of the solubility of 33 polymers and resins in 90 solvents and 10 plasticizers. Solvents and plasticizers can be located as points in a three dimensional system, and regions of solubility are found for polymers and resins when solubility data are plotted. Non-interacting solvents which in a mixture become interacting have been found with better than 95% accuracy in over 400 cases.

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.

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

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

2353. McBride, R.T., and J.H. Rogers Jr., “Adheribility treatment of thermoplastic film,” U.S. Patent 3284331, Nov 1966.

2317. Winder, R.P.H., “Method and apparatus for treating plastic coated paper,” U.S. Patent 3281347, Oct 1966.

691. Wolinski, L.E., “Surface treatment of polymeric shaped structures,” U.S. Patent 3274089, Sep 1966.

2352. Gould, D.E., and L.A. Preli Jr., “Treating of plastic coated foils,” U.S. Patent 3257303, Jun 1966.

1781. Dettre, R.H., and R.E. Johnson, Jr., “Surface properties of polymers I: The surface tensions of some molten polyethylenes,” J. Colloid and Interface Science, 21, 367-377, (Apr 1966).

A modified Wilhelmy plate technique has been developed for the measurement of surface tensions of viscous polymers. The method requires no knowledge of liquid density and provides a means of assuring a zero contact angle for the polymer on the plate. The surface tensions of several silicone polymers with viscosities as high 106 centipoises have been measured. The method has also been used to determine the surface tensions of several molten polyethylenes as a function of temperature over the range 115° to 215°C.

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

1650. Good, R.J., “On the estimation of surface energies from contact angles,” Nature, 212, 276-277, (1966).

1523. Good, R.J., “Estimation of surface energies from contact angles,” Nature, 212, 276-277, (1966).

A RECENT communication by Gray1 illustrates a possible pitfall in the use of the theories of Fowkes2–5 and Good and Girifalco6,7 to estimate surface energies, and the various components of surface energy, from contact angles. This source of error is the incorrect identification of the surface tension terms, and the equating of the contact angle in a contaminated, experimental system to that in a system composed of properly pure components. Thus, Gray wrote Fowkes's equation in the form

mathmatical formual
and used his observed contact angle data for mercury on polyethylene, paraffin wax and polytetrafluoroothylene, together with Fowkes's estimates of γds for the solids and of γdL for mercury, to calculate values for γL for mercury. The fact that the values of γL turned out to be very much larger than 485 dynes/cm was then taken to be an unexplained discrepancy in the theory. In his discussion, Gray apparently also misinterpreted a remark of Fowkes5 about the effect of a contaminant in the mercury on the observed contact angle.

945. Gray, V.R., “Contact angles, their significance and measurement,” in S.C.I. Monograph #25 : Wetting, 99-119, S.C.I., 1966.

462. Gardon, J.L., “The influence of polarity upon the solubility parameter concept,” J. Paint Technology, 38, 43, (1966).

365. Timmons, C.A., and W.A. Zisman, “The effect of liquid structure on contact angle hysteresis,” J. Colloid and Interface Science, 22, 165-171, (1966).

Contact angle hysteresis was measured for a variety of liquids on condensed monolayers of 17-(perfluoroheptyl)heptadecanoic acid adsorbed on polished chromium. The hysteresis was shown to be simply related to the molecular volume of the liquid and to result from the penetration of liquid molecules into the porous monolayer. However, contact angle hysteresis was negligible when the average diameter of the liquid molecules was larger than the average cross-sectional diameter of the intermolecular pores. It is shown that it is possible to estimate intermolecular pore dimensions of such adsorbed monolayers by contact angle hysteresis measurements on a series of liquids having gradations in molecular volume. The results of this investigation reveal that liquid penetration, even into pores of molecular dimensions, is a cause of significant contact angle hysteresis, and it is also shown how liquids can be selected for contact angle investigations on organic solid surfaces so that there will be freedom from this source of hysteresis. The results also suggest that under these experimental conditions, liquid water, on the average, behaves as if it were associated in clusters of about six water molecules. Similarly, both ethylene glycol and glycerol behave as associated clusters of about two molecules.

155. Hansen, R.H., and H. Schonhorn, “A new technique for preparing low surface energy polymers for adhesive bonding,” J. Polymer Science, Polymer Letters Edition, 4, 203-209, (1966).

Contact time of activated gas with polymer film of as little as 1 sec. under these relatively mild conditions resulted in greatly improved adhesive joint strength for polyethylene. Longer contact times were required for polymers such as polytetrafluoroethylene. Helium, argon, krypton, neon, and xenon, and even hydrogen and nitrogen were all effective crosslinking agents although the latter also changed wettability of the surface. Adhesive joints were prepared by sandwiching 1041 films of polyethylene (Marlex 5003, Phillips Petroleum Co., Bartlesville, Oklahoma) and polytetrafluoroethylene (G-80, Allied Chemical Co., Morristown, New Jersey), before and after CASING, between epoxy-coated aluminum strips (3). The values obtained for tensile shear strengths of these joints are shown in Figure 1. In these instances, the polyethylene film was treated for 10 sec. and the polytetrafluoroethylene film was treated for 10 min.

2351. Rosenthal, L.A., “Treating of plastic surfaces,” U.S. Patent 3196270, Jul 1965.

2316. Brandt, R., and C.H. Hartford, “Corona treating of shaped articles,” U.S. Patent 3183352, May 1965.

2337. Zisman, W.A., “Surface properties of plastics,” Record of Chemical Progree, 26, 23+, (1965).

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

1839. Roe, R.-J., “Parachor and surface tension of amorphous polymers (letter),” J. Physical Chemistry, 69, 2809-2810, (1965).

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).

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).

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

154. Hansen, R.H., J.V. Pascale, T. DeBenedictis, and P.M. Rentzepis, “Effect of atomic oxygen on polymers,” J. Polymer Science, 3, Part A, 2205-2214, (1965).

2338. Mantell, R.M., and W.L. Ormand, “Activation of plastic surfaces in a plasmajet,” Industrial & Engineering Chemistry, 3, 300-303, (Dec 1964).

 

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