Fluorocarbon surfaces

The best known aspect, and the first one to find commercialization in the direct fluorination area, was the fluorination of polymer surfaces. This Lagow-Margrave invention, trademarked Fluorokote, involved many types of polymeric materials in various forms e.g., polyethylene bottles, polypropylene objects, and rubber gloves. Polyethylene bottles are easily given fluorocarbon surfaces (>0.1 mm), and this has been commercialized. Air Products has at least 20 licenses for what is known as their Aeropak process and Union Carbide has a Linde Fluorination process as well. Applications in chemical, pharmaceutical, and cosmetic storage are widespread. 

Aliphatic dissolution inhibitors, low molecular weight, 15 177 Aliphatic endoperoxides, 18 442, 443 Aliphatic fluorocarbon production Europe, 11 870-871 Pacific Rim/India, 11 871 United States, 11 869-870 Aliphatic fluorocarbons, surface energy of, 21 604... 

Lee, S., Kim, Y., Metering and mixing of nanoliter liquid in the microchannel networks driven by fluorocarbon surfaces and pneumatic control. Micro Total Analysis Systems, Proceedings 5th p,TAS Symposium, Monterey, CA, Oct. 21-25, 2001. Kluwer Academic Publishers, Dordrecht, the Netherlands, 2001, 205-206. 

Sodium napthalene solutions in tetrahydrofuran solvent have been used to provide surface treatment of fluorocarbon surfaces for several decades. A commercial surface treatment based on this process has been Tetra-Etch.63 Recently the manufacturers of Tetra-Etch introduced Fluoro-Etch, which has several advantages. Fluoro-Etch requires no refrigeration, is easier to handle, and offers significant cost, efficiency, and safety advantages. It offers a 1-year shelf life and is manufactured in both the United States and Europe. 

Flexible epoxy adhesives generally give good bond strengths to heated fluorocarbon surfaces. Table 16.11 shows the effect of surface treatments on the bondability of epoxy... 

In the coagulation of PTFE latices by cationic hydrocarbon surfactants> however, a dilTerent behavior is observed in that only very small differences are observed in the magnitude of the ccc with variation of chain length (Richardson, 1979). This effect is illustrated by the data in Table V. Again, it appears to demonstrate the lack of affinity of hydrocarbon chains for fluorocarbon surfaces. 

Liquid Membrane Stability. While studies of other investigators have indicated that the blood has good compatibility with the liquid fluorocarbon surface, they also indicate that fluorocarbon droplets should not be introduced to the bloodstream of animals (6, 7, 8). Liquid membrane rupture in the oxygenator apparatus could produce droplets from the fluorocarbon which had formed the liquid membrane. These droplets would be entrained and returned to a test animal with the oxygenated blood. As a preliminary test for liquid membrane rupture and droplet formulation, the oxygen flow into apparatus was momentarily stopped, and blood samples were withdrawn for examination. 

In addition to the two fluorocarbon surfaces, it is informative to consider data for two hydrocarbon solid surfaces paraffin and polyethylene. Adhesion tension data for these surfaces have been presented by Fox and Zisman [35]. Selections of these data are given also in Table I, as are some additional data of Bascom and Singleterry for polyethylene [10]. 

In relation to this result, it is of interest to refer to the solid-liquid interfacial tensions evaluated previously for the glassy fluorocarbon surface studied by Fowkes and Sawyer [31]. From Table II, we note that the difference between the solid-liquid tensions for benzene and 1-methylnaphthalene on this surface is about 5 dynes per cm. 

These estimates are given in Table IV. Also presented are estimates appropriate to fluorocarbon surfaces. In the latter case, the values for benzene and tert-butylnaphthalene are chosen to correspond with the results obtained by use of the interaction parameter method, as given in Table H. For both the fluorocarbon surfaces and the hydrocarbon surfaces, the estimates given are also in agreement with the differences between the values for n-decane and isopropylbiphenyl, as deduced from two-liquid adhesion tension data. 

Referring to the form in which Yoimg s equation was finally expressed (Equation 16b), it is seen that with the information at hand it is possible to obtain estimates of the surface tensions of the bare solids. The discussion is restricted to three of the solid surfaces for which data were given in Table I. The data for the glassy fluorocarbon surface have been fully treated by the method of interaction parameters, as given in Table II. The liquids of interest for the three surfaces are those for which solid-liquid interfacial tension estimates are given in Table IV, and, in addition, water. 

Solid-liquid interfacial tensions can be estimated from experiments involving crystallization rate phenomena. For hydrocarbon surfaces, the estimated values range from 10 to 18 dynes per cm., while for fluorocarbon surfaces the range is from 6 to 14 dynes per cm. 

Teflon and other fluorocarbon surfaces may be altered by chemical treatments using solvent solutions of sodium naphthalene complex or molten sodium. Teflon etchants, for example, Tetra-Etch , a tradename and product of W. L. Gore Associates, are effective in improving adhesion to Teflon. Oxidation treatments for metals such as copper or aluminum also produce highly polar oxide surfaces that are more easily bondable. The reader is referred to several sources for a more comprehensive... 

Fluorocarbon and hydrocarbon modified PDMS surfaces are compared in Table 2. The contact angle data are obtained by the Good-Girifalco-Fowkes equation. It is striking that the hydrocarbon contact angle liquid gives better agreement with the JKR result for the hydrocarbon surface whereas the fluorocarbon liquid data better fit the fluorocarbon surface... 

Weidner, T., Samuel, N.T., McCrea, K., Gamble, L.J., Ward, R.S., Casmer, D.G. Assembly and structure of ot-helical peptide films on hydrophobic fluorocarbon surfaces. Biointerphases 5, 9-16 (2010)... 

As an example, a fluorocarbon surface layer can be obtained by dissolving a small amount (less than 1%) of a polymerizable fluorosurfactant in a lacquer and cross-linking the surfactant monolayer formed at the surface. Figure 17.31 shows two fluorocarbon surfactants, one polymerizable (a) and the other non-reactive (b), used in such an experiment. The surfactants were added to a poly(methyl methacrylate) (PMMA) lacquer. PMMA is more polar than the hydrocarbon part of the surfactant so the surfactant orients at the film-air interface with... 

The fluorocarbon surface film is unstable at elevated temperatures and decomposes to form gaseous fluorocarbons ... 

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