Surfaces fluorinated

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

Polyester cloth-backed flat PP sheets (fleece-backed sheets) are normally used to manufacture large reservoirs for liquid containment purposes. Typically, such reservoirs are reinforced on the outside with fiberglass. The polyester mat backing serves as an adhesion key between the PP and the fiberglass resin. Fluorine surface activation can be used as a substitute for the fleece-backed material at a considerable cost-saving. Table 16.12 shows a comparison between the adhesive performance of the materials with two polyester resins. 

Adhesive strength may possibly be predicted by using the acid-base theory.39 We have already found linear relationships between adhesive strength and either the acid or base component of the fluorinated surface.40... 

Polyolefin containers, fluorine surface treatment of, 11 846 Polyolefin dust, 20 230 Polyolefin fibers, 11 224 24 614. See also Olefin fibers... 

The electron density of PE and PTFE is also different. The electronegativity value for C = 2.5, F = 4.0, and H = 2.1. Thus, the electron density on the fluorine surface of PTFE is greater than that for PE. 

The fluorous silica concept involves the selective partitioning of a fluorous-modified catalyst between an organic liquid phase and the fluorinated surface phase. In the absence of CO2, the fluorinated catalyst prefers the fluorous surface phase and remains partitioned onto the silica. When CO2 pressure is added, the catalyst will partition off of the silica and into the GXL phase (containing reactants), where homogeneous reaction can take place. After the reaction is completed, the CO2 is removed and the catalyst will partition back onto the fluorous silica surface, which can be easily recovered by filtration. A cartoon schematic is shown as Figure 2. 

The potential of other nuclei for the study of surfaces is yet to be explored. Gottlieb and Luz (388) measured 2H spectra of a number of perdeuterated molecules adsorbed on active alumina and interpreted the results in terms of quadrupolar tensors. Yesinowski and Mobley (369) have shown that 19F MAS NMR can provide useful information about fluorinated surfaces of calcium hydroxyapatite, Cas(0H)(P04)3. In particular, l9F, 2H, and H MAS NMR may become powerful techniques for the study of interface systems in general. 

Jahangir AR, McClung WG, Cornelius RM, McCloskey CB, Brash JL, Santerre JP. Fluorinated surface-modifying macromolecules modulating adhesive protein and platelet interactions on a polyether-urethane. Journal of Biomedical Materials Research 2002, 60, 135-147. 

Presently DOE is funding Air Products Chemical Company for the development of a fluorine surface treatment of tire rubber (crumb rubber) to modify its adhesion properties. This modified rubber could be used in making polymers such as polyurethane and epoxies. The tire rubber might also be used in certain plastics such as polystyrene and PVC, and in rubber products (68). 

Ernsting, M.J., Labow, R.S., and Santerre, J.P. "Human monocyte adhesion onto RGD and PHSRN peptides delivered to the surface of a polycarbonate polyurethane using bioactive fluorinated surface modifiers". ] Biomed. Mater. Res. A 83A(3), 759-769 (2007). Ewbank, P.C., Nuding, G., Suenaga, H., McCullough, R.D., and Shinkai, S. "Amine functionalized polythiophenes Synthesis and formation of chiral, ordered structures on DNA substrates". Tetrahedron Lett 42(2), 155-157 (2001). 

K. Kojio, A. Takahara and T. Kajiyama, ACS Symp. Ser. Fluorinated Surfaces, Coatings, and Films, American Chemical Society, Vol. 787, 2001, p. 31. 

Su et al. have undertaken a detailed examination of the mechanism by which perfluoroalkyl end-groups enrich the surfaces of blends of homopolymers with their end-group fluorinated equivalents 43. Their studies aimed to assess the parameters involved in determining whether the enthalpic gain from fluorine surface enrichment outweighed the entropic penalty of polymer chains having... 

Polypropylene has been oxyfluorinated using a gas mixture consisting of fluorine, nitrogen, and water. When cured with mortar slurry, oxyfluorinated surfaces had 20% greater shear bond strength than fluorinated surfaces. 

We envisioned a two-step process [114,115] for the insertion and association of fluorinated transmembrane (TM) helices. First, the hydrophobic TM peptides would partition into micelles or vesicles and form a-helices by main-chain hydrogen bonding. Upon secondary structure formation, one face of the helices would present a highly fluorinated surface. Second, phase separation of fluorinated surfaces within hydrophobic environments would mediate helix-helix interactions, driving bundle formation. 

Chemical resistance and thermostability of nano-heterogenic coatings with fluorine surface active additives (FSAA) are approximately 5%-10% higher than for unmodified ones. At the same time, addition of about 3 mass% of metal oxides in epoxy-rubber nanostructured compositions significantly decreases their permeability and increases their chemical resistance in water and water solutions of acids, salts, and alkalis (Figure 6.3) [8],... 

Figure 12. Contact angles for n-alkanes on various fluorinated surfaces [17,96]...

Fig. 22.20 Sequences of images from a slow debonding of two adhesives from a fluorinated surface (a) pure SIS adhesive (b) SIS+42% SI adhesive.

Unfortunately, a-Si H surfaces will probably always lack the reproducibility of cleaved or high-temperature annealed crystalline surfaces. The results of surface chemical studies on a-Si H will depend on whether the surface is freshly prepared in situ and hydrated or oxidized. Dehydrated surfaces obtained by sputtering or annealing above 300°C are expected to be more reactive than hydrogenated or fluorinated surfaces. 

P.H. BUt, K.G. Battiston, K.A. Woodhouse, J.P. Santerre, Surface immobilization of elastin-like polypeptides using fluorinated surface modifying additives, J. Biomed. Mater. Res. 96 (2011) 648-662. 

Fluorinated surfaces derive their character from the unique molecular properties associated with C-F bonding chemistry that imparts specific, unique chemistry and physics of interfaces (ACS Symposium Series, 2001). Two basic properties seem to be sought in the development of perfluorinated surfaces low interfacial tension, and chemical resistance and durabihty, which means film-coating stability. 

---