Teflon, thin coating

Dispersion Processing. A commercial aqueous dispersion of Teflon PEA 335 contains more than 50 wt % PEA particles, about 5 wt % surfactants and fillers. This dispersion is processed by the same technique as for PTEE dispersion. It is used for coating various surfaces, including metal, glass, and glass fabrics. A thin layer of Teflon PEA coating can also serve as an adhesive layer for PTEE topcoat. 

Fig. 1 shows the cyclic voltammetry of an FePc/XC-72 dispersion, heated at 280°C in an inert atmosphere, in the form a thin porous Teflon bonded coating electrode in a 1 M NaOH solution. A description of the methodology involved in the preparation of this type of electrode may be found in Ref. 3. As can be clearly seen, the voltammetry of this specimen exhibits two sharply defined peaks separated by about 330 mV. The potentials associated with these features are essentially identical to those found by other workers for the reduction and oxidation of films of iron oxy-hydroxide formed on a number of host surfaces, including iron and carbon.(5)... 

Fig. 1. Cyclic voltammetry of 7% w/w iron phthalocyanine, FePc dispersed on Vulcan XC-72 carbon, after a heat treatment at 280°C in a flowing inert atmosphere. The measurement was conducted with the material in the form a thin porous Teflon bonded coating in 1 M NaOH at 25°. Sweep rate 5 mV/s. (Reproduced with permission from ref. 3. Copyright 1985 Elsevier.)...

Another unique development, which significantly reduced the amount of reagent necessary for an assay, is an extension of the continuous-flow analyzer technology called capsule chemistry. The core of die system is a capillary Teflon tube coated on the inside with a thin, flowing film of... 

RTV silicone samples were obtained from a thin coating which had been cured on a Teflon-coated steel or aluminum plate according to the standard cure schedule (room temperature and final oven cure). For RTV diluted to 50% by weight of the xylene, 20 grams of the material coated on the 5"x5" Teflon-coated aluminum plate will result in a 25 mil uniformly thick sample. 

Teflon AF can be designed to have some solubility in selected perfluorinated solvents but remains chemically resistant to all other solvents and process chemicals. The solubility is typically only 3—15% by weight, but this allows solution-cast extremely thin coatings in the submicron thickness range. 

Critical Dimensions of Unreflected BeO Systems Fueled by Thin Enriched Uranium Foils, F. A. Kloverslrom, R. M. Deck and A. J. Reyenga (UCRL-L). A series of criti cal. measurements on unreflccied parallelepipeds built of enriched (93.299 uranium foils and BcO blocks have been made for five fuel densities. The object of this program was to provide data for normalization of machine criticality calculations, and.the systems were therefore made clean. The only material present other than BeO and U was a small amount of Teflon (foil coatings) and a steel diaphragm, the effect of which was experimentally determined. 

Hosner and Allendorf ( ) have replaced the silica discharge tube by one fabricated from pure fused alimiina, which is inert to attack by fluorine atoms. However, this reduces the efficiency of dissociation somewhat. The pyrex or silica flow tube may be protected from attack by F atoms by application of a thin coating of teflon or Kel-F fluorocarbon polymer (2). A technique for coating with a thin fused layer of teflon has been described ( ). The presence of undissociated F2 in the discharge products causes complications in kinetic studies involving hydrogen atoms or alkyl radicals, which react rapidly with F2. However, F2 appears to be unreactive towards such other common atoms as O P, N S,... 

FIGURE 12, In situ Mossbauer spectra of a 50% w/w Fe-enriched hydrated ferric oxide precipitated on Shawinigan black high-area carbon in the form of a Teflon-bonded electrode in 4 M KOH at (a) -0.3 V and (b) -1.1 V versus Hg/HgO, OH". Inset Cyclic voltammogram of the same, although nonenriched, material as in (a) in the form of a thin porous Teflon-bonded coating electrode deposited on an ordinary pyrolytic graphite electrode, in 4 M KOH. Scan rate 10 mV s" ... 

Powder Coating. Teflon PEA is also available in a finely divided powder form. It can be used to produce thin layers on various surfaces by heating these surfaces above the melting point of PEA and then bringing the powder in contact with them. This allows a thin layer of the powder to melt on the surface of the substrate. 

Another development features a nonmetallic belt [Pla.st. Des. Process., 13 (July 1968)]. When rapid heat transfer is the objective, a glass-fiber, Teflon-coated construction in a thickness as httle as 0.08 mm (0.003 in) is selected for use. No performance data are available, but presumably the thin belt permits rapid heat transfer while taking advantage of the nonsticking property of Teflon. Another development [Food Process. Mark., 69 (March 1969)] is extending the capa-bihty of belt solidification by providing use of subzero temperatures. 

Filtering the tube suspension through a 0.2 xm pore ceramic paper leaves a uniform black deposit on the paper and can produce aligned CNT films [30]. The deposited material was transferred on a thin Teflon sheet by pressing the tube-coated side of the filter on the plastic and then the filter was lifted off to expose the surface. Scanning electron microscopic study reveals that the tubes are highly aligned perpendicular to the Teflon surface [30]. 

Preparation of coatings as free films. The oligomeric esterdlols were mixed with the crosslinkers HMMM or polyfunctional isocyanate. The molar ratio esterdlol/HMMM was 2 1 leading to an OH/OCH3 ratio of 4 6. The OH/NCO ratio was 1 1. Some 1 wt% diethanolamine salt of p-toluene sulphonlc acid, respectively 0.2 wt% Dabco were used as catalyst. The coatings were applied to Bonder 101 plates which had been sprayed with a thin layer (1-2 pm) of teflon. 

The reactor (V = 168 cm3) was coated with a thin film of teflon in order to inhibit wall reactions, and its temperature was controlled by circulating a thermostatted liquid through the outer jacket. The escape aperture had a diameter of 5 mm and the escape constants of various species were given by the expression kcsc M = 1.86 (T/M)l/2 s 1 where T is the reactor temperature, and M is the molecular mass of the escaping species. The total pressure inside the reactor was low in the range 0.5 - 1.5 mTorr to inhibit secondary reactions. 

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