Polytetrafluoroethylene composite

Xing, D. M., Yi, B. L., Liu, F. Q., Fu, Y. Z. and Zhang, H. M. 2005. Characterization of sulfonated poly (ether ether ketone)/polytetrafluoroethylene composite membranes for fuel cell applications. Fuel Cells 5 406M11. 

The rheology of lubricated polytetrafluoroethylene compositions was studied by Lewis and Winchester. The mechanism appeared to be a combination of permanent and elastic deformations in the region just before the orifice of the die in the extruder. As a result of permanent deformation, the polymer particles are partially transformed into long fibers. The relative amounts of permanent and recoverable deformation were related to the rate and temperature of extrusion and the geometry of the extruder. Plastic deformation is favored by extruding at temperatures above the 19 and 30° transitions (Snelling and Lontz). 

Subodh and coworkers [25] observed that the incorporation of ceramic powder filler into polytetrafluoroethylene composites had no effect on the polymer melting point, but as the filler level increased, the coefficient of thermal expansion decreased while the thermal conductivity increased. 

Yang L, Li H, Ai F et al (2013) A new method to prepare high performance fluorinated sulfonic acid ionomer4>orous expanded polytetrafluoroethylene composite membranes based on perfluorinated sulfo-nyl fluoride polymer solution. J Power Sources 243 392-3%... 

D. W. Wisander, C. E. Maley, and R. L. Johnson, Wear and Friction of Filled Polytetrafluoroethylene Compositions in Liquid Nitrogen, Paper Presented at ASME-ASLE Lubrication Conference, Los Angeles, California, Oct. 13-15 (1958). 

Wang, S., Li, Q., Zhang, S., Pan, L., 2013. Tribological behavior of poly (phenyl p-hydroxybenzoate)/polytetrafluoroethylene composites filled with hexagonal boron nitride under dry sliding condition. Materials and Design 43, 507—512. 

Commercial interpenetrating polymer networks (not including thermoplastic compositions) include artificial teeth (Dentsply) made Ifom crosslinked PMMA mixed with MMA monomer and polymerized (sequential IPN), sound and vibration damping compositions (e.g., vinyl-phenolic Hitachi) and sheet molding compositions (acryhc/urethane/polystyrene Ferro Chemical) [164]. Water-borne acrylic methane semi-IPNs are commercial Ifom several sources where acrylate monomers are polymerized in the presence of a polymethane water dispersion. A silicone/polytetrafluoroethylene composition described as an IPN is offered by Biomed Sciences under the Silon tradename. The fluoropolymer provides the mechanical strength and the silicone rubber offers the softness and oxygen and moisture permeability for applications in the wound care area. 

Xing, D., He, G., Hou, Z., Ming, P, and Song, S. (2013) Properties and morphology of Nafion/polytetrafluoroethylene composite membrane fabricated by a solution-spray process, Int. J. Hydrogen Energ., 38, 8400-8408. 

A pyrotechnic composition contains one or more oxidizers in combination with one or more fuels. Oxidizers used in pyrotechnics, such as potassium nitrate, KNO, are soflds at room temperature and release oxygen when heated to elevated temperatures. The oxygen then combines with the fuel, and heat is generated by the resulting chemical reaction. Chemicals that release fluorine or chlorine on heating, such as polytetrafluoroethylene (Teflon)... 

Fluorocarbon soHds are rare in defoamer compositions, presumably on account of their cost. SoHd fluorine-containing fatty alcohols and amides are known. The most familiar fluorocarbon soHd is polytetrafluoroethylene [9002-84-0]. Because it is more hydrophobic than siHcone-treated siHca, it might be expected to perform impressively as a defoamer component (14). However, in conventional hydrocarbon oil formulations it works poorly because the particles aggregate strongly together. In lower surface tension fluids such as siHcone and fluorocarbon oils, the powdered polytetrafluoroethylene particles are much better dispersed and the formulation performs weU as a defoamer. 

Composites. Another type of electro deposit in commercial use is the composite form, in which insoluble materials are codeposited along with the electro-deposited metal or alloy to produce particular desirable properties. Polytetrafluoroethylene (PTFE) particles are codeposited with nickel to improve lubricity (see Lubrication and lubricants). SiHcon carbide and other hard particles including diamond are co-deposited with nickel to improve wear properties or to make cutting and grinding tools (see Carbides Tool materials). 

Compositions whose products of combustion produce energy in the infrared wave band are generally composed of magnesium powder, polytetrafluoroethylene (PTFE) and a binder. For efficient tactical utilization of the energy developed by the combustion process the composition is normally formed into pellets either by press consolidation or by press extrusion. The process being used at Longhorn at the time the electrostatic problem was encountered was press consolidation. The composition was being consolidated into a pellet... 

Figure 4. Relative charge density persisting in various polymer compositions as a function of time after initial charging. The polytetrafluoroethylene system traps retain charge indefinitely whereas those in the polyethylene terephthalate decay...

J. Xu et al. [283] have shown that immobilization of enzymes can be done using a specially designed composite membrane with a porous hydrophobic layer and a hydrophilic ultrafiltration layer. A polytetrafluoroethylene (PTFE) membrane with micrometer pores as an excellent hydrophobic support for immobilization was employed for the porous hydrophobic layer, and a biocompatible material of polyvinyl alcohol (PVA) which provided a favourable environment to retain the lipase activity was used to prepare the hydrophilic... 

Figure 29. Fiuman osteoblast-like MG 63 cells in cultures on material surfaces modified with carbon nanoparticles. A fullerene Cgo layers deposited on carbon fibre-reinforced carbon composites (CFRC), B fullerene C o layers deposited on microscopic glass coverslips, C terpolymer of polytetrafluoroethylene, polyvinyldifluoride and polypropylene, mixed with 4% of single-wall carbon nanohorns, D the same terpolymer with high crystalline electric arc multi-wall nanotubes, E diamond layer with hierarchically organized micro- and nanostmcture deposited on a Si substrate, F nanocrystalline diamond layer on a Si substrate. Standard control cell culture substrates were represented by a PS culture dish (G) and microscopic glass coverslip (FI). Immunofluorescence staining on day 2 (A) or 3 (B-Fl) after seeding, Olympus epifluorescence microscope IX 50, digital camera DP 70, obj. 20x, bar 100 pm (A, C, D, G,H)or 200 pm (B, E, F) [16].

Fig. 6.9. Normalized fracture toughness, (Kc - AKQ)/K. of short glass fiber-thermoplastics injection molded composites as a function of reinforcing effectiveness parameter, ft (O) polyetheretherketone (PEEK) matrix (K = 6.5 MPa m) (A) polytetrafluoroethylene (PTFE) matrix (K = 1.9 MPaym).

Early in the history of polytetrafluoroethylene, W. A. Zisman recognized its unusual surface properties, and the polymer now finds many uses because its low coefficient of friction eliminates the need for lubrication (Fitzsimmons and Zisman). Shooter and Thomas called attention to the remarkable resistance of polytetrafluoroethylene to seizure, and Bowden (1950) described use of composite structures. These and other investigations have been reviewed and summarized by Allan (1958) (also Allan and Chapman), who showed that the dependence of the coefficient of kinetic friction, fk, on the load in grams, W, is given by the following equation ... 

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