Polymer fluorocarbon

In blends, fluoropolymers are used in small quantities to enhance throughput, reduce the frictional properties, and increase the wear resistance. Blends comprising 0.3-50 wt% of a low molecular weight PTFE (T , 350 °C) with engineering resin showed improved antifriction properties (Asai et al. 1991). LLDPE generally exhibits sharkskin melt fracture, but the use of fluoropolymer additives, such as the copolymer of vinyUdene fluoride and hexafluoropropylene, can help to eliminate the extrusion instability (Hatzikiriakos and Migler 2005). 

PPS and PEEK which blended with fluoro(co)polymers and reinforced with either CF or GF were wear resistant with a short break-in period for forming a self-lubricating film (Davies and Hatton 1994). Many commercial blends contain fluoropolymers (primarily PTFE) for the improved weatherability and wear and solvent resistance SUPEC - self-lubricating blend of crystalline PPS with 

Simple abrasion is usually a very poor surface treatment for fluorocarbon polymers. This may be seen from the results shown in Table 4.2 where joint strengths for PTFE and PCTFE, bonded using an epoxy-polyamide adhesive, are given and the fluorocarbons have been pretreated by either abrasion or a 

Fluorocarbon treatment Abraded Etched Abraded and etched 

Abraded beneath adhesive Abraded in air (epoxy-vinyl acetate mixture) 

The treatment for fluorocarbon polymers is usually based upon metallic sodium dissolved in a solution of naphthalene in a polar aprotic solvent such as tetrahydrofuran, although other etch treatments such as a solution of alkali metal in liquid ammonia [12] have been reported [13]. Details for the preparation of the treatment solutions have been published [14] and solutions of sodium naphthalenide are commercially available, e.g. under the trade name Tetraetch from W. L. Gore Associates Inc. These commercial pretreatments are relatively easy and safe to operate and widely used in industry. Also, it is possible to purchase fluorocarbon polymers already treated by such chemical processes. 

The sodium naphthalenide pretreatment requires immersion of the polymer in fresh treating solution, which typically contains about 15-23 g of sodium per litre, at room temperature for a few seconds, then rinsing in water, then in acetone, followed by thorough washing in water again and finally drying. The etching process produces a dull brown-black surface layer and this coloration 

The most important polymer in this group is polytetrafluoroethylene (PTFE). Because PTFE has such a high heat of polymerization (172kJmol ) it is polymerized in water (at 75 °C), using air (O2) or persulphates as catalysts. Either granular or dispersion (using fluorocarbon surfactants) polymerization techniques can be used. 

The melt viscosity of PTFE at its potential fabrication temperature (Tm + 50 °C) is extremely high as a result of its high MW and regular structure. Also, because is 327 °C, prolonged time at these temperatures ( 400°C) causes decomposition. PTFE is therefore fabricated by compression and sintering the powder at 350-400 °C. 

Melt processing is achieved by reducing the crystallinity (PTFE 95% crystalline) through incorporation of a small concentration of a fluoro comonomer, e.g. hexafluoropropene or perfluoroalkoxy compounds. 

PTFE is highly dense, resistant to most chemicals (except liquid sodium) including O2, has low flammability and high temperature stabihty. It has low temperature flexibility and an extremely low coefficient of friction. 

Other commercial fluoropolymers (all made by free-radical mechanisms) include polychlorotrifluoroethylene (Kel-F), which is similar to PTFE but which can be moulded at temperatures 300 °C. Polyvinylidene difluoride (PVDF) is a thermoplastic (T 160°C) and films of this material show piezoelectric behaviour. When copolymerized with hexafluropropene a very chemically resistant elastomer is obtained (Viton). Polyvinylfluoride (PVF) is another highly crystalline polymer (T 197°C) which is used for high-performance protective coatings. 

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The extensive use of the Young equation (Eq. X-18) reflects its general acceptance. Curiously, however, the equation has never been verified experimentally since surface tensions of solids are rather difficult to measure. While Fowkes and Sawyer [140] claimed verification for liquids on a fluorocarbon polymer, it is not clear that their assumptions are valid. Nucleation studies indicate that the interfacial tension between a solid and its liquid is appreciable (see Section K-3) and may not be ignored. Indirect experimental tests involve comparing the variation of the contact angle with solute concentration with separate adsorption studies [173]. 

More recently, solid supports made from glass beads or fluorocarbon polymers have been introduced. These supports have the advantage of being more inert than diatomaceous earth. 

Hydrocarbon Polymers. It is difficult to produce perfluorocarbon polymers by the usual methods. Many monomers, such as hexafluoropropylene, polymerize only slowly because of the steric hindrance of fluorine. Furthermore, some monomers are not very stable and are difficult to synthesize. Direct fluorination can be used for the direct synthesis of fluorocarbon polymers (68—70) and for producing fluorocarbon coatings on the surfaces of hydrocarbon polymers (8,29,44—47,49,68—71). 

Surface Protection. The surface properties of fluorosihcones have been studied over a number of years. The CF group has the lowest known intermolecular force of polymer substituents. A study (6) of liquid and solid forms of fluorosihcones has included a comparison to fluorocarbon polymers. The low surface tensions for poly(3,3,3-trifluoropropyl)methylsiloxane and poly(3,3,4,4,5,5,6,6,6-nonafluorohexyl)methylsiloxane both resemble some of the lowest tensions for fluorocarbon polymers, eg, polytetrafluoroethylene. 

A/-Chloro fatty acid amides have been synthesized from the direct halogenation of the amide in boiling water (28). They are useful as reactive intermediates for further synthesis. Fluorination has also been reported by treating the fatty amide with fluorine-containing acid reagents at 200 °C to reach a fluorinated amide with less reactivity toward fluorocarbon polymers (29). 

They show good to excellent resistance to highly aromatic solvents, polar solvents, water and salt solutions, aqueous acids, dilute alkaline solutions, oxidative environments, amines, and methyl alcohol. Care must be taken in choice of proper gum and compound. Hexafluoropropylene-containing polymers are not recommended for use in contact with ammonia, strong caustic (50% sodium hydroxide above 70°C), and certain polar solvents such as methyl ethyl ketone and low molecular weight esters. However, perfluoroelastomers can withstand these fluids. Propylene-containing fluorocarbon polymers can tolerate strong caustic. 

Commonly accepted practice restricts the term to plastics that serve engineering purposes and can be processed and reprocessed by injection and extmsion methods. This excludes the so-called specialty plastics, eg, fluorocarbon polymers and infusible film products such as Kapton and Updex polyimide film, and thermosets including phenoHcs, epoxies, urea—formaldehydes, and sdicones, some of which have been termed engineering plastics by other authors (4) (see Elastol rs, synthetic-fluorocarbon elastol rs Eluorine compounds, organic-tdtrafluoroethylenecopolyt rs with ethylene Phenolic resins Epoxy resins Amino resins and plastics). 

A major development in fluoroplastks is the recent small scale production of Teflon AF, a noncrystaUme (amorphous) fluorocarbon polymer with a high glass transition temperature (240 °C) This optically transparent TFE copolymer is soluble m certan fluorocabons and has the same chemical and oxidative stability as crystallme TFE homopolymers [5]... 

Unless laboratory studies on material compatibility establish otherwise, it is recommended that equipment used to collect groundwater samples for pesticide analysis be constructed of metal, fluorocarbon polymer, or glass.However, for a water-supply well, inert well, pump, and plumbing materials are not likely to have been installed for all components. In this case, in-place well, pump type, and plumbing materials should be documented. 

The reservoir materials may be PVC, stainless steel, or a fluorocarbon polymer, and the porous cup may be constructed of ceramic, stainless steel, or fluorocarbon polymer. Ceramic cups have a smaller pore size, a greater bubble pressure (pressure under which the cup produces bubbles), and a greater operational suction range, and are preferred to other porous cup materials. All materials used for the construction of the suction lysimeter should be tested in the laboratory to determine if any bias in the sample analysis will result from their use. 

Fluorocarbon polymers Kirk-Othmer (3rd ed.), 1982, Vol. 19, 495 Compressed mixtures are used as special igniters. 

See Fluorocarbon polymers, above Polytetrafluoroethylene, below See Bromomethane Metals... 

Plasma-deposited fluorocarbon polymers or vacuum-deposited Teflon, polyimide, or parylene... 

While several fluorocarbon polymers that contain the hexafluorocyclobutane ring have been prepared, there is little precedent in the chemical literature for the... 

The reason for Nafion LB-film fabrication was the wish to obtain the highly ordered systems from perfluorinated ion exchange polymer with multilayered structure, where the ionic layers (conductors) would alternate with fluorocarbon polymer layers (insulators), and to investigate the properties of such films.74 This polymer contains a hydrophobic fluorocarbon polymeric chain and hydrophilic ionic groups, so it is sufficiently amphiphilic it has a comblike structure that makes it a suitable polymer for LB-film deposition. 

At the other end of the spectrum are substances that do not interact well with water oils, fats, waxes, and Teflon provide four examples. Oils are hquids that create films on the surface of water many are hydrocarbons. Fats, waxes, and Teflon, a fluorocarbon polymer, are solids upon which water beads. Think about what the waxed hood of your car looks like after rain. Substances in this class are hydrophobic. We have a spectrum extending from very hydrophilic substances, on the one hand, to very hydrophobic ones, on the other hand. There is a comfortable middle ground and many substances are balanced in their hydrophobic/hydrophilic character. 

Uses. Fluorinating agent incendiary igniter and propellant for rockets in nuclear reactor fuel processing pyrolysis inhibitor for fluorocarbon polymers... 

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