Polytetrafluoroethylene particles

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. 

Forum Wear-preventive additive containing polytetrafluoroethylene particles 0.4 micrometers in diameter. Dramatically reduces noise and oil loss. 

Free Flow PTFE - Suspension pol nnerized PTFE (polytetrafluoroethylene) particles first undergo size reduction followed by granulation and drying which result in a free flowing powder. Free flow PTFE has a similar consistency to sugar contrasted with fine cut PTFE which resembles flour. 

Name(s) polytetrafluoroethylene particles, beads, fibers, tridecafluoro-l,l,2,2-tetrahydrooctyltrichlorosilane, perfluoroalkyl group-containing compound CAS 9002-84-0... 

Coating molds with Chemniflon (nickel containing polytetrafluoroethylene particles distributed evenly throughout the matrix) reduced the adhesive wear of the mold surface and resulted in a reduction of the demolding force by 35%. ... 

Stoylov, S.P, Stoylova, E., Sturm, J., and Weill, G. 1996. Electric birefringence of polytetrafluoroethylene particles in agarose gels. Biophys. Chem. 58 157. 

AUoys of ceUulose with up to 50% of synthetic polymers (polyethylene, poly(vinyl chloride), polystyrene, polytetrafluoroethylene) have also been made, but have never found commercial appUcations. In fact, any material that can survive the chemistry of the viscose process and can be obtained in particle sizes of less than 5 p.m can be aUoyed with viscose. 

In some cases particles have been added to electrical systems to improve heat removal, for example with an SF -fluidized particulate bed to be used in transformers (47). This process appears feasible, using polytetrafluoroethylene (PTFE) particles of low dielectric constant. For a successful appHcation, practical problems such as fluidizing narrow gaps must be solved. 

Dispersion Resins. Polytetrafluoroethylene dispersions in aqueous medium contain 30—60 wt % polymer particles and some surfactant. The type of surfactant and the particle characteristics depend on the appHcation. These dispersions are appHed to various substrates by spraying, flow coating, dipping, coagulating, or electro depositing. 

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). 

Some authors have suggested the use of fluorene polymers for this kind of chromatography. Fluorinated polymers have attracted attention due to their unique adsorption properties. Polytetrafluoroethylene (PTFE) is antiadhesive, thus adsorption of hydrophobic as well as hydrophilic molecules is low. Such adsorbents possess extremely low adsorption activity and nonspecific sorption towards many compounds [109 111]. Fluorene polymers as sorbents were first suggested by Hjerten [112] in 1978 and were tested by desalting and concentration of tRN A [113]. Recently Williams et al. [114] presented a new fluorocarbon sorbent (Poly F Column, Du Pont, USA) for reversed-phase HPLC of peptides and proteins. The sorbent has 20 pm in diameter particles (pore size 30 nm, specific surface area 5 m2/g) and withstands pressure of eluent up to 135 bar. There is no limitation of pH range, however, low specific area and capacity (1.1 mg tRNA/g) and relatively low limits of working pressure do not allow the use of this sorbent for preparative chromatography. 

Powdered Teflon for use in pyrots is covered by US Mil Spec MIL-P-48296IPA) (1 May 1974), Polytetrafluoroethylene (TFE) . Three classes of material are specified (1,2 3). The requirements are purity, 99.4% min infrared spectrum, peaks consistent with figure shown color, TFE shall be opaque and the color shall range from white to gray moisture, 0.05% max ash, 0.1% max mp, 337° 10°C packing density, Class 1 — 1.18 0.13g/cc, Class 2 - 1.25 0.02g/cc, Class 3- 1.14 0.09g/cc particle size by sieve analysis, Class 1 — 95 15 microns, Class 2 — 237 27 microns, Class 3 — 200 30 microns particle size distribution by sieve analysis, as specified in Table 1... 

Fig. 1 a and b. Micrographs of granular and dispersion particles of polytetrafluoroethylene. a) Cross-section of... 

There are various kinds of polytetrafluoroethylene. One is granular polymer consisting of spongy, white particles having a median size of about 600/l The specific surface of this polymer is on the order of 2 m2/g (determined by nitrogen adsorption and calculations by the method of Brunauer, Emmett, and Teller). Since this specific surface area is about 1700 times the observed outer surface of the particles, these measurements confirm the porous, spongelike structure that can be seen in the photomicrograph of a cross section of several particles in Fig. la. 

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). 

Filters can be grouped on the basis of different characteristics. For example, they can be grouped on the basis of the design capacity of the filters according to the particle concentration or loading [Svarovsky, 1981] or they can be grouped on the basis of the materials of the filters, e.g., fabric or nonfabric [Cooper and Freeman, 1982], Most filters in use are bag filters, which are fabric. The common fabric materials include cotton, polyester, wool, asbestos, glass, acrylic, polytetrafluoroethylene (Teflon), poly (m-phenylene isophthalate) (Nomex), polycaprolactam (Nylon), and polypropylene. 

At the co-deposition of nanocomposite components formation of M/SC particles proceeds simultaneously with formation of a dielectric matrix, and the relationship between these processes determines the nanocomposite structure. This problem has been in detail investigated for the case of M/SC nanoparticles formation in polymer matrices. Synthesis of nanocomposite films by simultaneous PVD of polytetrafluoroethylene (PTFE) and Au has been carried out in works [62-64], Polymer and metal were sputtered under action of Ar ions and then the obtained vapors were deposited on substrates (quartz, glass, silica, mica, etc.) at various temperatures. Here, it is necessary to note that polymer sputtering cannot be considered as only physical process PFTE polymer chains destruct under action of high-energy ions, and formed chemically active low-molecular fragments are then deposited and polymerized on a substrate surface. 

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