Poly tetrafluoroethylene , PTFE

This polymer is the completely fluorine-substituted analogue of poly(ethylene) i.e. [CF2CF2—The amount of this polymer produced commercially is very small compared with the output of many other synthetic polymers, but it has a number of important specialised uses and so is worth considering briefly. 

PTFE is a white solid with a waxy appearance. It is very tough and flexible, with a good electrical insulation properties. The surface energy and coefficient of friction are both very low, the latter being the lowest of any solid. The combination of low surface energy and low coefficient of friction cause PTFE to have excellent non-stick characteristics, a feature which underlies many of the everyday uses of this polymer. 

In addition to its unique mechanical properties, PTFE has excellent chemical resistance to a very wide range of reagents, with the exception of molten alkali metals and fluorine. There is no known solvent for PTEE. 

PTEE is a linear polymer of the addition type, formed by polymerisation of the unsaturated monomer tetrafluoroethylene, CF2=Cp2. Despite the fact 

Because PTFE cannot be dissolved or melted, there are problems with fabricating articles out of the polymer. These are overcome by using a technique similar to powder metallurgy, in which granular particles are fused under high pressures and temperatures. 

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In spite of the high effort focused on the carbon electrochemistry, very little is known about the electrochemical preparation of carbon itself. This challenging idea appeared in the early 1970s in connection with the cathodic reduction of poly(tetrafluoroethylene) (PTFE) and some other perfluorin-ated polymers. The standard potential of the hypothetical reduction of PTFE to elemental carbon ... 

The first example will deal with polymer blends consisting of polyamide (PA) and poly(tetrafluoroethylene) (PTFE). These polymer types are frequently used... 

Poly(tetrafluoroethylene) (PTFE) Poly(chlorotrifluoroethylene) (PCTFE) Perfluoroalkoxy (PFA) resin Fluorinated ethylene-propylene (FEP) resin... 

On the other hand, poly tetrafluoroethylene (PTFE) has been shown to be electrochemically reducible [4]. Very recently, electrochemical reduction of saturated perfluoroalkanes has been observed on an analytical scale and it was found that the reduction potentials of perfluorocycloalkanes are only slightly more negative than those of the corresponding perfluoroaromatics perfluorode-caline (Ep = — 2.60 V vs Ag/O.OIM AgC104) vs. octafluoronaphthalene ( — 2.58 V) perfluoromethylcyclohexane ( — 2.9 V) vs. perfluorotoluene ( - 2.75 V) [5],... 

Poly(tetrafluoroethylene) (PTFE), which is also known by DuPont s trade-name Teflon, is a solid at room temperature and has a dielectric constant in the range of 2.00-2.08, while its monomer, tetrafluoroethylene, is a gas at room temperature. PTFE is exceptionally chemically inert, has excellent electrical properties and outstanding stability, and retains its mechanical properties at high temperatures. The problem with PTFE is that it is not processable. A family of commercial polymeric materials known as Teflon AF is believed to be a... 

Chemically universally stabile is poly-tetrafluoroethylene (PTFE, Teflon ), but it is relatively expensive. A problem is the cold flow , that is, the polymer is slowly deformed under the mechanical stress of the pressure on the gaskets and a leakage of the cell can occur (PTFE compounds, e.g. with glass powder or graphite, show a better behavior.)... 

The materials used in nonwoven fabrics include a single polyolefin, or a combination of polyolefins, such as polyethylene (PE), polypropylene (PP), polyamide (PA), poly(tetrafluoroethylene) (PTFE), polyvinylidine fluoride (PVdF), and poly(vinyl chloride) (PVC). Nonwoven fabrics have not, however, been able to compete with microporous films in lithium-ion cells. This is most probably because of the inadequate pore structure and difficulty in making thin (<25 /rm) nonwoven fabrics with acceptable physical properties. 

Polymers have found two specific applications in orthopedics. First, they are used for one of the articulating surface components in joint prostheses. Thus, they must have a low coefficient of friction and low wear rate when they are in contact with the opposing surface, which is usually made of metal or ceramic. Initially, poly(tetrafluoroethylene), PTFE, was used in this type of application, but its accelerated creep rate and poor stress corrosion caused it to fail in vivo. Ultimately, this material was replaced with... 

As for enviromnental resistance, there exists a design chart that is somewhat useful for this case study, but, more importantly, may be of use in other designs. The compatibility of various materials in six common environments is shown in Figure 8.16. The suitability of a material for each of the six environments improves as you move from the center of the chart outward. In this case, resistance to organic solvents is of primary importance. We see that all ceramics and glasses, all alloys, and some polymers such as poly(tetrafluoroethylene), PTFE, will provide excellent resistance. Composites will provide good resistance, which may be satisfactory for our application. 

A Kjeldahl flask was charged with ,/V -dimethyl-1,6-diaminohexane (5.75 mmol) dissolved in 10 ml of THF and then treated with the dropwise addition of -butyl-lithium (5.75 mmol) while vigorously stirring. This solution was then treated with chlorotrimethylsilane (5.75 mmol) and stirred at ambient temperature for 30 minutes and then filtered off through a poly(tetrafluoroethylene) (PTFE) filter and 15 mL of the filtrate charged into a 150-ml glass bottle. This aliquot was then treated with tetramethylethylene diamine (4.23 mmol) and n-butyllithium (4.23 mmol) and used immediately as a polymerization initiator. 

A study has been conducted on PBXs based on TATB using various binders such as polyurethane (Estane 5703-Goodrich), Viton-A (copolymer of vinylidene fluoride and hexafluoropropylene Du Pont), silicone resin (Chemlok), Kel-F800 [copolymer (3 1) of chlorotrifluoroethylene and vinylidene fluoride 3M Company] and Teflon [poly (tetrafluoroethylene), PTFE Du Pont] etc. and it was concluded that... 

In order to fabricate a resin laminated copper foil, the composition is poured over a glass cloth placed on a glass fiber reinforced poly-(tetrafluoroethylene) (PTFE) film. Another sheet PTFE film is placed... 

As usual, certain additives can be added to the composition. Among others, the use of an anti-drip agent has been proposed, namely poly(tetrafluoroethylene) (PTFE)). The anti-drip agent may be encapsulated by a rigid copolymer, for example, SAN, which is known as teflon encapsualed in SAN (TSAN) (29). 

J,m poly(tetrafluoroethylene) (PTFE) syringe-tip filters High-performance liquid chromatography (HPLC) system equipped with Quaternary pump Diode array detector Vacuum degasser... 

The first-order dependence of the deactivation constant was found to be proportional not only to the power imparted by the impeller but also to the area between the liquid and the glass wall, air surface, or poly(tetrafluoroethylene) (PTFE) surface (Colombie, 2001). Hydrophobic PTFE and air interfaces increased lysozyme inactivation fourfold over glass. In addition, the number and thus the molecular surface of inactivated enzymes, which are more hydrophobic than native enzymes, enhanced lysozyme inactivation and aggregation. 

An aliquot of 30 pL is transferred in 250 pi buffer. The solution is shaken for 24 hours at 25 °C. If precipitation occurs the sample is centrifuged and filtrated. The following procedure is the same as for the solubility from solids described above. The achieved throughput is mainly limited by the gradient time. Pan et al. investigated the effect of filtration on the quantification of solubility. They recommend poly(tetrafluoroethylene) (PTFE) as filter material of choice. In their compound set they found 98% recovery after filtration. 

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