Polytetrafluoroethylene electrical stability

Electrical stability of polytetrafluoroethylene is outstanding over a wide range of frequency and environmental conditions. This plastic makes an excellent electrical insulator at normal operating temperatures. Dissipation factor and dielectric constant values are virtually constant up to 10 MHz. Dielectric strength of PTFE drops off with increasing frequency slower than most other material. 

Figure 1. Implantation of electrons in polytetrafluoroethylene films to form electric transducer of high stability and sensitivity.

Fluorocarbon Resins. This term includes polytetrafluoroethylene, polymers of chloro-trifluoroethylene (fluorothene), vinylidene fluoride (H2C CF2)j hexafluoropropylene (C3Ffl) and similar compds. These polymers are thermoplastic, inert to chemicals and oxidation. They have high heat stability, retain their useful props at both extremely low and high temps, have high electrical resistance to moisture. The materials are available as re sins, powders, and dispersions, and as films, sheets, tubes, rods and tapes. Some of them are rubber-like. Commercially available varieties are Kel-F , Teflon , Fluorel , Aclar and "Halon ... 

Special Property Membranes. In the literature, there are numerous methods reported for the preparation of ion-exchange membranes with special properties,87-89 for instance, for use as battery separators, ion-selective electrodes, or in the chlor-alkali process. Especially membranes recently developed for the chlor-alkali industry are of commercial significance. These membranes are based on polytetrafluoroethylene and carry sulfone groups in the bulk of the membrane phase and carboxyl-groups on the surface as the charged moiety. They combine good chemical stability with high selectivity and low electric resistance. 

In recent decades, various electrode materials have been investigated to improve the performance of fuel cells [299]. A conventional low-temperature fuel cell electrode is composed of polytetrafluoroethylene, a high-surface-area carbon black loaded with a precious metal catalyst, and a current collector, as well as other minor components. The most challenging issue for electrode performance is the electrocatalyst [327]. Carbon has been established as the best catalyst support because of its good electrical conductivity, high surface area, surface hydro-phobicity, and stability [328-331]. In the past few years, template-synthesized carbons with various structures have been tried as components of fuel cells. 

Electrical Properties. Polytetrafluoroethylene is an excellent electrical insulator because of its mechanical strength and chemical and thermal stability, as well as excellent electrical properties (Table 6). 

The van der Waals interactions in perfluoroplastics are extremely low. As a result, polytetrafluoroethylene (PTFE) has the lowest coefficient of friction of any known polymer. This property is due to the chemistry and structure described above which also give rise to the excellent electrical properties, thermal stability and chemical inertness. 

PTFE Fluoroplastic n Polytetrafluoroethylene is prepared by free radical polymerization of tetrafluor-oethylene in aqueous systems with persulphate or peroxide initiators to give granular or dispersion polymers. The polymers have exceptionally high thermal and thermo-oxidative stability and are completely solvent resistant. PTFEs are tough, relatively flexible materials which have outstandingly good electrical insulation properties as well as unusually low coefficients of friction. 

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