Wire insulation electrical properties

Electrical Properties. CeUular polymers have two important electrical appHcations (22). One takes advantage of the combination of inherent toughness and moisture resistance of polymers along with the decreased dielectric constant and dissipation factor of the foamed state to use ceUular polymers as electrical-wire insulation (97). The other combines the low dissipation factor and the rigidity of plastic foams in the constmction of radar domes. Polyurethane foams have been used as high voltage electrical insulation (213). 

Electrical Properties. Erom a chemical standpoint, HDPE is a saturated aUphatic hydrocarbon and hence a good insulator. Its electrical characteristics are given in Table 1. Because polymer density and molecular weight affect electrical properties only slightly, HDPE is widely used for wire and cable insulation. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

Its excellent electrical insulation properties lead to its use in wire insulation, in valve holders, in insulated transformers, in hermetic seals for condensers, in laminates for printed ciruitry and for many other miscellaneous electrical applications. 

The first commercial applications of polypyromellitimides were as wire enamels, as insulating varnishes and for coating glass-cloth (Pyre.ML, Du Pont). In film form (Kapton) many of the outstanding properties of the polymer may be more fully utilised. These include excellent electrical properties, solvent resistance, flame resistance, outstanding abrasion resistance and exceptional heat resistance. After 1000 hours exposure to air at 300°C the polymer retained 90% of its tensile strength. 

Polyesters exhibit excellent electrical properties. They resist breakdown when exposed to continual electrical loads and have a high electrical resistance. For this reason, they are often used in electrical housings, as insulating films in electrical components, and as wire insulation where high temperatures are likely to be encountered. 

Two other important electrical properties must be taken into consideration when polymers are used as insulation for a high-voltage power cable or electronic wires. ° These are the dielectric constant and the dielectric loss factor, which characterize the energy dissipation in the insulation, the capacitance, the impedance, and the attenuation. 

Using scanning probe microscope one can follow the manipulation process. For instance, the nanotweezers were shown to be able to grab and pick up clusters or nanowires with diameter of 500 nm. Moreover, one can immediately probe their electrical properties, since the tweezer arms serve as conducting wires. The probing may not be limited to manmade materials but it can also be used to manipulate and modify substructures within cells once the nanowire tips will be insulated. 

High water absorption is die other problem with insulation materials, because it causes corrosion of metal wiring and instability of electrical properties such as the dielectric constant. Conventional polyimides have relatively high water absorption because of tiie presence of polar imide rings. However, the water absorption decreases when fluorine is introduced into polyimide molecules because of the former s hydrophobic nature. ... 

Because EVA waxes tend to exhibit relatively strong adhesive properties, such waxes have been added to plastic sheathing compositions to form wire sheaths that adhere with relatively high strength to the wire cores of insulated electrical conductors (24). 

Perfluoroalkyl-l,3,5-triazines are very stable to oxidation and heat. They have potential as lubricating fluids for use in aerospace work (B-74MI22003). Their polymeric products are stable elastomers with excellent rubber-like properties for use as electrical wire insulation and seals for hydraulic, lubricating and fuel systems of aircraft (B-80MI22001). Perfluoro-2,4,6-tri-n-heptyl-l,3,5-triazine is a valuable reference standard for precise mass... 

Electrical Properties. LDPE s electrical properties make it extremely well suited for wire and cable insulation for electrical power supplies at high transmission, lower domestic voltage, and high frequency, very high frequency, or ultrahigh frequency applications in electronics. As a dielectric, i,e., electric insulator, LDPE for all practical purposes does not transmit electrical current. 

HTE fluoroplastic exhibits exceptional balance of tensile strength, good electrical properties, good resistance to permeation of vapors and fuels, as well as excellent chemical resistance. Because of its relatively low melting temperature, it is easy to process and can be processed on equipment without the high level of corrosion protection usually required by many other fluoroplastics. HTE is suitable for wire and cable insulation and for extruded Aims used for chemically resistant linings, release layers, and other applications. A summary of properties of the two current grades of HTE is shown in Table 3.13. 

Electro-insulation materials. The retention of dielectric properties in a high-temperature environment, coupled with good corrosion resistance in contact with certain reactive chemicals, suggests excellent possibilities of polybenzimidazole use in electrical insulation and other dielectric applications at high operating temperatures and/or in aggressive chemical environments. Typical applications, hence, can be foimd in special cable and wire insulation, in the manufacture of circuit boards and radomes for supersonic aircraft, as battery and electrolytic cell separators, and as fuel cell frame structural materials. Some recent publications in the patent and technical report literature may serve to illustrate such applications. 

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