Materials for insulation

Sulfur hexafluoride was first prepared in 1902 (1). The discovery in 1937 that its dielectric strength is much higher than that of air (2) led to its use as an insulating material for cables, capacitors (3), and transformers (4) (see Insulation,electric). Sulfur hexafluoride has been commercially available as AccuDri, SF (AUiedSignal Inc.) since 1948. It is also produced by Air Products and Chemicals in the United States and by others in Germany, Italy, Japan, and Russia. 

F. Clark, Insulating Materials for Design and Engineering Practice, John Wiley Sons, Inc., New York, 1962. 

Other sohd-state apphcations of sihcon carbide include its use as an electroluminescent diode for use in sound recording equipment and photomultipliers and controllers. It has been studied as a reflective surface for lasers. By combining its excellent thermal conductivity and high electrical resistance, sihcon carbide has also found apphcation as an insulating material for integrated circuit substrates. 

Test procedure for, evaluation of system of insulating materials for random wound a.c. electrical machines. 

Polymers containing each of these configurations are known, the most common being the cis- A and the 1,4-isomers. The first of these, poly(c/ -l,4-isoprene), is the macromolecular constituent of natural rubber the second is the material known as gutta percha. The latter, unlike natural rubber, has no elastomeric properties, but has a leathery texture. It has been used for diverse applications such as golf-ball covers and as an insulating material for the trans-Atlantic cables of the late nineteenth century. 

P. Mazzoldi, G. Righini, in F. Agullo-Lopez (ed.) Glasses for Optoelectronic Devices, in Insulating Materials for Optoelectronics, World Scientific, Singapore, 1995, 367. 

True synthetic polymers came into use when Bakeland came from Belgium and applied his knowledge of the formation of a moldable plastic from phenol and formaldehyde to give the product named Bakelite. This was about 1914. This product, under heat and pressure, set up to a thermo-setting resin and had useful properties especially as an insulating material for electrical items. 

The loss tangent is an important quantity. The product of the loss tangent and the dielectric constant, tan 5, is called the loss factor and is the primary criterion for judging the usefulness of a dielectric as an insulator material. For this purpose, it is desirable to have a low dielectric constant and a small loss angle. For applications in which it is desirable to obtain a high capacitance in the smallest physical space, a high dielectric constant must be used, and a low value of the loss angle is needed. 

Proebster, M. (1988) Insulating materials for the insulating layers on solid rocket propellants. Ger. Offen DE 3,706,368 Chem. Abstr., (1988) 109, 24931z. 

Herring, LG. (1985) Elastomeric insulating materials for rocket motors. 

Coagulation is not the only problem with materials intended for implantation, however. Cardiac pacemakers are intended to correct arrhythmias. Insulating materials for a pacemaker lead must be tough and long lasting. The first leads were insulated with polyethylene or silicone rubber. Neither material was considered ideal because of endocardial reactions (polyethylene) and limited durability (silicone rubber). The strength and flexibility of polyurethanes led to their introduction in 1978 as lead insulators. 

TABLE 8.19. Thermal Conductivities of Insulating Materials for Low Temperatures [k Btu/(hr)(sqft)(°F/ft)]... 

Excellent dielectric characteristics at all frequencies and high electrical resistivity have made polyethylene one of the most important insulating materials for wire and cable. 

The above analysis applies to insulating materials. For electrically conductive materials such as metals the dielectric constant is infinite and Eq. (6.24) does not apply. In this case we... 

Due to the inability to deposit eleetrochemically stable gate-insulating materials for GaAs, another approach was developed based on amorphous silicon (a-Si), prepared as a thin layer for LAPS devices on transparent glass substrates [40]. The diffusion length in this material was reported to be as small as 120 nm [41] and a resolution down to 1 gm has been demonstrated, which was mainly limited by the optical set-up. The electrochemical properties of the a-Si-based structures were investigated later with a LAPS device thus, the above results for SPIM were transferred back and proved for the LAPS, too [42,43]. 

Polyphenyldiethylsiloxane varnishes are solutions of phenyldiethylsi-loxane polymer in petrol, toluene or a mixture of petrol and turpentine. They are liquids ranging in colour from yellow to brown. The varnishes are heat-resistant they are used to produce insulating materials for temperatures up to 180 °C and high humidity. Heat-resistant insulation of polyphenyldiethylsiloxane varnishes is widely used in electric engines, in rotors of turbogenerators, etc. 

Tucker DS. Hurley GF, Kennedy JC (1986) Mechanical properties of three candidate organic insulator materials for fusion reactors. In Hartwig G, Evans D (eds) Nonmetallic materials and composites at low temperature, vol 3. Plenum, New York, p 21... 

FLAME RETARDANCY OF RADIATION CROSS-LINKED POLY (VINYL CHLORIDE)(PVC) USED AS AN INSULATING MATERIAL FOR WIRE AND CABLE... 

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