Plastic High voltage resistant

See also arc resistance track resistance high voltage high-voltage-resistant plastic. 

See also high-voltage resistant plastic dielectric strength... 

See also corona resistance high-voltage-resistant plastic arc- and track-resistant plastic. 

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. Poly(methyl methacrylate) has specific electrical properties that make it unique (Table 4). The surface resistivity of poly(methyl methacrylate) is higher than that of most plastic materials. Weathering and moisture affect poly(methyl methacrylate) only to a minor degree. High resistance and nontracking characteristics have resulted in its use in high voltage appHcations, and its excellent weather resistance has promoted the use of poly(methyl methacrylates) for outdoor electrical appHcations (22). 

The resistance of most plastics to the flow of direct current is very high. Both surface and volume electrical resistivities are important properties for applications of plastics insulating materials. The volume resistivity is the electrical resistance of the material measured in ohms as though the material was a conductor. Insulators will not sustain an indefinitely high voltage as the applied voltage is increased, a point is reached where a drastic decrease in resistance takes place accompanied by a physical breakdown of the insulator. This is known as the dielectric strength, which is the electric potential in volts, which would be necessary to cause the failure of a 1/8-in. thick insulator (Chapter 4, ELEC-TRICAL/ELECTR ONICS PRODUCT). 

Paints and Coatings. Ethoxysilanes are used in high temperature, zinc-rich paints (see Paint) (51,52). Methyl- and phenyltrialkoxysilanes are used to prepare abrasion-resistant coatings for plastics (53), particularly polycarbonate (54,55), and dielectric coatings and seals for high voltage electrical components, including television tubes. 

High-voltage methods are not restricted to glass ampoules indeed, they may be used for other materials with high resistances such as plastics, and for other types of containers such as vials. 

The time required for a given electrical current to render the plastic surface of a material conductive because of carbonization by the arc flame. Also ability to resist the action of a high voltage electrical arc, usually in terms of time required to render the material electrically conductive. The total time (in sec) that intermittent arc may play across the plastic surface with rendering the surface conductive. 

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