Electrical properties tracking resistance

Flammability properties Spread of flame Burn rate (ISO 3795) Limiting Oxygen Ind UL flammability Electrical properties Tracking resistance BS476 mm/min % 1.3-10 mm Volts 22 22 22 45... 

Limiting oxygen ind UL flammability Electrical properties Tracking resistance Comp, tracking resist Surface resistivity Volume resistivity Dissipation factor... 

Testing of polyurethanes for their electrical properties due to the voltages required must be carried out using properly designed equipment. The electrical tests that are normally carried out are resistivity, insulation resistance, electric strength, tracking resistance, power factor, and permittivity. 

Electrical Resistivity Dielectric loss Antistatic properties Tracking resistance... 

The use of ABS has in recent years met considerable competition on two fronts, particularly in automotive applications. For lower cost applications, where demands of finish and heat resistance are not too severe, blends of polypropylene and ethylene-propylene rubbers have found application (see Chapters 11 and 31). On the other hand, where enhanced heat resistance and surface hardness are required in conjunction with excellent impact properties, polycarbonate-ABS alloys (see Section 20.8) have found many applications. These materials have also replaced ABS in a number of electrical fittings and housings for business and domestic applications. Where improved heat distortion temperature and good electrical insulation properties (including tracking resistance) are important, then ABS may be replaced by poly(butylene terephthalate). 

Although the structure is polar much of the polarity is frozen in at normal service temperatures. In such conditions electrical insulation properties are quite good even at high frequencies. As with many aromatic polymers, tracking resistance leaves something to be desired. 

Glass-reinforced melamine-formaldehyde laminates are valuable because of their good heat resistance (they can be used at temperatures up to 200°C) coupled with good electrical insulation properties including resistance to tracking. 

Good electrical insulation properties with exceptional tracking resistance for an engineering thermoplastic and, in particular, for an aromatic polymer. In tracking resistance most grades are generally superior to most grades of polycarbonates, modified PPOs, PPS and the polyetherimides. 

Good electrical insulation properties with a high dielectric strength and good microwave transparency but with a low tracking resistance typical of aromatic polymers with a high C H ratio in the structure. 

Other requirements. These could include electrical insulation properties, including resistance to tracking and arcing, transparency, frictional properties, surface finish, scuff resistance and specific gravity. 

Where plastics are to be used for electrical applications, then electrical properties as well as mechanical and other properties need to be considered. Whilst properties such as resistivity, power factor and dielectric constant are important, they may not be all-important. For example, although polyamides and many thermosetting plastics may show only moderate values for the above properties, they have frequently been used successfully in low-frequency applications. Perhaps more important for many purposes are the tracking and arcing resistance, which are frequently poor with aromatic polymers. 

Electrical Properties Traditionally plastics have established themselves in applications which require electrical insulation. PlFt and polyethylene are among the best insulating materials available. The material properties which are particularly relevant to electrical insulation are dielectric strength, resistance and tracking. 

Alkyd molding compounds, when molded into finished parts, may have excellent arc resistance (180 sec. minimum) and excellent arc track resistance. Other good electricals such as dielectric strength and insulation resistance can be obtained. The filler combinations may also result in excellent dimensional stability and outstanding retention of electrical and physical properties after exposure to elevated temperatures (450°F.) for long periods of time. Water absorption values are extremely low, which helps to maintain electrical values. 

Parts molded from melamine compounds have a hard scratch resistant surface, practically no odor or taste, good electrical properties, fair arc track resistance, decorative appearance, and color fast characteristics. 

The cycloaliphatic epoxy resins are characterized by the saturated ring in their chemical structure. They are almost water-white, very low-viscosity liquids. They provide excellent electrical properties such as low dissipation factor and good arc-track resistance, good weathering, and high heat distortion temperature. They are also free of hydrolyzable chlorine, sometimes present in DGEBA resins, which adversely affects certain electronic applications. 

Within their temperature limitations, UFs have good electrical properties. They have high dielectric strength, high arc resistance, no tendency to track after arcing, and a low order power factor. Their... 

The volume resistivity of polytetrafluoroethylene remains unchanged even after a prolonged soaking in water, because it does not absorb water. The surface arc-resistance of PTFE resins is high and is not affected by heat aging. They do not track or form a carbonized path when subjected to a surface arc in air [39]. The electrical properties of PTFE are summarized in Table 3.6. 

The two compounds which contain glass- and mineral-fillers provide the best arc resistance and tracking Index. All three materials provide a good balance of electrical properties. 

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