Electrical insulators compressive properties

There has been some recent interest in polymers containing very small proportions (<2000 ppm) of a second comonomer. These can interfere with crystallisation and the resulting products are claimed to have improved compression strength, electrical insulation properties, weldability and transparency compared with the unmodified homopolymers. 

Molding powders are B-stage silicone resin plus glass fiber and catalyst. They are compression molded 5 to 20 min at 1000 to 4000 psi and 160°C and then post-cured several hours to achieve optimum properties. Electrical insulation and resistance to heat and moisture are outstanding (Table 3.44). Molded parts are used in electric motors and switches. 

The main attributes of properly cured epoxy systems are outstanding adhesion to a wide variety of substrates, including metals and concrete ability to cure over a wide temperature range very low shrinkage on cure excellent resistance to chemicals and corrosion excellent electrical insulation properties and high tensile, compressive, and flexural strengths. 

FIFE tape is used in many applications, including sealing joints, insulating conductive wires, and protecting materials from corrosive elements. FIFE demonstrates a good chemical and heat resistance, electrical insulation characteristics, as well as a low coefficient of friction. However, in general, it has less than desirable mechanical properties, in particular with respect to abrasion resistance and compression strength. 

PROPERTIES OF SPECIAL INTEREST High compressive strength, less weight, good weatherability, and excellent properties of electrical insulation. 

A relatively new development is the combination of metals and ceramic in compacts called cermets. The purpose is to combine the high refractoriness, resistance to osidation, electrical insulation, and retention of compression strength on heating—all properties d ceramic bodies—with the ductibility and thermal shock resistance of metals. ... 

The most important characteristics of ceramic materials are high hardness, resistance to high compressive force, resistance to high temperature, brittleness, chemical inertness, electrical insulator properties, superior electrical properties, high magnetic permeability, special optic and conductive properties, and so forth. 

Thermoplastic vulcanizates (TPVs) are composed of a vulcanized rabber component, such as EPDM, nitrile rubber, and butyl rubber in a thermoplastic olelinic matrix. TPVs have a continuous thermoplastic phase and a discontinuous vulcanized rubber phase. The most common TPV polymer systan is PP/EPDM rubber however, a number of other polymer systems have been commercially developed. These include PP/NBR, PP/butyl and PP/halobutyl, PP/NR, and PP/EVA/EPDM. Producers include Advanced Elastomers Systems (Santoprene, Geolast, and Trefsin). The highly rubberlike properties of TPV have enabled than to perform as engineered thermoplastic rubbers. In numerous application areas they have directly replaced premium-performance thermoset rubber compounds. Prominent among these are dananding automotive applications, electrical insulation and connectors, compression seals, appliance parts, medical devices, and food and beverage contact applications. 

The final products of cast phenol-formaldehyde polymers have a number or exceptional properties, including high tensile and compressive strengths, good electrical insulating capabilities, and excellent adhesive qualities. Also, they can be polished and machined. Finally, the presence of very small water droplets in the material gives the surface a superb appearance. 

Polytetrafluoroethylene is a white solid with a waxy appearance and feel. It is a tough flexible material of moderate tensile strength with a tendency to creep under compression. Comparative values for some properties of various fluoro-polymers are given in Table 7.1. The electrical insulation properties are outstanding and are nearly as good as those of polyethylene. The coefficient of friction is unusually low and stated to be lower than that of any other solid the non-stick properties are also excellent. 

Silicone rubber polymers have the more stable Si atom compared with carhon. Silicone s property signature is its combined (1) high-temperature resistance [>500°F (260°C)], (2) good flexibility at <-100°F (-73°C), (3) good electrical properties, (4) good compression set, and (5) tear resistance and stability over a wide temperature range. When exposed to decomposition level temperature, the polymer forms Si02, which can continue to serve as an electrical insulator. ... 

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