Insulating materials, properties

Current market trends indicate a gaining momentum of corrosion and temperature-resistant MEMS devices for the use in mass market applications. Silicon-on-insulator material properties make way for a whole new range of uses and applications while being available in sufficiently large quantities to satisfy large volume production requirements. A breakthrough of these devices can be expected through automotive applications, if they can meet the price pressure. 

IEC 60216, Electrical insulating materials - Properties of thermal endurance, 1990-2001. 

DIN EN 60216 Electrical insulating materials — Properties of thermal endurance (lEC 60216) German version EN 60216... 

Phenol—formaldehyde resins are used as mol ding compounds (see Phenolic resins). Their thermal and electrical properties allow use in electrical, automotive, and kitchen parts. Other uses for phenol—formaldehyde resins include phenoHc foam insulation, foundry mold binders, decorative and industrial laminates, and binders for insulating materials. 

Two parallel plates of conducting material separated by an insulation material, called the dielectric, constitutes an electrical condenser. The two plates may be electrically charged by connecting them to a source of direct current potential. The amount of electrical energy that can be stored in this manner is called the capacitance of the condenser, and is a function of the voltage, area of the plates, thickness of the dielectric, and the characteristic property of the dielectric material called dielectric constant. 

R. Bartnikas, "Engineering Dielectrics Vol. II A—Electrical Properties of SoHd Insulating Materials Molecular Stmcture and Electrical Behavior," ASTM Special Technical Publication 783, 1983, Chapts. 1—5, pp. 3—515. 

Moisture. Absorbed and retained moisture, especially as ice, has a significant effect on the stmctural and thermal properties of insulation materials. Most closed-ceU plastic foams have low permeance properties most notably where natural or bonded low permeance surface skins exist (29,30). Design, building, and constmction practices requite adequate vapor retarders, skins, coatings, sealants, etc, in order to prevent the presence of moisture. However, moisture vapor cannot be completely excluded, thus the possibiUty of moisture absorption and retention is always present. The freezing of moisture and mpturing of cells result in permanent reduction of thermal and stmctural performance. 

Applications. The high heat tolerance and good salt compatibiUty of welan gum indicate its potential for use as an additive in several aspects of oil and natural gas recovery. Welan also has suspension properties superior to xanthan gum, which is desirable in oil-field drilling operations and hydraulic fracturing projects. It is compatible with ethylene glycol, and a welan—ethylene glycol composition that forms a viscous material useful in the formulation of insulating materials has been described (244). 

Properties desired in cable insulation and flexible circuit substrate materials include mechanical flexibiUty, fatigue endurance, and resistance to chemicals, water absorption, and abrasion. Both thermoplasts and thermosets are used as cable-insulating materials. Thermoplastic materials possess excellent electrical characteristics and are available at relatively low cost. 

Table 14. Mechanical and Electrical Properties of Cable Insulating Materials...

Silicone foam thus formed has an open ceU stmcture and is a relatively poor insulating material. Cell size can be controlled by the selection of fillers, which serve as bubble nucleating sites. The addition of quartz as a filler gready improves the flame retardancy of the foam char yields of >65% can be achieved. Because of its excellent dammabiUty characteristics, siUcone foam is used in building and constmction fire-stop systems and as pipe insulation in power plants. Typical physical properties of siUcone foam are Hsted in Table 10. 

General-Purpose Polystyrene. Polystyrene is a high molecular weight M = 2 — 3 x 10 ), crystal-clear thermoplastic that is hard, rigid, and free of odor and taste. Its ease of heat fabrication, thermal stabiUty, low specific gravity, and low cost result in mol dings, extmsions, and films of very low unit cost. In addition, PS materials have excellent thermal and electrical properties that make them useful as low cost insulating materials (see Insulation, ELECTRIC Insulation, thermal). 

The properties of ati insulating material are greatly affected by moisture, temperature, repeat overvoltages, and chemical vapour. Care must be taken to avoid these harmful effects to achieve prolonged life of the machine. 

Temperature rise at the guaranteed output to ascertain the adequacy of the insulating material and life of the motor. If the temperature rise is more than permissible for the type of insulation used, it will deteriorate the insulating properties and cause thermal ageing. As a... 

With the advent of these compounds in the 1960s, the hitherto more conventional insulating materials, such as phenol formaldehyde (popularly known as Bakelite) and wood (veneered impregnated) have been almost replaced by them. These compounds offer better electromechanical properties than conventional materials. Below we describe the basic mix and properties of these two basic compounds, for a brief reference. 

Insulating materials and their properties Ageing of insulation Practices of insulation systems Procedure for vacuum pressure impregnation Maintenance of insulation Monitoring the quality of insulation of HT formed coils during manufacturing... 

Most plastics materials may be considered as electrical insulators, i.e., they are able to withstand a potential difference between different points of a given piece of material with the passage of only a small electric current and a low dissipation energy. When assessing a potential insulating material, information on the following properties will be required ... 

The insulating properties of polyethylene compare favourably with those of any other dielectric material. As it is a non-polar material, properties such as power factor and dielectric constant are almost independent of temperature and frequency. Dielectric constant is linearly dependent on density and a reduction of density on heating leads to a small reduction in dielectric constant. Some typical data are given in Table 10.6. 

Polystyrene is now available in certain forms in which the properties of the product are distinctly different from those of the parent polymer. Of these by far the most important is expanded polystyrene, an extremely valuable insulating material now available in densities as low as 1 Ib/ft (16kg/m ). A number of processes have been described in the literature for the manufacture of the cellular product of which four are of particular interest in the manufacture of large slabs. 

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. 

The insulating property of any insulator will break down in a sufficiently strong electric field. The dielectric strength is defined as the electric strength (V/m) which an insulating material can withstand. For plastics the dielectric strength can vary from 1 to 1000 MV/m. Materials may be compared on the basis of their relative permittivity (or dielectric constant). This is the ratio of the permittivity of the material to the permittivity of a vacuum. The ability of a... 

The toughness of a material is a design driver in many structures subjected to impact loading. For those materials that must function under a wide range of temperatures, the temperature dependence of the various material properties is often of primary concern. Other structures are subjected to wear or corrosion, so the resistance of a material to those attacks is an important part of the material choice. Thermal and electrical conductivity can be design drivers for some applications, so materials with proper ranges of behavior for those factors must be chosen. Similarly, the acoustical and thermal insulation characteristics of materials often dictate the choice of materials. 

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