Glass fibers electrical properties

Fillers. Fillers are used to improve strength and stiffness, to lower cost, and to control gloss. The most common filler is calcium carbonate, which ranges in size from 0.07 to well over 50 m. Some forms are treated with a stearic acid coating. Clay fillers, such as calcined clay, improve electrical properties. Glass fibers, talc, and mica improve tensile strength and stiffness, but at a loss in ductility. 

Excellent electrical properties. Glass fibers have high dielectric strengths and low dielectric constants. 

Keywords glass fiber (GF), composition, physical properties, chemical resistance, electrical properties, optical properties, glass fiber production, glass fiber reinforced composites. 

Diallyl phthlates (DAP) and diallyl isophthlates (DAIP) are the principal thermosets in the allyl family, with DAP used predominantly. They are used for glass-preimpregnated cloth and paper that must undergo a heat, time, and pressure cycle to produce parts. Molding compounds are reinforced with fibers to improve their mechanical and physical properties. Glass fibers impart mechanical performance, acrylic fibers provide improved electrical performance, polyester fibers enhance impact resistance, and other fibers and fillers can impart different performance traits. 

Epoxy, polyester, phenolic and other resins are used as coatings and linings with or without reinforcement. Glass fiber, silica, carbon and many other materials can be used as filters or reinforcement to produce materials with specific properties of strength, flexibility, wear resistance and electrical conductivity. 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

In addition to glass fibers, PBT can also be reinforced with carbon fibers. Many of the general trends seen with glass fibers are also observed with carbon fibers. One important aspect of carbon fibers is that they may bring electrical conductivity to PBT if sufficient fiber connectivity is achieved in the final part. Metal fibers and metal-coated carbon fibers have also been compounded with PBT, giving not only improved mechanical properties but also molded parts with enhanced ability to shield components from electromotive and radiofrequency interference (EMI-RFI) [33],... 

Highly pure lanthanum oxide is used to make optical glass of high refractive index for camera lenses. It also is used to make glass fibers. The oxide also is used to improve thermal and electrical properties of barium and strontium titanates. Other applications are in glass polishes carbon arc electrodes fluorescent type phosphors and as a diluent for nuclear fuels. In such apph-cations, lanthinum oxide is usually combined with other rare earth oxides. 

Some electrical properties of reinforcing fibers, composite resins, and the resulting composites are given in Tables 6.12, 6.13, and 6.14, respectively. These values should be taken as approximate only, especially for the composites, since fiber orientation, content, and field strengfh have an enormous impacf on fhe dielecfric properties of these materials. Some of the most widespread electrical applications for glass-fiber-reinforced epoxy systems are in printed circuit boards and electrical housing such as junction boxes. 

Table 6.12 Some Electrical Properties of Selected Reinforcing Glass Fibers...

Table 6.14 Some Electrical Properties of Selected Glass-Fiber-Reinforced Resins...

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