Electrical glass conductive fillers

Calcium Carbonate, Calcium Silicate, Powdered Aluminium, Copper Alumina, Flint Powder, Carborundum, Silica, Molybdenum Disulphide Chopped Glass Mica, Silica, Powdered or flaked Glass Metallic Filler or Alumina Colloidal Silica, Bentonite Clay Improved Thermal Conductivity Improved Machinability Improved Abrasion Resistance Improved Impact Strength Improved Electrical Conductivity Improved Thixotropic Response... 

An alternative to the use of antistatic additives is the incorporation of electrically conductive fillers or reinforcements into the polymer to make the whole structure conductive. Typical additives that are used for this purpose include aluminum, steel, or carbon powders, and metal-coated glass fibers or carbon fibers. Powdered fillers are generally less expensive than fibers. Maintaining the desired fiber distribution during processing is also problematic. 

Examples of electrically conductive fillers are carbon black, graphite (flake and fiber), and metal (copper, silver, steel, flake, and fiber). Metallized mica or glass beads offer high electrical conductivity but at lower cost than using pure metals. 

For certain products, skill is required to estimate a product s performance under steady-state heat-flow conditions, especially those made of RPs (Fig. 7-19). The method and repeatability of the processing technique can have a significant effect. In general, thermal conductivity is low for plastics and the plastic s structure does not alter its value significantly. To increase it the usual approach is to add metallic fillers, glass fibers, or electrically insulating fillers such as alumina. Foaming can be used to decrease thermal 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. 

Electrical conduction ceramics, 5 585-587 glasses, 5 592-593 Electrical conductivity. See also Conductivity of foams, 12 11 fillers and, 10 434 silver, 22 639... 

Composite-based PTC thermistors are potentially more economical. These devices are based on a combination of a conductor in a semicrystalline polymer—for example, carbon black in polyethylene. Other fillers include copper, iron, and silver. Important filler parameters in addition to conductivity include particle size, distribution, morphology, surface energy, oxidation state, and thermal expansion coefficient. Important polymer matrix characteristics in addition to conductivity include the glass transition temperature, Tg, and thermal expansion coefficient. Interfacial effects are extremely important in these materials and can influence the ultimate electrical properties of the composite. 

To improve the properties of the raw polymer (wear resistance, creep resistance, thermal and electrical conductivity), various fillers, such as glass fibers, powdered metals, and graphite, are combined with all three types of PTFE polymers mostly by intimate mixing. Filled fine powders are produced mostly by adding fillers into a dispersion and then coagulating the mixture. 

Fillers are relatively nonadhesive substances added to the adhesive formulation to improve its working properties, strength, permanence, or other qualities. The improvements resulting from the use of fillers are listed in Table 1.8. Fillers are also used to reduce material cost. By selective use of fillers, the properties of an adhesive can be changed significantly. Thermal expansion, electrical and thermal conduction, shrinkage, viscosity, and thermal resistance are only a few properties that can be modified by the use of fillers. Common fillers are wood flour, silica, alumina, titanium oxide, metal powders, china clay and earth, slate dust, and glass fibers. Some fillers may act as extenders. 

Some fillers impart specialist secondary functions to the polymer. Glass in the form of fibres, flakes and hollow microbaUoons or microspheres has been used to fill polymers (Walker and Shashoua, 1996). Metal flakes or powdered metals are used as fillers in electrically conductive plastics, which are used to overcome electromagnetic interference in office equipment. Carbon-filled polymers are good conductors of electricity and heat. 

It is common practice to add fillers, such as talc or glass fibers, to a thermoplastic matrix to achieve cost reduction and mechanical reinforcement, as well as to enhance various properties such as electrical conductivity, thermal properties, and dimensional stability. Large amoimts of conventional micron-size fillers are typically required in these formulations, which results in deterioration of processability and surface appearance. 

Metallized glass n. Glass spheres, flaks, or fibers that have been coated with silver or aluminum and, as fillers, provide increased electrical conductivity and fight-reflecting pigmentation. 

Encapsulation is often performed with resins containing fillers such as mica, aluminum oxide, milled glass fibers, and many others. Although epoxies are the resins most generally used, polyesters, filled and unfilled silicones, urethanes, and polysulfides are also used. By the proper choice of fillers it is possible to match expansion rates of the electronic part and the encapsulant, increase the thermal conductivity of the part, and considerably upgrade the electrical and mecharucal properties of the assembly. 

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