Polymer electrical components

PTFE is outstanding in this group. In thin films it provides the lowest coefficient of friction (0.03—0.1) of any polymer, is effective from —200 to 250°C, and is generally unreactive chemically. The low friction is attributed to the smooth molecular profile of PTFE chains which allows easy sliding (57). Typical apphcations include chemical and food processing equipment, electrical components, and as a component to provide improved friction and wear in other resin systems. 

Low viscosity urethane polymers have been prepared from castor od and polymeric isocyanates (82). These low mix viscosity systems are extremely usehd for potting electrical components where fast penetration without air voids, and fast dispensing cycles are desirable. Very low viscosity urethane systems containing castor polyols have been prepared for use in reclaiming water-logged buried telephone cable and for encapsulating telephone cable sphces (83—86). 

Polypropylenes are cost-effective polymers for casings, caps, frameworks for ventilation, fan blades, air filters, filters and pumps of industrial dishwashers, softeners, washing machines, detergent product vats, parts of pumps for handling chemicals, frames, cable rollers, parts with a film hinge, electrical components, translucent parts, cases, pipes. .. 

Major polymer applications automotive industry (radiator end tanks, inlet manifolds, rocker covers), electrical components (connectors, switches, motor frames), bearing cages, mechanical handling components, fibers, carpets, tire reinforcement, many other applications... 

Major polymer applications automotive, packaging, furniture, electrical components, fibers, tapes, many others... 

FRs are chemicals that can inhibit ignition and/or reduce the burning rate of a product. These are often used by manufacturers to help them meet fire safety standards set down by law for products such as electrical equipment, furnishings, and vehicles. These compounds are added to polymers, paint, textiles, and other materials to improve their fireproof properties. The main applications are in plastic housings of electronic products such as TV sets and computers, car parts, circuit boards, electric components, and cables. There are currently over 100 different substances used as FRs and these can be classihed in four categories (Figure 31.1) ... 

Polymer blends for packaging and materials handling of electrical components would require a degree of electrical conductivity to provide for static charge dissipation. This can be achieved either by a conductive additive, such as carbon black, carbon nano-tubes or metal fibers, or via blending with a conductive polymer like polyanUine. Blending of the latter is necessary to provide flow... 

We can find polymers as components of many of the objects that surround us, as well as in a broad diversity of applications in daily life clothing, shoes, personal care products, furniture, electrical and electronic appliances, packaging, utensils, automobile parts, coatings, paints, adhesives, tires, and so on. The list is endless, and these few examples should provide an idea of the importance of synthetic polymers to modern society, in terms of both their usefulness and the economic value that they represent. 

Other thermosetting polymers are cyanate esters (CEs), benzoxazines, PU acrylates, bismaleimides (BMIs), dicy-clopentadienes (DCPDs), diallyl phthalates (DAPs), etc. Formulations based on these polymers are used for specific applications where their particular properties are required. For example, DAP has long been the material of choice for electrical components where long-term reliability is required. 

While the adsorption theory is the most accepted one, mechanical interlocking comes into play in case of substrates with a special kind of roughness such as galvannealed steel where the liquid can spread into cavities and thereby interlock with the substrate. The diffusion theory does not play an important role for polymer-metal interfaces. The contribution of the electrostatic theory is not easy to estimate. However, the electrical component of the adhesive force between the planar surfaces of solids becomes important if the charge exchange density corresponds to 10 electronic charges, meaning about 1% of the surface atoms [71]. 

Owing to their unique electric insulation properties, polymers are widely used in electrical products. However, many electrical components are required to operate at high temperatures, for example, electric motors and some domestic appliances. 

Liquid Crystal Polymers Thermoplastic aromatic copolyesters with highly ordered structure. Has good tensile and flexural properties at high temperatures, chemical, radiation and fire resistance, and weatherabil-ity. Processed by sintering and injection molding. Used to substitute ceramics and metals in electrical components, electronics, chemical apparatus, and aerospace and auto parts. Also called LCP. 

The electrical properties of polymers are of considerable importance in various applications—the insulation of electrical or telecommunication cables, electrical components, electrical appliances and accessories, printed circuits, radar and electronics. Semiconductors based on polymers should also be mentioned. It is also possible to use electrical properties for monitoring or tests without fracture on stmcture or properties such as sequence of polymerization, degradation, and transition temperatures. Let s discuss briefly some major electrical properties. 

The polymers retain their shape up to 160° C, although they are brittle. The brittleness can be reduced by copolymerization with a little isoprene. Poly(V-vinyl carbazole) is used for insulation layers in high-frequency electrical components. More recently, most interest has been shown in its photoconductivity, which, together with its resistance in darkness, promises applications in electrostatic copying processes, television camera tubes, etc. 

A review of the history of the development of silicon MEMS shows that production of single devices for mass markets has been the dominant pattern in commercialization. The first products were pressure sensors for the automobile mass market. Next came the accelerometers for the same market, and more recently optical switches and ink-jet printheads. Similar parallels can be seen in the development of conducting polymer devices. Of the wide variety of prototype sensors, actuators, and electrical components that have been demonstrated over the past 10-15 years, only polymer LEDs have been completely commercialized. Smart systems utilizing MEMS and conjugated polymers, which were anticipated to be the killer app, have yet to make their appearance. 

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