Insulating plastics

These polymers commonly are described as PVC plastics or less specifically as vinyl. They are materials that may be either flexible or rigid according to what they are mixed with, and they are used in the manufacture of many familiar articles such as plastic curtains, rainwear, floor tile, synthetic leather goods, upholstery, table mats, phonograph records, insulation, plastic pipes, tubing, and packaging materials. 

Polychloroethene (polyvinyl chloride), as usually prepared, is atactic and not very crystalline. It is relatively brittle and glassy. The properties of polyvinyl chloride can be improved by copolymerization, as with ethenyl ethanoate (vinyl acetate), which produces a softer polymer ( Vinylite ) with better molding properties. Polyvinyl chloride also can be plasticized by blending it with substances of low volatility such as tris-(2-methylphenyl) phosphate (tricresyl phosphate) and dibutyl benzene-1,2-dicarboxylate (dibutyl phthalate) which, when dissolved in the polymer, tend to break down its glasslike structure. Plasticized polyvinyl chloride is reasonably flexible and is widely used as electrical insulation, plastic sheeting, and so on. 

Vinyl chloride H2C=CH—Cl Poly(vinyl chloride) Insulation, plastic pipe... 

For cells that lack IR loss-increasing membranes, the Swiss-roll cell design (Ibl, 1975) may be the answer. Two metal foils act as electrodes and are separated by two insulating plastic masks that act as turbulence promoters. This cell gives large area and low IR. It is shown in Fig. 11.6. 

Chapter 26 Plastics this includes foam plastic insulation, plastic veneer, and light transmitting plastics. 

For reasons of ease of manufacture, the majority of solid electrodes have a circular or rectangular form. External links are through a conducting epoxy resin either to a wire or to a solid rod of a metal such as brass, and the whole assembly is introduced by mechanical pressure into an insulating plastic sheath (Kel-F, Teflon, Delrin, perspex, etc.) or covered with epoxy resin. It is very important to ensure that there are no crevices between electrode and sheath where solution can enter and cause corrosion. Examples of electrodes constructed by this process will be shown in Chapter 8. 

Thermal Insulation. Plastics offer very good insulation against heat and cold, and can be foamed to increase their insulating qualities much further. 

Electrical Insulation. Plastics are excellent electrical insulators. They can also be formulated to provide semi-conductivity, and high or low dielectric constant and loss. 

In the production of printed circuit boards for the electronics industry, a 0.60-mm layer of copper is laminated onto an insulating plastic board. Next, a circuit pattern made of a chemically resistant polymer is printed on the board. The unwanted copper is removed by chemical etching and the protective polymer is finally removed by solvents. One etching reaction is... 

Calorimetric probes were done as previously described (10), using a 1-1.5M solution of epoxide In solvent in the presence of a relatively small amount (approximately 10 M) of catalyst. The reaction was run In an Insulated plastic-coated paper cup fitted with a magnetic stirring bar, cover and thermocouple. Temperature-rises were recorded versus time using a Hewlett-Packard 7127A strip-chart recorder. 

Polystyrene Heat insulation, plastic cups Flamingo foam... 

Fig. 19. Apparatus for continuous extraction of hash oil. Thin tubing brings the mixture of cannabinoids in solvent from the first pressure cooker in the background through the top of the second cooker which is painted black to absorb heat. Heat lamps are used to evaporate the solvent which rises through the insulated plastic pipe. The DEA stated that this apparatus produced 2.5 quarts of oil from about 82 pounds of marijuana in one hour. The time is unquestionably too short, but if the other figures are correct and grass with 1% THC content was used, the oil would contain about 20% THC. (Reprinted from Drug Enforcement, 1973.)...

Resistivity of Insulating Plastics Measurements of insulating polymers or polymer blends are usually carried out using a sheet specimen in form of a disc or a square [ASTM D257]. 

Electrochemical reactor used for wastewater treatment A new undivided "bipolar electrochemical reactor" of channel type with flat parallel electrodes has been developed in our laboratory. Its design is very simple, it consists of a bipolar stack of 5 - 30 metallic sheets (electrodes) separated from each other by insulating plastic spacers at a fixed distance. 

Figure 65 An insulated plastic greenhouse suitable for mushroom growing.

Thin Film Systems. An ideal low-cost system could be continuously processed into rolls of arrays. These rolls would consist of a clear, flexible, electrically insulating plastic front cover, a thin layer of pottant or adhesive on either side of the flexible thin film PV circuit, and an opaque, flexible, electrically insulating plastic back cover. These rolls could then simply be unrolled on the roof, nailed into place, and connected to the household circuitry. All components would have to be flexible. Figure 6 illustrates the possible components of an all flexible system — both hermetic and non-hermetlc depending on future cell requirements. 

The breakdown voltage increases proportionally less than thickness increases, and as a result the dielectric strength of a material decreases with the thickness of specimen (Figure 3.52b). For this reason, testing of insulation plastic should be done with approximately the thickness in which it is to be used in service. 

Flame retardants work by minimizing at least one of the three factors necessary for fire to exist, i.e. fuel, heat and oxygen. They may produce char from the polymer which shields the surfeces from oxygen, retards the diffusion of volatile combustible products and insulates plastic from the heat of fire. Phosphorus and boron flame retardants catalyse the formation of char. 

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