Primary insulation

For primary insulation or cable jackets, high production rates are achieved by extmding a tube of resin with a larger internal diameter than the base wke and a thicker wall than the final insulation. The tube is then drawn down to the desked size. An operating temperature of 315—400°C is preferred, depending on holdup time. The surface roughness caused by melt fracture determines the upper limit of production rates under specific extmsion conditions (76). Corrosion-resistant metals should be used for all parts of the extmsion equipment that come in contact with the molten polymer (77). 

Asbestos-Based Grade. Grade MM is more resistant to heat than Grade C but not recommended for primary insulation at any voltage. It exhibits small dimensional changes when exposed to moisture. 

The electrical properties of the polyurethanes are not adequate for use as primary insulations, but their general toughness leads to their use as cable jacketing materials. 

Electrical properties not adequate for primary insulation Cost... 

Wire and cable coating dies are used in the extrusion process for primary insulation of single conducting wires as well as the jacketing or sheathing of a group of wires already insulated electrically, for mechanical strength and environmental protection purposes. 

They can be processed by techniques commonly used for thermoplastics, such as extrusion, injection molding, rotational molding, dip, slush molding, and powder and fluidized bed coating,16 and can be expanded into foams.17 Compression and transfer molding of FEP resins can be done, but with some difficulty. Extrusion of PEP is used for primary insulation or cable jackets and for tubing and films. 

The single largest application for ECTFE has been as primary insulation and jacketing55 for voice and copper cables used in building plenums.56 In automotive... 

TFIV is used for wire and cable jacketing, which is often cross-linked by electron beam to improve its strength and increase its softening temperature. It is also used as primary insulation in less demanding applications, where high flexibility is required.61... 

Calcium silicate mineral filler has been proposed as a replacement for calcium carbonate in primary insulation cable compound (83). Calcined calcium sulfate has been suggested to effectively replace calcium carbonate in cable insulation (283). 

The single largest application for ECTEE has been as primary insulation and jacketing [62] for voice and copper cables used in building plenums [63]. In automotive applications, ECTEE is used for jackets of cables inside fuel tanks for level sensors, for hookup wires, and in heating cables for car seats. Chemically foamed ECTEE is used in some cable constructions [64]. In the chemical process industry, it is often used in chlorine/caustic environment in cell covers, outlet boxes, lined pipes (Eigure 4.26), and tanks. 

Regnlus. [Advanced Web Prods.] Poly-imide thermoplastic film heat-resistant film for wire and cable, thermoplastic composites, pressure-sensitive adhesive Ugrra, primary insulation. 

Though there are metals other than copper (such as iron, manganese and cobalt) that can accelerate thermal oxidation of polyolefins and related polymers such as EPDM, in practice, however, the inhibition of copper-catalyzed degradation of polyolefins is of paramount importance because of the steadily increasing use of polyolefin insulation over copper conductors. Among polyolefins, polyethylene is still the most common primary insulation material for wire and cable. In the United States, high-density polyethylene and ethylenepropylene copolymers are used in substantial amounts for communications wire insulation. 

Polyesters in wire and cable apphcations include Hytrel (Du Pont), a thermoplastic polyester elastomer for the offshore industry Kapton (Du Pont), a polyimide film offering weight saving and chemical resistance and Mylar (Du Pont), used in primary insulation, shield isolation, chemical barrier, and... 

Transmission insulators provide mechanical support and electrical isolation for overhead, open wire, power transmission fines. The primary insulation on these lines is air. 

Uses PVC stabilizer/lubricant for primary insulation up to 105 C rating and for cable sheathing Features One-pack high efficiency Pb-free Properties Wh. powd. dens. 1.8 cm ... 

Uses Stabilizer, lubricant for]acketing and primary insulation up to 90 C rating... 

Uses Antioxidant, metal deactivator for polymers, PP, HDPE, LDPE, some thermoplastic elastomers used as primary insulation in wire/cable applies., EPDM, peroxide- and radiation-crosslinked PE, nylon, polyacetal, polybutene, PU, styrenic copolymers, unsat. rubber, PVC, PVB, hot-melt and sol n. adhesives, powd. coatings, metal coatings, rubber/plas-tic gaskets, plastic fabricated parts in contact with catalytic metals, oils/ lubricants in contact with metals, food pkg. 

Uses Metal deactivator in stabilization of polyolefins shelf life extender for PP, PE, and poly-(ethylene-propylene) and certain thermoplastic elastomers used as primary insulators in contact with copper for elec, parts, plugs, wire insulation and jacketing, polymer powd. and other coatings on metal, hot melt and sol n. adhesives, deactivation of catalyst residue, oils and lubricants in contact with metals and contaminants at high temps. Regulatory DOT nonregulated Properties Wh. powd. m.w. 204 m.p. 302 C... 

ETFE), and silicone rubber is used as the primary insulator an additional thin layer of polyurethane coats the soft silicone rubber (Fig. 1.23b). 

Selection of plasticizers depends on destination such as primary insulation or sheat-ing. It also depends on required electrical volatihty and low temperature performance in which plasticizers play a decisive role. Plasticizers mustprodrree thermally stable nonvolatile products. ... 

The low-pressure encapsulation compounds, which exhibit the same high-performance characteristics as the high-pressure compounds, have become the primary insulating medium for the encapsulation of components such as integrated circuits, resistors, coils, diodes, capacitors, relays, and bobbins. 

Applications Primary insulation, compounding base resin Primary insulation, coaxial and electronic cables, compounding base resin... 

In general, these products are composites of less expensive polymers with the PVDF layer incorporated as an inner liner or embedded barrier PVDF is not suitable as a primary insulation on AC power wiring because of absorption of the electromagnetic field and heating... 

Equipment current, (i) Protective equipment used for the primary insulation of employees from energized circuit parts shall be capable of passing a current test when subjected to the highest nominal voltage on which the equipment is to be used. 

Note 1 to paragraph (b)(2) This paragraph applies to equipment that provides primary insulation of employees from energized parts. It does not apply to equipment used for secondary insulation or equipment used for brush contact only. 

One of its earliest applications, in fact, was the primary insulator on computer hookups used in back panels and installed by high speed, automatic wiring machines While satisfactory electrical properties of the polymer were important, automatic wiring equipment also required a wire insulation material of exceptional physical toughness. KYNAR pvDF easily fit this requirement. 

The plenum concept has been so successful that many plenums contain abandoned cables where each cable can individually pass the smoke and flame spread requirements, but when added together, they can have a measurable fuel value. The next logical evolution in fire safety is to limit the overall fuel load in the plenum, which has led to the definition of a limited combustible cable [12], These cables have a maximum potential heat value of 3500 BTU/lb (NEPA 259) in addition to the smoke and flame spread requirements common to other plenum cables. As described earlier, the best way to minimize fuel load with a polymer is to use a perfluorinated compound, and in this case, both primary insulation and jacket benefit from this attribute [13],... 

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