Materials Cable insulation

Nonstick cookware, containers for corrosive materials, cable insulation, polymer membranes for buildings. 

Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

The relationship of the dielectric constant of the cable insulation to crosstalk can be measured by testing two cables for crosstalk with the same dimension, but different insulation materials. The cable with the lower dielectric constant has less capacitance unbalance, thus resulting in lower crosstalk than the cable with the higher dielectric constant. 

Properties desired in cable insulation and flexible circuit substrate materials include mechanical flexibiUty, fatigue endurance, and resistance to chemicals, water absorption, and abrasion. Both thermoplasts and thermosets are used as cable-insulating materials. Thermoplastic materials possess excellent electrical characteristics and are available at relatively low cost. 

Commonly used materials for cable insulation are poly(vinyl chloride) (PVC) compounds, polyamides, polyethylenes, polypropylenes, polyurethanes, and fluoropolymers. PVC compounds possess high dielectric and mechanical strength, flexibiUty, and resistance to flame, water, and abrasion. Polyethylene and polypropylene are used for high speed appHcations that require a low dielectric constant and low loss tangent. At low temperatures, these materials are stiff but bendable without breaking. They are also resistant to moisture, chemical attack, heat, and abrasion. Table 14 gives the mechanical and electrical properties of materials used for cable insulation. 

Table 14. Mechanical and Electrical Properties of Cable Insulating Materials...

Anode supports, cable insulators and the coating on the object to be protected can be destroyed by anodic evolution of chlorine (see Section 7.1), Only chorine-resistant materials should be used. Anodes on retaining walls or between pile foundations can be installed in perforated or fabricated plastic tubes (half-shells) (see Fig. 16-8). They must naturally be provided with very many holes to avoid uneven removal of anode material. Filter tubes of a chlorine-resistant special material or... 

Interest in EVA as a cable-insulating material has arisen because of the good resistance to stress cracking and because the polymer may be more easily cross-linked (see Table 11.12). 

During the next few years PVC was steadily developed in the United States and in Germany. Both countries were producing the material commercially before World War II. In Great Britain, ICI in 1942 and the Distillers Company in 1943 also commenced pilot-plant production of PVC, a material then in demand as a rubber substitute for cable insulation. Paste-forming grades suitable for the production of leathercloth also became available soon afterwards. 

The market for PPVC film and sheet is only slightly less than for wire and cable insulation. Uses are as diverse as seepage barriers, factory doors, inflatables, baby pants, car trim, covering materials for book bindings and document cases and shower curtains. UPVC film has also been widely used for packaging of food, particularly for shrink-wrap purposes, but this market has been subject to some substitution by polypropylene. 

These materials are developed from the polyetherimides introduced by General Electric (see also Section 18.14.2). At the time of writing one grade, Ultem Siltem STM 1500, is being offered. It is of particular interest as a material for wire and cable insulation, as it not only has excellent flame resistance coupled with low smoke generation but also avoids possible toxic and corrosion hazards of halogenated polymers. This can be of importance where there are possible escape problems in the event of a fire, such as in tunnels, aircraft and marine (particularly submarine) vessels. 

Flexible RP These materials are used with elastomeric materials providing special engineered products such as conveyor belts, mechanical belts, high temperature or chemical resistant suits, wire and cable insulation, and architectural designed shapes. 

The power factor of an insulating material indicates its tendency to generate heat in service. The electrical energy loss is directly proportional to the frequency and at high frequencies only materials of very low power factor may be used as cable insulation. 

Electrical conductors are normally insulated for protection and avoidance of electrical shorting. Typical insulating materials are plastics that can readily bum with toxic vapors. The NEC specifies certain fire resistant rating to electrical cables to lessen the possibility of cable insulation ignitability and fire spread. 

Cable coating extrusion, 29 548-549, 790 Cable insulating materials, mechanical and electrical properties of, 27 849t Cable insulation HDPE, 20 174-175 LLDPE, 20 208-209 Cable materials, in electronic materials packaging, 27 848... 

A report (37) on the effect of different types of radiation on the elongatlon-at-break of certain commercial cable Insulating materials pointed to several aspects requiring fundamental Investigations on well-characterised materials under defined conditions. It showed the Importance of antl-oxldant stabilisers, particularly In relation to long term ageing. It was concluded that the differences observed could be attributed to dose rate effects rather than to the types of radiation studied. The Irradiated samples were standard dumb hell shaped tensile samples. 

EVA is a copolymer of ethylene with minor amounts (ca. 10 0%) of vinyl acetate. EVA has many uses as a foam rubber in everyday goods (like shoes etc.), as cable insulation and as encapsulation material in photovoltaic cells. 

The largest volume of polymeric materials used for wire and cable insulation are thermoplastics, namely, polyethylene (PE) and polyvinylchloride (PVC), and to a lesser degree elastomeric compounds. The main reason for the prevalence of PE and PVC in wire and cable insulation is their easy processing and relatively... 

Comparison of Radiation and Peroxide Cross-Linking of Wire and Cable Insulation Materials... 

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