Polyethylene cable insulation

Figure 2. A comparison of the sensitivity of impurity detection in polyethylene cable insulation achieved with a) NAA of 1 mg samples, the solid points, b) NAA with 1 g samples, the open points and c) PIXE with 2.0 MeV protons, the two solid curves are for detection of the K and the L X-rays (data taken from ref. 2).

Figure 4 FTIR microscopy of polyethylene cable insulation. (A) Water-tree, (B) undamaged area, and (C) the difference spectrum (A) (B). (Parker SF (1995) Industrial applications of vibrational spectroscopy and the role of the computer. In George WO and Steele D (eds.) Computing Applications in Molecular Spectroscopy, pp. 181-199. Cambridge The Royal Society of Chemistry reproduced by permission of The Royal Society of Chemistry.)...

Figure 10.1 Bright-field transmission optical micrograph showing a methylene blue-stained water tree grown from a reamed hole in a sample of medium-voltage polyethylene cable insulation. From...

Figure 10.7 An etched surface within a sample of medium-voltage polyethylene cable insulation, as revealed in reflection using DIC optics. The dendritic structure of a water tree is evident, together with rectangular regions which correspond to beam damage as a result of prior examination in the SEM. From Olley et al. (1992) [7].

G Grzybowski A Rakowska, JE. Tompson. Examination of ageing process in polyethylene cable insulation. Proceedings of IEEE International Symposium on Electrical Insulation, Montreal, 1984,... 

R. B. Blodgett, "Ethylene—Propylene Rubber and Crosslinked Polyethylene as Insulations for 90°C Rated Medium Voltage Cables," Rubber Chem. Technol, 52, 410-424 (1978). 

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. 

Electrical Applications. Plastics are used for electrical insulation, conduit and enclosures, lighting fixtures, and mechanical devices. The most widely used plastic for wire and cable insulation is flexible, plasticized PVC, which constitutes well over half the market in insulating wires for buildings, automobiles, appHances, and power and control lines. Polyethylene is also a factor. Higher performance plastics such as nylon and fluoropolymers also play a smaller role in this area. 

Polymers are widely used as electrical insulators in applications such as wire and cable insulation, electrical appliance housings and capacitor films. Polymers used in these applications include polyvinyl chloride, polyethylene, and isotactic polypropylene. 

Low density polyethylene is used in making film and sheeting, injection moulding, wire and cable insulator, coating and blow moulding. 

The cross-linked polyethylene retains shape upto 140°C and is used for cable insulation. Polyethylene is the most widely used plastic due to its low cost and ease of processing. 

Additional curing is often achieved with sulfur, peroxide, or maleimide formulations. Chloro-sulfonated polyethylene has improved resistance to oil, ozone, and heat compared to many other elastomers. Applications include harrier membranes and liners, surface coatings on fabrics, automobile air-conditioner hose, electrical cable insulation, and spark-plug boots [Andrews and Dawson, 1986],... 

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... 

Cross-linkable polymers used for wire and cable insulations are polyolefins, certain fluoropolymers, and elastomers. Among these, radiation cross-linked polyethylene is the most widely used. The radiation cross-linking process of PE has also been the most widely studied. ... 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

Irradiation of polyolefins, particularly the family of polyethylenes, represents an important segment of the radiation processing. Polyolefins can be irradiated in many forms, such as pellets and powders, films, extruded and molded parts or as wire and cable insulation. 

The fact that these graft copolymers contain polyethylene chains makes them crosslinkable by organic peroxides. One of them has already found industrial application as a peroxide crosslinkable material in cable insulation. 

Bottles, drums, pipes, conduits, sheets, films, wire and cable insulations Blending with low-density polyethylene, films, packaging, bottles Automobile and appliance parts, ropes, cordages, webbing, carpeting, films Films, pipes... 

Chlorinated paraffins, which contain up to 60-70% chlorine, are low in cost and are used as secondary plasticizer in PVC wire and cable insulations. Perchlorobicyclopentadiene has little plasticizing action and is used in polyethylene. Some of the more expensive bromine-containing fire retardants which have been used in the ratio of 5 p.p.h. in polystyrene foam, may be reduced to 0.5 p.p.h. by adding synergists such as peroxides or nitroso compounds. The reaction-type retardants, such as chlorendic acid and anhydride, hydroxy-terminated phosphonated esters, and specific brominated aliphatic esters, are admixed to rigid and flexible polyurethane foams, reinforced polyesters, phenolics, and epoxy resins. 

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