Polymeric wire insulation materials

Table 29.3 Polymeric Wire Insulation Materials and Their Advantages...

Synthetic polymeric plastic materials accumulate in the environment at a rate of 25 million metric tonnes per armum. Polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP) and polystyrene (PS) are all used globally in large quantities. In terms of consumption, PVC is the third most important thermoplastic material with widespread applications ranging from packaging to healthcare devices, toys, building materials, electrical wire insulation, clothes and furnishing [2],... 

The search for flexible, noncorrosive, inexpensive conductive materials has recently focused on polymeric materials. This search has increased to include, for some applications, nanosized fibrils and tubes. The conductivity of common materials is given in Figure 19.1. As seen, most polymers are nonconductive and, in fact, are employed in the electronics industry as insulators. This includes PE and PVC. The idea that polymers can become conductive is not new and is now one of the most active areas in polymer science. The advantages of polymeric conductors include lack of corrosion, low weight, ability to lay wires on almost a molecular level, and ability to run polymeric conductive wires in very intricate and complex designs. The topic of conductive carbon nanotubes has already been covered (Section 12.17). 

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... 

Other significant uses of PCBs included heat exchangers and hydraulic fluids. Prior to controls PCBs were also used in adhesives, coatings, plasticizers and inks for microencapsulating dyes for carbonless duplicating paper as extenders in pesticide formulations and catalyst carriers in olefin polymerizations to impart hydrophobicity to materials and surfaces in bactericide formulations (combined with insecticides), and in immersion oil for microscopes. Mixed with chloronaphthalenes, PCBs were also used in wire and cable insulation in the mine and shipbuilding industries (ref. 80, p. 455). 

At the end of the 19th century, rubber, with gutta-percha, was used mainly as an electrical insulator on wires and cables. Demand was limited, and the supply of natural rubber at a reasonable price (about 1.00/lb in 1900) was ensured. Some work was done during these years on practical syntheses of isoprene and on the replacement of isoprene by its simpler homolog, butadiene, which had been known since 1863. However, advent of the automobile and accelerated use of electric power rapidly increased the demand for rubber, thus raising its price to about 3.00/lb in 1911. These circumstances focused new attention on the production of a synthetic rubber. S. B. Lebedev polymerized butadiene in 1910, and Carl Dietrich Harries, between 1900 and 1910 established qualitatively the structure of rubber as a 1,A-polyisoprene and synthesized larger quantities of rubberlike materials from isoprene and other dienes. 

Most polymeric applications call for materials with high resistivities that act as Insulators of electrical wire, etc. More recently a number of polymeric semiconductors and conductors have been developed. 

Initially, two-component, PVC/TPU blends were proposed [B. F. Goodrich Co., 1960], but soon, PVC/TPU blends with a modifier, e.g., ABS [Waugaman et al., 1963] NBR or PA [Kepes, 1959] were disclosed. Blending was also carried out by mixing PVC with polyols and isocyanates then polymerizing these two [Dainichiseika Color Chemicals, 1983]. Commercial PVC/TPU (with NBR) are represented by Duralex . The materials are usually formulated for extrusion, e.g., for wire and cable insulation, hoses and packaging. 

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