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I saw two wires going into a halogen light bulb whose outer sheathes were not a plastic (like PVC, or polyurethane), but rather a woven fabric (like a nylon shoelace). Why is woven fabric better for this high current application? Sure, PVC may not have as high of a temperature rating, but why specifically does the material transition from solid to woven construction?

PJazz
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I haven't made a study of the matter, but a reasonable hypothesis is that the insulation needs to withstand high temperature, which limits the choice of materials, and the particular material chosen would not be sufficiently flexible if it were made in a solid tube rather than a weave.

For example, a quick web search suggests that materials used for high-temperature insulation may be "mineral textile fibre or fibreglass". If fiberglass insulation was not made of strands, it would just be glass, and thus very rigid.

Of course, solid glass and ceramic are also used in high-temperature applications, but you think of them as custom-made fittings rather than strange insulation on ordinary wire.

Kevin Reid
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  • It's usually silicone impregnated woven fiberglass -- the silicone keeps it together especially at the end and resists high temps too. – bobflux Mar 24 '18 at 08:45
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The woven fabric is typically not plastic but glass based, for the temperature performance.

Solid glass tends to be difficult to bend, woven fibre is more flexible.

Neil_UK
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The reason that the fabric is woven is that it is made from what would otherwise be brittle in solid form. Typical fibers are glass, but ceramic fibers are also a possibility.

crj11
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