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Dielectric Strength of Insulating Materials

The dielectric strength of a material is the ability to the material to act as an insulator.

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The dielectric strength of a material is the ability to the material to act as an insulator.

The dielectric strength of a material is the voltage that a material of a given thickness will resist. With higher voltage than the dielectric strength a spark will pass through the material.

Dielectric Strength of Insulating Materials
MaterialDielectric Strength
(106 V/m)(V/mil)
Mica (muscovite) 39.4 1000
Glass 35.5 900
Mica (phlogopite) 31.5 800
Porcelain (electrical) 31.5 800
Steatite 29.6 750
Rubber, hard 27.6 700
Rubber, silicone 23.6 600
Polystyrene 23.6 600
Pyroxylin 23.6 600
Rubber, buna 20.3 515
PTFE 19.7 500
Vinylidene chloride 19.7 500
Fish paper 19.7 500
Methyl methacrylate 18.9 480
Cellulose acetate 15.8 400
Casein plastic 15.8 400
Shellac 15.8 400
Varnished cambric 15.8 400
Alumina 13.4

The dielectric strength is usually given in volts per mil where 1 mil equals 0.001 in, or volts per meter.

  • 1 V/m = 2.54 10-5 V/mil
  • 1 V/mil = 3.94 104 V/m
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