Dielectric Strength of Insulating Materials

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

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

Conversion factors:

  • 1 V/m = 2.54×10⁻⁵ V/mil
  • 1 V/mil = 3.94×10⁴ V/m
MaterialDielectric Strength (10⁶ V/m)Dielectric Strength (V/mil)
Mica (muscovite)39.41000
Glass35.5900
Mica (phlogopite)31.5800
Porcelain (electrical)31.5800
Steatite29.6750
Rubber, hard27.6700
Rubber, silicone23.6600
Polystyrene23.6600
Pyroxylin23.6600
Rubber, buna20.3515
PTFE19.7500
Vinylidene chloride19.7500
Fish paper19.7500
Methyl methacrylate18.9480
Cellulose acetate15.8400
Casein plastic15.8400
Shellac15.8400
Varnished cambric15.8400
Alumina13.4