Welcome to Imerys Performance Minerals

Electrical properties

Electrical properties

The use of certain minerals can lead to excellent electrical insulation, especially in high voltage applications.  Having certain materials with low ionic or surface modification raises the significance of this benefit in certain applications.

Imerys calcined kaolins deliver excellent electrical insulating properties in low, medium and high voltage cables.

Electrical insulation

Rubber Cable insulation is primarily based upon Ethylene-Vinyl Acetate (EVA) or Ethylene-Propylene Rubber (EPR or EPDM).


The major filler used within low/medium EPR and EPDM cable insulation to achieve low dielectric loss and excellent electrical performance is calcined kaolin.

Calcined kaolins, such as our Glomax LX grade,  impart excellent electrical insulation properties to low and medium voltage power cables. Their low moisture absorption properties ensure that insulation properties are maintained under wet operating conditions.


For medium to high-voltage compounds, silane-treated calcined kaolins are more suitable. Our Polarite 503S is a vinyl functional silane-treated calcined clay developed for use in very high voltage cable insulation based on EPR. Polarite 503S imparts extremely good dielectric properties at high working temperatures and under wet conditions for the working life of the cable. It also gives good insulating properties in other polymers such as EPDM, crosslinked polyethylene and ethylene vinyl acetate copolymers.

Calcined kaolins not only impart excellent insulation properties but also provide very smooth surface finish and excellent dimensional control, due to the low die swell imparted by the mineral.

We offer a full range of custom formulation and technical and process support services to help you match the right mineral grade to your application requirement.

Please contact us, we will be only too happy to help.

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