Electrical properties for rubber

Imerys calcined kaolins deliver excellent electrical insulating properties in low, medium and high voltage cables, and our conductive carbon blacks are a good choice for boosting electrical conductivity in rubber compounds.

Enhancing the electrical properties of rubber  

Electrical insulation

Rubber cable insulation is primarily based on 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 Polestar™ 200R, 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 product is a vinyl functional silane-treated calcined clay developed for use in very high voltage cable insulation based on EPR. It 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.

Electrical conductivity

Conductive carbon blacks are the solution of choice where electrical conductivity is a performance criteria.

Our Ensaco® carbon blacks are a special family of highly pure carbon blacks, produced through a proprietary method that delivers products with a high structure/low surface area or very high structure/very high surface area, depending on the grade. 

Ensaco carbon blacks are suitable for boosting electrical conductivity in EPDM and NBR among others.

For document downloads and enquiries about our graphite and carbon solutions, please see the Graphite & Carbon business documentation in our Media section.