Silane Crosslinked Cable Compounding

Polyethylenes (PE) have outstandingly good insulation properties. A temporary temperature rise, e.g. due to peak loading, can however cause a complete breakdown of PE cable insulation. The relatively low softening or melting point leads to thermo-mechanical failure or even dripping of the Insulation. Cross-linked polyethylene (PEX) is more thermosetting than thermoplastic. It can therefore be used at significantly higher operating temperatures, is mechanically stronger, more resistant to organic liquids, and often enables thinner wall thicknesses. Various cross-linking methods are used. Silane cross-linkable cable compounds are also known as PEX-b or Sioplas®.

Sioplas® was developed in 1968 by Midland Silicones (now Dow). In the first stage of this two-stage process, vinyl silane is grafted onto the polymer chain with peroxide activation. In the second stage, pipe is conventionally extruded from the grafted compound with a catalyst masterbatch. Cross-linking takes place offline in an aqueous or steam environment. Ever since this process was developed, Buss Co-Kneaders have been used in the first stage and for producing the catalyst masterbatch.

For cable insulation up to 10 kV, silane cross-linkable PE compounds have been globally proven as the most cost-effective materials and are produced in large quantities.