A peroxide is incorporated in the polymer and activated at a high temperature. In order to avoid premature crosslinking, the extrusion temperature should be only slightly above the melting point of the polymer.
Immediately after extrusion, the tubing is heated to the decomposition temperature of the peroxide, untill the crosslinking has been completed.
Usually, the heating of the tubing requires a high pressure tank to prevent void formation in the insulation which is caused by gaseous decomposition products from the peroxide reaction.
The peroxide crosslinking method, has been successfully implemented in thick wall heat-shrinkable products for low voltage, medium voltage and high voltage applications.

PTL has developed a wide range of peroxide crosslinkable compounds for extrusion, press moulding and injection moulding for products such as:
- cable break-outs
- end-caps
- rain-sheds
- protective tubing
- wrap-around sleeves
- non-tracking tubing