The principle of peroxide crosslinking is that a peroxide is incorporated in the compound. The peroxide is activated at a high temperature. In order to avoid premature crosslinking the extrusion of the wire or cable insulation or jacketing must take place at temperatures only slightly above the melting point of the compound.
Immediately after extrusion the wire or cable is heated to the decomposition temperature of the peroxide, until the crosslinking is complete. The heating must be done under high pressure to prevent void formation in the insulation which is caused by gaseous decomposition products from the peroxide reaction.