Abstract: In accordance with an exemplary embodiment of the instant invention, a volatile cross-linking agent such as liquid peroxide is introduced, at ambient temperature and under atmospheric pressure directly into the input of an extruder at the same pressure as a polyolefin compound to be cross-linked. The resulting compounds are put under pressure within the extruder as the temperature increases so that the mixture reaches its definitive shape at the extruder output and may be fed directly into a hot cross-linking enclosure which is maintained under pressure. The peroxide is thus incorporated in a single operation permitting complete control of the ingredients mixed and allowing perfect homogenization of the mixture while defusion and consequent loss of the highly volatile peroxide are avoided. The system for introducing the highly volatile cross-linking agent includes a peroxide storage tank, a filling pump, a feed vessel, an incremental feed pump with a pressure meter, a flow meter and numerous safety features.

Abstract: Production of extruded products wherein a polyolefin composition, a volatile, flammable liquid organic peroxide cross-linking agent and an antioxidant are introduced into the inlet of an extruder, with the antioxidant being a thio-bisphenol soluble in the peroxide having a melting point of less than 125.degree. C. of the general formula(R' C.sub.6 H.sub.2 --R" OH).sub.2 S.sub.xwherein x is a whole number equal to 1, 2 or 3. The preferred antioxidant is 2,2'-thio-bis(6-t-butyl-p-cresol).

Abstract: A volatile cross-linking agent such as liquid peroxide is introduced, at ambient temperature and under atmospheric pressure directly into the input of an extruder at the same pressure as a polyolefin compound to be cross-linked. The resulting compounds are put under pressure within the extruder as the temperature increases so that the mixture reaches its definitive shape at the extruder output and may be fed directly into a hot cross-linking enclosure which is maintained under pressure. The peroxide is thus incorporated in a single operation permitting complete control of the ingredients mixed and allowing perfect homogenization of the mixture while defusion and consequent loss of the highly volatile peroxide are avoided. The system for introducing the highly volatile cross-linking agent includes a peroxide storage tank, a filling pump, a feed vessel, an incremental feed pump with a pressure meter, a flow meter and numerous safety features.