In the extrusion of insulation made from high pressure low density polyethylene, organic peroxide compounds are commonly mixed with the polyethylene to provide a catalyst for crosslinking subsequent to extrusion. It is difficult, if not impossible, to find an acceptable extrusion temperature for linear polymers (such as those produced in gas phase fluidized reactors) as well as highly viscous polymers and compounds under production type conditions with conventional peroxides because the high extrusion temperatures encountered while extruding these materials results in decomposition of the peroxide in the extruder leading to premature crosslinking known as scorch. This problem also occurs in processes other than extrusion processes such as rotomolding, injection molding, and blow molding.
USPTO Backgrounds
USPTO Backgrounds