Abstract: Disclosed is an improved semi-conductive heating cable having semi-conductive material surrounded by a jacket that is imparted with improved resistance to color change upon exposure to elevated temperatures and is able to minimize changes in the ambient electrical resistivity of the semi-conductive composition arising from exposure of the cable to elevated temperatures by reason of the jacket being made from a radiation crosslinked composition comprising a mixture of at least one elastomer with at least one polyolefin and at least one heat stabilizer wherein the preferred elastomer comprises either or both a terpolymer of ethylene, propylene and at least one diene or an ethylene propylene rubber and the polyolefin is a polypropylene polymer.

Abstract: Disclosed is a method of radiation grafting a shape retaining jacket (32) made from an elastomeric polyurethane to an olefinic semi-conductive composition electrically interconnecting at least two elongate spaced-apart conductors (28) to provide an improved, flexible, elongate semi-conductive heating cable (8) that is provided with improved mechanical and electrical integrity and diminished imperfections and improved handling characteristics by reason of a substantially improved bond between the jacket and the olefinic semi-conductive composition arising from radiation grafting in a process that includes a means (14) of oxidizing the outer surface of the semi-conductive surface in combination with application of vacuum able to draw the jacket against the semi-conductive composition within not more than about one and one-half inches from the exit of a die head (4) through which the product is passed.