Title: Method of making self-temperature regulating electrical heating cable

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Abstract: Disclosed are improved melt processable, self-temperature regulating, irradiation cross-linkable, electrically semi-conductive polymeric compositions which in conjunction with annealing at a temperature at or above their melt point temperatures subsequent to their having been radiation cross-linked provide for improved self-temperature regulating electrical heating devices including flexible electrical heating cables. Heating cables made in accordance with the invention comprise two or more elongate substantially parallel spaced-apart electrical conductors that are electrically inter-connected by means of extruded forms of the compositions which have been annealed at a temperature at or above their melt point temperatures prior and subsequent to their having been cross-linked by irradiation. The compositions of the invention have an amount of electrically conductive particles, such as carbon black, dispersed therein, that is controlled within the range of 17% to 25% by weight to the total weight of the compositions. The semi-conductive compositions are characterized by exhibiting a positive temperature coefficient of electrical resistance and by having sufficient crystallinity in their polymeric portion to provide attractive self-temperature heat regulating characteristics in conjunction with a lessening of criticality in their annealing requirements from that heretofore associated with the process of making electrical heating cables utilizing electrically semi-conductive polymeric materials.


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