Novel polymer crosslinking chemistries for cable insulation

Peroxide crosslinked polyethylene is the major insulation material used in today's electric cables carrying voltages above 5 kV. Peroxide-mediated crosslinking presents cable manufacturing challenges in that there is a propensity for premature crosslinking (scorch) in the extruder. Additionally, peroxide-mediated crosslinking generates byproducts that need to be removed from the cable before final cable construction. Novel organic peroxides and crosslinking coagent technologies have been designed to address these challenges. A novel peroxide, isopropenyl dicumyl peroxide, was found to greatly improve the resistance to scorch. In addition, the novel peroxide reduced the need for degassing, since a significant amount of the crosslinking byproducts became grafted to the polyethylene during crosslinking. A novel coagent, 2-methoxy-4-allylphenyl allyl ether, provided significantly higher scorch retardance at a given level of crosslinking when compared to compositions without coagent. Polyethylene insulation compounds crosslinked using these new additives demonstrated excellent dissipation factor and dielectric constant values, indicating promise for demanding high voltage insulation applications.