Moisture cross-linkable insulation compounds with flame retardant properties

Ethylene vinyl trimethoxy silane copolymer is shown to be suitable for flame retardant cable applications. A silane copolymer compound with 28% thermal black filler is shown to retain its melt flow rate by 90% when stored for a year at 23°C and 55% relative humidity. Cables of filled silane copolymer insulation are cured at 90°C in water, and at ambient temperature and humidity conditions. Equivalent properties are achieved whether the fillers are fully compounded with the copolymer or used in the form of a masterbatch. The extruded flame retardant cables are shown to have the fillers well dispersed in the polymer insulation to yield optimum flammability, tensile and dielectric properties. Statistical methods are used to compare the dielectric performance before and after a mechanical impact. The advantages and disadvantages of the silane copolymer technology over peroxide and radiation cross-linking technologies are discussed