Self Healing Cables
Since the conductors in cables are degraded by moisture and the protective insulation can be cracked exposing the conductors to moisture, techniques have been developed to heal and damage or defects and prevent moisture access to the conductors. Self healing materials is not new. Aproaches include microcapsules containing solidifying liquid or sealant, low moleuclar weight polymers acting as a sealant. Easter of General Cable Technologies has developed a self-healing cable based on a conductor insulated with a composite containing water-swellable fillers. When water reaches the exposed insulation, the filler expands and fills voids, punctures or cracks, sealing the damaged insulation. The polymeric carrier can be petroleum jelly, polyisobutene, polyisoprene, natural terpolymers, propylene/ethylene copolymers, polyolefins or amorphous ethylene copolymers with unsaturated esters. The water-swellable filler can be bentonite, lignite, alumina trihydrate, barytes, calcium carbonate, chlorite, clays, pyrophyllite, talc, polyacrylic acid, polyacrylamide, sodium polyacrylate, cellulose esters, ethylene vinyl chloride, acrylic resins, alkyd resins, polyethylene oxide, collagens, gelatins and ethylene acrylic acid copolymers. Of these fillers, sodium bentonite or polyethylene oxide is preferred. The composites contain enough water-swellable fillers to cause 15 to 150 percent swelling. Instead of a water swellable filler, a water soluble polymer can be used. Candidate polymers include polyethylene vinyl chloride, polyacrylic resins, polyalkyd resins, polyethylene oxide and polyethylene acrylate. Most preferable polymers are polyethylene oxides with a molecular weight of from about 100,000 to about 8,000,000, more preferable from about 100,000 to about 1,000,000, and ethylene acrylic acid with a melt index of from about 1 to about 500. Easter, US Patent 7,66,503 (2/23/2010)
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As the literature is reviewed, and items of interest concerning this topic are found. These may be added in an abbreviated form with the reference. Readers and contributors are invited to add their own notes. Contributors may add them directly and other readers can simply send their notes to the editor, Roger Corneliussen at rcorneliussen@4spe.org. He may edit and add them to this page at his discretion.