CHO-BOND???® 4660 and 4669 ONE COMPONENT FLEXIBLE ELECTRICALLY CONDUCTIVE POLYISOBUTYLENE SEALANT. CHO-BOND 4660 is a silver-plated copper filled, one-component conductive polyisobutylene. It is designed for use as a fillet, gap filler and seam sealant on electrical enclosures for EMI shielding or electrical grounding.