Electrical circuit protection devices comprising ptc conductive liquid

Abstract

Electrical circuit protection devices containing PTC elements comprised of conductive polymers which exhibit PTC behavior and are used to protect a load in an electrical circuit, in which the PTC conductive polymers are based on highly crystalline and highly ordered liquid crystal polymers and particulate conductive fillers dispersed therein, which are cross-linked by radiation. These circuit protection devices operate as automatically resettable current limiters and are particularly useful for protecting motors, solenoids, telephone lines and batteries, and for enhancing circuit interruption capability when used in conjunction with breakers and contactors. The liquid crystal polymers include aromatic polyesters, e.g., poly(p-phenylene terephthalate) and poly(p-hydroxybenzoate); aromatic copolyesters, e.g., poly(p-hydroxybenzoate-co-2,6-hydroxynaphthoate), poly(deca-methyleneterephthaloyl di-p-hydroxybenzoate, and poly(ethylene terephthalate-co-oxybenzoate); aromatic copolyester amides, e.g., poly(2,6-hydroxy-naphoate-phenoxyaminoterephthoate); aromatic polyamides, e.g., poly(p-phenylene terephthalamide), Kevlar, poly(p-benzamide), poly(2-chloro-1,4-phenylene terephthalamide), poly(p,p'-biphenylamide), and poly(2,6-napthalamide); aromaticpolyazomethines, e.g., poly (nitro-2-methyl-1,4-phenylenenitriloethylidine-1,4-phenylenethylidine), poly(nitrilo-2-methyl-1,4-phenylenenitrilomethylidine-1,4-phenylenemethyli dine), and poly(nitrolo-2-chloro-1,4-phenylenenitrilomethylidine-1,4-phenylenemethyli dine); and, blends thereof. The particulate conductive fillers include carbon black, carbon fibers, graphite, and metal flakes.