Positive temperature coefficient conductive polymer made from thermosetting polyester resin and conductive fillers

摘要

An improved PTC current limiting composition has been provided which comprises a chemically cross-linked thermosetting polyester resin and conductive particles dispersed in the resin. The thermosetting polyester resin is selected from the group consisting of polyethylene glycol fumarate, polypropylene glycol adipate fumarate, neopentyl glycol isophthalate fumarate, and neopentyl glycol phthalate fumarate. The conductive additive particles are selected from the group consisting of graphite and/or carbon black. The composition exhibits PTC behavior when cross-linked by a vinyl monomer selected from the group consisting of styrene, vinyl toluene and tertiary butyl styrene. Curing proceeds by free-radical addition across double bonds of the thermosetting polyester resin and is initiated by organic peroxides. Initial gelation which causes cross-linking but not final curing takes about 0.5 to 4 hours at a temperature of about 25 DEG C. to 125 DEG C. The final cure takes about 0.5 to 8 hours at a temperature of about 100 DEG C. to 160 DEG C. An effective amount of alumina trihydrate can be added to the current limiting composition to prevent dielectric breakdown, arcing and carbon tracking under high voltage conditions. It is respectfully submitted that the MPEP 608.01(b) states that abstracts should be between 50 and 250 words and up to 25 lines. Applicants' abstract in within these limits.