CONDUCTIVE POLYMER COMPOSITIONS CONTAINING FILLERS

摘要

The invention relates to conductive polymer compositions. The compositions of the invention have improved electrial stability when exposed to thermal cycling. They comprise a polymer component and a filler component which has a total surface area of at least 1800 m<2> per cc. of composition and which comprises carbon black and non-conductive particulate filler, each present in amount at least 4% by volume of the composition. In one preferred class of compositions, the polymer component is crystalline. In another preferred class the polymer is amorphous and the amount of filler is such that the composition may an elongation of at most 10% at 23 DEG C. The compositions has have PTC, ZTC or NTC resistivity/temperature charactcristics. Figure 2 shows the resistivity/temperature characteristics of a PTC composition of the invention. The new compositions arc useful in a variety of electrical devices, including heaters, circuit control devices and temperature sensors.