Abstract: A plastic thermistor comprising a polyamide composition which comprises 100 wt. parts of a polyamide and 5.3 to 30 wt. parts of zinc iodide, or a polyamide composition which comprises a polyamide, an iodine-containing compound, and a metal oxide such as zinc oxide. Ion carrier properties of a metal iodide greatly increases temperature dependence of impedance, and the metal oxide such as zinc iodide functions as a receptor for iodide ions and prevents the formation of a metal iodide on the surfaces of metal electrodes. Furthermore, a linked cycle can be established that zinc oxide forms zinc iodide and then formed zinc iodide functions to increase the stability of half-wave current passage. Accordingly, the thermal stability of the plastic thermistor is improved for a long time, and the heat resistance stability of temperature sensors or thermosensitive heaters comprising the plastic thermistor is improved greatly.

Abstract: The present invention provides a temperature self-controlling heating composition containing crystalline resins, elastomers and electrically conductive particles, and additional material for giving an affintiy to the resins and the elastomers if both are not compatible, in which the electrically conductive particles are stably dispersed in the medium of the resin and the elastomer, and the agglomeration of the dispersed particles can be prevented, even if the temperature exceeds the melting point of the crystalline resin because the apparent viscosity of the resin is not lowered so much by the network structure of the elastomers, so that the electrical resistance does not become lower even at such a high temperature.