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Electrical devices with improved resistance stability comprise a PTC element comprising a conductive polymer and two electrodes. The conductive polymer composition comprises an organic crystalline polymer and carbon black with a pH of less than 5.0. Particularly preferred conductive polymer composit

Electrical devices with improved resistance stability comprise a PTC element comprising a conductive polymer and two electrodes. The conductive polymer composition comprises an organic crystalline polymer and carbon black with a pH of less than 5.0. Particularly preferred conductive polymer compositions comprise carbon blacks which have a pH of less than 5.0, a dry resistivity RCB and a particle size D in nanometers such that RCB/D is at most 0.1. Electrical devices of the invention include heaters and circuit protection devices.

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An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior, which has a resistivity Rcp at 20°C. and which comprises (a) an organic polymer which has a crystallinity of at least 5% and a melting point Tm, and (b) carbon black which

An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior, which has a resistivity Rcp at 20°C. and which comprises (a) an organic polymer which has a crystallinity of at least 5% and a melting point Tm, and (b) carbon black which has a pH of less than 4.0; and (2) two electrodes which can be connected to a source of electrical power to pass current through the PTC element, said electrical device having a resistance Ri at 20°C. and being such that if the device is maintained at a temperature equal to Tm for a period of 50 hours and is then cooled to 20°C., its resistance at 20°C., Rf50, is from 0.25Ri to 1.75Ri.