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Electrical devices which comprise a PTC element composed of a PTC conductive polymer composition and a contiguous CW element composed of a conductive polymer composition which comprises an organic thermoplastic polymer and a conductive carbon black having a particle size (D) in millimicrons and surf

Electrical devices which comprise a PTC element composed of a PTC conductive polymer composition and a contiguous CW element composed of a conductive polymer composition which comprises an organic thermoplastic polymer and a conductive carbon black having a particle size (D) in millimicrons and surface area (S) in m2/g such that S/D is at least 10. D is preferably less than 27 millimicrons, especially less than 18 millimicrons. S/D is preferably at least 12, especially at least 18. Particularly useful devices are in the form of heaters.

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An electrical device comprising (a) A CW element composed of a CW composition which comprises (i) a continuous phase of a first crystalline organic thermoplastic polymer and (ii), dispersed in said first polymer, a first conductive carbon black having a particle size (D) which is less than 27 millim

An electrical device comprising (a) A CW element composed of a CW composition which comprises (i) a continuous phase of a first crystalline organic thermoplastic polymer and (ii), dispersed in said first polymer, a first conductive carbon black having a particle size (D) which is less than 27 millimicrons and a surface area (S) in m2/g such that the ratio S/D is at least 12; (b) a PTC element composed of a PTC composition which comprises (i) a continuous phase of a second crystalline organic thermoplastic polymer and (ii), dispersed in said second polymer, a second conductive carbon black, said PTC element being electrically and structurally directly bonded to the CW element; and (c) at least two electrodes which are connectable to a source of electrical power and which are so placed in the device that, when they are connected to a source of electrical power, current flows between the electrodes through the device along a path which, at least at some temperatures, passes sequentially through said PTC element and said CW element.