초록 ▼

The resistivity/temperature characteristics of PTC conductive polymers which have little or no cross-linking can be modified by stretching. The rate at which resistivity rises with temperature is increased, and the peak resistivity is decreased; however, the decrease in peak resistivity is substanti

The resistivity/temperature characteristics of PTC conductive polymers which have little or no cross-linking can be modified by stretching. The rate at which resistivity rises with temperature is increased, and the peak resistivity is decreased; however, the decrease in peak resistivity is substantially smaller than that observed with PTC conductive polymers having a high degree of cross-linking. Therefore, heat-recoverable electrical devices, particularly for covering telephone and other cable splices, comprise (a) a layer of a PTC conductive polymer which has little or no cross-linking, (2) an adjacent heat-recoverable layer of a PTC or ZTC conductive polymer which has a relatively high level of cross-linking, and (3) electrodes which can be connected to a power supply so that current passes through the layers and causes recovery of the device; preferably an uncrosslinked PTC layer is sandwiched between two cross-linked ZTC layers. Non-recoverable devices, e.g. heaters, can have valuable characteristics when they comprise PTC conductive polymer elements which have been given a relatively low degree of orientation by stretching.

대표청구항 ▼

A heat-recoverable electrical device which comprises (1) a first component which is composed of a cross-linked conductive polymer and which is heat-recoverable; (2) a second component which is composed of a conductive polymer exhibiting PTC behavior; and (3) electrodes which can be connected to a so

A heat-recoverable electrical device which comprises (1) a first component which is composed of a cross-linked conductive polymer and which is heat-recoverable; (2) a second component which is composed of a conductive polymer exhibiting PTC behavior; and (3) electrodes which can be connected to a source of electrical power; the electrodes and the first and second components being such that, when the electrodes are connected to a suitable source of electrical power, current passes through the first and second components so that the device recovers; and the second component having at least one of the following characteristics (a) it is substantially free from cross-linking; (b) it has been cross-linked by irradiation to a dosage of less than 6 Mrads; (c) when the first component has been cross-linked by irradiation, the second component has been cross-linked by irradiation to a dosage which is at least 2 Mrads below the dosage used to cross-link the first component; and (d) it has an M100 value at a temperature 15°C. above its crystalline melting temperature which is at most 0.65 times the M100 value, at the same temperature, of a sample of the same material, having a thickness of 40 mils, which has been irradiated on one surface with a 2.7 MeV electron beam to a dosage of 10 Mrads.