Low resistivity PTC compositions
US4237441A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 1, 1978 |
| Grant date | Dec 2, 1980 |
| Priority date | — |
| Expiry date | Dec 1, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T29/49082
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Compositions which exhibit PTC behavior with a switching temperature (T.sub.s) above 0.degree. C., which have a resistivity at a temperature below T.sub.s of less than 7 ohm. cm, and which comprise a crystalline polymer and a particulate filler component which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area S in m.sup.2 /gram such that S/D is not more than 10. The composition preferably has a peak resistivity of at least 1000 ohm. cm and is electrically stable when aged at elevated temperature. The quantity ##EQU1## is preferably less than 1, especially less than 0.5. Shaped articles of such compositions are prepared by a process in which the carbon black is dispersed in the molten polymer and the dispersion is then melt-shaped, the total energy used in preparing and melt-shaping the dispersion being 1 to 300 hp. hr. ft.sup.-3, preferably 1 to 100 hp. hr. ft.sup.-3, especially 1 to 50 hp. hr. ft.sup.-3. The compositions are particularly useful in circuit protection devices.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.