Patent US4980541A successfully refreshed from Google Patents.
US4980541A
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US
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Conductive polymer composition
Assignee: Littelfuse Inc
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Filing: 1989-10-03
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Granted: 1990-12-25
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Expires: 2009-10-03
Abstract
Abstract 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.
Inventors
- 👤 Jeff Shafe
- 👤 O. James Straley
- 👤 Gordon McCarty
- 👤 Ravinder K. Oswal
- 👤 Bernadette A. Trammell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 16:49
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
138 words
An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior, which has a resistivity R cp at 20° C. and which comprises (a) an organic polymer which has a crystallinity of at least 5% and a melting point T m , 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 R i at 20° C. and being such that if the device is maintained at a temperature equal to T m for a period of 50 hours and is then cooled to 20° C., its resistance at 20° C., R f50 , is from 0.25R i to 1.75R i .
Claim 2
Dependent Claim
138 words
An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior, which has a resistivity R cp at 20° C. and which comprises (a) an organic polymer which has a crystallinity of at least 5% and a melting point T m , 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 R i at 20° C. and being such that if the device is maintained at a temperature equal to T m for a period of 50 hours and is then cooled to 20° C., its resistance at 20° C., R f50 , is from 0.25R i to 1.75R i .
Claim 3
Dependent Claim
54 words
An electrical device according to claim 1 wherein the device is such that if the device is maintained at a temperature equal to T m for a period of 300 hours and is then cooled to 20° C., its resistance at 20° C., R f300 , is from 0.5R i to 1.5R i .
Claim 4
Dependent Claim
18 words
An electrical device according to claim 1 wherein the carbon black has a pH of less than 3.0.
Claim 5
Dependent Claim
17 words
An electrical device according to claim 1 wherein the conductive polymer comprises a polymer thick film ink.
Claim 6
Dependent Claim
14 words
An electrical device according to claim 1 wherein the electrical device comprises a heater.
Claim 7
Dependent Claim
16 words
An electrical device according to claim 1 wherein the electrical device comprises a circuit protection device.
Claim 8
Dependent Claim
17 words
An electrical device according to claim 1 wherein the polymer has a crystallinity of at least 10%.
Claim 9
Dependent Claim
14 words
An electrical device according to claim 1 wherein the conductive polymer has been crosslinked.
Claim 10
Dependent Claim
19 words
An electrical device according to claim 1 wherein the carbon black is present at at least 4% by weight.
Claim 11
Dependent Claim
19 words
An electrical device according to claim 9 wherein the carbon black is present at at least 6% by weight.
Claim 12
Dependent Claim
13 words
An electrical device according to claim 1 wherein the composition further comprises graphite.
Claim 13
Dependent Claim
41 words
An electrical device according to claim 1 wherein the composition further comprises carbon black which has a pH which is at least 5.0 and at least 1.0 pH unit greater than the carbon black having a pH of less than 4.0.
Claim 14
Dependent Claim
13 words
An electrical device according to claim 1 wherein the polymer is a fluoropolymer.
Claim 15
Dependent Claim
66 words
A conductive polymer composition which exhibits PTC behavior and which comprises (1) an organic polymer which has a crystallinity of at least 5% and a melting point T m , and (2) carbon black which has a pH of less than 4.0, a particle size of D nanometers and a dry resistivity R CB such that (R CB /D) is less than or equal to 0.1.
Claim 16
Dependent Claim
66 words
A conductive polymer composition which exhibits PTC behavior and which comprises (1) an organic polymer which has a crystallinity of at least 5% and a melting point T m , and (2) carbon black which has a pH of less than 4.0, a particle size of D nanometers and a dry resistivity R CB such that (R CB /D) is less than or equal to 0.1.
Claim 17
Dependent Claim
18 words
A composition according to claim 14 wherein the carbon black is present at at least 4% by weight.
Claim 18
Dependent Claim
18 words
A composition according to claim 15 wherein the carbon black is present at at least 6% by weight.
Claim 19
Dependent Claim
96 words
An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior and which comprises (a) an organic polymer which has crystallinity of at least 5% and a melting point T m , and (b) carbon black which has a pH of less than 4.0, a particle size of D nanometers and a dry resistivity R CB such that (R CB /D) is less than or equal to 0.1; and (2) two electrodes which can be connected to a source of electrical power to pass current through the PTC element.
Claim 20
Dependent Claim
96 words
An electrical device which comprises (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior and which comprises (a) an organic polymer which has crystallinity of at least 5% and a melting point T m , and (b) carbon black which has a pH of less than 4.0, a particle size of D nanometers and a dry resistivity R CB such that (R CB /D) is less than or equal to 0.1; and (2) two electrodes which can be connected to a source of electrical power to pass current through the PTC element.
Claim 21
Dependent Claim
64 words
An electrical device according to claim 17 wherein said electrical device has a resistance R i at 20° C. and being such that if the device is maintained at a temperature equal to T m for a period of 50 hours and is then cooled to 20° C., its resistance at 20° C., R f50 , is from 0.25R i to 1.75R i .
Claim 22
Dependent Claim
54 words
An electrical device according to claim 17 wherein the device is such that if the device is maintained at a temperature equal to T m for a period of 300 hours and is then cooled to 20° C., its resistance at 20° C., R f300 , is from 0.50R i to 1.5R i .
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-12-24 | 1994-06-25 | 1994-12-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-24 | 1998-06-25 | 1998-12-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-24 | 2002-06-25 | 2002-12-25 | $7700.00 | Window Closed / Lapsed |