US4743321A
Expired / Lapsed
US
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Devices comprising PTC conductive polymers
Assignee: Raychem Corp
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Filing: 1985-10-04
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Granted: 1988-05-10
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Expires: 2005-10-04
Abstract
Abstract 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.
Inventors
- 👤 Pravin L. Soni
- 👤 Peter H. van Konynenburg
- 👤 Mark Wartenberg
- 👤 Randolph W. Chan
- 👤 Stephen M. Jacobs
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 16:32
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; B; B29; B29C; B29C61/00; B29C61/06; B29C61/0608; B29C61/0625; H05; H05B; H05B3/00; H05B3/10; H05B3/12; H05B3/14; H05B3/146; Y; Y10; Y10S; Y10S174/00; Y10S174/08
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
219 words
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 M 100 value at a temperature 15° C. above its crystalline melting temperature which is at most 0.65 times the M 100 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.
Claim 2
Dependent Claim
219 words
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 M 100 value at a temperature 15° C. above its crystalline melting temperature which is at most 0.65 times the M 100 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.
Claim 3
Dependent Claim
37 words
A device according to claim 1 which further comprises (4) a third component which is composed of a cross-linked conductive polymer and which is heat-recoverable, and wherein the second component lies between the first and third components.
Claim 4
Dependent Claim
25 words
A device according to claim 2 which is heat-shrinkable and wherein the first, second and third components are in the form of continuous laminar sheets.
Claim 5
Dependent Claim
68 words
A device according to claim 3 which has been prepared by a process which comprises (A) laminating together, in order, (a) a sheet composed of a cross-linked conductive polymer, (2) a sheet composed of a substantially uncrosslinked conductive polymer which exhibits PTC behavior, and (3) a sheet composed of a cross-linked conductive polymer; and (B) subjecting the laminate from step (A) to a treatment which renders it heat-shrinkable.
Claim 6
Dependent Claim
20 words
A device according to claim 4 wherein the conductive polymers in the first, second and third sheets are the same.
Claim 7
Dependent Claim
102 words
A device according to claim 3 which has been prepared by a process which comprises (A) laminating together, in order, (1) a sheet composed of a cross-linked conductive polymer which exhibits ZTC behavior, (2) a sheet composed of a cross-linked conductive polymer which exhibits PTC behavior, (3) a sheet composed of a substantially uncrosslinked conductive polymer which exhibits PTC behavior, (4) a sheet composed of a cross-linked conductive polymer which exhibits PTC behavior, and (5) a sheet composed of a cross-linked conductive polymer which exhibits ZTC behavior; and (B) subjecting the laminate from step (A) to a treatment which renders it heat-shrinkable.
Claim 8
Dependent Claim
49 words
A device according to claim 6 wherein sheets (1) and (5) are composed of a conductive polymer comprising a first crystalline polymer and sheets (2), (3) and (4) are composed of a conductive polymer comprising a second crystalline polymer having a melting point higher than the first crystalline polymer.
Claim 9
Dependent Claim
23 words
A device according to claim 7 wherein the second polymer has a melting point at least 5° C. higher than the first polymer.
Claim 10
Dependent Claim
81 words
A device according to claim 3 which has been prepared by a process which comprises (A) irradiating a sheet composed of conductive polymer under conditions such that, after irradiation, the sheet comprises an inner layer which is composed of a conductive polymer exhibiting PTC behavior and which has a relatively low degree of cross-linking, and two outer layers which have a relatively high degree of cross-linking; and (B) subjecting the irradiated sheet from step(A) to a treatment which renders it heat-shrinkable.
Claim 11
Dependent Claim
31 words
A device according to claim 9 wherein the sheet is of uniform composition prior to the irradiation and wherein the sheet is irradiated with low energy radiation on each surface thereof.
Claim 12
Dependent Claim
38 words
A device according to claim 9 wherein prior to the irradiation, the susceptibility of the conductive polymer to cross-linking by irradiation is lower at the center of the sheet than it is at the surfaces of the sheet.
Claim 13
Dependent Claim
66 words
A device according to claim 11 wherein the sheet comprises, prior to irradiation, a first layer composed of a conductive polymer which contains a radiation cross-linking agent, a second layer composed of a conductive layer which comprises a radiation cross-linking inhibitor, and a third layer composed of a conductive polymer which contains a radiation cross-linking agent, the second layer lying between the first and third layers.
Claim 14
Dependent Claim
15 words
A device according to claim 3 which has a recovery ratio of at least 2.
Claim 15
Dependent Claim
15 words
A device according to claim 3 which has a recovery ratio of at least 3.
Claim 16
Dependent Claim
28 words
A device according to claim 3 wherein the second component is composed of a conductive polymer which comprises a polyethylene having a molecular weight of 150,000 to 400,000.
Claim 17
Independent Claim
249 words
A method of covering a substrate which comprises (A) placing around the substrate 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 M 100 value at a temperature 15° C. above its cystalline melting temperature which is at most 0.65 times the M 100 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, and (B) connecting the electrodes to a power supply so that the device recovers towards the substrate.
Claim 18
Independent Claim
249 words
A method of covering a substrate which comprises (A) placing around the substrate 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 M 100 value at a temperature 15° C. above its cystalline melting temperature which is at most 0.65 times the M 100 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, and (B) connecting the electrodes to a power supply so that the device recovers towards the substrate.
Claim 19
Dependent Claim
23 words
A method according to claim 16 wherein the second component has been cross-linked by irradiation to a dosage of less than 3 Mrads.
Claim 20
Dependent Claim
42 words
A method according to claim 16 wherein 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 5 Mrads below the dosage used to cross-link the first component.
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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) | 1991-05-10 | 1991-11-09 | 1992-05-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-10 | 1995-11-09 | 1996-05-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-10 | 1999-11-09 | 2000-05-10 | $7700.00 | Window Closed / Lapsed |