EP0038714A2
Expired / Lapsed
EP
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PTC conductive polymer compositions containing fillers
Assignee: Raychem Corp
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Filing: 1981-04-21
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Granted: —
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Expires: 2001-04-21
Abstract
Abstract The invention relates to PTC conductive polymers. The compositions of the invention comprise at least 10% by volume of a first filler which is composed of highly conductive particles and at least 4% by volume of a second filler which is composed of particles which are less conductive than the particles of the first filler and/or which are substantially smal- lerin size than the particles of the first filler. Figure 1 shows the resistivity/temperature curve of a composition of the invention. The compositions are useful in electrical devices such as circuit protection devices, heaters and EMI shields.
Inventors
- 👤 Robert Warrington J.R. Fouts
- 👤 Andrew N.S. Au
- 👤 Burton E. Miller
- 👤 Alan Jeffrey Gotcher
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 14:08
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/02; H01C7/027; H01B; H01B1/00; H01B1/20
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
199 words
A conductive polymer composition which (i) exhibits PTC behavior with a switching temperature T s ; (ii) has a minimum resistivity between -40°C and T s of less than 10 5 ohm-cm, preferably less than 10 ohm-cm; (iii) has a maximum resistivity between T s and (T s +100)°C which is at least 1000 times, preferably at least 10,000 times, the minimum resistivity between -40°C and T s , said maximum resistivity being preferably at least 10 3 ohm-cm; and (iv) comprises a polymeric component, preferably a crystalline polymeric component, having dispersed therein a filler component which comprises: (a) a first filler which is present in amount at least 10%, preferably 30 to 60%, by volume of the composition and which consists of conductive particles composed of material having a resistivity at 25°C of less than 10 -3 ohm-cm, preferably less than 10 -5 ohm-cm; and (b) a second filler which is present in amount at least 4%, preferably 6 to 25%, by volume of the composition and which consists of particles which are less conductive than the particles of the first filler and/or which have a substantially smaller average particle size than the particles of the first filler.
Claim 2
Dependent Claim
199 words
A conductive polymer composition which (i) exhibits PTC behavior with a switching temperature T s ; (ii) has a minimum resistivity between -40°C and T s of less than 10 5 ohm-cm, preferably less than 10 ohm-cm; (iii) has a maximum resistivity between T s and (T s +100)°C which is at least 1000 times, preferably at least 10,000 times, the minimum resistivity between -40°C and T s , said maximum resistivity being preferably at least 10 3 ohm-cm; and (iv) comprises a polymeric component, preferably a crystalline polymeric component, having dispersed therein a filler component which comprises: (a) a first filler which is present in amount at least 10%, preferably 30 to 60%, by volume of the composition and which consists of conductive particles composed of material having a resistivity at 25°C of less than 10 -3 ohm-cm, preferably less than 10 -5 ohm-cm; and (b) a second filler which is present in amount at least 4%, preferably 6 to 25%, by volume of the composition and which consists of particles which are less conductive than the particles of the first filler and/or which have a substantially smaller average particle size than the particles of the first filler.
Claim 3
Dependent Claim
30 words
A composition according to Claim 1 characterised in that the first filler consists of particles having an average particle size of 0.02 to 25 microns, preferably 0.1 to 5 microns.
Claim 4
Dependent Claim
58 words
3 . . A composition according to Claim 1 or 2 characterised in that the first filler consists of metal particles having an average particle size d 1 , and the second filler consists of metal particles having an average particle size d 2' where d 1 /d 2 is from 2 to 10,000, preferably 10 to 5,000.
Claim 5
Dependent Claim
37 words
A composition according to Claim 1 or 2 characterised in that the second filler consists of carbon black or a non-conductive filler having an average particle size of 0.001 to 50 microns, preferably 0.01 to 5 microns.
Claim 6
Dependent Claim
105 words
A composition according to any of Claims 1 to 4 characterised in that the polymeric component is a thermoplastic or cross-linked thermoplastic material having a crystallinity of at least 10%, and the filler component comprises (a) a first filler which consists essentially of metal particles having an average particle size of 0.1 to 5 microns and which is present in amount 10 to 60% by volume of the composition and (b) a second filler which consists essentially of carbon black particles having an average particle size of 0.01 to 0.07 microns and which is present in amount 4 to 50% by volume of the composition.
Claim 7
Dependent Claim
46 words
An electrical device which comprises an element composed of a PTC conductive polymer composition and two electrodes for passing current through the element, characterised in that the PTC element is composed of a conductive polymer composition as claimed in any one of Claims 1 to 5.
References Cited (Backward Citations)
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