Conductive polymer compositions and devices
AssigneeRaychem Corporation
InventorsRobert W. Fouts, Jr., Andrew N. S. Au, Burton E. Miller, Alan J. Gotcher
Life of this patent
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Abstract
Conductive polymer compositions comprises a polymeric material having dispersed therein (a) conductive particles composed of a highly conductive material and (b) a particulate filler. The compositions exhibit a positive temperature coefficient of resistivity and undergo a large increase in resistivity as the temperature increases above a certain value. The compositions are useful in preparing electrical devices such as current limiting devices, heaters, EMI shields and the like.
Claims49
A conductive polymer composition which exhibits PTC behavior with a switching temperature T.sub.s and which comprises:
- (1) an organic polymeric material which comprises a crystalline, thermoplastic polymer, and
- (2) dispersed in said polymeric material a filler component which comprises
- (a) at least about 10% by volume, based on the total volume of the composition of a first conductive particulate filler which has a first particle size D.sub.1 from 0.01 to 200 microns and which consists of a metal having a resistivity at 25.degree. C. of less than 10.sup.-3 ohm. cm;
- and
- (b) at least 4% by volume, based on the total volume of the composition, of a second particulate filler which has a second average particle size D.sub.2 from 0.001 to 50 microns and which is composed of non-metallic material;
- said composition having a resistivity at 25.degree. C., .rho..sub.25, of less than 10.sup.5 ohm-cm and a resistivity at a temperature in the range T.sub.s to (T.sub.s +100).degree.C. which is at least 1000.times..rho..sub.25.
A conductive polymer composition which exhibits PTC behavior with a switching temperature T.sub.s and which comprises
- (1) an organic polymeric material which comprises a crystalline thermoplastic polymer, and
- (2) dispersed in said polymeric material, a filler component which comprises
- (a) at least 10% by volume, based on the total volume of the composition, of a first conductive particulate filler which has a first average particle size, D.sub.1, from 0.01 to 200 microns and which consists of a metal having a resistivity at 25.degree. C. of less than 10.sup.-3 ohm.cm;
- and
- (b) at least 4% by volume, based on the total volume of the composition, of a second conductive particulate filler which (i) has a second average particle size D.sub.2, which is less than 0.5.times.D.sub.1 and is from 0.001 to 50 microns and (ii) consists of a metal having a resistivity at 25.degree. C. of less than 10.sup.-3 ohm.cm;
- the composition having a resistivity at 25.degree. C., .rho..sub.25, of less than 10.sup.5 ohm.cm and a resistivity at a temperature in the range T.sub.s to (T.sub.s +100).degree.C. which is at least 1000.times..rho..sub.25.
Dependencies are inferred from the claim text.