Conductive polymers and devices containing them

Claim 2

A conductive polymer composition, particularly a PTC composition, which comprises (a) a polymeric component, and (b) dispersed in the polymeric component, a first filler which is electrically conductive, characterized in that that the composition also contains at least 2% by volume, based on the volume of the polymeric component, of a second filler which has an aspect ratio of at least 10 and a thermal conductivity of at least 5 Btu. ft/hr. sq ft.°F.

Claim 3

A composition according to claim 1, characterized in that the second filler has an aspect ratio of at least 20, preferably at least 50.

Claim 4

A composition according to claim 1 or 2, characterized in that the second filler has a thermal conductivity of at least 20 Btu. ft/hr. sq ft.°F., preferably at least 50 Btu. ft/hr. sq. ft. °F.

Claim 5

A composition according to any one of claims 1 to 3, characterized in that it contains at least 6% by volume of the second filler.

Claim 6

A composition according to any one of claims 1 to 4, characterized in that the second filler is highly crystalline graphite.

Claim 7

A composition according to any one of claims 2 to 5, characterized in that the first filler is carbon black and the second filler is graphite.

Claim 8

A composition according to any one of claims 1 to 6, characterized in that it has a thermal conductivity in at least one direction which is at least 2.5 times the thermal conductivity of a composition which is identical except that the second filler is not present therein.

Claim 9

A self-limiting heater which comprises I

Claim 10

A self-limiting heater which comprises I

Claim 11

(1) a PTC element composed of a conductive polymer which exhibits PTC behavior and

Claim 12

(1) a PTC element composed of a conductive polymer which exhibits PTC behavior and

Claim 13

(2) at least two electrodes which can be connected to a source of electrical power and which, when so connected, cause current to flow through the conductive polymer element; characterized in that the conductive polymer composition is a composition as claimed in any one of claims 1 to 7.

Claim 14

A heater according to claim 8 characterized in that the PTC element is in the form of an elongate strip having the electrodes embedded therein, the distance between the electrodes being at least 7 times, preferably at least 10 times, the thickness of the strip.

Claim 15

A self-limiting strip heater which comprises (1) a PTC element which is in the form of an elongate strip and which is composed of a conductive polymer, the conductive polymer exhibiting PTC behavior and comprising (a) a first polymeric component and (b) dispersed in the first polymeric component, (i) a first filler which is electrically conductive and (ii) a second filler which is thermally conductive; and (2) two elongate parallel electrodes which are surrounded by said PTC element, the distance between the electrodes being at least 7 times the thickness of the PTC element.

Claim 16

A self-limiting strip heater which comprises (1) a PTC element which is in the form of an elongate strip and which is composed of a conductive polymer, the conductive polymer exhibiting PTC behavior and comprising (a) a first polymeric component and (b) dispersed in the first polymeric component, (i) a first filler which is electrically conductive and (ii) a second filler which is thermally conductive; and (2) two elongate parallel electrodes which are surrounded by said PTC element, the distance between the electrodes being at least 7 times the thickness of the PTC element.