Conductive polymer compositions
AssigneeRaychem Corporation
InventorsEdward S. Sherman, Mark S. Thompson, Andrew Tomlinson
Life of this patent
Estimating the term…
Abstract
A conductive polymer composition which exhibits PTC behavior comprises a crystalline organic polymer, carbon black, and a high resistivity particulate filler. The high resistivity filler is semiconductive and has a resistivity at least 100 times that of the carbon black. Compositions of the invention exhibit good resistance stability when exposed to thermal cycling. They are useful in electrical devices requiring compositions with high resistivity.
Claims30
A conductive polymer composition which exhibits stable PTC behavior and which comprises
- (1) a crystalline organic polymer which has a melting point T.sub.m ;
- (2) a first particulate conductive filler which (i) comprises carbon black, (ii) has a particle size D.sub.1, and (iii) is present at a volume loading V.sub.1 ;
- and
- (3) a second particulate filler which (i) is semiconductive, (ii) has a particle size D.sub.2, and (iii) is present at a volume loading V.sub.2,
- wherein
- (a) the resistivity of the second filler p.sub.2 is at least 100 times the resistivity of the first filler p.sub.1, and
- (b) the resistivity of the composition is at least 100 ohm-cm.
An electrical device which exhibits PTC behavior and which comprises
- (1) a PTC element comprising a conductive polymer composition which exhibits PTC behavior and which comprises
- (a) a crystalline organic polymer which has a melting point T.sub.m ;
- (b) a first particulate conductive filler which (i) comprises carbon black, (ii) has a particle size D.sub.1, and (iii) is present at a volume loading V.sub.1 ;
- and
- (c) a second particulate filler which (i) is semiconductive, (ii) has a particle size D.sub.2, and (iii) is present at a volume loading V.sub.2,
- wherein
- (A) the resistivity of the second filler p.sub.2 is at least 100 times the resistivity of the first filler p.sub.1, and
- (B) the resistivity of the composition is at least 100 ohm-cm, and
- (2) at least two electrodes which can be connected to a source of electrical power to cause current to flow through the PTC element.
Dependencies are inferred from the claim text.