Conductive polymer composition

• US 5,093,036 A
• Filed: 09/20/1988
• Issued: 03/03/1992
• Est. Priority Date: 09/20/1988
• Status: Expired due to Term

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Raychem Limited (TE Connectivity Limited)
• Inventors: Dharia, Amitkumar N., McCarty, Gordon, Straley, O. James, Shafe, Jeff, Oswal, Ravinder K.
• Primary Examiner(s): Barr, Josephine
• Application Number:
  US07/247,026
• Time in Patent Office: 1,260 Days
• Field of Search: 252/502, 252/511, 524/495, 524/496, 427/256, 219/543, 219/548
• US Class Current: 252/511
• CPC Class Codes: H01C 7/027 consisting of conducting or semi-conducting material dispersed in a non-conductive organic material
• CPC Class Codes: H05B 3/146 Conductive polymers, e.g. polyethylene, thermoplastics

Abstract

A polymer thick film ink which exhibits PTC behavior comprising an organic polymer which is crystalline, an active solvent suitable for dissolving the polymer, and carbon black which has a pH of less than 4.0. The ink is particularly useful in producing electrical devices such as heaters and circuit protection devices.

Claims

1. A polymer thick film ink which exhibits PTC behavior, said ink comprising

(1) an organic polymer which has a crystallinity of at least 5%;

(2) an active solvent which is suitable for dissolving the polymer at room temperature; and

(3) carbon black which has a pH of less than 4.0.

2. An ink according to claim 1 wherein the carbon black has a pH of less than 3.0.

3. An ink according to claim 1 wherein the carbon black has been oxidized.

4. An ink according to claim 1 wherein the polymer comprises a fluoropolymer.

5. An ink according to claim 4 wherein the polymer comprises a terpolymer of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene.

6. An ink according to claim 1 wherein the solvent comprises dimethyl formamide, isophorone, or cyclohexanone.

7. An ink according to claim 1 wherein the viscosity is 7500 to 10,000 cps.

8. An ink according to claim 1 wherein the polymer has a crystallinity of at least 10%.

9. An ink according to claim 8 wherein the polymer has a crystallinity of at least 15%.

10. An ink according to claim 1 which further comprises graphite.