Vapor sensor and materials therefor

• US 7,645,422 B2
• Filed: 08/28/2006
• Issued: 01/12/2010
• Est. Priority Date: 04/11/2003
• Status: Active Grant

• Current Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Original Assignee: Therm-O-Disc Incorporated (Emerson Electric Company)
• Inventors: Starling, Jared, Amadio, Blase S., Ramamurthy, Praveen C., Blok, Edward J.
• Primary Examiner(s): SIEFKE, SAMUEL P
• Application Number:
  US11/510,942
• Publication Number:
  US 20060292033A1
• Time in Patent Office: 1,233 Days
• Field of Search: 422/82.01, 422/50, 422/55, 422/56, 422/68.1, 422/82.02, 422/82.03, 422/57, 436/149
• US Class Current: 422/504
• CPC Class Codes: G01N 27/126 comprising organic polymers

Abstract

The present disclosure relates to a composition for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e., conductometric sensors). The present disclosure provides robust sensor film compositions that have low resistance, high conductivity, and greater temperature stability and sensitivity to chemical analytes, as well as methods of making these sensor films. Sensor film compositions according to the present disclosure include a matrix having a polymer resin comprising siloxane and a plurality of conductive particles including at least two distinct species.

Claims

1. A conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a crosslinked polymer and a plurality of conductive particles homogeneously distributed within said matrix;

wherein said crosslinked polymer comprises a siloxane monomer;

wherein said plurality comprises at least two distinct species of conductive particles, where a first species of said conductive particles comprises carbon black having an N₂ adsorption of between about 8 to about 25 m²/g and a DBP of about 1 to about 180 ml/100 g, wherein the sensor film exhibits a change in resistance in the presence of the one or more chemical analytes.

2. The conductometric sensor film according to claim 1, wherein a second species of said plurality of conductive particles is selected from the group consisting of nickel, gold, silver, manganese, copper, iron, cobalt, magnesium, aluminum, and mixtures and alloys thereof.

3. The conductometric sensor film according to claim 1, wherein said second species of said conductive particles comprises nickel.

4. The conductometric sensor film according to claim 3, wherein the sensor film has a base resistance of less than or equal to about 700 Ohms.

5. The conductometric sensor film according to claim 3, wherein said conductive particles comprising nickel have an average particle size of less than about 500 nm.

6. The conductometric sensor film according to claim 3, wherein a ratio of said first species to said second species of conductive particles comprising nickel is from about 3:

1 to about 10;

1 on a weight basis.

7. The conductometric sensor film according to claim 1, wherein a second species of said plurality of conductive particles comprises a particle having an axial geometry.

8. The conductometric sensor film according to claim 7, wherein said axial geometry particle comprises a carbon fiber.

9. The conductometric sensor film according to claim 8, wherein the sensor has a base resistance of less than or equal to about 50 mOhms.

10. The conductometric sensor film according to claim 1, wherein said first species of said plurality of conductive particles has a first resistance that is greater than a second resistance of said second species of said plurality of conductive particles.

11. The conductometric sensor film according to claim 10, wherein a ratio of said low conductivity first species to said high conductivity second species is from about 8:

1 to about 15;

1 on a weight basis.

12. The conductometric sensor film according to claim 1, wherein said second species comprises a high conductivity carbon black.

13. The conductometric sensor film according to claim 12, wherein the sensor film has a base resistance of less than or equal to about 50 Ohms.

14. The conductometric sensor film according to claim 1, wherein said plurality of conductive particles comprises at least one conductive particle selected from the group consisting of:

nickel, gold, platinum, silver, manganese, copper, iron, cobalt, magnesium, aluminum, and alloys thereof, conductive metal borides, nitrides and carbides, conductive whiskers, wires, fibers, and filaments, carbon black, graphite, and mixtures thereof.

15. The conductometric sensor film according to claim 1, wherein said siloxane monomer has at least one hydrocarbon side group with greater than or equal to two carbon atoms.

16. The conductometric sensor film according to claim 1, wherein said crosslinked polymer comprises an octylmethylsiloxane monomer.

17. A low resistance conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a polymer and a plurality of conductive particles homogeneously distributed within said polymer;

wherein said polymer comprises a siloxane monomer having at least one hydrocarbon side group with greater than or equal to two carbon atoms; and

said plurality comprises at least two distinct species of conductive particles, wherein a first species of said conductive particles comprises carbon black, and wherein the sensor film exhibits a base resistance that is less than or equal to about 700 Ohms.

18. The low resistance conductometric sensor film according to claim 17, wherein said carbon black has an N₂ adsorption of between about 8 to about 25 m²/g, a DBP of about 1 to about 180 ml/100 g.

19. The low resistance conductometric sensor film according to claim 17, wherein said second species comprises an axial geometry particle comprising carbon.

20. The low resistance conductometric sensor film according to claim 17, wherein said second species comprises a conductive particle selected from the group consisting of nickel, gold, silver, manganese, copper, iron, cobalt, magnesium, aluminum, and mixtures and alloys thereof.

21. The low resistance conductometric sensor film according to claim 17, wherein said first species of said plurality of conductive particles has a first resistance that is greater than a second resistance of said second species of said plurality of conductive particles.

22. A low resistance conductometric sensor film for detecting one or more chemical analytes comprising:

a polymer matrix comprising a polymer and a plurality of conductive particles homogeneously distributed within said polymer;

wherein said polymer comprises a siloxane monomer having at least one hydrocarbon side group with greater than or equal to two carbon atoms; and

said plurality comprises at least two distinct species of conductive particles, wherein a first species of said conductive particles comprises carbon black having an N₂ adsorption of between about 8 to about 25 m²/g and a DBP of about 1 to about 180 ml/100 g, and a second species is selected from the group consisting of;

high conductivity carbon black, a conductive axial geometry particle comprising carbon, and particles comprising nickel, wherein the sensor film has a base resistance of less than or equal to about 700 Ohms and the sensor film exhibits a change in resistance in the presence of one or more chemical analytes.