ADDITIVES PACKAGE AND MAGNETORHEOLOGICAL FLUID FORMULATIONS FOR EXTENDED DURABILITY

Abstract

An additives package for use in an MR fluid formulation is provided, as well as an MR fluid formulation containing the additives package. In one embodiment, the additives package comprises an organomolybdenum dithiocarbamate, an ashless dithiocarbamate, and a triazole compound, such as a tolutriazole compound. In another embodiment, the additives package may further include an aminic antioxidant, such as an alkylated diphenylamine. In another embodiment, the additives package is free of an organomolybdate ester. In another embodiment, the additives package consists of the organomolybdenum dithiocarbamate, the ashless dithiocarbamate, the triazole compound, and optionally the aminic antioxidant. In addition to the additives package, the magnetorheological fluid formulation comprises magnetizable particles, a carrier fluid, and a thickening agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

FIG. 1 is a plot of the variation in off-state damping load with cycle count after the initiation of thickening in prior art MR fluids.

FIG. 2 is a plot depicting antioxidant depletion during durability testing of prior art MR fluids.

FIG. 3 is a plot of the variation in off-state damping force with cycle count for an MR fluid of the invention compared to a prior art MR fluid.

Claims

1. An additive package for use in an MR fluid formulation, comprising: an organomolybdenum dithiocarbamate,an ashless dithiocarbamate, anda triazole compound.

2. The additive package of claim 1 further comprising an aminic antioxidant.

3. The additive package of claim 2 wherein the aminic antioxidant is an alkylated diphenylamine.

4. The additive package of claim 1 with the proviso that the additive package is free of an organomolybdate ester.

5. The additive package of claim 1 wherein the ashless dithiocarbamate is methylene bis-dibutyl dithiocarbamate.

6. An antioxidant additive package for use in an MR fluid formulation, consisting of: an organomolybdenum dithiocarbamate,an ashless dithiocarbamate,a tolutriazole compound, andoptionally, an alkylated diphenylamine.

7. The additive package of any of claim 6 wherein the ashless dithiocarbamate is methylene bis-dibutyl dithiocarbamate.

8. A magnetorheological fluid formulation comprising magnetizable particles, a carrier fluid, a thickening agent and the additives package of claim 1.

9. The fluid formulation of claim 8, wherein the organomolybdenum dithiocarbamate is present in an amount of about 0.0025 to about 2.5% by weight of the formulation;the ashless dithiocarbamate is present in an amount of about 0.0025 to about 2.5% by weight of the formulation, andthe triazole compound is present in an amount of about 0.0025 to about 2.5% by weight of the formulation.

10. The fluid formulation of claim 9, further comprising an alkylated diphenylamine present in an amount of about 0.0025 to about 2.5% by weight of the formulation.

11. The fluid formulation of claim 9, wherein the magnetizable particles are present in an amount of about 50 to about 95% by weight of the formulation.

12. The fluid formulation of claim 11, wherein the magnetizable particles are of spherical or near-spherical morphology, with mean diameter of between about 1 to about 100 microns.

13. The fluid formulation of claim 12, wherein mean diameter of the magnetizable particles is between about 5 to about 20 microns.

14. The fluid formulation of claim 9, wherein the carrier fluid is present in an amount of about 5 to about 50% by weight of the formulation.

15. The fluid formulation of claim 9, wherein the thickening agent is present in an amount of about 0.025 to about 10% by weight of the formulation.

16. The fluid formulation of claim 8 with the proviso that the fluid formulation is free of an organomolybdate ester.

17. The fluid formulation of claim 8, wherein the ashless dithiocarbamate is methylene bis-dibutyl dithiocarbamate.

18. The fluid formulation of claim 8, wherein the additives package is present in an amount of at least about 0.05% by weight of the formulation.

19. The fluid formulation of claim 8, wherein the additives package is present in an amount of no more than about 5% by weight of the formulation.

20. A magnetorheological fluid formulation comprising magnetizable particles, a carrier fluid, a thickening agent and the additives package of claim 6.

21. The fluid formulation of claim 20, wherein the alkylated diphenylamine is present in an amount of about 0.0025 to about 2.5% by weight of the formulation.

22. A magnetorheological fluid formulation comprising about 50 to about 95% by weight magnetizable particles, about 5 to about 50% by weight of a carrier fluid, about 0.025 to about 10% by weight of a thickening agent, and an additives package, wherein the additives package comprises, based on the total weight of the formulation: about 0.0025 to about 2.5% by weight of an organomolybdenum dithiocarbamate,about 0.0025 to about 2.5% by weight of an ashless dithiocarbamate, andabout 0.0025 to about 2.5% by weight of a tolutriazole compound.

23. The fluid formulation of claim 22, wherein the additive package further comprises about 0.0025 to about 2.5% by weight of an alkylated diphenylamine.

24. The fluid formulation of claim 23 with the proviso that the fluid formulation is free of an organomolybdate ester.

25. The fluid formulation of claim 22 with the proviso that the fluid formulation is free of an organomolybdate ester.