Method of reducing friction and wear between surfaces under a high load condition

1. A method of reducing wear between two surfaces placed under a load condition in excess of 1 GPa, said method comprising providing a lubricant composition between the two surfaces, the lubricant composition comprising a polysiloxane base oil corresponding to the structural formula:

wherein each R, R′, and R″ is independently selected, such that R is an alkyl group having between 1-3 carbon atoms; R′ is an alkylaryl group comprising alkyl functionality with 3-12 carbon atoms and aryl functionality with 6 to 12 carbon atoms; R″ is an alkyl group having between 1-12 carbon atoms or an alkylaryl group comprising alkyl functionality with 2-12 carbon atoms and aryl functionality with 6 to 12 carbon atoms; m is an integer, and n is an integer or 0, with the proviso that 8<(m+n)<500.

2. The method according to claim 1 , wherein the R in the polysiloxane base oil is a methyl group, the R′ is an alkylphenyl group with the alkyl functionality having between 5-8 carbon atoms; and the R″ is a methyl group or an alkylphenyl group with the alkyl functionality having between 2-5 carbon atoms.

3. The method according to claim 1 , wherein the polysiloxane base oil corresponds to the structural formula:

4. The method according to claim 1 , wherein the polysiloxane base oil corresponds to the structural formula:

5. The method according to claim 1 , wherein the integers m and n in the structure of the polysiloxane base oil are selected such that the sum of (m+n) is greater than 8 and less than 250 and optionally, the ratio of the integer m to the sum of the integers (m+n) in the polysiloxane base oil is between 0.1 and 1.00.

6. The method according to claim 1 , wherein the polysiloxane base oil exhibits at least one of the following, a molecular mass between 1,500 g/mol and 35,000 g/mol or a viscosity at zero shear and 303 K between 50 and 5,000 mPa-sec.

7. The method according to claim 1 , wherein the lubricant composition further comprises at least one functional additive selected as one from the group of extreme pressure additives, anti-wear additives, antioxidants, antifoams, and corrosion inhibitors.

8. The method according to claim 1 , wherein the two surfaces represent an elastohydrodynamic lubrication (EHL) contact point in a machine element.

9. The method according to claim 8 , wherein the machine element is a rolling element bearing, a plane bearing, a sliding bearing, a gear, a cam and a cam follower, or a traction drive; and optionally, the two surfaces are metal surfaces.

10. The method according to claim 1 , wherein the lubricant composition provides one or more of the following, an EHL film thickness on the surface between 10 and 2,000 nm at a temperature of 303 K and an entrainment speed between 0.05 and 5.00 m/s or an EHL film thickness on the surface between 10 and 1,000 nm at a temperature of 398 K and an entrainment speed between 0.05 and 5.00 m/s.

11. The method according to claim 10 , wherein the lubricant composition provides one or more of the following, a coefficient of friction less than 0.07 at a temperature of 303 K and an entrainment speed between 0.05 and 5.00 m/s or a coefficient of friction less than 0.05 at a temperature of 398 K and an entrainment speed between 0.05 and 5.00 m/s.

12. A method of reducing wear between rolling or sliding surfaces in a machine element, the method comprising the steps of:

providing a machine element having a first surface and a second surface; the first and second surfaces representing an elastohydrodynamic lubrication (EHL) contact point in the machine element;

providing a lubricant composition between the first surface and second surface, the lubricant composition comprising:

a polysiloxane base oil corresponding to the structural formula:

 in which each R, R′, and R″ is independently selected, such that R is an alkyl group having between 1-3 carbon atoms; R′ is an alkylaryl group comprising alkyl functionality with 3-12 carbon atoms and aryl functionality with 6 to 12 carbon atoms; R″ is an alkyl group having between 1-12 carbon atoms or an alkylaryl group comprising alkyl functionality with 2-12 carbon atoms and aryl functionality with 6 to 12 carbon atoms; m is an integer, and n is an integer or 0, with the proviso that 8<(m+n)<500; and

allowing the first surface to roll or slide past the second surface under a load condition in excess of 1 GPa.

13. The method according to claim 12 , wherein the R in the polysiloxane base oil is a methyl group, the R′ is an alkylphenyl group with the alkyl functionality having between 5-8 carbon atoms; and the R″ is a methyl group or an alkylphenyl group with the alkyl functionality having between 2-5 carbon atoms.

14. The method according to claim 12 , wherein the polysiloxane base oil corresponds to the structural formula:

15. The method according to claim 12 , wherein the polysiloxane base oil corresponds to the structural formula:

16. The method according to claim 12 , wherein the integers m and n in the structure of the polysiloxane base oil are selected such that the sum of (m+n) is greater than 8 and less than 250 and the ratio of the integer m to the sum of (m+n) is between 0.5 and 1.00.

17. The method according to claim 12 , wherein the machine element is a rolling element bearing, a sliding bearing, a gear, a cam and a cam follower, or a traction drive, and optionally, with the first and second surfaces being metal surfaces.

18. The method according to claim 12 , wherein the lubricant composition provides an EHL film thickness between the first surface and the second surface that is between 90 and 900 nm at a temperature of 303 K and between 20 and 200 nm at a temperature of 398 K at an entrainment speed between 0.05 and 5.00 m/s.

19. The method according to claim 18 , wherein the lubricant composition provides a coefficient of friction less than 0.07 at a temperature of 303 K and less than 0.05 at a temperature of 398 K at an entrainment speed between 0.05 and 5.00 m/s.