Friction-improved polymers for DLC-coated surfaces

1. An element comprising at least two components movable with respect to one another, between surfaces of which is disposed a film comprising a lubricant oil composition, wherein a surface of at least one of the movable components comprises a diamond-like-carbon layer (DLC layer) and the lubricant oil composition comprises 0.5 to 15% by weight of a polymer comprising a repeat unit derived from an amine derivative of at least one polar ethylenically unsaturated monomer, the amine derivative being derived from N-phenyl-1,4-phenylenediamine,

wherein:

the polar ethylenically unsaturated monomer from which the amine derivative is derived is maleic anhydride.

2. The element of claim 1 , wherein the DLC layer comprises carbon present in a graphite structure, wherein a proportion of the carbon present in a graphite structure, based on an overall amount of carbon, is in a range from 30 to 70 mol %.

3. The element of claim 1 , wherein the DLC layer comprises carbon present in a diamond structure, wherein a proportion of the carbon present in a diamond structure, based on an overall amount of carbon, is in a range from 30 to 70 mol %.

4. The element of claim 1 , wherein a thickness of the DLC layer is in a range from 1 to 20 μm.

5. The element of claim 1 , wherein the polymer comprises 0.1 to 10% by weight of the repeat unit derived from the amine derivative of the polar ethylenically unsaturated monomer.

6. The element of claim 1 , wherein the polymer is a polyolefin.

7. The element of claim 1 , wherein the polymer is a polyalkyl(meth)acrylate.

8. The element of claim 1 , which is an engine.

9. The element of claim 8 , wherein at least one of the components movable with respect to one another is a camshaft or a valve.

10. The element of claim 1 , wherein the polymer is a graft copolymer where a graft layer comprises the repeat unit derived from the amine derivative of the polar ethylenically unsaturated monomer.

11. The element of claim 10 , wherein a graft base of the graft copolymer comprises a polyolefin or a polyalkyl(meth)acrylate.

12. The element of claim 11 , wherein the polyolefin is an ethylene-propylene copolymer, and the polyalkyl(meth)acrylate comprises alkyl radicals having from 12 to 18 carbon atoms.

13. The element of claim 12 , wherein a thickness of the DLC layer is in a range from 2 to 3 μm.

14. The element of claim 13 , wherein the lubricant oil composition further comprises an API group III oil.

15. The element of claim 14 , which

(i) exhibits a reduction in friction, integrated over a range of sliding speeds of 0.005 to 2.5 m/s, of 20% or more compared to a reference element, and

(ii) exhibits a reduction in friction, integrated over a range of sliding speeds of 0.01 to 0.1 m/s, of 35% or more compared to a reference element,

wherein the reference element is identical to the element of claim 1 except that the lubricant oil composition of the reference element does not comprise the polymer.

16. The element of claim 1 , which exhibits a reduction in friction, integrated over a range of sliding speeds of 0.005 to 2.5 m/s, of 20% or more compared to a reference element, wherein the reference element is identical to the element of claim 1 except that the lubricant oil composition of the reference element does not comprise the polymer.

17. The element of claim 1 , which exhibits a reduction in friction, integrated over a range of sliding speeds of 0.01 to 0.1 m/s, of 35% or more compared to a reference element, wherein the reference element is identical to the element of claim 1 except that the lubricant oil composition of the reference element does not comprise the polymer.