Thermally Conductive Lubricant
A method of lubricating a bearing, a bearing, and a lubricant with high thermal conductivity including a base oil, a polymeric thickener, and thermally conductive powder particles. The lubricant is, at atmospheric pressure, liquid above a transition temperature and a gel below said transition temperature.
1 . A lubricant with high thermal conductivity, comprising:
a base oil;
a polymeric thickener; and
thermally conductive powder particles;
the lubricant being, at atmospheric pressure, liquid above a transition temperature and a gel below said transition temperature.
2 . The lubricant of claim 1 , wherein the thermally conductive powder particles are present in an amount within the range of 1-30 wt % of the lubricant, preferably within the range of 6-15 wt %.
3 . The lubricant of claim 1 , wherein the thermally conductive powder particles have an average aspect ratio of at least 1:10 such as within the range of 1:10 to 1:100.
4 . The lubricant of claim 1 , wherein the thermally conductive powder particles form a percolated network in the lubricant.
5 . The lubricant of claim 1 , wherein the thermally conductive powder particles are surface modified with thermally conducive molecules, e.g., ethylene, able to bond with each other to improve thermal conductivity between the particles.
6 . The lubricant of claim 5 , wherein at least one of the thermally conducive molecules of a first particle of the thermally conductive powder particles is bound, e.g., by hydrogen or covalent bonds, to at least one of the thermally conducive molecules of a second particle of the thermally conductive powder particles.
7 . The lubricant of claim 1 , wherein the thermally conductive powder particles comprise any of: boron nitride, BN, e.g. hexagonal BN, h-BN; and/or a graphene material e.g. graphene, modified graphene and/or any graphene oxide; and/or any metal oxide e.g. Fe 3 O 4 , Fe 2 O 3 , ZnO, Al 2 O 3 , SiO 2 , CeO 2 , TiO 2 and/or MgO; preferably h-BN and/or graphene, especially h-BN.
8 . The lubricant of claim 1 , wherein the lubricant, at a temperature below the transition temperature, has a viscosity index, VI, of at least 200, 300, 500, 800 or 1000, such as within the range of 200-1000, 500-1000 or 800-1000.
9 . The lubricant of claim 1 , wherein the transition temperature is within the range of 100-160° C.
10 . The lubricant of claim 1 , wherein the polymeric thickener is or comprises a styrenic thermoplastic elastomer such as a styrenic block copolymer, e.g. a tri-block copolymer such as polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene, polystyrene-b-poly(ethylene/propylene)-b-polystyrene and/or polystyrene-b-poly(ethylene/butylene)-b-polystyrene, and/or a di-block copolymer such as polystyrene-b-poly(ethylene/propylene), preferably polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene.
11 . The lubricant of claim 1 , wherein the polymeric thickener is present in an amount within the range of 0.001-50 wt % of the lubricant, preferably within the range of 5-20 wt %.
12 . The lubricant of claim 1 , wherein the base oil is or comprises a mineral oil, an iso-paraffinic oil and/or a hydrocarbon oil.
13 . A bearing comprising:
rolling elements and
a solid structure arranged to separate the rolling elements from each other, the solid structure including pores holding a lubricant, having:
a base oil;
a polymeric thickener; and
thermally conductive powder particles;
the lubricant being, at atmospheric pressure, liquid above a transition temperature and a gel below said transition temperature.
14 . The bearing of claim 13 , wherein the solid structure comprises thermally conductive powder particles, e.g. of the same material as the thermally conductive powder particles of the lubricant.
15 . A method of lubricating a bearing, the method comprising:
heating the lubricant of claim 1 , to a temperature above the transition temperature whereby the lubricant liquifies;
applying the liquid lubricant into the bearing; and
cooling the lubricant to a temperature below the transition temperature whereby the lubricant gelifies.
16 . The lubricant of claim 7 , wherein the powder particles are h-BN.
17 . The lubricant of claim 10 , wherein the polymeric thickener is polystyrene-b-poly(ethylene-ethylene/propylene)-b-polystyrene.
18 . The lubricant of claim 2 , wherein the thermally conductive powder particles have an average aspect ratio of at least 1:10 such as within the range of 1:10 to 1:100.
19 . The lubricant of claim 2 , wherein the thermally conductive powder particles form a percolated network in the lubricant.