CN115926868B - Lubricant for super-slip system and super-slip system comprising lubricant - Google Patents

Abstract

The present invention provides a lubricant for an ultra-lubricating system and an ultra-lubricating system comprising the lubricant. The ultra-lubricating system uses bearing steel/polyimide as a friction pair and monohydric alcohol, oleic acid or poly-α-olefin synthetic oil as a lubricant. The friction coefficient of the motion system is as low as 0.001, thereby achieving a stable ultra-low friction phenomenon.

Description

Lubricant for super-lubricating system and super-lubricating system including the lubricant

Technical Field

The invention relates to the technical field of lubricating materials, in particular to a lubricant for a super-lubricating system and a super-lubricating system comprising the lubricant.

Background technique

At present, with the progress of science and technology, the rapid development of industrial technologies such as automobiles, aerospace and precision instruments has put forward higher requirements for lubricants, and advanced lubrication technology has also had greater room for development, among which superlubrication technology is particularly eye-catching. The superlubrication phenomenon was first proposed by Japanese scientist M.Hirano et al. in 1990. Through theoretical calculations and molecular dynamics simulations, they found that when two completely clean atomically flat crystal planes come into non-commensurate contact, the friction force may be zero. It was not until 2004 that Dutch scientist J.Frenken et al. measured the friction force between graphene and graphite substrate at different angles and found that the system had a large friction force only at certain specific angles (0° and 60°, etc.), while the friction force of the system was extremely small at other angles. In the nearly two decades since then, people have observed extremely low friction phenomena with friction coefficients of 0.001 or below in multiple systems. These and the structural lubrication phenomena predicted by M.Hirano et al. are all called superlubrication phenomena.

According to the different lubricating materials, superlubrication can be divided into two categories: solid superlubrication and liquid superlubrication. The key to achieving liquid superlubrication is: how to ensure the stable existence of liquid molecules on the two friction pairs under external pressure while providing very low shear strength. Although the current research on liquid superlubrication has made some progress, it is still quite far from practical application.

Polyimide (PI) is a type of organic polymer material developed after the 1950s. Due to its outstanding high and low temperature resistance, excellent mechanical properties, diverse preparation methods and simple and feasible processing methods, it is considered to be one of the most promising engineering materials in this century and has been widely used in many fields. At the same time, PI is also a solid self-lubricating material, but in fact, it still has problems such as excessive friction and high friction coefficient when used directly as a self-lubricating wear-resistant material. Therefore, when used as a friction pair, lubricating fluid is often added to ensure that the entire system is in a good lubrication state. At present, studies have found that the polyimide/GCr15 bearing steel pairing system can produce oriented superlubrication under liquid crystal lubrication, but because the liquid crystal compound is relatively expensive and is not widely used in industry, we must use lubricants that are more easily and widely available to design and obtain a superlubrication system that is more easily and universally used, expand the superlubrication system, and also make certain preparations for the superlubrication system to become practical.

Summary of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention discloses a lubricant for an ultra-lubricating system and an ultra-lubricating system comprising the lubricant. The friction coefficient of the motion system is as low as 0.001, achieving a stable ultra-low friction phenomenon.

The technical solution provided by the present invention is a lubricant for a super-lubricating system, wherein the lubricant is selected from any one of monohydric alcohol, oleic acid or poly alpha olefin (PAO) synthetic oil.

Furthermore, the monohydric alcohol is selected from any one of n-octanol, n-nonanol, n-decanol, n-undecanol, 6-chloro-1-hexanol or N-benzylaminoethanol.

Furthermore, the poly-α-olefin synthetic oil is selected from any one of low-viscosity poly-α-olefins.

The invention discloses a super-lubricating system, which uses monohydric alcohol, oleic acid or poly-alpha-olefin synthetic oil as lubricant and bearing steel/polyimide as friction pair.

The monohydric alcohol is used in a super-lubricating system. The monohydric alcohol is used as a lubricant, and the bearing steel/polyimide is used as a friction pair to form a super-lubricating system.

Application of oleic acid in super-lubricating system. The oleic acid is used as lubricant and bearing steel/polyimide is used as friction pair to form super-lubricating system.

The invention discloses an application of poly-alpha-olefin synthetic oil in a super-lubricating system. The poly-alpha-olefin synthetic oil is used as a lubricant, and bearing steel/polyimide is used as a friction pair to form a super-lubricating system.

Furthermore, the polyimide is a PMDA-ODA type polyimide material, which is polymerized from pyromellitic dianhydride and 4,4′-diaminodiphenyl ether.

Furthermore, the bearing steel is GCr15 bearing steel.

The invention discloses an application of monohydric alcohol, oleic acid or poly-alpha-olefin synthetic oil in a super-lubricating system. The monohydric alcohol, oleic acid or poly-alpha-olefin synthetic oil is a lubricant for mechanical parts, and bearing steel and polyimide are used as matching materials for the mechanical parts.

Polyalphaolefin synthetic oil (PAO) is an artificially synthesized oil, so it can artificially avoid impurities, has good viscosity-temperature properties and low-temperature fluidity, and has a neat molecular structure. It is a saturated hydrocarbon and a non-polar molecule, so the physical and chemical properties are very stable. Compared with mineral oil, it is not easy to be oxidized during use. Monohydric alcohol or oleic acid is a common polar organic molecule. Compared with expensive liquid crystal materials, monohydric alcohol, oleic acid or polyalphaolefin synthetic oil is widely available and cheap, and is widely promoted and used. In the existing oriented superlubrication system of polyimide/GCr15 bearing steel pairing under liquid crystal lubrication, the liquid crystal molecules used are nematic rod-shaped liquid crystal molecules, which are one-dimensional ordered phases, and the long axes of the molecules are basically arranged in parallel in one direction. The lubricating effect of liquid crystal as a lubricant in the system mainly depends on the anisotropic properties of liquid crystal molecules in the liquid crystal state. In the liquid crystal state, the liquid crystal molecules have fluidity similar to that of ordinary liquids. The molecules are not arranged in layers. They can slide up and down, left and right, and front and back, but the long axes of the molecules remain parallel or nearly parallel to each other. The short-range interaction between molecules is weak. This type of liquid crystal has low viscosity and rich fluidity. Under the action of friction, the rod-shaped liquid crystal molecules will undergo oriented super-slippery effect under the anchoring force of polyimide. However, monoalcohol, oleic acid or poly-α-olefin synthetic oil is a kind of ordinary isotropic liquid. The mechanism of superlubricity of PI/GCr15 bearing steel pairing under the lubrication of this kind of substance is found through calculation to be related to molecular structure parameters such as solvent accessible area of lubricant molecules, charge spatial distribution and hydrogen bond forming ability. That is, the application of monoalcohol, oleic acid or poly-α-olefin synthetic oil in ultra-low friction system has completely different mechanism and characteristics from the application of liquid crystal molecules in superlubricity system. Monoalcohol, oleic acid or poly-α-olefin synthetic oil plays a lubricating role in the corresponding friction system to make the system reach superlubricity, and its application range will be wider.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a molecular structural formula of a PMDA-ODA type polyimide material used in the present invention;

2 is a graph showing the change in friction coefficient over time when lubricating a GCr15/PI (PMDA-ODA) pair with n-octanol, n-nonanol, n-decanol, 6-chloro-1-hexanol or N-benzylaminoethanol;

3 is a graph showing the change in friction coefficient over time for a GCr15/PI (PMDA-ODA) pair lubricated with n-undecyl alcohol according to the present invention;

FIG4 is a graph showing the change in friction coefficient over time for a GCr15/PI (PMDA-ODA) pair lubricated with oleic acid according to the present invention;

5 is a graph showing the change of friction coefficient over time at different speeds for a GCr15/PI (PMDA-ODA) pair lubricated with PAO4 according to the present invention;

6 is a graph showing the change in friction coefficient over time when the GCr15/GCr15 pair is lubricated with n-undecyl alcohol or oleic acid, respectively;

7 is a graph showing the change in friction coefficient over time for a GCr15/PS pair lubricated with oleic acid according to the present invention;

FIG8 is a graph showing the change in friction coefficient over time for the GCr15/PE pair lubricated with n-undecyl alcohol, oleic acid or PAO4, respectively.

Detailed ways

The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and drawings.

In the following embodiments, a UTM-3 micro-friction tester (Bruker, Germany) was used to carry out micro-friction tests. During the test, a GCr15 steel ball (diameter of 4.76 mm) was used as a static specimen, and a PMDA-ODA polyimide material was attached to a fixed disk as a rotating disk specimen, rotating at a corresponding speed, and the radius of the annular friction path was 8.5 mm. The test load was applied vertically through the center line of the ball specimen, and the test was carried out in a point-to-surface contact mode. The load condition was 5N, and 0.1-0.2 ml of lubricant was dripped between the GCr15 steel ball and the PMDA-ODA polyimide material, and the test was carried out at room temperature. During the test, the coefficient of friction (COF) was automatically recorded by a computer, and then the software calculated the average friction coefficient.

Example 1

1-octanol, 1-nonanol, 1-decanol, 6-chlorohexanol or N-benzylethanolamine were used as lubricants for the motion system under the GCr15/PI (PMDA-ODA) pair. The system rotated at a speed of 250 rpm and the tests were carried out on different friction pairs for 1 hour each. The change of friction coefficient over time is shown in Figure 2. -(1-octanol)-GCr15/PI(PMDA-ODA)/250rpm, represents the change of friction coefficient over time under 5N load, n-octanol lubrication, GCr15/PI(PMDA-ODA) pairing, rotating at a speed of 250rpm, 5N-(1-nonanol)-GCr15/PI(PMDA-ODA)/250rpm, 5N-(1-decanol)-GCr15/PI(PMDA-ODA)/250rpm, etc., and the same applies.

The average friction coefficient of the process is recorded in Table 1. The friction systems using n-octanol, n-nonanol, n-decanol, 6-chloro-1-hexanol or N-benzylaminoethanol as lubricants were all in a super-slip state during the test.

Table 1 Average friction coefficient of the system when different liquid lubrication GCr15/PI (PMDA-ODA) pairings

Example 2

Taking 1-undecanol as the lubricant of the motion system under the GCr15/PI (PMDA-ODA) pair, the system rotates at a speed of 250 rpm. Three cycles of 1 hour each are tested on the same friction pair. The change of friction coefficient over time is shown in Figure 3, where 5N-(1-undecanol)-GCr15/PI(PMDA-ODA)/250rpm/1 represents the change of friction coefficient over time in the first test cycle under a load of 5N, with 1-undecanol lubrication and the GCr15/PI (PMDA-ODA) pair rotating at a speed of 250 rpm, 5N-(1-undecanol)-GCr15/PI(PMDA-ODA)/250rpm/2, 5N-(1-undecanol)-GCr15/PI(PMDA-ODA)/250rpm/3, and so on.

The average friction coefficient of the process is recorded in Table 2. When n-undecanol is used as a lubricant, the system is in a super-slip state during the test.

Table 2 Average friction coefficient of each test cycle under n-undecyl alcohol lubrication GCr15/PI (PMDA-ODA) pair

Example 3

Oleic acid was used as the lubricant of the motion system under the GCr15/PI (PMDA-ODA) pair, and the rotation speed was 250 rpm. Three cycles of 1 hour each were tested on the same friction pair. The change of the friction coefficient over time is shown in Figure 4, where the curve in the figure is as described in Example 2.

The average friction coefficient of the process is recorded in Table 3. When oleic acid is used as lubricant, the system is in a super-slip state during the test.

Table 3 Average friction coefficient of each test cycle under oleic acid lubrication GCr15/PI (PMDA-ODA) pair

Example 4

Using low viscosity PAO4 as the lubricant for the motion system under the GCr15/PI (PMDA-ODA) pairing, friction tests were carried out on the same friction pair at different speeds for 1 hour each. The variation of the friction coefficient over time is shown in Figure 5, where the curve in the figure is as described in Example 1.

The average friction coefficient of the process is recorded in Table 4. The friction system with PAO4 as lubricant at different speeds is in a super-slip state during the test.

Table 4 Average friction coefficient of GCr15/PI (PMDA-ODA) pair at different speeds under PAO4 lubrication

Comparative Example 1

Lubricated with n-undecyl alcohol or oleic acid, GCr15/GCr15 pair, rotated at a speed of 250 rpm, and tests were carried out on different friction pairs for 1 hour each. The change of friction coefficient over time is shown in Figure 6, where the curve description in the figure is as in Example 1. During the process, when these two substances were used as lubricants, the friction coefficient was always large. When n-undecyl alcohol was used as a lubricant, the average friction coefficient of the system was 0.09296, and when oleic acid was used as a lubricant, the average friction coefficient of the system was 0.08030, both of which were greater than 0.001 order of magnitude. Both motion systems were not in a super-slip state.

Comparative Example 2

The GCr15/PS (polystyrene, PS) pair was lubricated with oleic acid and rotated at 250 rpm for 1 hour. When the test was carried out for 25 minutes, the friction coefficient fluctuated violently, so the test was stopped. The test results recorded for 25 minutes are shown in Figure 7, where the curves in the figure are as described in Example 1. The average friction coefficient of the system during the recording process was 0.01916, which is greater than 0.001, indicating that the motion system is not in a super-slip state.

Comparative Example 3

Lubricated with n-undecyl alcohol, oleic acid or PAO4, GCr15/PE (polyethylene, PE) pair, rotated at a speed of 250rpm, and tests were carried out on different friction pairs for 1h each. The change of friction coefficient over time is shown in Figure 8, where the curve description in the figure is as in Example 1. During the process, when these three substances were used as lubricants, the friction coefficients were always large. When n-undecyl alcohol was used as a lubricant, the average friction coefficient of the system was 0.02930, when oleic acid was used as a lubricant, the average friction coefficient of the system was 0.02641, and when PAO4 was used as a lubricant, the average friction coefficient of the system was 0.03052, all of which were greater than 0.001 order of magnitude. These three motion systems were not in a super-slip state.

The test results show that under the lubrication of the corresponding liquid reagents, when the GCr15/GCr15 pairing, GCr15/PS pairing or GCr15/PE pairing is used, the friction coefficient of the running system does not reach the order of 0.001, and the super-lubricity phenomenon is not achieved. However, when the monohydric alcohol, oleic acid or poly-α-olefin synthetic oil provided by the present invention is used as a lubricant, and the GCr15/PMDA-ODA type polyimide material pairing is used, the friction between the friction pairs can be effectively reduced, and the friction coefficient in the stable motion state is as low as the order of 0.001, achieving the super-lubricity behavior of the system.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (8)

1. A lubricant for an ultra-slip system, wherein the lubricant is selected from any one of monohydric alcohol or poly-alpha olefin synthetic oil, and the friction pair of the ultra-slip system is bearing steel/polyimide.

2. The lubricant for an ultra-smooth system according to claim 1, wherein the monohydric alcohol is selected from any one of N-octanol, N-nonanol, N-decanol, N-undecanol, 6-chloro-1-hexanol, or N-benzylaminoethanol.

3. The lubricant for an ultra-smooth system according to claim 1, wherein the poly-alpha-olefin synthetic oil is selected from any one of low viscosity poly-alpha-olefins.

4. An ultra-slip system characterized by using monohydric alcohol or poly alpha-olefin synthetic oil as a lubricant and bearing steel/polyimide as a friction pair.

5. The ultra-slip system of claim 4, wherein the polyimide is a PMDA-ODA polyimide material polymerized from pyromellitic dianhydride and 4,4' -diaminodiphenyl ether.

6. The ultra-slip system of claim 4, wherein the bearing steel is GCr15 bearing steel.

7. Use of a monohydric alcohol in an ultra-slip system, wherein the monohydric alcohol acts as a lubricant and the bearing steel/polyimide acts as a friction pair, forming the ultra-slip system.

8. The application of the poly alpha-olefin synthetic oil in an ultra-sliding system is characterized in that the poly alpha-olefin synthetic oil is used as a lubricant, and bearing steel/polyimide is used as a friction pair to form the ultra-sliding system.