Application of phenyl ester compounds or polyethylene glycol in ultra-low friction systems

Abstract

The present invention provides an application of a phenyl ester compound or polyethylene glycol in an ultra-low friction system. The ultra-low friction system uses silicon nitride / polyimide as a friction pair and a phenyl ester compound or polyethylene glycol as a lubricant. The friction coefficient of the motion system is as low as 0.001, achieving a stable ultra-low friction phenomenon.

Description

Technical Field

[0001] The present invention relates to the technical field of lubricating materials, in particular to the application of phenyl ester compounds or polyethylene glycol in ultra-low friction systems. Background Art

[0002] Human survival and development are inseparable from energy. However, in recent years, the contradiction between growing energy demand and dwindling existing energy resources has intensified. Reducing energy consumption while maintaining a certain level and speed of development has become a global concern. Improving energy efficiency and reducing energy loss are effective solutions. It is estimated that over one-third of the world's primary energy consumption is caused by friction and wear, approximately 80% of mechanical equipment parts are scrapped due to wear, and over 50% of serious mechanical equipment accidents are caused by lubrication failure or excessive wear. For example, in my country, annual expenditures due to friction and wear already account for approximately 5% of its GDP. Based on the economic scale of 2022, this loss would amount to trillions of RMB. Therefore, improving the friction between mechanical parts and effectively reducing the friction coefficient are of paramount importance. The development of such technologies has significant practical significance for my country's new industrialization path, the development of a circular economy, and the realization of energy conservation and emission reduction strategies.

[0003] Polyimide (PI) is a class of organic polymer materials with excellent heat resistance. Its long-term operating temperature range is -200°C to 300°C, and its thermal decomposition temperature reaches up to 600°C, making it one of the most thermally stable organic polymers to date. Due to its excellent mechanical properties, radiation resistance, tribological properties, and processing properties, polyimide is often used as an engineering material in bearing manufacturing, such as as the main material for sliding bearings. Bearings are a critical core component in modern mechanical equipment. The bearing industry is a national strategic foundation, playing a vital role in supporting national economic development and national defense. Bearing performance directly determines the operational reliability of various types of equipment. However, my country's current bearing design and manufacturing level still lags behind international advanced standards. This severely restricts the application of mechanical equipment in harsh working conditions and extreme environments, and it is one of the core technologies that is being "stuck" by foreign countries. The primary function of a bearing is to support a rotating mechanical object, reduce the coefficient of friction during its motion, and ensure rotational accuracy. Lubrication is crucial for bearings.

[0004] Ceramic materials are also important materials for bearing manufacturing, among which silicon nitride (Si3N4) is a very important structural ceramic. Silicon nitride is a stable inorganic compound composed of two elements, Si and N. It is an atomic crystal with a regular octahedral structure. As a material, it is hard, inherently lubricating, wear-resistant, and resistant to oxidation at high temperatures. It can also withstand thermal shock and will not break even when heated to over 1000°C in air, rapidly cooled, and then rapidly heated. Its hardness is twice that of bearing steel, and its elastic modulus is about one-third higher. Under the same load conditions, silicon nitride ceramics have low elastic deformation. Therefore, machine tool spindles using ceramic hybrid bearings have excellent operating accuracy.

[0005] Although the excellent properties of polyimide and silicon nitride have received considerable attention in the industry, and some scholars have discovered the super-lubricity phenomenon of liquid crystal or di(2-ethylhexyl) adipate as lubricants and polyimide / silicon nitride pairing systems in previous studies, there are still problems such as the relatively high price of liquid crystal compounds used as lubricants and the limited application of di(2-ethylhexyl) adipate as a lubricant. Summary of the Invention

[0006] In response to the above-mentioned deficiencies in the prior art, the present invention discloses the application of phenyl ester compounds or polyethylene glycol in an ultra-low friction system. The friction coefficient of the motion system is as low as 0.001, achieving a stable ultra-low friction phenomenon.

[0007] The technical solution provided by the present invention is the application of phenyl ester compounds or polyethylene glycol in an ultra-low friction system, using phenyl ester compounds or polyethylene glycol as lubricants and silicon nitride / polyimide as friction pairs to form an ultra-low friction system.

[0008] Furthermore, the phenyl ester compound is a phenyl diester compound or a phosphorus-containing phenyl triester compound.

[0009] Furthermore, the phenyl ester compound is selected from any one of dibutyl phthalate, tricresyl phosphate or triphenyl phosphite.

[0010] Furthermore, the polyimide is a PMDA-ODA type polyimide material, which is polymerized from pyromellitic dianhydride and 4,4'-diaminodiphenyl ether.

[0011] Furthermore, the phenyl ester compound or polyethylene glycol is a lubricant for mechanical parts, and silicon nitride and polyimide are used as supporting materials for mechanical parts.

[0012] An ultra-low friction system uses phenyl ester compounds or polyethylene glycol as lubricants and silicon nitride / polyimide as friction pairs.

[0013] Phenyl ester compounds or polyethylene glycol as isotropic organic liquid molecules have obvious differences in physical and chemical properties from liquid crystals, which are anisotropic liquid substances. They also have obvious differences in friction reduction properties. For example, liquid crystals used as lubricants are mainly nematic liquid crystals, that is, one-dimensional ordered phases, in which the long axes of the molecules are basically arranged in parallel in one direction. Common nematic liquid crystals are mostly rod-shaped structures and are easy to orient. During the friction process, polyimide is oriented, and the oriented polyimide macromolecules will induce the liquid crystal small molecules to orient themselves and produce orderly directional arrangement of rod-shaped molecules in the polyimide wear grooves, resulting in stable super-slip behavior of the friction system. Phenyl ester compounds or polyethylene glycol are generally isotropic organic liquid molecules. Their friction-reducing properties are highly correlated with the solvent-accessible surface area of ​​polar atoms in the molecules, such as O or P atoms. The larger the solvent-accessible surface area of ​​polar atoms, the better the friction-reducing performance. At the same time, the distribution area of ​​hydrophobic groups and hydrophilic groups in the molecules is also a key factor affecting the friction-reducing performance. Molecules with a large total hydrophobic surface area are conducive to friction reduction. Increasing the solvent-accessible surface area of ​​the maximum positive charge or reducing the number of positive charges can improve their friction-reducing performance. Smaller molecular volume and reducing hydrogen bond donors can also improve the friction-reducing performance of lubricant systems using this type of liquid molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the molecular structural formula of the PMDA-ODA type polyimide material used in the present invention;

[0015] Figure 2 The present invention is a graph showing the change of point-to-surface contact friction coefficient over time for Si3N4 / PI (PMDA-ODA) lubricated with dibutyl phthalate, tricresyl phosphate, triphenyl phosphite and polyethylene glycol 400 respectively;

[0016] Figure 3 This is a curve showing the change in friction coefficient of the system with speed and time under the Si3N4 / PI (PMDA-ODA) pairing when polyethylene glycol 400 is used as a lubricant during point-to-surface contact according to the present invention;

[0017] Figure 4 The figure is a graph showing the variation of the friction coefficient of the Si3N4 / PI (PMDA-ODA) pairing system with load and time when polyethylene glycol 400 is used as a lubricant during point-to-surface contact according to the present invention;

[0018] Figure 5 This is a curve diagram of the change in friction coefficient of the system over time under the Si3N4 / PI (PMDA-ODA) pairing when polyethylene glycol 400 is used as a lubricant in the present invention. DETAILED DESCRIPTION

[0019] The technical solutions of the present invention will be described clearly and completely below with reference to specific embodiments and accompanying drawings.

[0020] In the following examples, micro-friction tests were performed using a UTM-3 micro-friction tester (Bruker, Germany). During the test, a Si3N4 steel ball (4.76 mm in diameter) was used as a static specimen, and a PMDA-ODA polyimide material was attached to a fixed disk as a rotating disk specimen, rotating clockwise at a corresponding speed, with a radius of 8.5 mm on the annular friction path. The test load was applied vertically through the center line of the ball specimen, and the test was performed in a point-to-surface or surface-to-surface contact mode. A corresponding load was applied, and 0.1-0.2 mL of lubricant was dripped between the Si3N4 steel ball and the PMDA-ODA polyimide material, and the test was performed 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.

[0021] Example 1

[0022] Dibutyl phthalate (C 16 H 22 O4), tricresyl phosphate (C 21 H 21 O4P), triphenyl phosphite (C 18 H 15 O3P) and polyethylene glycol 400 (PEG400) were used as lubricants for the motion system under the Si3N4 / PI (PMDA-ODA) pair. The load was 5N and the speed was 250rpm. The tests were carried out on different friction pairs in a point-surface contact mode for 1 hour each. The change of the friction coefficient over time is shown in the figure below. Figure 2 As shown, 5N-C 16 H 22 O4-Si3N4 / PI(PMDA-ODA) / 250rpm, represents the change of friction coefficient over time under 5N load, dibutyl phthalate lubrication, Si3N4 / PI(PMDA-ODA) pair, 5N-C 21 H 21 O4P-Si3N4 / PI(PMDA-ODA) / 250rpm, 5N-C 18 H 15 O3P-Si3N4 / PI(PMDA-ODA) / 250rpm, etc., and so on.

[0023] The average friction coefficient of the process is recorded in Table 1. The friction systems using dibutyl phthalate, tricresyl phosphate, triphenyl phosphite and polyethylene glycol 400 as lubricants were all in a super-slip state during the test.

[0024] Table 1 Average friction coefficient of the system when Si3N4 / PI (PMDA-ODA) pairs are lubricated by different liquids

[0025]

[0026] Example 2

[0027] When the load is 5N, polyethylene glycol 400 is used as a lubricant and a number of cycles are tested on the friction pair in a point-to-surface contact mode. The initial speed is 50 rpm, and each cycle is tested for 3600 seconds. The speed is increased by 50 rpm each cycle until it reaches 400 rpm. The friction coefficient of the system with polyethylene glycol 400 as a lubricant changes with speed and time. Figure 3 The average friction coefficient of the process is recorded in Table 2.

[0028] The results show that when polyethylene glycol 400 is used for lubrication, when the speed increases from 50 rpm to 400 rpm, the friction coefficient of the system has no obvious relationship with the speed. Figure 3 It can be seen that the friction coefficient curve fluctuates little with increasing speed. At 50-400 rpm, the system's friction coefficient remains below 0.005, demonstrating excellent friction reduction. Therefore, this polymer can be used under high-speed conditions, meeting the requirements of an ideal lubricant with excellent friction reduction performance and good stability.

[0029] Table 2 Velocity and average friction coefficient of the system when polyethylene glycol 400 lubricates Si3N4 / PI (PMDA-ODA) pairing

[0030]

[0031] Example 3

[0032] Using polyethylene glycol 400 as a lubricant, the rotation speed was 250 rpm, and a number of cycles were tested on the friction pair in a point-to-surface contact mode. The initial load was 5 N, and each cycle was tested for 3600 seconds. The load was increased by 10 N with each subsequent cycle until the polyimide film broke. The friction coefficient of the system with polyethylene glycol 400 as a lubricant in point-to-surface contact was plotted as a function of load and time. Figure 4 The average friction coefficient of the process is recorded in Table 3.

[0033] Table 3 Load and average friction coefficient of the system when polyethylene glycol 400 lubricates Si3N4 / PI (PMDA-ODA) pairing

[0034]

[0035] Test results show that at 250 rpm, the friction coefficient of the polyethylene glycol 400-lubricated Si3N4 / PI friction pair system changes little, demonstrating a very stable friction-reducing effect. When a load of 5 N is applied, the system's friction coefficient reaches its minimum, 0.00524, and the system is in a stable super-lubricious state. As the load increases, the system's friction coefficient gradually increases. When loads of 25-45 N are applied, the friction coefficient changes little, stabilizing around 0.01, but the system is no longer in a super-lubricious state. The maximum load that the polyethylene glycol 400-lubricated Si3N4 / PI friction pair system can carry is 45 N, meaning that the polyimide film breaks at a load of 55 N.

[0036] Example 4

[0037] Before the friction test, a Si3N4 ceramic ball was mounted on a UTM-3 micro-tribometer as a static specimen. Metallographic sandpaper was attached to a fixed disc with double-sided tape to serve as the rotating disc specimen. The disc was then polished to a smooth circular surface without lubrication. After the Si3N4 ceramic ball was secured, it was first polished with 180-grit metallographic sandpaper at a load of 10N and a speed of 60 rpm for 8 minutes. The Si3N4 ceramic ball specimen was then rotated 90° clockwise, replaced with new 180-grit metallographic sandpaper, and polished under the same conditions. The Si3N4 ceramic ball specimen was then rotated 180° clockwise again, and the 180-grit metallographic sandpaper was replaced with 2000-grit metallographic sandpaper. The same polishing conditions were followed for 5 minutes. Finally, the Si3N4 ceramic ball specimen was rotated another 90° clockwise, replaced with new 2000-grit metallographic sandpaper, and polished under the same conditions for 5 minutes, resulting in a smaller Si3N4 surface with a diameter of approximately 1.5 mm. If the grinding time is extended (each grinding time is doubled based on the above grinding time), a larger Si3N4 plane with a diameter of about 2.5mm can be obtained. The obtained Si3N4 plane is matched with the PI plane for surface-to-surface contact tribology test: polyethylene glycol 400 is used as a lubricant, the load is 5N, the speed is 250rpm, and three cycles of 3600s each are tested. The friction coefficient of the system with polyethylene glycol 400 as a lubricant in point-to-surface contact or surface-to-surface contact is as follows: Figure 5 As shown, the average friction coefficient of the process is recorded in Table 4. Figure 55N-PEG400-Si3N4(point) / PI / 250rpm means the change of friction coefficient over time under point-surface contact of Si3N4 / PI (PMDA-ODA) pair with polyethylene glycol 400 as lubricant under 5N load; 5N-PEG400-Si3N4(flattened-1.5mm) / PI / 250rpm and 5N-PEG400-Si3N4(flattened-2.5mm) / PI / 250rpm mean the change of friction coefficient over time under surface-surface contact of Si3N4 / PI (PMDA-ODA) pair with polyethylene glycol 400 as lubricant under 5N load, when the Si3N4 plane diameter is 1.5mm or 2.5mm respectively.

[0038] Table 4 Friction coefficient of the system when polyethylene glycol 400 lubricates Si3N4 / PI (PMDA-ODA) pairing

[0039]

[0040] Tests found that when lubricated with polyethylene glycol 400, the Si3N4 / PI (PMDA-ODA) pairing system exhibited stable superlubricity in point-to-surface contact or surface-to-surface contact with different contact areas. The occurrence of superlubricity was independent of the contact mode and area.

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. Application of phenyl ester compounds or polyethylene glycol in ultra-low friction systems, characterized in that: Using phenyl ester compounds or polyethylene glycol as lubricants and silicon nitride / polyimide as friction pairs to form an ultra-low friction system; The phenyl ester compound is a phenyl diester compound or a phosphorus-containing phenyl triester compound.

2. Use of the phenyl ester compound or polyethylene glycol according to claim 1 in an ultra-low friction system, characterized in that: The phenyl ester compound is selected from any one of dibutyl phthalate, tricresyl phosphate or triphenyl phosphite.

3. Use of the phenyl ester compound or polyethylene glycol according to claim 1 in an ultra-low friction system, characterized in that: The polyimide is a PMDA-ODA type polyimide material, which is prepared by polymerizing pyromellitic dianhydride and 4,4'-diaminodiphenyl ether.

4. An ultra-low friction system, characterized in that: Phenyl diester compounds, phosphorus-containing phenyl triester compounds or polyethylene glycol are used as lubricants, and silicon nitride / polyimide is used as friction pairs.

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