A method for synergistic lubrication and friction reduction of liquid crystal alignment agent and running surface

Abstract

This invention discloses a method for synergistic lubrication and friction reduction of liquid crystal alignment agents and running surfaces, belonging to the field of running-in lubrication technology. This invention reduces the friction coefficient of the friction pair by adding an alignment agent to the liquid crystal, under the synergistic effect of the running surface. Adding a parallel alignment agent alters the orientation of the liquid crystal molecules, achieving parallel alignment of the liquid crystal molecules relative to the friction surface. This structure gives the liquid crystal higher load-bearing capacity and lower shear resistance, effectively reducing frictional resistance and the friction coefficient during the friction process. After running-in, grooves are generated on the friction surface, and friction forces the liquid crystal molecules to align along the groove direction, further enhancing the alignment effect of the liquid crystal molecules. Simultaneously, the generated grooves form a textured surface, and the running surface itself also plays a role in lubrication and friction reduction. The generated grooves can store lubricating oil and, based on cavitation and hydrodynamic effects, can increase the load-bearing capacity of the lubricating film and improve the lubrication effect.

Description

Technical Field

[0001] This invention belongs to the field of break-in lubrication technology, specifically relating to a method for synergistic lubrication and friction reduction of liquid crystal alignment agent and break-in surface. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Friction exists in any moving system; it is an unavoidable natural phenomenon, and wear caused by friction is a major cause of machine part failure. Improving the anti-wear properties of lubricants is a primary way to extend the life of mechanical parts. Lubrication is an important means of reducing the coefficient of friction and improving anti-wear performance. Currently, the main method of lubrication technology is to add lubricant to the friction interface. The lubrication performance of the base lubricant plays a decisive role in lubrication; therefore, selecting a suitable base lubricant is crucial.

[0004] Liquid crystal alignment technology enables liquid crystal molecules to form a neat arrangement on a relative surface, exhibiting optimal alignment angles and sufficient stability, demonstrating long-range order. This structure gives liquid crystals higher load-bearing capacity and lower shear resistance, effectively reducing friction and wear in friction pairs. Simultaneously, liquid crystals do not contain harmful substances such as organic solvents, making them non-toxic, odorless, and pollution-free green lubricants, harmless to the environment and human health. Liquid crystal lubrication is a promising new lubrication technology; however, in actual production, its research and application still face some challenges and limitations. For example, the coating process of the liquid crystal alignment layer is relatively complex, and factors such as coating thickness, pre-baking temperature and time, curing time, and friction intensity all affect the alignment effect. While directly using liquid crystals as a lubricant can achieve a lower coefficient of friction than traditional lubricants, the improvement is not significant. This is because the shear resistance between liquid crystal molecules is affected by molecular orientation, and directly using liquid crystals as a lubricant does not consider the control of liquid crystal molecule orientation. Currently, controlling liquid crystal alignment is mostly applied in the optical field, rarely in lubrication and friction reduction. Therefore, it is necessary to comprehensively utilize multiple lubrication methods to overcome the limitations of using liquid crystal lubrication alone, in order to achieve better lubrication and friction reduction effects. This invention is proposed for this purpose. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for synergistic lubrication and friction reduction of liquid crystal alignment agents and mating surfaces. This invention involves adding a parallel alignment agent to liquid crystal to obtain a liquid crystal lubricant, which, under the synergistic effect of the mating surfaces, reduces the friction coefficient of the friction pair.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for synergistic lubrication and friction reduction of a liquid crystal alignment agent and a running surface, comprising: dripping a liquid crystal lubricant containing an alignment agent onto the running surface, wherein the alignment agent and the running textured surface work synergistically to reduce the coefficient of friction of the friction pair.

[0008] Liquid crystal alignment technology enables liquid crystal molecules to form a neat arrangement on a relative surface, exhibiting optimal alignment angles and sufficient stability, thus demonstrating long-range order. This structure gives liquid crystals higher load-bearing capacity and lower shear resistance, effectively reducing friction and wear in friction pairs. Furthermore, liquid crystals do not contain harmful substances such as organic solvents, making them non-toxic, odorless, and pollution-free green lubricating materials, harmless to the environment and human health. However, liquid crystal lubrication, as a novel lubrication technology, is still in the research stage, with a lack of relevant data accumulation and research.

[0009] Friction surface pretreatment technology is a surface treatment method that can improve the wear resistance of mechanical systems and reduce the coefficient of friction. On the one hand, surface pretreatment can reduce the roughness of friction surfaces, improve surface quality and friction performance, and, in conjunction with the application of lubricants, enhance the ability of friction surfaces to retain lubricating oil, forming a more robust and stable friction interface, thereby reducing friction loss and energy consumption in mechanical systems. On the other hand, surface pretreatment can remove oxide layers and impurities from friction surfaces, providing certain anti-corrosion and anti-oxidation functions, thus extending the service life of mechanical systems.

[0010] Therefore, this invention combines the liquid crystal alignment agent with the running surface to further improve the friction reduction performance of liquid crystal lubrication.

[0011] In some embodiments of the present invention, the method includes the following steps:

[0012] S1: Add the parallel alignment agent to the liquid crystal and disperse it fully to obtain a liquid crystal lubricant containing the alignment agent;

[0013] S2: Clean and dry the surfaces of the friction pair, then drop the running agent onto the friction surfaces for running-in treatment; after running-in, clean and dry the surfaces of the friction pair again; the running agent is a diamond suspension with a particle size of W2.5;

[0014] S3: Add the liquid crystal lubricant containing the alignment agent described in S1 between the friction pairs after break-in, so that it evenly covers the friction area.

[0015] In some embodiments of the present invention, the parallel orientation agent includes, but is not limited to, polyvinyl alcohol (PVA), trixton-100 (with the structural formula C6H9N3O), and dicarboxylic acids (e.g., HOOC(CH2)). nCOOH, n = 3-12) or crown ether (general structural formula C) n H 2n +2O2 (n≥3)). The parallel alignment agents used in this invention are all conventional commercially available products.

[0016] In some embodiments of the present invention, the dicarboxylic acid includes, but is not limited to, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, or sebacic acid (SA).

[0017] In some embodiments of the present invention, the liquid crystal is a pure liquid crystal or a lubricant containing liquid crystal; the pure liquid crystal includes alkyl biphenyl cyanide liquid crystals or alkoxy biphenyl cyanide liquid crystals. All liquid crystals used in the present invention are conventional commercially available products.

[0018] In some embodiments of the present invention, the pure liquid crystal may be selected as 4-n-pentyl-4'-cyanobiphenyl, with the molecular formula C 18 H 19 N, abbreviated as 5CB.

[0019] In some embodiments of the present invention, the concentration of the parallel alignment agent in the liquid crystal lubricant containing the alignment agent is 2.5-15 wt.%, preferably 5-10 wt.%.

[0020] In some embodiments of the present invention, in step S1, the parallel orientation agent is fully dispersed by mechanical stirring and water bath ultrasonication;

[0021] Preferably, the water bath ultrasonic temperature is 20-50℃ and the ultrasonic time is 15-60min.

[0022] In some embodiments of the present invention, in step S2, alcohol and / or acetone are used to clean the surfaces of the friction pair to remove any residues on the friction surfaces.

[0023] In some embodiments of the present invention, in step S2, the running-in process is as follows: an appropriate amount of diamond suspension is added to the friction surface, and running-in is performed according to the actual working load and speed of the friction pair. Then, the machine is stopped and unloaded, and the moving and stationary parts are separated.

[0024] In some embodiments of the present invention, in step S2, during the break-in process, diamond suspension is appropriately replenished to avoid a dry friction state where the diamond suspension is depleted.

[0025] In some embodiments of the present invention, in step S3, the relative angle between the running surfaces is changed after running-in, and the liquid crystal lubricant is uniformly covered in the friction area. Then, running-in is carried out according to the actual working load and speed of the friction pair to obtain a lower coefficient of friction.

[0026] The angle is 60°.

[0027] The present invention unexpectedly discovered that by changing the relative angle between the running surfaces, that is, by deflecting the position of the upper friction surface relative to the lower friction surface, a lower coefficient of friction can be obtained, which greatly improves the lubrication effect of liquid crystal with added orientation agent.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention utilizes the synergistic effect of a liquid crystal alignment agent and a mating surface to reduce the friction coefficient of liquid crystal lubrication. This method involves adding an alignment agent to the liquid crystal, which, under the synergistic effect of the mating surface, reduces the friction coefficient of the friction pair. On one hand, the addition of a parallel alignment agent alters the orientation of the liquid crystal molecules, achieving a parallel alignment of the liquid crystal molecules relative to the friction surface. This structure gives the liquid crystal higher load-bearing capacity and lower shear resistance, effectively reducing frictional resistance and the friction coefficient during the friction process. On the other hand, the friction surface after mating generates grooves, and friction forces the liquid crystal molecules to align along the groove direction, further enhancing the alignment effect of the liquid crystal molecules. Simultaneously, the generated grooves form a textured surface, and the mating surface itself also plays a role in lubrication and friction reduction. The generated grooves can store lubricating oil and, based on cavitation and hydrodynamic effects, can increase the load-bearing capacity of the lubricating film and improve the lubrication effect. Therefore, the liquid crystal alignment agent and the mating surface can work synergistically to improve the friction-reducing effect of liquid crystal lubrication. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 A schematic diagram of liquid crystal molecule orientation, i.e., surface anchoring types: where a is random planar anchoring, b is uniform planar anchoring, c is vertical anchoring, and d is inclined anchoring;

[0032] Figure 2 This is a schematic diagram illustrating how liquid crystal alignment agents induce the orientation of liquid crystal molecules.

[0033] Figure 3 This is a schematic diagram of the deflection of the friction pair after the break-in period;

[0034] Figure 4 A schematic diagram illustrating how the grooves created by friction induce the orientation of liquid crystal molecules.

[0035] Figure 5 The graphs show the coefficient of friction versus time when the liquid crystal lubricant containing 5 wt.% sebacic acid (SA), a parallel alignment agent, is used after the break-in period when the liquid crystal is deflected at 0°, 30°, 45°, 60°, and 90° respectively. The horizontal axis represents time, and the vertical axis represents the coefficient of friction.

[0036] Figure 6 The graph shows the coefficient of friction versus time when the object is deflected at 0°, 30°, 45°, 60°, and 90° after break-in, and then lubricated with liquid crystal lubricant without orientation agent. The horizontal axis represents time, and the vertical axis represents the coefficient of friction.

[0037] Figure 7 This is the three-dimensional morphology of the friction ball after a 0° deflection and friction test using 5CB + 5wt.%SA lubrication following the break-in period in Example 2.

[0038] Figure 8 This is the three-dimensional morphology of the friction ball after a 60° deflection and lubrication test using 5CB + 5wt.%SA lubricant following the break-in period in Example 5;

[0039] Figure 9 Curves showing the change in friction coefficient over time when pure 5CB and W2.5 diamond suspensions are run-in and deflected 60° on silicon nitride ceramics using 5CB and 5CB+5wt.%SA; the horizontal axis represents time and the vertical axis represents friction coefficient. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] For different deflection angles after break-in, the coefficient of friction was measured. The specific measurement method is as follows:

[0042] The coefficient of friction was determined using a tribological testing machine (THT, Anton Paar). The instrument was calibrated before measurement, and all deflection tests were repeated to ensure data stability. Measurement conditions were 23-25℃ and 40%-55%RH. In this example, the metal friction pair consisted of a 6mm diameter bearing steel ball and a bearing steel flat surface. After break-in, 1mL of lubricant was added, and the load between the ball and the flat surface was 3N. The ball slid on the flat surface at a speed of 0.63m / s (300r / min, rotation radius 20mm), and the total test time was 900 seconds (15 minutes).

[0043] The liquid crystal used in the following examples is 4-cyano-4'-pentylbiphenyl, with the molecular formula C2. 18 H 19 N, abbreviated as 5CB, is a commercially available product that can be purchased independently.

[0044] Example 1: Preparation of Diamond Suspension

[0045] Diamond grinding paste with a particle size of W2.5 (diamond content of 20 wt.%) and deionized water were mixed at a mass ratio of 1:1, mechanically stirred and subjected to water bath ultrasonication to obtain a diamond suspension containing 10 wt.% diamond.

[0046] If necessary, add an appropriate amount of dispersant to increase the stability and dispersibility of diamond particles in water.

[0047] The diamond particle size in the above embodiments corresponds to a particle size of 1-3 μm.

[0048] Example 2: Preparation of a liquid crystal lubricant containing a specific concentration of alignment agent

[0049] 0.25 g of sebacic acid (SA), a parallel alignment agent, was added to 4.75 g of liquid crystal. The mixture was mechanically stirred and subjected to ultrasonication in a water bath to fully disperse the liquid crystal alignment agent, resulting in a liquid crystal lubricant with an alignment agent concentration of 5 wt.%. The ultrasonication temperature in the water bath was 20-50℃, and the ultrasonication time was 15 min.

[0050] Example 3: Application of 5CB + 5wt.%SA as a lubricant when the deflection reaches 0° after break-in.

[0051] Step 1: The friction surfaces of the metal friction pair are ultrasonically cleaned with alcohol and acetone in a water bath and then dried to remove residues. 1 mL of a 10 wt.% diamond suspension (prepared in Example 1) with a particle size of W2.5 is added dropwise to the friction surface, and the surface is run-in for 60 seconds. Due to the poor adsorption of the diamond suspension, it needs to be replenished in a timely manner according to the running-in time to avoid dry friction. The replenishment amount is 1 mL each time. The friction surfaces are then cleaned after running-in to remove any remaining residues. The machine is then stopped, the components are unloaded, and the moving and stationary parts are separated.

[0052] Step 2: Add 1 mL of 5CB + 5 wt.% SA lubricant (i.e., the liquid crystal lubricant containing SA prepared in Example 2) dropwise between the friction pairs after break-in, so that the lubricant is evenly covered in the friction area.

[0053] The host is started, and the friction pair begins to work. The coefficient of friction after stabilization is 0.086.

[0054] Step 3: After the friction experiment, the lubricant residue on the friction ball was first cleaned with anhydrous ethanol, then ultrasonically cleaned in alcohol and acetone solutions respectively, and then dried. The three-dimensional morphology of the dried friction ball was characterized by a white light vertical scanning interferometer.

[0055] In contrast, the coefficient of friction for liquid crystal lubricant without an alignment agent is 0.109 under the same conditions.

[0056] Example 4: Application of 5CB + 5wt.% SA as a lubricant when deflecting at 30° after break-in.

[0057] As described in Example 2, the difference is: Step 2: Deflect the position of the upper friction surface relative to the lower friction surface so that the relative angle between the friction surfaces is 30°, and then add 1 mL of 5CB + 5wt.% SA lubricant (i.e., the liquid crystal lubricant containing SA prepared in Example 2).

[0058] The host is started, and the friction pair begins to work. The coefficient of friction after stabilization is 0.122.

[0059] In contrast, the coefficient of friction for liquid crystal lubricant without an alignment agent is 0.103 under the same conditions.

[0060] Example 5: Application of 5CB + 5wt.%SA as a lubricant when deflecting at 45° after break-in.

[0061] As described in Example 2, the difference is: Step 2: Deflect the position of the upper friction surface relative to the lower friction surface so that the relative angle between the friction surfaces is 45°, and then add 1 mL of 5CB + 5wt.% SA lubricant (i.e., the liquid crystal lubricant containing SA prepared in Example 2).

[0062] The host is started, and the friction pair begins to work. The coefficient of friction after stabilization is 0.107.

[0063] In contrast, the coefficient of friction for liquid crystal lubricant without an alignment agent is 0.083 under the same conditions.

[0064] Example 6: Application of 5CB + 5wt.%SA as a lubricant when deflecting at 60° after break-in.

[0065] As described in Example 2, the difference is: Step 2: Deflect the position of the upper friction surface relative to the lower friction surface so that the relative angle between the friction surfaces is 60°, and then add 1 mL of 5CB + 5wt.% SA lubricant (i.e., the liquid crystal lubricant containing SA prepared in Example 2).

[0066] The host is started, and the friction pair begins to work. The coefficient of friction after stabilization is 0.040.

[0067] In contrast, the coefficient of friction for liquid crystal lubricant without an alignment agent is 0.100 under the same conditions.

[0068] Example 7: Application of 5CB + 5wt.%SA as a lubricant when deflecting 90° after break-in.

[0069] As described in Example 2, the difference is: Step 2: Deflect the position of the upper friction surface relative to the lower friction surface so that the relative angle between the friction surfaces is 90°, and then add 1 mL of 5CB + 5wt.% SA lubricant (i.e., the liquid crystal lubricant containing SA prepared in Example 2).

[0070] The host is started, and the friction pair begins to work. The coefficient of friction after stabilization is 0.129.

[0071] In contrast, the coefficient of friction for liquid crystal lubricant without an alignment agent is 0.117 under the same conditions.

[0072] Example 8: Application of 5CB + 5wt.%SA on silicon nitride ceramics after 60° deflection following break-in.

[0073] As described in Example 5, the difference is that in step 1, the metal friction pair material is changed from bearing steel to silicon nitride ceramic friction pair.

[0074] The host machine is started, and the friction pair begins to operate. The stable coefficient of friction is 0.017. Figure 9 ).

[0075] In comparison, the coefficients of friction for the lubricant in pure 5CB under conditions of no break-in and after break-in with a deflection of 60° were 0.052 and 0.046, respectively. Figure 9 ).

[0076] Examples 3-8 revealed that the friction direction has a significant impact on liquid crystal lubrication, with a friction-reducing effect only observed at specific angles (0° and 60°). This can be explained by the fact that the lower coefficient of friction without the alignment agent (i.e., the friction results in Examples 4, 5, and 7) indicates that the running-in process itself provides friction reduction. Adding the alignment agent disrupts this effect, reducing friction reduction and increasing the coefficient of friction. However, the alignment agent produces a synergistic lubrication effect when rubbing at 60°, with the best results observed, while no synergistic effect is observed in other directions.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synergistic lubrication and friction reduction of a liquid crystal alignment agent and a running surface, characterized in that, include: A liquid crystal lubricant containing an orientation agent is dropped onto the running surface. The orientation agent and the running textured surface work synergistically to reduce the friction coefficient of the friction pair. The method includes the following steps: S1: Add the parallel alignment agent to the liquid crystal and disperse it fully to obtain a liquid crystal lubricant containing the alignment agent; S2: Clean and dry the surfaces of the friction pair, then drop the running agent onto the friction surfaces for running-in treatment; after running-in, clean and dry the surfaces of the friction pair again; the running agent is a diamond suspension with a particle size of W2.5; S3: Add the liquid crystal lubricant containing the alignment agent described in S1 between the friction pairs after break-in, so that it evenly covers the friction area; In step S3, after running-in, the relative angle between the running surfaces is changed, and liquid crystal lubricant is uniformly covered in the friction area. Then, running-in is carried out according to the actual working load and speed of the friction pair to obtain a lower coefficient of friction. The angle is 60°.

2. The method as described in claim 1, characterized in that, The parallel alignment agent includes polyvinyl alcohol and Trixton.

100. Dicarboxylic acid or crown ether; The liquid crystal is a pure liquid crystal or a lubricant containing liquid crystal; the pure liquid crystal includes alkyl biphenyl cyanide liquid crystal or alkoxy biphenyl cyanide liquid crystal.

3. The method as described in claim 2, characterized in that, The parallel alignment agent is sebacic acid; The pure liquid crystal is 4-n-pentyl-4-cyanobiphenyl.

4. The method as described in claim 1, characterized in that, In the liquid crystal lubricant containing the alignment agent, the concentration of the parallel alignment agent is 2.5-15 wt.%.

5. The method as described in claim 4, characterized in that, The concentration of the parallel alignment agent is 5-10 wt.%.

6. The method as described in claim 1, characterized in that, In step S1, the mixture is fully dispersed by mechanical stirring and ultrasonic bath in a water bath.

7. The method as described in claim 6, characterized in that, The water bath ultrasonic temperature is 20-50℃, and the ultrasonic time is 15-60 min.

8. The method as described in claim 1, characterized in that, In step S2, alcohol and / or acetone are used to clean the surfaces of the friction pair.

9. The method as described in claim 1, characterized in that, In step S2, the running-in process is as follows: an appropriate amount of diamond suspension is added to the friction surface, and the running-in is carried out according to the actual working load and speed of the friction pair. Then, the machine is stopped and the unloaded, and the moving and stationary parts are separated.

10. The method as described in claim 1, characterized in that, In step S2, during the break-in process, diamond suspension is appropriately replenished to avoid a dry friction state where the diamond suspension is depleted.

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