Long-acting lubrication-corrosion integrated coating based on friction-induced piezoelectric effect and preparation method

Abstract

The application discloses a long-acting lubrication-corrosion integrated coating based on a friction-induced piezoelectric effect and a preparation method, and solves the bottleneck problem that the existing bonded solid lubricating coating is accelerated to deteriorate in tribological performance under a salt spray corrosion environment and is insufficient in long-acting service life. The specific technical scheme is as follows: polyamide-imide (PAI) is used as a matrix to construct a polyamide-imide / polyvinylidene fluoride (PVDF) binary composite resin matrix, and barium titanate (BTO) piezoelectric nanoparticles and graphene which are surface-modified by a silane coupling agent are doped, and polytetrafluoroethylene (PTFE) microparticles are added. Through mechanical energy-electric energy conversion effect in a friction process, the BTO / PVDF composite phase generates a piezoelectric potential under the action of a contact stress, and a three-dimensional electric field network is formed in the coating, the electric field produces a directional repulsion effect on negative charged corrosion ions such as Cl⁻, and penetration of a corrosion medium is delayed.

Description

Technical Field

[0001] This invention belongs to the field of functional coating materials technology, specifically relating to a long-lasting lubrication-corrosion integrated coating based on the friction-induced piezoelectric effect and its preparation method, which is suitable for the surface protection and lubrication functions of mechanical parts in corrosive environments. Background Technology

[0002] Traditional solid lubricant coatings (such as those containing molybdenum disulfide or polytetrafluoroethylene) typically have a thickness not exceeding 30 μm to balance lubrication performance and load-bearing capacity. Due to this limited thickness, their ability to isolate corrosive media, especially Cl, is insufficient. - Small corrosive ions (atomic radius approximately 0.181 nm) can easily penetrate coatings, initiating corrosion. ASTM G119-09, "Standard Guide for Determining Synergism Between Wear and Corrosion," clearly states that frictional behavior in corrosive media poses a more severe challenge to solid lubricating coatings. The coupled damage from corrosion and friction is greater than the simple sum of corrosion and wear, leading to a significant reduction in coating lifespan. To improve the service life of solid lubricating coatings in corrosive media, current coating design and preparation mainly focus on the following aspects: First, improving the density of the coating material (CN112521836B, CN202411220714.3) to achieve physical isolation from corrosive media; second, adding corrosion inhibitors to the coating (CN202410601066.X, CN202211506367.1), releasing the corrosion inhibitors through frictional motion, thereby delaying the erosion of the metal substrate by corrosive media; and third, preparing superhydrophobic coating materials (CN109232964B), utilizing the low surface energy of the material interface to block the penetration of corrosive media. Although the above methods can improve the performance and service life of coatings to a certain extent, they still have significant limitations. Improving the density of the coating not only requires high-quality materials but also high-performance processes; corrosion inhibitor doping suffers from strong targeting and poor controllability of slow release; while superhydrophobic coatings can achieve high contact angle surface characteristics, it is difficult to simultaneously achieve high mechanical strength and tribological properties. Furthermore, most of the above methods are limited by equipment, and friction tests and salt spray tests are conducted independently, without verifying their actual performance under corrosion-friction coupling conditions. Therefore, considering practical applications, it is necessary to develop a coating and its preparation method that combine corrosion protection and lubrication functions under corrosion-friction coupling conditions. Summary of the Invention

[0003] Therefore, the application aims to provide a long-acting lubrication-corrosion integrated coating based on friction-induced piezoelectric effect and a preparation method thereof. - By constructing a composite lubricating coating containing piezoelectric materials, the piezoelectric electric field generated in the friction process is used to actively repel Cl

[0004] I. Preparation of long-acting lubrication-corrosion integrated coating based on friction-induced piezoelectric effect

[0005] 1) Surface modification of barium titanate nanoparticles: add silane coupling agent into a mixed solvent of anhydrous ethanol and deionized water, adjust the pH value to 4.0-4.5 by adding glacial acetic acid dropwise, then add barium titanate nanoparticles, heat at 60-70°C and stir for 2-3h, centrifugal wash multiple times after the reaction is completed, vacuum dry the barium titanate precipitate, and obtain surface-modified barium titanate nanoparticles. Fourier infrared spectrum test is performed on the modified barium titanate, and the spectrum is as shown in Figure 1 -1 , 2860cm -1 , 1080cm -1 , 553cm -1 respectively correspond to O-H stretching vibration peak, C-H stretching vibration peak, Si-O-Ba vibration peak, Ti-O stretching vibration peak, and the appearance of the above group peaks indicates that the surface barium titanate modification is successful;

[0006] The silane coupling agent is KH560, and the amount of silane coupling agent is 4.0-6.0% of the mass of barium titanate nanoparticles;

[0007] The mass ratio of anhydrous ethanol to deionized water is 8:1-10:1;

[0008] 2) Preparation of coating: add the surface-modified barium titanate nanoparticles obtained in step 1) and PVDF resin into an agate mortar, grind until the particle size of barium titanate and PVDF resin is less than 2μm, then add graphene and a dispersing agent and grind until they are uniformly mixed; then blend the obtained BTO / PVDF / graphene mixed particles together with PAI and PTFE resin particles in an organic solvent, shear and disperse uniformly to obtain the required coating;

[0009] The organic solvent is at least one of N-methyl pyrrolidone or N-N dimethylacetamide; the dispersing agent is BYK-192 wetting dispersing agent;

[0010] ​The main component content in the coating is PAI 30.0wt%-40.0wt%, PVDF 20.0wt%-30.0wt%, surface modification BTO 0.5wt%-1.0wt%, PTFE 5.0wt%-10.0wt%, graphene 0.1wt%-0.5wt%;

[0011] 3) Preparation of the coating: the coating obtained in step 2) is coated on the conductive metal substrate by spraying, dripping, spin coating or scraping, and then placed in the middle of a parallel plate capacitor after curing, and polarized by applying an electric field until the absolute value of the coating in the quasi-static d33 / d31 measuring instrument is greater than or equal to 0.5.

[0012] The coating curing process is 150 DEG C for 2h, 250 DEG C for 1h, and the prepared coating thickness is 10-30mu m;

[0013] The internal electric field strength of the parallel plate capacitor is set to 6-7kV / mm, and the sample polarization time is 25-30min.

[0014] The application constructs a friction-induced piezoelectric lubricating coating, generates an internal normal electric field in the coating during friction, repels the negative ions (such as Cl-) in the corrosion medium under the action of the electric field force, delays the penetration of the corrosion medium into the coating, reduces the performance degradation of the coating caused by the penetration of the corrosion medium, and prolongs the time for the corrosion medium to reach the metal substrate; on the other hand, the external direction electric field generated by friction makes the cations generated by corrosion at the coating / substrate interface diffuse under the resistance of the electric field, so that the cations accumulate at the interface, thereby inhibiting the occurrence of the corrosion reaction and prolonging the service life of the coating, and the mechanism is as shown in the figure. Figure 2 Based on the above idea, the application constructs a high-toughness hydrophobic material system based on a polyamide-imide (PAI) / polyvinylidene fluoride (PVDF) binary composite resin matrix, modifies the surface of barium titanate (BTO) piezoelectric nanoparticles by a silane coupling agent, reduces the agglomeration ratio of the nanoparticles, and improves the dispersibility of BTO in the coating; the doping of BTO enhances the generation of beta phase in the PVDF material, and enhances the piezoelectric effect of the coating; by adding a small amount of graphene sheet, the graphene, BTO and PVDF form a three-dimensional electric field network in the coating, further enhancing the piezoelectric effect of the coating; by adding polytetrafluoroethylene (PTFE) microparticles, the porosity of the coating is enhanced and the friction coefficient of the coating is greatly reduced.

[0015] II. Performance of long-acting lubrication-corrosion integrated coating based on friction-induced piezoelectric effect

[0016] Salt fog atmosphere friction and wear test: the test completed sample is clamped to the salt fog atmosphere friction and wear tester, the salt fog concentration is adjusted to 85%RH, the friction tester conditions are load 5N, reciprocating frequency 5Hz, full amplitude 5mm, the test time is 2h, and the test result is as shown in Table 1. Figure 4 As shown in Table 1, the friction coefficient is still not greater than 0.14 after 4 hours of salt fog friction test, the friction coefficient is smaller than that of the same type of lubricating coating, and the coating service life is greater than that of the same type of lubricating coating.

[0017] In summary, the present application constructs a composite lubricating coating containing piezoelectric material, actively repels negative charged corrosion medium such as Cl- by using the piezoelectric electric field generated in the friction process, and realizes the lubrication and corrosion prevention synergistic protection from passive isolation to dynamic electric field defense. The coating uses polyamide-imide (PAI) / polyvinylidene fluoride (PVDF) as a binary composite matrix, so that the resin phase of the coating has strong toughness and hydrophobicity, piezoelectric properties; and is doped with barium titanate (BTO) piezoelectric nanoparticles and graphene modified by a silane coupling agent on the surface, so as to enhance the piezoelectric effect and carrying capacity of the coating; by adding micron-sized polytetrafluoroethylene particles, the lubricating performance and hydrophobicity of the coating are further enhanced. By using the mechanical energy-electric energy conversion effect in the friction process, the BTO / PVDF composite phase generates a piezoelectric potential under the action of contact stress, forming a three-dimensional electric field network inside the coating. The electric field produces directional repulsion effect on negative charged corrosion ions such as Cl-, delays the penetration rate of the medium, suppresses the degradation rate of the lubricating coating, and prolongs the service life of the solid lubricating coating. The technical innovation from "passive isolation" to "active defense" is realized, and a new idea is provided for the design and preparation of lubrication and corrosion prevention integrated coating. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The Fourier infrared spectrum of the modified barium titanate nanoparticles of the present application is shown.

[0019] Figure 2 The lubrication mechanism diagram for preparing the coating of the present application is shown.

[0020] Figure 3 The polarization diagram for preparing the coating of the present application is shown.

[0021] Figure 4 The change rule diagram of the friction coefficient of the coating prepared in the present application in the salt fog friction tester test for 4h is shown. DETAILED DESCRIPTION

[0022] The preparation method and performance of the present application are further described below through specific examples.

[0023] Example 1

[0024] 1. Material preparation

[0025] Resin: Polyamide-imide (PAI), non-volatile content 23.4%; Polyvinylidene fluoride (PVDF), non-volatile content 20%;

[0026] Filler: BaTiO3 nanoparticles, particle size 200 nm; Polytetrafluoroethylene (PTFE) particles, particle size 2 μm; Graphene, flake size 8-20 μm, 5-10 layers;

[0027] Solvent: N-methyl pyrrolidone (NMP), analytical pure, purity 99%; N-N dimethylacetamide (DMAc), analytical pure, purity 99%;

[0028] Auxiliary agent: Germany BYK-192 wetting dispersant.

[0029] 2. Synthesis of the coating

[0030] 1) Take 18 g of anhydrous ethanol and 2 g of deionized water, add to a three-necked flask, drop in glacial acetic acid to adjust the pH value to 4.5; add 0.5 g of silane coupling agent KH560, stir uniformly; add 10 g of nano-barium titanate (particle size 100 nm) particles, heat at 60°C and stir for 2 h; after the reaction is completed, the barium titanate nanoparticles are centrifuged at a speed of 10000 rpm / min for 2 min; remove the supernatant of the barium titanate, add 20 mL of anhydrous ethanol, stir uniformly, and centrifuge again, and repeat this process three times; put the barium titanate precipitate into a vacuum oven, and keep it at 100°C for 6 h;

[0031] 2) Take the dried BTO 0.45 g, PVDF 12.50 g to a mortar, grind for 20 min, until the particle size is less than 2 μm; add graphene 0.05 g and BYK-192 dispersant 0.010 g, grind for 10 min; add PAI 17.09 g, PTFE 3.00 g, DMAc 8.45 g, NMP 8.45 g, high-speed shear dispersion 8000 rpm / min, for 5 min, the coating synthesis is completed.

[0032] 3. Preparation of the coating

[0033] Take 304 stainless steel test pieces, sandblast the surface, and clean with acetone. Use the coating process method to spray the coating on the 304 stainless steel test pieces, the spraying pressure is 0.15 MPa, use the method of a small amount of multiple times, the coating thickness is 20 μm. After spraying is completed, put the test pieces into a high-temperature oven for curing, keep it at 150°C for two hours and then at 250°C for one hour;

[0034] Polarize the cured coating, the positive electrode of the direct current power supply is connected to the metal matrix of the test piece, the negative electrode is connected to a metal plate, the metal plate is placed parallel to the surface of the coating, and the metal matrix and the metal plate form a parallel-plate capacitor, as shown inFigure 3 The direct current power voltage was adjusted to 0.12 kV, and maintained for 30 min;

[0035] Finally, the sample polarized by the electric field was placed on a quasi-static d33 / d31 measuring instrument, the gear selection was d33, the metal substrate was in contact with the lower end of the holding clamp, the coating was in contact with the upper end of the holding clamp, the measuring instrument was turned on for testing, and the test result was -0.8 pC / N.

[0036] 4. Salt spray corrosion friction test

[0037] Salt spray atmosphere friction and wear test: the tested sample was clamped to a salt spray atmosphere friction and wear tester, the salt spray concentration was adjusted to 85% RH, the friction tester conditions were a load of 5 N, a reciprocating frequency of 5 Hz, a full amplitude of 5 mm, the test duration was 2 h, the friction coefficient after 4 h of salt spray friction test was still not greater than 0.14, and the test result is shown in Figure 4 . Figure 4 Friction tests of different PAI-based bonded solid lubricating coatings in a salt spray atmosphere, wherein the blue curve is a PAI / MoS2 coating, the red curve is a PAI / graphite coating, and the green curve is a PAI / polytetrafluoroethylene coating. It can be seen from the comparison of the friction coefficient and the coating life that the coating has stable performance, the friction coefficient is smaller than that of similar lubricating coatings, and the coating life is higher than that of similar lubricating coatings.

Claims

1. A method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect, characterized in that, Includes the following steps: 1) Surface modification of barium titanate nanoparticles: Add silane coupling agent to a mixed solvent of anhydrous ethanol and deionized water, and adjust the pH value to 4.0~4.5 by adding glacial acetic acid dropwise; then add barium titanate nanoparticles, heat at 60~70℃ and stir for 2~3 hours. After the reaction is completed, centrifuge and wash several times, and vacuum dry the barium titanate precipitate to obtain surface-modified barium titanate nanoparticles. 2) Coating preparation: The surface-modified barium titanate nanoparticles obtained in step 1) and PVDF resin are added to a mortar and ground until the particle size of barium titanate and PVDF resin is less than 2 μm. Then, graphene and dispersant are added and ground to mix evenly. The resulting BTO / PVDF / graphene mixed particles, together with PAI and PTFE resin particles, are mixed in an organic solvent and sheared and dispersed evenly to obtain the desired coating. The main components of the coating are PAI 30.0wt%-40.0wt%, PVDF 20.0wt%-30.0wt%, surface-modified barium titanate nanoparticles 0.5wt%-1.0wt%, PTFE 5.0wt%-10.0wt%, and graphene 0.1wt%-0.5wt%. 3) Coating preparation: The coating obtained in step 2) is applied to the conductive metal substrate by spraying, dripping, spinning or scraping. After curing, it is placed in the middle of the parallel plate capacitor and polarized by applying an electric field until the absolute value of the coating on the quasi-static d33 / d31 measuring instrument is ≥0.

5.

2. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 1), the silane coupling agent is KH560, and the amount of silane coupling agent used is 4.0~6.0% of the mass of barium titanate nanoparticles.

3. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 1), the mass ratio of anhydrous ethanol to deionized water is 8:1 to 10:

1.

4. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 2), the organic solvent is at least one of N-methylpyrrolidone or N-N dimethylacetamide, and the dispersant is BYK-192 wetting and dispersing agent.

5. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 3), the thickness of the prepared coating is 10~30μm.

6. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 3), the coating curing process is to cure at 150°C for 2 hours and then at 250°C for 1 hour.

7. The method for preparing a long-lasting integrated lubrication-corrosion coating based on the triboelectric effect as described in claim 1, characterized in that, In step 3), the electric field strength inside the parallel plate capacitor is set to 6~7kV / mm, and the sample polarization time is 25~30min.

8. A long-lasting integrated lubrication-corrosion coating based on the triboelectric effect prepared by the method described in claim 1.

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