Modified friction-reducing and wear-resistant carbon fiber based on self-assembly, self-lubricating material containing modified fiber and preparation method thereof

Abstract

The present invention discloses a self-assembled modified anti-friction and wear-resistant carbon fiber, a self-lubricating material containing the modified fiber, and a preparation method thereof. The self-assembled modified anti-friction and wear-resistant carbon fiber comprises: carbon fiber and an organic coating layer formed on the surface of the carbon fiber, wherein the organic coating layer comprises nanosheets formed from cyclodextrin and sodium lauryl sulfate. The self-lubricating material containing the modified fiber comprises: 5-20% of the self-assembled modified anti-friction and wear-resistant carbon fiber, 0-10% of polytetrafluoroethylene fiber, and more than 70% of an epoxy resin matrix. The self-assembled modified anti-friction and wear-resistant carbon fiber of the present invention can improve the anti-friction and wear properties of the self-lubricating material.

Description

Technical Field

[0001] The invention relates to modified anti-friction and wear-resistant carbon fibers based on self-assembly, a self-lubricating material containing the modified fibers and a preparation method thereof, and belongs to the technical field of carbon fiber surface modification. Background Art

[0002] Carbon fiber, due to its high strength, superior specific modulus, heat transfer properties, low coefficient of friction, and wide temperature resistance, has become an important structural and functional material in resin-based composites. However, in some mechanical lubrication systems, the presence of hard particles on the surface of carbon fiber, due to its high surface modulus, can cause severe scratches on the friction pair. While carbon fiber enhances the mechanical properties of the matrix, it significantly weakens the friction-reducing effect of the lubricating phase, further exacerbating abrasive and adhesive wear, and even leading to mechanical system failure and irreparable damage.

[0003] In recent years, researchers have modified the surface of carbon fibers physically or chemically to address various surface issues. Modification methods typically include chemical grafting, physical coating, and high-energy radiation. The operation of these methods is often cumbersome and complex, and while improving the surface properties of the carbon fibers, they also affect the strength of the carbon fibers. These modification methods are generally designed to address the problem of poor interfacial bonding between the carbon fibers and the matrix. By strengthening the interaction between the carbon fibers and the matrix, the bonding effect between the carbon fibers and the matrix is ​​improved, thereby increasing the application value of the carbon fibers in engineering. As for surface modification of carbon fibers to enhance the anti-friction and anti-wear properties of the matrix, there is a lack of relevant reports in this field. Summary of the Invention

[0004] To solve the above technical problems, the present invention aims to provide a self-assembled modified anti-friction and anti-wear carbon fiber, a self-lubricating material containing the modified fiber, and a preparation method thereof. The self-assembled modified anti-friction and anti-wear carbon fiber of the present invention can improve the anti-friction and anti-wear properties of the self-lubricating material.

[0005] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a modified friction-reducing and wear-resistant carbon fiber based on self-assembly, which includes: carbon fiber, and an organic outer coating layer formed on the surface of the carbon fiber, the organic outer coating layer including nanosheets formed by cyclodextrin and sodium lauryl sulfate; wherein the mass ratio of the carbon fiber to the organic outer coating layer is 8:1 to 10:1.

[0006] According to a specific embodiment of the present invention, preferably, the diameter of the carbon fiber is 5 to 10 μm.

[0007] According to a specific embodiment of the present invention, preferably, the average thickness of the organic coating layer is 20 to 60 nm.

[0008] According to a specific embodiment of the present invention, preferably, the molar ratio of cyclodextrin to dodecyl sulfate in the nanosheets formed by cyclodextrin and sodium dodecyl sulfate is 1.8:1 to 2.2:1.

[0009] According to a specific embodiment of the present invention, preferably, the nanosheets formed by the cyclodextrin and sodium lauryl sulfate have a planar size of 1 to 20 μm and a thickness of 1 to 8 nm.

[0010] The second aspect of the present invention provides a method for preparing the above-mentioned modified friction-reducing and wear-resistant carbon fiber based on self-assembly, which comprises the following steps:

[0011] The carbon fiber is immersed in a nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate, wherein the solvent in the nanosheet solution is a first solvent, which is a good solvent for the nanosheet. Then, a second solvent is added dropwise, which is a poor solvent for the nanosheet. The solution is allowed to stand, and the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate spontaneously settle and precipitate on the surface of the carbon fiber, assemble to form an organic coating layer, and obtain the modified anti-friction and wear-resistant carbon fiber based on self-assembly.

[0012] According to a specific embodiment of the present invention, preferably, the carbon fiber is desizing carbon fiber, and the desizing comprises: placing the carbon fiber in ethanol and ultrasonically treating it at 30-60°C for 2-4 hours, then washing the ethanol-treated carbon fiber with water, and then vacuum drying it at 80-120°C for 12-24 hours to obtain the desizing carbon fiber.

[0013] According to a specific embodiment of the present invention, preferably, the preparation step of the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate includes: adding cyclodextrin and sodium dodecyl sulfate to a first solvent, stirring, and spontaneously assembling into nanosheets formed by cyclodextrin and sodium dodecyl sulfate, and then freeze-drying to obtain nanosheet powder, and then using the first solvent to prepare the nanosheet powder into a solution to obtain the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate. More preferably, the molar ratio of the cyclodextrin to the sodium dodecyl sulfate is 1.8:1 to 2.2:1. More preferably, the stirring conditions include: stirring at 40-70°C and a speed of 300-800 rpm for 12-24 hours. More preferably, the concentration of the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate is 1-6 mg / mL.

[0014] According to a specific embodiment of the present invention, preferably, the mass ratio of the carbon fibers to the nanosheets formed by cyclodextrin and sodium lauryl sulfate is 5:(0.1-1.5).

[0015] According to a specific embodiment of the present invention, preferably, the volume ratio of the nanosheet solution formed by the cyclodextrin and sodium lauryl sulfate to the second solvent is 1:2 to 2:1.

[0016] According to a specific embodiment of the present invention, preferably, the standing time is 2 to 8 hours.

[0017] The third aspect of the present invention provides a self-lubricating material containing modified fibers. Taking the total mass of the self-lubricating material containing modified fibers as 100%, the self-lubricating material comprises: 5 to 20% of the self-assembled modified anti-friction and wear-resistant carbon fibers, 0 to 10% of polytetrafluoroethylene fibers, and more than 70% of an epoxy resin matrix.

[0018] A fourth aspect of the present invention provides a method for preparing the above-mentioned self-lubricating material containing modified fibers, comprising the following steps:

[0019] The modified anti-friction and wear-resistant carbon fiber based on self-assembly and the selectively added polytetrafluoroethylene fiber are added to a mixture of epoxy resin prepolymer and curing agent, mixed evenly, poured into a mold, and cured to obtain the self-lubricating material containing the modified fiber.

[0020] According to a specific embodiment of the present invention, preferably, the curing includes two stages of curing, the first stage of curing is curing at 60-100° C. for 2-5 hours, and the second stage of curing is curing at 100-140° C. for 2-5 hours.

[0021] The present invention has at least the following beneficial effects:

[0022] (1) The present invention uses nanosheets formed by cyclodextrin and sodium dodecyl sulfate to coat the surface of carbon fiber to form an organic coating layer, which plays a role in reducing friction and resisting wear. Its mechanism can be attributed to the synergistic effect of multiple factors. First, SCD (nanosheets formed by cyclodextrin and sodium dodecyl sulfate) is a layer of organic nanocoating. Unlike the inorganic coatings in the prior art (such as MoS2 nanosheets grown on the surface of carbon fiber, or flaky nickel-cobalt double hydroxides, etc.), the organic nanocoating of the present invention is relatively soft. It coats the hard particles with high modulus on the surface of carbon fiber, reduces the surface modulus of carbon fiber, makes its surface area relatively mild, and reduces the damage of sharp and rough particles to the friction film during relative motion, thereby facilitating the formation of a more stable, complete and continuous transfer film, avoiding direct contact between the contact pair rough peaks, and achieving low friction wear through interlayer shear of the lubricating film. Secondly, the carbon fiber surface introduces nanosheets containing hydroxyl groups to improve its surface activity and roughness, and chemical action and mechanical interlocking improve the interface bonding strength between carbon fiber and matrix, reducing the interface failure problems such as debonding and pulling out of carbon fiber, thereby making the degree of integration of self-lubricating material higher, reducing the adhesive wear and abrasive wear caused by the formation of large wear debris in the friction and wear process. Thirdly, although the organic nano coat of the present invention reduces the carbon fiber surface modulus, it does not affect the overall hardness of the self-lubricating material, and the hardness is slightly improved after modification, which is also conducive to improving wear resistance. In addition, during the friction process, SCD will decompose into multiple molecular fragments and interact with polytetrafluoroethylene and the stainless steel ball of the friction pair, forming F0 bonds and metal organic compounds, which act like a lubricant of alcohol, thereby forming a rich mixed lubricating film at the interface, and, since there is no strong polar group in SCD, it has poor adhesion to metal, which improves the anti-adhesion of the lubricating film on the contrary, thereby reducing the wear debris attached to the steel ball surface, and improving the quality of the steel ball surface. Therefore, the present invention assembles SCD on the surface of carbon fiber, thereby effectively improving the friction reduction and anti-wear performance of the self-lubricating material, which is mainly due to the synergistic effect of physical coating and surface chemical composition.

[0023] (2) The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly of the present invention is simple and efficient, and avoids the complicated process of using strong acid or other toxic and dangerous chemical reagents for treatment. It is environmentally friendly and non-toxic. Moreover, the present invention adopts a two-step method to prepare the modified anti-friction and anti-wear carbon fiber based on self-assembly, first preparing nanosheets formed by cyclodextrin and sodium lauryl sulfate, and then assembling them on the surface of the carbon fiber to form an organic coating layer. This preparation method can more accurately regulate the size of the nanosheets on the surface of the carbon fiber, and can better control the content of the nanosheets assembled on the surface of the carbon fiber, and has the advantages of strong operability and strong adjustability.

[0024] (3) The self-lubricating material containing the modified anti-friction and wear-resistant carbon fiber based on self-assembly of the present invention has a significantly lower friction coefficient compared to the self-lubricating material without the modified anti-friction and wear-resistant carbon fiber of the present invention, and the degree of wear rate reduction can reach more than one order of magnitude. The modified carbon fiber of the present invention significantly improves the overall anti-friction and wear performance of the self-lubricating material. Therefore, the use of the modified anti-friction and wear-resistant carbon fiber based on self-assembly of the present invention can alleviate or avoid the wear of the carbon fiber in the self-lubricating material caused by the hard particles on its surface rubbing against the friction pair.

[0025] (4) The modified anti-friction and anti-wear carbon fiber based on self-assembly of the present invention improves the anti-friction and anti-wear properties of the self-lubricating material without weakening the mechanical properties of the self-lubricating material and the interface bonding between the carbon fiber and the resin matrix. Instead, it slightly improves the two. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 These are the SEM and TEM images of the desized carbon fiber and the modified friction-reducing and wear-resistant carbon fiber based on self-assembly in Example 1.

[0027] Figure 2 These are thermogravimetric graphs of the desized carbon fiber in Example 1, the modified friction-reducing and wear-resistant carbon fiber based on self-assembly, and the nanosheets formed by cyclodextrin and sodium dodecyl sulfate.

[0028] Figure 3 These are SEM images of modified friction-reducing and wear-resistant carbon fibers based on self-assembly obtained by assembling SCD aqueous solutions with different concentrations on the CF surface.

[0029] Figure 4 This is the SEM image of the modified carbon fiber in Comparative Example 4.

[0030] Figure 5 Friction curves and average friction coefficients of self-lubricating materials with different CF-SCD contents.

[0031] Figure 6 is the friction coefficient of the self-lubricating material of Example 1 and Comparative Examples 1-2.

[0032] Figure 7 is the average wear rate of self-lubricating materials with different CF-SCD contents.

[0033] Figure 8 The three-dimensional white light image and wear scar depth of the surface wear scar of self-lubricating materials with different CF-SCD contents.

[0034] Figure 9 The wear scar morphology and depth of the self-lubricating materials of Example 1 and Comparative Examples 1-2 are shown.

[0035] Figure 10is the wear rate of the self-lubricating materials of Example 1 and Comparative Examples 1-2.

[0036] Figure 11 The bending properties, tensile properties and compression properties of the self-lubricating materials and pure epoxy resins of Example 11 and Comparative Examples 6-7 are shown. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0038] It should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0040] According to a specific embodiment of the first aspect of the present invention, the present invention provides a modified friction-reducing and wear-resistant carbon fiber based on self-assembly, which includes: carbon fiber, and an organic outer coating layer formed on the surface of the carbon fiber, the organic outer coating layer including nanosheets formed by cyclodextrin and sodium dodecyl sulfate; wherein the mass ratio of the carbon fiber to the organic outer coating layer is 8:1 to 10:1, for example but not limited to 8:1, 9:1 or 10:1, etc., preferably 9:1.

[0041] In some embodiments, the carbon fibers have a diameter of 5 to 10 μm.

[0042] In some embodiments, the average thickness of the organic coating layer is 20-60 nm.

[0043] In some embodiments, the molar ratio of cyclodextrin to dodecyl sulfate in the nanosheets formed by cyclodextrin and sodium dodecyl sulfate is 1.8:1 to 2.2:1, for example but not limited to 1.8:1, 2:1 or 2.2:1, and preferably 2:1.

[0044] In some embodiments, the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate have a planar size of 1 to 20 μm and a thickness of 1 to 8 nm.

[0045] In some embodiments, the cyclodextrin is β-cyclodextrin.

[0046] According to a specific embodiment of the second aspect of the present invention, the present invention provides a method for preparing the above-mentioned modified anti-friction and anti-wear carbon fiber based on self-assembly, which comprises the following steps:

[0047] The carbon fiber is immersed in a nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate, wherein the solvent in the nanosheet solution is a first solvent, which is a good solvent for the nanosheet. Then, a second solvent is added dropwise, which is a poor solvent for the nanosheet. The solution is allowed to stand, and the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate spontaneously settle and precipitate on the surface of the carbon fiber, assemble to form an organic coating layer, and obtain the modified anti-friction and wear-resistant carbon fiber based on self-assembly.

[0048] In some embodiments, the first solvent comprises one or more of water, N,N-dimethylformamide, and dimethyl sulfoxide, which have good solubility in the nanosheets of the present invention. The second solvent comprises one or more of acetone and tetrahydrofuran, which have poor solubility in the nanosheets of the present invention.

[0049] In some embodiments, the carbon fiber is desizing carbon fiber, and the desizing includes: placing the carbon fiber in ethanol and ultrasonically treating it at 30-60°C for 2-4 hours, then repeatedly washing the ethanol-treated carbon fiber with deionized water, and then vacuum drying it at 80-120°C for 12-24 hours to obtain the desizing carbon fiber.

[0050] In some embodiments, the preparation of the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate comprises the following steps: adding cyclodextrin and sodium dodecyl sulfate to a first solvent, stirring, and spontaneously assembling into nanosheets formed by cyclodextrin and sodium dodecyl sulfate, followed by freeze-drying to obtain a nanosheet powder; and then preparing the nanosheet powder into a solution using the first solvent to obtain the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate. Preferably, the molar ratio of cyclodextrin to sodium dodecyl sulfate is 1.8:1 to 2.2:1. Preferably, the stirring conditions include stirring at 40-70°C and 300-800 rpm for 12-24 hours. Preferably, the concentration of the nanosheet solution formed by cyclodextrin and sodium dodecyl sulfate is 1-6 mg / mL. The present invention can achieve directionally controlled nanosheet size by regulating conditions such as the concentration of the nanosheet solution and the assembly time (i.e., stirring time). Furthermore, the nanosheets prepared by the method of the present invention have the advantages of being uniform and isotropic.

[0051] In some embodiments, in the above preparation method, the mass ratio of the carbon fiber to the nanosheets formed by the cyclodextrin and sodium lauryl sulfate is 5:(0.1-1.5), for example but not limited to 5:0.1, 5:0.5, 5:1, or 5:1.5.

[0052] In some embodiments, the volume ratio of the nanosheet solution formed by the cyclodextrin and sodium lauryl sulfate to the second solvent is 1:2 to 2:1, for example but not limited to 1:2, 1:1 or 2:1.

[0053] In some embodiments, the standing time is 2 to 8 hours, for example but not limited to 2 hours, 4 hours, 6 hours or 8 hours.

[0054] In some embodiments, after the standing, conventional washing, vacuum drying and other steps may be performed. For example, deionized water may be used for repeated washing. The vacuum drying temperature may be 80-100° C. and the time may be 12-24 hours.

[0055] According to a specific embodiment of the third aspect of the present invention, the present invention provides a self-lubricating material containing modified fibers, which comprises, based on the total mass of the self-lubricating material containing modified fibers as 100%, 5 to 20% of the modified friction-reducing and wear-resistant carbon fibers based on self-assembly, for example, but not limited to 5%, 10%, 15% or 20%, etc., preferably 10 to 15%, more preferably 10%; 0 to 10% of polytetrafluoroethylene fibers, for example, but not limited to 0%, 2%, 4%, 6%, 8% or 10%, etc.; and more than 70% of an epoxy resin matrix, for example, but not limited to 70%, 75%, 80%, 85%, 90% or 95%, etc.

[0056] According to a specific embodiment of the fourth aspect of the present invention, the present invention provides a method for preparing the above-mentioned self-lubricating material containing modified fibers, which comprises the following steps:

[0057] The modified anti-friction and wear-resistant carbon fiber based on self-assembly and the selectively added polytetrafluoroethylene fiber are mixed, and then added to a mixture of epoxy resin prepolymer and curing agent. After mixing evenly, the mixture is poured into a mold and cured to obtain the self-lubricating material containing the modified fiber.

[0058] In some embodiments, the epoxy resin prepolymer and the curing agent can be epoxy resin prepolymers and curing agents in the prior art, and the present invention does not specifically limit them. It will be understood by those skilled in the art that after the epoxy resin prepolymer and the curing agent react, an epoxy resin matrix is ​​formed. The mass ratio of the epoxy resin prepolymer to the curing agent can be conventionally adjusted by those skilled in the art and can be 5:0.9 to 5:1.5.

[0059] In some embodiments, before pouring the uniformly mixed mixture into the mold, the mixture may be vacuumed to remove air bubbles therein.

[0060] In some embodiments, the curing includes two stages of curing, wherein the first stage of curing is performed at 60-100° C. for 2-5 hours, and the second stage of curing is performed at 100-140° C. for 2-5 hours.

[0061] The present invention will be specifically described below with reference to Examples. However, the present invention is not limited to these Examples and can be implemented with various modifications within the scope of the gist of the present invention.

[0062] Test method:

[0063] The mass ratio of carbon fiber and organic outer layer: obtained by thermogravimetric analysis (TGA). The specific testing method includes: using a TGA Q5000IR thermogravimetric analyzer, at a heating rate of 10°C / minute and a test temperature of 25°C to 750°C, to perform thermogravimetric analysis on the modified carbon fiber sample to obtain a thermal gravimetric curve; in the thermal gravimetric curve, the ratio of the weight percentage of the modified carbon fiber sample at the weight loss inflection point (i.e., the weight percentage at the bottom of the inflection point) to the weight percentage lost at the weight loss inflection point is the mass ratio.

[0064] Carbon fiber diameter: Obtained through scanning electron microscopy (SEM) observation. A certain number of carbon fiber samples (e.g., more than 30) need to be tested to determine the diameter range.

[0065] Average thickness of the organic coating layer: Obtained by transmission electron microscopy (TEM) observation. Five or more points must be randomly selected on the surface of each modified carbon fiber sample to measure the thickness of the organic coating layer. A certain number of modified carbon fiber samples (e.g., more than 30) must be tested and the average value taken to obtain the average thickness.

[0066] The molar ratio of cyclodextrin to dodecyl sulfate in the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate is obtained by the amounts of cyclodextrin and sodium dodecyl sulfate used in the preparation method.

[0067] The planar dimensions of nanosheets formed from cyclodextrin and sodium lauryl sulfate were determined by scanning electron microscopy (SEM). Note that the planar dimensions of a nanosheet refer to the maximum linear distance between two points on the nanosheet. A sufficient number of nanosheet samples (e.g., 30 or more) should be tested to determine the range of planar dimensions.

[0068] The thickness of the nanosheets formed by cyclodextrin and sodium lauryl sulfate is determined by atomic force microscopy (AFM) scanning. A certain number of nanosheet samples (e.g., more than 30) need to be tested to determine the thickness range.

[0069] Example 1

[0070] (1) 7.1 g of β-cyclodextrin and 0.9 g of sodium dodecyl sulfate (the molar ratio of the two is 2:1) were weighed and added to 18.7 g of deionized water. The mixture was stirred at 500 rpm at 60°C for 12 h to allow cyclodextrin and sodium dodecyl sulfate to spontaneously assemble into a sheet structure, thereby obtaining a uniform, isotropic aqueous solution of self-assembled nanosheets with a mass fraction of 30%. The aqueous solution of the nanosheets was then freeze-dried to obtain nanosheet powder. The nanosheet powder was then prepared into an aqueous solution using deionized water to obtain an aqueous solution of nanosheets formed by cyclodextrin and sodium dodecyl sulfate (SDS@2β-CD, abbreviated as SCD), the concentration of which was 5 mg / mL. The nanosheets formed by cyclodextrin and sodium dodecyl sulfate (SDS@2β-CD) had a planar size of 1 to 15 μm and a thickness of 3 to 5 nm.

[0071] (2) The carbon fibers were ultrasonically treated in ethanol at 50°C for 3 h, and then the ethanol-treated carbon fibers were repeatedly washed with deionized water, and then vacuum-dried at 100°C for 12 h to obtain desizing carbon fibers.

[0072] (3) 5 g of the desized carbon fiber (with a diameter of 5 to 10 μm) prepared in step (2) was soaked in 100 mL of an aqueous solution (5 mg / mL) of SDS@2β-CD prepared in step (1), and 100 mL of acetone was added dropwise thereto. The mixture was allowed to stand for 3 h to allow the SDS@2β-CD to spontaneously settle and precipitate on the surface of the carbon fiber, assembling to form an organic coating layer. The product was then repeatedly washed with deionized water and then vacuum dried at 80°C for 12 h to obtain a modified anti-friction and anti-wear carbon fiber (CF-SCD) based on self-assembly.

[0073] The modified friction-reducing and wear-resistant carbon fiber based on self-assembly includes: carbon fiber, and an organic outer coating layer formed on the surface of the carbon fiber, the organic outer coating layer includes nanosheets formed by cyclodextrin and sodium lauryl sulfate; wherein the mass ratio of the carbon fiber to the organic outer coating layer is 9:1; and the average thickness of the organic outer coating layer is 50nm.

[0074] Figure 1 The SEM image of the desizing carbon fiber prepared in step (2) ( Figure 1 a1 in the figure), TEM image ( Figure 1 b1) in step (3) and the SEM image of the modified anti-friction and anti-wear carbon fiber based on self-assembly ( Figure 1 a2 in the figure), TEM image ( Figure 1 In b2), the difference in the carbon fiber surface before and after the organic coating layer is assembled can be clearly seen.

[0075] Figure 2The thermogravimetric images of desized carbon fiber (CF), modified anti-friction and wear-resistant carbon fiber based on self-assembly (CF-SCD), and nanosheets SDS@2β-CD (SCD) formed by cyclodextrin and sodium dodecyl sulfate prove that the nanosheets formed by cyclodextrin and sodium dodecyl sulfate are successfully assembled on the surface of carbon fiber in this example.

[0076] (4) Taking the total mass of the self-lubricating material containing modified fibers as 100%, 10% of the modified anti-friction and anti-wear carbon fibers based on self-assembly and 10% of polytetrafluoroethylene fibers were mixed evenly, and then the mixture was added to 80% of the mixture of E51 epoxy resin prepolymer and curing agent isophorone diamine, with the mass ratio of epoxy resin prepolymer to curing agent being 5:1.2. The mixture was stirred and mixed evenly, vacuumed to remove bubbles, and then poured into a silicone mold. The mixture was cured at 80°C for 2h, then heated to 120°C and continued to cure for 2h to obtain a modified anti-friction and anti-wear carbon fiber reinforced self-lubricating material based on self-assembly (EP+CF-SCD+PTFE).

[0077] Example 2

[0078] The difference from Example 1 is that in step (1), the aqueous solution of β-cyclodextrin and sodium dodecyl sulfate is stirred at a speed of 700 rpm for 12 hours at 60°C, and the concentration of the prepared SDS@2β-CD aqueous solution is the same as that in Example 1; in step (3), the standing time is 4 hours. The rest is the same as Example 1. The planar size of the nanosheets formed by cyclodextrin and sodium dodecyl sulfate in this embodiment is 1 to 10 μm, and the thickness is 3 to 5 nm. The modified anti-friction and wear-resistant carbon fiber based on self-assembly in this embodiment includes: carbon fiber, and an organic coating layer formed on the surface of the carbon fiber, the organic coating layer including nanosheets formed by cyclodextrin and sodium dodecyl sulfate; wherein the mass ratio of the carbon fiber to the organic coating layer is 9.5:1; the average thickness of the organic coating layer is 45 nm.

[0079] The modified anti-friction and wear-resistant carbon fibers based on self-assembly of this embodiment are used to prepare a self-lubricating material containing modified fibers, and the amount used and the preparation method are the same as those in Example 1.

[0080] Example 3

[0081] The difference from Example 1 is that in step (1), the aqueous solution of β-cyclodextrin and sodium dodecyl sulfate is stirred at 300 rpm for 12 hours at 60°C, and the concentration of the prepared SDS@2β-CD aqueous solution is the same as that in Example 1; in step (3), the standing time is 2 hours. The rest is the same as in Example 1. The planar size of the nanosheets formed by cyclodextrin and sodium dodecyl sulfate in this embodiment is 10 to 20 μm, and the thickness is 3 to 5 nm. The modified anti-friction and wear-resistant carbon fiber based on self-assembly in this embodiment includes: carbon fiber, and an organic coating layer formed on the surface of the carbon fiber, the organic coating layer including nanosheets formed by cyclodextrin and sodium dodecyl sulfate; wherein the mass ratio of the carbon fiber to the organic coating layer is 9.7:1; and the average thickness of the organic coating layer is 40 nm.

[0082] The modified anti-friction and wear-resistant carbon fibers based on self-assembly of this embodiment are used to prepare a self-lubricating material containing modified fibers, and the amount used and the preparation method are the same as those in Example 1.

[0083] Example 4

[0084] The difference from Example 1 is that the mass ratio of the carbon fiber to the organic coating layer in the modified anti-friction and anti-wear carbon fiber based on self-assembly is 10:1, and the average thickness of the organic coating layer is 40 nm. In the preparation step, 5 g of the desized carbon fiber (with a diameter of 5 to 10 μm) prepared in step (2) is immersed in 100 mL of an aqueous solution of SDS@2β-CD with a concentration of 3 mg / mL prepared in step (1) (the preparation process of the nanosheet powder is the same as that in Example 1), and then 100 mL of acetone is added dropwise thereto. The remaining steps are the same as those in Example 1. The modified anti-friction and anti-wear carbon fiber based on self-assembly of this embodiment is used to prepare a self-lubricating material containing the modified fiber, and the amount and preparation method are the same as those in Example 1.

[0085] Example 5

[0086] The difference from Example 1 is that the mass ratio of the carbon fiber to the organic coating layer in the modified anti-friction and anti-wear carbon fiber based on self-assembly is 8:1, and the average thickness of the organic coating layer is 60 nm. In the preparation step, 5 g of the desized carbon fiber (with a diameter of 5 to 10 μm) prepared in step (2) is immersed in 100 mL of an aqueous solution of SDS@2β-CD with a concentration of 6 mg / mL prepared in step (1) (the preparation process of the nanosheet powder is the same as that in Example 1), and then 100 mL of acetone is added dropwise thereto. The remaining steps are the same as those in Example 1. The modified anti-friction and anti-wear carbon fiber based on self-assembly of this embodiment is used to prepare a self-lubricating material containing the modified fiber, and the amount and preparation method are the same as those in Example 1.

[0087] Figure 3SEM images of modified friction-reducing and wear-resistant carbon fibers (Examples 1, 4 and 5) based on self-assembly obtained by assembling SCD aqueous solutions with different concentrations on the CF surface.

[0088] Example 6

[0089] The difference from Example 1 is that the molar ratio of β-cyclodextrin to sodium lauryl sulfate is 1.8:1. In the preparation process, 6.1 g of β-cyclodextrin and 0.9 g of sodium lauryl sulfate are weighed and added to 16.3 g of deionized water. The remaining steps are the same as in Example 1. The concentration of the SDS@2β-CD aqueous solution is the same as in Example 1.

[0090] The modified anti-friction and wear-resistant carbon fibers based on self-assembly of this embodiment are used to prepare a self-lubricating material containing modified fibers, and the amount used and the preparation method are the same as those in Example 1.

[0091] Example 7

[0092] The difference from Example 1 is that the molar ratio of β-cyclodextrin to sodium lauryl sulfate is 2.2:1. In the preparation process, 7.5 g of β-cyclodextrin and 0.9 g of sodium lauryl sulfate are weighed and added to 19.6 g of deionized water. The remaining steps are the same as in Example 1. The concentration of the SDS@2β-CD aqueous solution is the same as in Example 1.

[0093] The modified anti-friction and wear-resistant carbon fibers based on self-assembly of this embodiment are used to prepare a self-lubricating material containing modified fibers, and the amount used and the preparation method are the same as those in Example 1.

[0094] Example 8

[0095] The difference from Example 1 is that the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is different from that in Example 1. Based on the total mass of the self-lubricating material containing the modified fiber as 100%, the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is 5%, the amount of the polytetrafluoroethylene fiber is 10%, and the amount of the mixture of E51 epoxy resin prepolymer and curing agent isophorone diamine is 85%.

[0096] Example 9

[0097] The difference from Example 1 is that the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is different from that in Example 1. Based on the total mass of the self-lubricating material containing the modified fiber as 100%, the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is 15%, the amount of the polytetrafluoroethylene fiber is 10%, and the amount of the mixture of E51 epoxy resin prepolymer and curing agent isophorone diamine is 75%.

[0098] Example 10

[0099] The difference from Example 1 is that the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is different from that in Example 1. Based on the total mass of the self-lubricating material containing the modified fiber as 100%, the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is 20%, the amount of the polytetrafluoroethylene fiber is 10%, and the amount of the mixture of E51 epoxy resin prepolymer and curing agent isophorone diamine is 70%.

[0100] Example 11

[0101] The difference from Example 1 is that polytetrafluoroethylene fibers are not added to the self-lubricating material containing modified fibers. By mass percentage, the self-lubricating material containing modified fibers (EP+CF-SCD) of this example comprises 10% of self-assembled modified anti-friction and wear-resistant carbon fibers and 90% of an epoxy resin matrix.

[0102] Comparative Example 1

[0103] This comparative example is compared with Example 1. The difference from Example 1 is that the self-lubricating material does not contain the self-assembled modified anti-friction and anti-wear carbon fibers. The self-lubricating material (EP+PTFE) in this comparative example comprises, by mass percentage, 10% polytetrafluoroethylene fibers and 90% epoxy resin matrix.

[0104] Comparative Example 2

[0105] This comparative example is compared with Example 1. The difference from Example 1 is that the modified anti-friction and wear-resistant carbon fiber based on self-assembly in the self-lubricating material containing modified fibers in Example 1 is replaced with unmodified desizing carbon fiber (prepared by step (2) of Example 1), and the amount remains unchanged to obtain the self-lubricating material (EP+CF+PTFE) of this comparative example.

[0106] Comparative Example 3

[0107] This comparative example is compared with Example 1, and the difference from Example 1 is that the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is different from that in Example 1. Based on the total mass of the self-lubricating material containing the modified fiber as 100%, the amount of the modified anti-friction and anti-wear carbon fiber based on self-assembly is 2.5%, the amount of the polytetrafluoroethylene fiber is 10%, and the amount of the mixture of E51 epoxy resin prepolymer and curing agent isophorone diamine is 87.5%.

[0108] Comparative Example 4

[0109] This comparative example is compared with Example 1, and the difference from Example 1 is that instead of assembling SCD nanosheets on the surface of carbon fiber, polydopamine (PDA) nanosheets are grown in situ on the surface of carbon fiber to form an organic coating layer to obtain modified carbon fiber, which is then introduced into the epoxy resin matrix together with PTFE fiber. Specifically, the preparation method of the modified carbon fiber of this comparative example comprises: dispersing 5g of desized carbon fiber (with a diameter of 5 to 10 μm) prepared in step (2) of Example 1 in 250mL of dopamine hydrochloride (0.5g) / Tris-HCl buffer solution with a pH of 8.5, stirring at a speed of 200rpm for 24h at room temperature, filtering the reaction mixture after completion, and then repeatedly washing the product with deionized water, and then drying to obtain modified carbon fiber (CF-PDA). The SEM image of the modified carbon fiber is shown in FIG. Figure 4 The modified carbon fiber of this comparative example was used to prepare a self-lubricating material containing the modified fiber, and the amount used and the preparation method were the same as those in Example 1.

[0110] Comparative Example 5

[0111] This comparative example is compared with Example 1. The difference from Example 1 is that sodium lauryl sulfate was not added during the preparation of the nanosheets, and it was found that no nanosheets were prepared.

[0112] Comparative Example 6

[0113] This comparative example is compared with Example 11, and the difference from Example 11 is that the self-assembled modified anti-friction and anti-wear carbon fibers are not added. Therefore, pure epoxy resin (EP) is prepared in this comparative example.

[0114] Comparative Example 7

[0115] This comparative example is compared with Example 11. The difference from Example 11 is that the modified anti-friction and wear-resistant carbon fibers based on self-assembly in the self-lubricating material containing modified fibers in Example 11 are replaced with unmodified desizing carbon fibers (prepared by step (2) of Example 1) in the same amount to obtain the self-lubricating material (EP+CF) of this comparative example.

[0116] Test Example 1

[0117] The self-lubricating materials provided in the above Examples 1 to 10 and Comparative Examples 1 to 4 were subjected to friction and wear performance tests.

[0118] The self-lubricating material was tested by UMT-5 reciprocating friction and wear testing machine. The test conditions include: load 10N, frequency 5Hz, stroke 3mm, test time of each sample 1h, and repeated 3 times. The test results are shown in Table 1 and Figure 5 、 Figure 6 As shown, Figure 5The friction curves of self-lubricating materials with different CF-SCD contents (Comparative Example 1, Comparative Example 3, Example 1, Examples 8 to 10) are shown in Figure 2. Figure 5 a) and the average friction coefficient ( Figure 5 b) in the above, Figure 6 The friction coefficients of the self-lubricating materials of Example 1 and Comparative Examples 1 to 2 show that the self-lubricating material containing the modified anti-friction and wear-resistant carbon fiber based on self-assembly according to the embodiment of the present invention has a significantly lower friction coefficient than the composite material without the modified anti-friction and wear-resistant carbon fiber of the present invention, the composite material with unmodified carbon fiber, the composite material with too little modified carbon fiber, and the composite material with carbon fiber modified with PDA nanosheets. The degree of reduction in friction coefficient can reach more than 50%.

[0119] The wear surface and wear volume of the wear scar after the friction test were observed by three-dimensional white light interferometry, and the wear rate was calculated. The test results are shown in Table 1. Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 As shown, Figure 7 is the average wear rate of self-lubricating materials with different CF-SCD contents (Comparative Example 1, Comparative Example 3, Example 1, Examples 8 to 10), Figure 8 The three-dimensional white light images and wear scar depths of the surface wear scars of self-lubricating materials with different CF-SCD contents (Comparative Example 1, Comparative Example 3, Example 1, Examples 8 to 10) are shown. Figure 9 The wear scar morphology and depth of the self-lubricating materials of Example 1 and Comparative Examples 1-2 are shown. Figure 10 The wear rates of the self-lubricating materials of Example 1 and Comparative Examples 1 to 2 show that the wear scar depth of the composite material containing unmodified carbon fibers is large and very obvious, the wear scar of the composite material without carbon fibers is shallow, and the wear scar of the self-lubricating material containing the modified anti-friction and anti-wear carbon fibers based on self-assembly according to the embodiment of the present invention is almost unobservable. By quantitatively calculating and comparing the wear rates, the self-lubricating material containing the modified anti-friction and anti-wear carbon fibers based on self-assembly according to the embodiment of the present invention can reduce the wear rate by more than one order of magnitude compared to the composite material without the modified anti-friction and anti-wear carbon fibers; and, compared to the composite material with unmodified carbon fibers and the composite material with too little modified carbon fibers, the wear rate of the self-lubricating material containing the modified anti-friction and anti-wear carbon fibers based on self-assembly according to the embodiment of the present invention is significantly reduced.

[0120] The calculation formula of wear rate Ws is: Where △V is the wear volume, F N is the normal load and d is the sliding distance.

[0121] Table 1

[0122]

[0123] It can be seen from Table 1 that the modified anti-friction and anti-wear carbon fibers based on self-assembly in the embodiments of the present invention significantly improve the overall anti-friction and anti-wear performance of the self-lubricating material.

[0124] Test Example 2

[0125] The self-lubricating materials and pure epoxy resins provided in Example 11 and Comparative Examples 6-7 were subjected to mechanical property tests, including bending, tensile and compression performance tests.

[0126] The bending performance can reflect the strength of the bonding between the fiber and the matrix, and the tensile and compressive performance can reflect the quality of the mechanical properties of the matrix. Figure 11 As shown, Figure 11 The bending properties of the self-lubricating materials and pure epoxy resins of Example 11 and Comparative Examples 6-7 ( Figure 11 a), tensile properties ( Figure 11 b) and compression performance ( Figure 11 c), it can be seen that the bending properties of the self-lubricating material containing the modified anti-friction and wear-resistant carbon fiber based on self-assembly according to the embodiment of the present invention are improved, indicating that the interface bonding between the modified carbon fiber and the resin matrix is ​​improved; the tensile properties of the self-lubricating material containing the modified anti-friction and wear-resistant carbon fiber based on self-assembly according to the embodiment of the present invention are slightly decreased, and the compression properties are slightly improved, indicating that the modified carbon fiber does not reduce the mechanical properties of the self-lubricating material. Therefore, while improving the anti-friction and wear properties of the self-lubricating material, the modified anti-friction and wear-resistant carbon fiber based on self-assembly according to the embodiment of the present invention does not weaken the original mechanical properties of the self-lubricating material and the interface bonding between the carbon fiber and the resin matrix, but instead slightly improves both.

Claims

1. A modified anti-friction and anti-wear carbon fiber based on self-assembly, comprising: Carbon fibers, and an organic coating layer formed on the surface of the carbon fibers, the organic coating layer comprising nanosheets formed of cyclodextrin and sodium lauryl sulfate; wherein the mass ratio of the carbon fibers to the organic coating layer is 8:1 to 10:1; The modified friction-reducing and wear-resistant carbon fiber based on self-assembly is prepared by the following preparation method: adding cyclodextrin and sodium lauryl sulfate to a first solvent, stirring the mixture, and spontaneously assembling into nanosheets formed of cyclodextrin and sodium lauryl sulfate; freeze-drying the mixture to obtain nanosheet powder; and then preparing the nanosheet powder into a solution using the first solvent to obtain a nanosheet solution formed of cyclodextrin and sodium lauryl sulfate; The carbon fiber is immersed in a nanosheet solution formed by the cyclodextrin and sodium dodecyl sulfate, wherein the solvent in the nanosheet solution is the first solvent, which is a good solvent for the nanosheets, and then a second solvent is added dropwise, which is a poor solvent for the nanosheets. The solution is allowed to stand, and the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate spontaneously settle and precipitate on the surface of the carbon fiber, assembling to form an organic coating layer, thereby obtaining the modified anti-friction and wear-resistant carbon fiber based on self-assembly; The first solvent includes one or more of water, N,N-dimethylformamide and dimethyl sulfoxide; The second solvent includes one or both of acetone and tetrahydrofuran.

2. The modified friction-reducing and wear-resistant carbon fiber based on self-assembly according to claim 1, wherein: The diameter of the carbon fiber is 5-10 μm.

3. The modified friction-reducing and wear-resistant carbon fiber based on self-assembly according to claim 1, wherein: The average thickness of the organic coating layer is 20-60 nm.

4. The modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 1, wherein: The molar ratio of cyclodextrin to dodecyl sulfate in the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate is 1.8:1 to 2.2:

1.

5. The self-assembled modified anti-friction and anti-wear carbon fiber according to claim 1, wherein: The nanosheets formed by the cyclodextrin and sodium lauryl sulfate have a plane size of 1-20 μm and a thickness of 1-8 nm.

6. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to any one of claims 1 to 5, comprising the following steps: adding cyclodextrin and sodium lauryl sulfate to a first solvent, stirring the mixture, and spontaneously assembling into nanosheets formed of cyclodextrin and sodium lauryl sulfate; freeze-drying the mixture to obtain nanosheet powder; and then preparing the nanosheet powder into a solution using the first solvent to obtain a nanosheet solution formed of cyclodextrin and sodium lauryl sulfate; The carbon fiber is immersed in a nanosheet solution formed by the cyclodextrin and sodium dodecyl sulfate, wherein the solvent in the nanosheet solution is the first solvent, which is a good solvent for the nanosheets, and then a second solvent is added dropwise, which is a poor solvent for the nanosheets. The solution is allowed to stand, and the nanosheets formed by the cyclodextrin and sodium dodecyl sulfate spontaneously settle and precipitate on the surface of the carbon fiber, assembling to form an organic coating layer, thereby obtaining the modified anti-friction and wear-resistant carbon fiber based on self-assembly; The first solvent includes one or more of water, N,N-dimethylformamide and dimethyl sulfoxide; The second solvent includes one or both of acetone and tetrahydrofuran.

7. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: The carbon fiber is desized carbon fiber, and the desizing comprises: placing the carbon fiber in ethanol and ultrasonically treating it at 30-60° C. for 2-4 hours, then washing the ethanol-treated carbon fiber with water, and then vacuum drying it at 80-120° C. for 12-24 hours to obtain the desized carbon fiber.

8. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: In the step of preparing the nanosheet solution formed by cyclodextrin and sodium lauryl sulfate, the molar ratio of the cyclodextrin to the sodium lauryl sulfate is 1.8:1 to 2.2:

1.

9. The method for preparing the modified friction-reducing and wear-resistant carbon fiber based on self-assembly according to claim 6, wherein: In the step of preparing the nanosheet solution formed by cyclodextrin and sodium lauryl sulfate, the stirring conditions include: stirring at 40-70° C. and a rotation speed of 300-800 rpm for 12-24 hours.

10. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: The concentration of the nanosheet solution formed by the cyclodextrin and sodium lauryl sulfate is 1-6 mg / mL.

11. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: The mass ratio of the carbon fiber to the nanosheets formed by the cyclodextrin and sodium lauryl sulfate is 5:(0.1-1.5).

12. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: The volume ratio of the nanosheet solution formed by the cyclodextrin and sodium lauryl sulfate to the second solvent is 1:2 to 2:

1.

13. The method for preparing the modified anti-friction and anti-wear carbon fiber based on self-assembly according to claim 6, wherein: The standing time is 2 to 8 hours.

14. A self-lubricating material containing modified fibers, comprising, based on the total mass of the self-lubricating material containing modified fibers being 100%,: 5-20% of the self-assembled modified anti-friction and wear-resistant carbon fiber according to any one of claims 1 to 5, 0-10% of polytetrafluoroethylene fiber, and more than 70% of the epoxy resin matrix.

15. The method for preparing the self-lubricating material containing modified fiber according to claim 14, comprising the following steps: The modified anti-friction and wear-resistant carbon fiber based on self-assembly and the selectively added polytetrafluoroethylene fiber are added to a mixture of epoxy resin prepolymer and curing agent, mixed evenly, poured into a mold, and cured to obtain the self-lubricating material containing the modified fiber.

16. The method for preparing a self-lubricating material containing modified fiber according to claim 15, wherein: The curing comprises two stages of curing, wherein the first stage of curing is performed at 60-100° C. for 2-5 h, and the second stage of curing is performed at 100-140° C. for 2-5 h.

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