Modified hexagonal boron nitride as well as preparation method and application thereof, and self-lubricating phenolic laminated composite material and preparation method thereof

Abstract

This invention belongs to the field of self-lubricating materials technology, specifically relating to a modified hexagonal boron nitride, its preparation method and application, and a self-lubricating phenolic laminate composite material and its preparation method. The modified hexagonal boron nitride provided by this invention comprises hexagonal boron nitride and silicon dioxide bonded to the hexagonal boron nitride by silicon-oxygen bonds. During water lubrication, hexagonal boron nitride and silicon dioxide particles are easily released to the friction interface. Under water lubrication conditions, the hexagonal boron nitride nanomaterials can form an excellent transfer film at the friction interface and can undergo a hydrolysis reaction with water to form a boric acid hydrate layer, providing excellent lubrication and significantly reducing material wear rate. The in-situ loaded silicon dioxide particles, under the action of frictional shear, can participate in the formation of the hexagonal boron nitride transfer film, enhancing the bonding force between the transfer film and the frictional pair, improving the elastic modulus, shear resistance, and load-bearing capacity of the transfer film, exhibiting excellent wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of self-lubricating materials technology, specifically relating to a modified hexagonal boron nitride and its preparation method and application, and a self-lubricating phenolic laminate composite material and its preparation method. Background Technology

[0002] Traditional phenolic laminated composites use thermosetting liquid phenolic resin or modified phenolic resin as the resin binder and cotton fiber fabric as the load-bearing reinforcement unit. These layers are stacked and then heated and pressurized to produce sheets, pipes, rods, etc., of various specifications. They possess high mechanical properties, heat resistance, dielectric properties, water resistance, moisture resistance, and oil resistance. Due to their excellent performance, they play an important role in the field of mechanical engineering, especially in the field of water-lubricated stern shaft bearings for shipping vessels, where they have long been crucial, such as the renowned British TENMAT series bearings.

[0003] However, traditional phenolic laminate composites lack good self-lubricating properties. To improve their self-lubricating performance, the industry has added a lubricating phase to the composites. Currently, the main lubricating phases are graphite or molybdenum disulfide. However, the addition of the lubricating phase results in high hardness and brittleness of the phenolic laminate. Under water lubrication conditions, the transfer of the lubricating phase material on the bearing surface during the running-in process can cause severe wear and scratching, making it difficult to promote the formation of an excellent boundary lubrication film. This affects bearing lubrication and wear, and consequently, the normal operation and lifespan of the bearing. Summary of the Invention

[0004] In view of this, the present invention provides a modified hexagonal boron nitride and its preparation method and application, as well as a self-lubricating phenolic laminate composite material and its preparation method. The self-lubricating phenolic laminate composite material prepared by using the modified hexagonal boron nitride provided by the present invention as a lubricating material can significantly improve its wear resistance.

[0005] To address the aforementioned technical problems, the present invention provides a modified hexagonal boron nitride, comprising hexagonal boron nitride and silicon dioxide bonded to the hexagonal boron nitride by silicon-oxygen bonds.

[0006] Preferably, the mass ratio of silicon dioxide to hexagonal boron nitride in the modified hexagonal boron nitride is 5-30:100.

[0007] Preferably, it includes the following steps:

[0008] Hexagonal boron nitride and a strong alkaline solution were first mixed and then surface hydrolyzed and activated to obtain hydroxylated hexagonal boron nitride.

[0009] The hydroxylated hexagonal boron nitride, tetraethoxysilane, surfactant, alkaline solution, and solvent are mixed and subjected to a hydrolysis reaction to obtain the modified hexagonal boron nitride.

[0010] Preferably, the strong alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution; the molar concentration of the strong alkali solution is 3-6 mol / L.

[0011] The particle size of the hexagonal boron nitride is 5-10 μm; the mass ratio of the hexagonal boron nitride to the volume ratio of the strong alkaline solution is 1 g: 10-30 mL;

[0012] The surface hydrolysis activation temperature is 90–120°C; the surface hydrolysis activation time is 10–36 h.

[0013] Preferably, the alkaline solution comprises one or more of the following: a mixed solution of NH3 and NH4Cl, a mixed solution of NH3 and NH4HCO3, and NH3·H2O; the pH value of the alkaline solution is 8 to 10.

[0014] The surfactant includes one or more of decaalkyltrimethylammonium chloride, N-dodecyldimethylamine, fatty acid soap, sodium cis-9-octadecenoate, and sodium laurate soap;

[0015] The solvent includes an organic solvent and water, wherein the organic solvent includes one or more of ethanol, ethylene glycol, glycerol, tetrahydrofuran, toluene, chlorobenzene and dichlorobenzene; the volume ratio of the organic solvent to water is 1:4 to 6.

[0016] The mass ratio of the surface-hydroxylated hexagonal boron nitride to the volume ratio of the solvent is 1 g: 10-50 mL;

[0017] The volume ratio of the tetraethoxysilane to the solvent is 1:4 to 30;

[0018] The mass ratio of the surfactant to the solvent is 1:20 to 100;

[0019] The mass ratio of the alkaline solution to the volume ratio of the solvent is 1g:20-35mL;

[0020] The hydrolysis reaction is carried out at a temperature of 15–35°C for a duration of 12–36 hours.

[0021] The present invention also provides the application of the modified hexagonal boron nitride described in the above technical solution or the modified hexagonal boron nitride prepared by the preparation method described in the above technical solution as a lubricant.

[0022] The present invention also provides a self-lubricating phenolic laminate composite material, comprising the following components in weight percentage:

[0023] Phenolic resin 40-55%;

[0024] Textile fiber fabric 35-57%;

[0025] Lubricant 3-15%;

[0026] The lubricant is the modified hexagonal boron nitride described in the above technical solution or the modified hexagonal boron nitride prepared by the preparation method described in the above technical solution.

[0027] Preferably, the fibers in the textile fiber fabric include one or more of polyester fibers, cotton fibers, acrylic fibers, polytetrafluoroethylene fibers, and aramid fibers.

[0028] This invention also provides a method for preparing the self-lubricating phenolic laminate composite material described in the above technical solution, comprising the following steps:

[0029] The lubricant, phenolic resin, and diluent are mixed to obtain a phenolic resin mixed solution;

[0030] The textile fiber fabric is impregnated with the phenolic resin mixture and then dried to obtain a pre-impregnated textile fiber fabric.

[0031] The pre-impregnated textile fiber cloth is shaped and then sintered and cured to obtain the self-lubricating phenolic laminate composite material.

[0032] Preferably, the amount of sizing after impregnating the textile fiber fabric with the phenolic resin mixture is 45-65%;

[0033] The drying temperature is 100–120°C, and the time is 1–10 min;

[0034] The sintering and curing process includes sequentially performing a first sintering and curing, a second sintering and curing, and a third sintering and curing.

[0035] The first sintering and solidification temperature is 75-85℃, and the first sintering and solidification holding time is 90-120 min;

[0036] The second sintering and curing temperature is 100-120℃, and the second sintering and curing holding time is 90-120 min;

[0037] The third sintering and curing temperature is 140–160°C, and the holding time for the third sintering and curing is 120–240 min.

[0038] This invention provides a modified hexagonal boron nitride, comprising hexagonal boron nitride and silicon dioxide bonded to the hexagonal boron nitride by silicon-oxygen bonds. This invention introduces high-hardness silicon dioxide onto the surface of the hexagonal boron nitride material, which enhances the synergistic effect between silicon dioxide and hexagonal boron nitride. During water lubrication, hexagonal boron nitride and silicon dioxide particles are easily released to the friction interface. On the one hand, under water lubrication conditions, the hexagonal boron nitride nanomaterials can form an excellent transfer film at the friction interface and can undergo hydrolysis with water to form a boric acid hydrate layer, providing excellent lubrication and significantly reducing material wear rate. On the other hand, the in-situ loaded silicon dioxide particles, under the action of frictional shear, can participate in the formation of the hexagonal boron nitride transfer film, enhancing the bonding force between the transfer film and the frictional pair, improving the elastic modulus, shear resistance, and load-bearing capacity of the transfer film, exhibiting excellent wear resistance. The self-lubricating phenolic laminate composite material prepared using the modified hexagonal boron nitride provided by this invention as a lubricating material can significantly improve its wear resistance and extend its service life. Attached Figure Description

[0039] Figure 1 The image shows a SEM image of the modified hexagonal boron nitride prepared in Example 1. Detailed Implementation

[0040] The present invention provides a modified hexagonal boron nitride, comprising hexagonal boron nitride and silicon dioxide bonded to the hexagonal boron nitride by silicon-oxygen bonds.

[0041] In one specific embodiment of the present invention, the mass ratio of silicon dioxide to hexagonal boron nitride in the modified hexagonal boron nitride can be 5-30:100, or even 8-20:100; the silicon dioxide is loaded on the surface of the hexagonal boron nitride; the average particle size of the silicon dioxide can be 10-30 nm, or even 10-20 nm; the average particle size of the hexagonal boron nitride can be 5-10 μm, or even 5-10 μm.

[0042] In this invention, hexagonal boron nitride possesses properties such as non-toxicity, high temperature resistance, corrosion resistance, high thermal conductivity, high insulation, and high lubricity. Under water lubrication conditions, it readily transfers to the surface of the friction-pair bearing. Furthermore, under frictional shearing, the hexagonal boron nitride nanomaterials undergo a hydrolysis reaction with water at the friction interface to form a boric acid hydrate layer, which provides excellent lubrication and significantly reduces material wear rate. This invention introduces silica into boron nitride to obtain modified hexagonal boron nitride. Using the modified hexagonal boron nitride provided by this invention to prepare phenolic laminated composite materials can more effectively improve the formation of a self-lubricating transfer film on the friction-pair surface under water lubrication conditions, greatly improving the tribological performance under water lubrication conditions.

[0043] This invention also provides a method for preparing the modified hexagonal boron nitride described in the above technical solution, comprising the following steps:

[0044] Hexagonal boron nitride and a strong alkaline solution were first mixed and then surface hydrolyzed and activated to obtain hydroxylated hexagonal boron nitride.

[0045] The hydroxylated hexagonal boron nitride, tetraethoxysilane, surfactant, alkaline solution, and solvent are mixed and subjected to a hydrolysis reaction to obtain the modified hexagonal boron nitride.

[0046] This invention involves surface hydrolysis and activation of a first mixture of hexagonal boron nitride and a strong alkaline solution to obtain hydroxylated hexagonal boron nitride. In one specific embodiment, the particle size of the hexagonal boron nitride can be 5–10 μm, specifically 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. In another specific embodiment, the strong alkaline solution can include one or more of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution, specifically sodium hydroxide solution, potassium hydroxide solution, or lithium hydroxide solution; the molar concentration of the strong alkaline solution can be 3–6 mol / L, specifically 3 mol / L, 4 mol / L, 5 mol / L, or 6 mol / L. In yet another specific embodiment, the mass ratio of the hexagonal boron nitride to the volume ratio of the strong alkaline solution can be 1 g:10–30 mL, specifically 1 g:10 mL, 1 g:15 mL, 1 g:20 mL, 1 g:25 mL, or 1 g:30 mL. In one specific embodiment of the present invention, the first mixing can be performed under ultrasonic conditions, and the ultrasonic time can be 10-30 minutes, or 15-25 minutes. The present invention does not have a particular limitation on the frequency of the ultrasonic waves, as long as the mixing is uniform.

[0047] In one specific embodiment of the present invention, the surface hydrolysis activation temperature can be 90–120°C, specifically 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C; the surface hydrolysis activation time can be 10–36 hours, specifically 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, or 36 hours. In another specific embodiment of the present invention, the surface hydrolysis activation can be accompanied by stirring. The present invention does not have any particular limitation on the stirring, as long as sufficient reaction is achieved.

[0048] This invention modifies hexagonal boron nitride with a strong alkali to obtain hydroxylated boron nitride. This improves the compatibility between the boron nitride surface and the resin, facilitating uniform dispersion. Furthermore, it provides active reaction sites for subsequent processing (hydrolysis reaction), allowing for in-situ growth of silica on the hexagonal boron nitride surface. On the other hand, the hydroxyl groups in the modified hexagonal boron nitride (from the hydroxyl groups on the surface of incompletely reacted hydroxylated boron nitride or the hydroxyl groups on the surface of silica particles) can undergo further chemical cross-linking reactions with phenolic resin and textile fibers, increasing the bonding strength between the hexagonal boron nitride nanomaterials and the phenolic resin and textile fibers, and further improving the material's wear resistance and compressive strength, among other mechanical properties.

[0049] In one specific embodiment of the present invention, the surface hydrolysis activation may further include: solid-liquid separation of the surface hydrolysis activated system, and sequential washing and drying of the solid obtained from the solid-liquid separation to obtain hydroxylated hexagonal boron nitride. In another specific embodiment of the present invention, the solid-liquid separation may be filtration; the washing agent may be water, and the water may be deionized water; the drying temperature may be 70–90°C, or 75–80°C. The present invention does not have special requirements for the drying time, as long as the solvent on the solid surface is removed.

[0050] After obtaining hydroxylated hexagonal boron nitride, the present invention further involves mixing the hydroxylated hexagonal boron nitride, tetraethoxysilane, surfactant, alkaline solution, and solvent in a second mixture, followed by a hydrolysis reaction to obtain the modified hexagonal boron nitride. As a specific embodiment of the present invention, the second mixing may include the following steps:

[0051] Tetraethoxysilane was dissolved in a portion of the solvent to obtain a tetraethoxysilane solution;

[0052] The hydroxylated hexagonal boron nitride was dispersed in the remaining solvent to obtain a hydroxylated hexagonal boron nitride dispersion.

[0053] An alkaline solution and a surfactant were added sequentially to the hydroxylated hexagonal boron nitride dispersion to obtain a mixed solution;

[0054] Add tetraethoxysilane solution dropwise to the mixed solution.

[0055] This invention dissolves tetraethoxysilane in a partial solvent to obtain a tetraethoxysilane solution. This invention does not have a specific limitation on the mass concentration of the tetraethoxysilane solution. This invention also does not have a specific limitation on the dissolution method, as long as complete dissolution is achieved. As a specific embodiment of this invention, the solvent includes an organic solvent and water; the organic solvent may include one or more of ethanol, ethylene glycol, glycerol, tetrahydrofuran, toluene, chlorobenzene, and dichlorobenzene, specifically ethanol, ethylene glycol, glycerol, tetrahydrofuran, toluene, chlorobenzene, or dichlorobenzene; the volume ratio of the organic solvent to water can be 1:4 to 6, specifically 1:4, 1:5, or 1:6.

[0056] This invention disperses hydroxylated hexagonal boron nitride in a residual solvent to obtain a hydroxylated hexagonal boron nitride dispersion. In one specific embodiment of this invention, the dispersion can be carried out under ultrasonic conditions for a duration of 10–20 min, or 15–18 min. This invention does not have a particular limitation on the power of the ultrasonic treatment, as long as it ensures uniform dispersion.

[0057] After obtaining the hydroxylated hexagonal boron nitride dispersion, the present invention sequentially adds an alkaline solution and a surfactant to the hydroxylated hexagonal boron nitride dispersion to obtain a mixed solution. As a specific embodiment of the present invention, the alkaline solution may include one or more of the following: a mixed solution of NH3 and NH4Cl, a mixed solution of NH3 and NH4HCO3, and NH3·H2O; specifically, it may be a mixed solution of NH3 and NH4Cl, a mixed solution of NH3 and NH4HCO3, or NH3·H2O; the pH value of the alkaline solution may be 8–10, specifically 8, 9, or 10. As a specific embodiment of the present invention, the surfactant includes one or more of the following: decaalkyltrimethylammonium chloride, N-dodecyl dimethylamine, fatty acid soap, sodium cis-9-octadecenoate, and sodium lauryl soap; specifically, it may be decaalkyltrimethylammonium chloride, N-dodecyl dimethylamine, fatty acid soap, sodium cis-9-octadecenoate, or sodium lauryl soap. In this invention, the surfactant can improve the dispersibility and stability of tetraethoxysilane and surface-hydroxylated hexagonal boron nitride in solution.

[0058] In one specific embodiment of the present invention, stirring may be carried out during the addition of alkaline solution and surfactant. The present invention does not have any special limitations on the stirring, as long as the mixture can be mixed evenly.

[0059] After obtaining the mixed solution, the present invention adds a tetraethoxysilane solution dropwise to the mixed solution. The present invention does not have a particular limitation on the rate of addition, as long as it can be added dropwise.

[0060] In one specific embodiment of the present invention, the mass ratio of the surface-hydroxylated hexagonal boron nitride to the solvent can be 1g:10-50mL, specifically 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL, 1g:30mL, 1g:35mL, 1g:40mL, 1g:45mL, or 1g:50mL; the volume ratio of the tetraethoxysilane to the solvent can be 1:4-30, or even 1:5-20; the mass ratio of the surfactant to the solvent can be 1:20-100, or even 1:30-80, or even more specifically 1:40-60; the mass ratio of the alkaline solution to the solvent can be 1g:20-35mL, or even 1g:25-30mL.

[0061] In one specific embodiment of the present invention, the temperature of the hydrolysis reaction can be 15–35°C, specifically 15°C, 20°C, 25°C, 30°C, or 35°C; the time of the hydrolysis reaction can be 12–36 hours, or 18–30 hours, or even 20–26 hours. In another specific embodiment of the present invention, the hydrolysis reaction can be accompanied by stirring. The present invention does not have any particular limitation on the stirring, as long as the reaction is sufficient. In the present invention, after the hydrolysis reaction, the hydroxyl groups on the surface of hexagonal boron nitride and silicon dioxide form silicon-oxygen bonds through hydrolytic condensation, and the silicon dioxide is loaded onto the surface of boron nitride through chemical bonding.

[0062] This invention involves treating hexagonal boron nitride with a strong alkali and then grafting it with silica. This not only enhances the synergistic lubrication effect between the two materials but also introduces hydroxyl active groups onto the surface of the silica. This increases the hydrophilicity of the silica-loaded hexagonal boron nitride hybrid material, ensuring uniform dispersion in phenolic resin. Furthermore, during the curing process, the silica binds to the phenolic resin and textile fibers through hydrogen bonds and chemical bonds, increasing the bonding force between the filler (modified hexagonal boron nitride) and the phenolic resin and textile fibers. This significantly improves the mechanical strength and wear resistance of the phenolic laminate composite material under water lubrication conditions.

[0063] In one specific embodiment of the present invention, the hydrolysis reaction may further include: solid-liquid separation of the hydrolysis reaction system, and sequential washing and drying of the solid obtained from the solid-liquid separation to obtain modified hexagonal boron nitride. In another specific embodiment of the present invention, the solid-liquid separation may be filtration; the washing agent includes sequential water washing and ethanol solution washing, wherein the water used for water washing may be deionized water, and the mass concentration of the ethanol solution used for ethanol solution washing may be 95-100%; the drying temperature may be 70-90℃, or 75-80℃. The present invention does not have special requirements for the drying time, as long as the solvent on the surface of the solid is removed.

[0064] The present invention also provides the application of the modified hexagonal boron nitride described in the above technical solution or the modified hexagonal boron nitride prepared by the preparation method described in the above technical solution as a lubricant.

[0065] The present invention also provides a self-lubricating phenolic laminate composite material, comprising the following components in weight percentage:

[0066] Phenolic resin 40-55%;

[0067] Textile fiber fabric 35-57%;

[0068] Lubricant 3-15%;

[0069] The lubricant is the modified hexagonal boron nitride described in the above technical solution or the modified hexagonal boron nitride prepared by the preparation method described in the above technical solution.

[0070] The self-lubricating phenolic laminated composite material provided by the present invention comprises 40-55% phenolic resin, which can be 45-50%, by weight percentage.

[0071] The self-lubricating phenolic laminated composite material provided by the present invention, by weight percentage, comprises 35-57% textile fiber fabric, which can be 40-50% or 45-48%. As a specific embodiment of the present invention, the fibers in the textile fiber fabric may include one or more of polyester fibers, cotton fibers, acrylic fibers, polytetrafluoroethylene fibers, and aramid fibers, specifically polyester fibers, cotton fibers, acrylic fibers, polytetrafluoroethylene fibers, or aramid fibers.

[0072] The self-lubricating phenolic laminated composite material provided by the present invention comprises 3-15% lubricant, which can be 5-13% or 8-11% by weight.

[0073] The self-lubricating phenolic laminate composite material provided by this invention has a compressive strength of 295–310 MPa, a compressive modulus of 4.8–5 GPa, a friction coefficient of 0.15–0.22 under water lubrication conditions, and a volumetric wear rate of (1.8–2.2) × 10⁻⁶. -6 mm 3 / Nm.

[0074] The self-lubricating phenolic laminated composite material provided by this invention has the characteristics of fast frictional running-in and high wear resistance under water lubrication conditions. The hydrated boric acid layer formed by the in-situ hydrolysis of hexagonal boron nitride and the excellent self-lubricating properties of boron nitride, together with the textile fiber cloth, promote the formation of the friction lubrication film at the friction interface. The in-situ composite of hard silica enhances the load-bearing capacity of the friction lubrication film.

[0075] This invention also provides a method for preparing the self-lubricating phenolic laminate composite material described in the above technical solution, comprising the following steps:

[0076] The lubricant, phenolic resin, and diluent are mixed to obtain a phenolic resin mixed solution;

[0077] The textile fiber fabric is impregnated with the phenolic resin mixture and then dried to obtain a pre-impregnated textile fiber fabric.

[0078] The pre-impregnated textile fiber cloth is shaped and then sintered and cured to obtain the self-lubricating phenolic laminate composite material.

[0079] This invention involves mixing the lubricant, phenolic resin, and diluent to obtain a phenolic resin mixed solution. As a specific embodiment of this invention, the mixing process may include the following steps:

[0080] A phenolic resin solution is obtained by mixing phenolic resin with a portion of the diluent.

[0081] The remaining diluent is added after the phenolic resin solution and lubricant are mixed.

[0082] In one specific embodiment of the present invention, the diluent may include ethanol or methanol; the solid content of the phenolic resin solution may be 60-80%, or even 70-75%. In another specific embodiment of the present invention, the phenolic resin solution and the lubricant may be mixed by a three-roll mill.

[0083] After obtaining the phenolic resin mixed solution, the present invention impregnates the textile fiber fabric with the phenolic resin mixed solution and then dries it to obtain a pre-impregnated textile fiber fabric. In one specific embodiment of the present invention, the amount of sizing after impregnating the textile fiber fabric with the phenolic resin mixed solution can be 45%–65%, specifically 45%, 50%, 55%, 60%, or 65%. In another specific embodiment of the present invention, the drying temperature can be 100–120°C, or even 110–115°C; the drying time can be 1–10 minutes, or even 2–8 minutes. 。

[0084] After obtaining the pre-impregnated textile fiber fabric, the present invention shapes and then sintersulates the pre-impregnated textile fiber fabric to obtain the self-lubricating phenolic laminate composite material. As a specific embodiment of the present invention, the shaping can be winding; the winding temperature can be 110–130°C, specifically 110°C, 115°C, 120°C, 125°C, or 130°C; the winding pressure can be 140–160N, specifically 140N, 145N, 150N, 155N, or 160N; the winding tension can be 140–160N, specifically 140N, 145N, 150N, 155N, or 160N. In one specific embodiment of the present invention, the sintering and curing includes sequentially performing a first sintering and curing, a second sintering and curing, and a third sintering and curing. The temperature of the first sintering and curing can be 75-85°C, specifically 75°C, 80°C, or 85°C. The holding time for the first sintering and curing can be 90-120 minutes, specifically 90 minutes, 95 minutes, 100 minutes, 105 minutes, 110 minutes, 115 minutes, or 120 minutes. The present invention can raise the temperature from room temperature to the required temperature for the first sintering and curing in 20 minutes. The room temperature can be 20-35°C, or even 25-30°C.

[0085] In one specific embodiment of the present invention, the second sintering and curing temperature can be 100–120°C, specifically 100°C, 105°C, 110°C, 115°C, or 120°C; the holding time for the second sintering and curing can be 90–120 min, specifically 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, or 120 min. The present invention allows the temperature to be increased from the first sintering and curing temperature to the required second sintering and curing temperature within 10 min.

[0086] In one specific embodiment of the present invention, the third sintering and curing temperature can be 140–160°C, specifically 140°C, 145°C, 150°C, 155°C, or 160°C; the holding time for the third sintering and curing can be 120–240 min, specifically 120 min, 150 min, 180 min, 200 min, 220 min, 230 min, or 240 min. The present invention allows the temperature to be increased from the second sintering and curing temperature to the required third sintering and curing temperature within 10 minutes.

[0087] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0088] Example 1

[0089] The preparation method of modified hexagonal boron nitride is as follows:

[0090] 30g of hexagonal boron nitride with an average particle size of 5μm and 300mL of sodium hydroxide solution with a molar concentration of 5mol / L were mixed under ultrasonic conditions for 20min; after surface activation hydrolysis (with stirring) at 110℃ for 15h, the mixture was filtered, and the solid obtained by filtration was washed with deionized water until neutral and then dried at 80℃ to obtain hydroxylated hexagonal boron nitride.

[0091] Tetraethoxysilane and a solvent (a mixture of ethanol and water in a volume ratio of 1:5) were mixed at a volume ratio of 1:10 to obtain a tetraethoxysilane ethanol solution. 10g of hydroxylated hexagonal boron nitride was dispersed in 200mL of the solvent and sonicated at room temperature for 15min to obtain a hydroxylated hexagonal boron nitride dispersion. 6g of ammonia alkaline solution and 2.4g of decaalkyltrimethylammonium chloride (surfactant) were added sequentially to the hydroxylated hexagonal boron nitride dispersion to adjust the pH of the system to 9. After stirring and dispersing evenly, 30mL of tetraethoxysilane ethanol solution was added dropwise, and the mixture was stirred at 30℃ for 18h for hydrolysis (with stirring). After the reaction was completed, the mixture was filtered, and the solid obtained by filtration was washed with deionized water and 95% ethanol solution until neutral. The solid was then dried at 80℃ to obtain modified hexagonal boron nitride.

[0092] The preparation method of self-lubricating phenolic laminate composite material is as follows:

[0093] Phenolic resin and ethanol were mixed to obtain a phenolic resin ethanol solution with a solid content of 70%. 300g of modified hexagonal boron nitride was added to 4285g of phenolic resin ethanol solution and dispersed evenly by three-roll milling. Then 2315g of ethanol was added and stirred at 1000rpm to obtain a phenolic resin mixed solution.

[0094] A 100-count textile fiber fabric (woven from a mixture of polyester and cotton fibers) that has been desized is impregnated in a phenolic resin mixture solution by continuous fiber impregnation and dried continuously at 110°C for 8 minutes to obtain a pre-impregnated textile fiber fabric with a resin content of 55%.

[0095] Pre-impregnated textile fiber cloth is continuously wound into tubes using a winding machine. The winding process parameters are: winding temperature of 120℃, winding pressure of 150N, and winding tension of 150N. After winding, the product is placed in a high-temperature sintering furnace for high-temperature sintering and curing. The sintering process is as follows: the temperature is linearly increased from 20℃ to 80℃ over 20 minutes and held at 80℃ for 120 minutes; the temperature is linearly increased from 80℃ to 100℃ over 10 minutes and held at 100℃ for 120 minutes; the temperature is linearly increased from 100℃ to 160℃ over 10 minutes and held at 160℃ for 120 minutes, and then allowed to cool naturally to obtain a self-lubricating phenolic laminate composite material.

[0096] Example 2

[0097] Modified hexagonal boron nitride was prepared according to the method in Example 1;

[0098] The preparation method of self-lubricating phenolic laminate composite material is as follows:

[0099] Phenolic resin and ethanol were mixed to obtain a phenolic resin ethanol solution with a solid content of 70%. 200g of modified hexagonal boron nitride was added to 4285g of phenolic resin ethanol solution and dispersed evenly by three-roll milling. Then, 2315g of ethanol was added and stirred at 1000rpm to obtain a phenolic resin mixed solution.

[0100] A 100-count textile fiber cloth (woven from a mixture of polyester and cotton fibers) that has been desized is impregnated in a phenolic resin mixture solution by continuous fiber impregnation and dried continuously at 110°C for 5 minutes to obtain a pre-impregnated textile fiber cloth. The amount of sizing on the pre-impregnated textile fiber cloth is 50%.

[0101] Pre-impregnated textile fiber cloth is continuously wound into tubes using a winding machine. The winding process parameters are: winding temperature of 120℃, winding pressure of 150N, and winding tension of 150N. After winding, the product is placed in a high-temperature sintering furnace for high-temperature sintering and curing. The sintering process is as follows: the temperature is linearly increased from 20℃ to 80℃ over 20 minutes and held at 80℃ for 120 minutes; the temperature is linearly increased from 80℃ to 100℃ over 10 minutes and held at 100℃ for 120 minutes; the temperature is linearly increased from 100℃ to 160℃ over 10 minutes and held at 160℃ for 120 minutes, and then allowed to cool naturally to obtain a self-lubricating phenolic laminate composite material.

[0102] Example 3

[0103] The preparation method of modified hexagonal boron nitride is as follows:

[0104] 30g of hexagonal boron nitride with an average particle size of 8μm and 300mL of sodium hydroxide solution with a molar concentration of 3mol / L were mixed under ultrasonic conditions for 25min; after surface activation hydrolysis (with stirring) at 120℃ for 30h, the mixture was filtered, and the solid obtained by filtration was washed with deionized water until neutral and then dried at 80℃ to obtain hydroxylated hexagonal boron nitride.

[0105] Tetraethoxysilane and a solvent (a mixture of ethanol and water in a volume ratio of 1:5) were mixed at a volume ratio of 1:10 to obtain a tetraethoxysilane ethanol solution. 10 g of hydroxylated hexagonal boron nitride was dispersed in 200 mL of the solvent and sonicated at room temperature for 15 min to obtain a hydroxylated hexagonal boron nitride dispersion. 6 g of ammonia alkaline solution and 2.4 g of decaalkyltrimethylammonium chloride (surfactant) were added sequentially to the hydroxylated hexagonal boron nitride dispersion to adjust the pH of the system to 10. After stirring and dispersing evenly, 45 mL of tetraethoxysilane ethanol solution was added dropwise, and the mixture was subjected to a hydrolysis reaction at 18 °C with stirring for 36 h. After the reaction was completed, the mixture was filtered, and the solid obtained by filtration was washed with deionized water and an ethanol solution with a mass concentration of ...% until neutral. The solid was then dried at 80 °C to obtain modified hexagonal boron nitride.

[0106] A self-lubricating phenolic laminate composite material was prepared according to the method in Example 1.

[0107] Comparative Example 1

[0108] The traditional self-lubricating phenolic laminate composite material is prepared as follows:

[0109] Take 200g of molybdenum disulfide and add it to 4285g of phenolic resin ethanol solution with a solid content of 70%. The modified phenolic resin solution with molybdenum disulfide uniformly dispersed is obtained by three-roll milling. Add 2315g of ethanol solution and stir at 1000rpm to obtain the modified phenolic resin diluted solution.

[0110] The surface-desized 100-count conventional cotton fiber cloth was impregnated in the above-mentioned modified phenolic resin diluted solution by continuous fiber impregnation, and then continuously dried at 100°C to obtain pre-impregnated cotton fiber cloth. The amount of resin on the pre-impregnated cotton fiber cloth was 50%.

[0111] Modified phenolic resin pre-impregnated cotton fiber cloth is continuously wound into tubes using a winding machine. The winding process parameters are: winding temperature 120℃, winding pressure 100N, and winding tension 150N. After winding, the cotton fiber cloth phenolic laminate tube is placed in a high-temperature sintering furnace for high-temperature sintering and curing. The sintering process is as follows: holding at 80℃ for 120 minutes; holding at 100℃ for 120 minutes; holding at 120℃ for 120 minutes; holding at 160℃ for 120 minutes; and then naturally cooled to obtain molybdenum disulfide modified cotton fiber cloth phenolic laminate material.

[0112] Comparative Example 2

[0113] The preparation method for traditional phenolic laminated composite materials, namely phenolic bakelite, is as follows:

[0114] Take 4285g of phenolic resin ethanol solution with a solid content of 70%, add 1715g of ethanol solution, and obtain a diluted phenolic resin adhesive by high-speed stirring;

[0115] A 100-count conventional cotton fiber cloth that has been desized is impregnated in the above-mentioned diluted phenolic resin solution by continuous fiber impregnation, and then continuously dried at 100°C to obtain a pre-impregnated cotton fiber cloth with a resin content of 50%.

[0116] Modified phenolic resin pre-impregnated cotton fiber cloth is continuously wound into tubes using a winding machine. The winding process parameters are: winding temperature 110℃, winding pressure 100N, and winding tension 150N. After winding, the cotton fiber cloth phenolic laminate tube is placed in a high-temperature sintering furnace for high-temperature sintering and curing. The sintering process is as follows: holding at 80℃ for 120 minutes; holding at 100℃ for 120 minutes; holding at 120℃ for 120 minutes; holding at 160℃ for 120 minutes. Then, it is allowed to cool naturally to obtain the cotton fiber cloth phenolic laminate material, i.e., phenolic bakelite material.

[0117] The modified hexagonal boron nitride prepared in Example 1 was examined by scanning electron microscopy, and the SEM and EDX elemental analysis maps were obtained, as shown below. Figure 1 As shown. By Figure 1 It can be seen that the modified hexagonal boron nitride surface is uniformly covered with nanoparticles with a particle size of 10–30 nm. EDX elemental analysis shows that the modified boron nitride surface is uniformly covered with a large amount of silicon and oxygen elements, indicating that silicon-oxygen bonded silica nanoparticles with a particle size of 10–30 nm were successfully synthesized on the modified boron nitride surface. The surface roughness and surface area of ​​the modified boron nitride are significantly increased. This will significantly enhance the contact area and mechanical interlocking effect at the interface between the modified boron nitride and phenolic resin, and greatly increase the interfacial bonding force between the modified boron nitride and phenolic resin.

[0118] The silica loading was calculated by subtracting the mass of unmodified boron nitride from the mass of modified hexagonal boron nitride and then dividing the result by the mass of unmodified boron nitride. The silica loading in the modified hexagonal boron nitride prepared in Examples 1-3 was 23.1 wt%, 23.1 wt%, and 18.4 wt%, respectively.

[0119] The mechanical properties and water lubrication properties of the phenolic laminates prepared in Examples 1-3 and Comparative Examples 1-2 were tested respectively. The test steps are as follows:

[0120] (1) The compressive strength test shall be conducted in accordance with the "Test Method for Compression Properties of Fiber Reinforced Plastics" (GB / T1448-2005), and the corresponding standard test specimen shall be processed and the compressive strength shall be measured by a universal testing machine.

[0121] (2) Friction and wear performance testing was conducted according to the "Test Method for Sliding Friction and Wear of Plastics" (GB / T3960-2016). The testing equipment was an MRH-1A ring-block friction and wear testing machine. All friction tests were conducted at room temperature. In the water lubrication test, the sample and the mating part were completely immersed in deionized water. The test conditions were as follows: the mating steel ring was QSn7-0.2, Ra was 0.1~0.2μm, the diameter of the mating ring was 50mm, the test load was 132N, the sliding speed was 0.36m / s, and the test time was 2h. During the test, the friction coefficient was read directly from the equipment. The wear width was measured using a three-dimensional surface profilometer, and the volumetric wear rate was calculated. The samples in the examples and comparative examples were tested for friction and wear performance at least three times, and the average value was taken. The test results are listed in Table 1.

[0122] Table 1. Performance of phenolic laminates in Examples 1-3 and Comparative Examples 1-2

[0123]

[0124] As can be seen from Table 1, compared with the phenolic laminated composite material prepared in the comparative example, the self-lubricating phenolic laminated composite material prepared by the present invention with modified hexagonal boron nitride as the lubricating phase has higher compressive strength and exhibits excellent friction and wear performance under water lubrication conditions. Among them, the self-lubricating phenolic laminated composite material prepared in Example 1 has a friction coefficient that is 36% lower than that in Comparative Example 2 under water lubrication conditions, and its wear resistance is improved by about 300%.

[0125] This invention uses modified hexagonal boron nitride as the lubricating phase to prepare self-lubricating phenolic laminate composites. This can further improve the compressive strength of phenolic laminate composites, and make phenolic laminate composites have both low friction and high wear resistance, with excellent water-lubricated tribological properties.

[0126] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A self-lubricating phenolic laminate composite material, characterized in that, The components include the following components by mass percentage: Phenolic resin 40-55%; Textile fiber fabric 35~57%; Lubricant 3~15%; The lubricant is modified hexagonal boron nitride, which comprises hexagonal boron nitride and silicon dioxide bonded to the hexagonal boron nitride by silicon-oxygen bonds; the mass ratio of silicon dioxide to hexagonal boron nitride in the modified hexagonal boron nitride is 5~8:100; the particle size of the hexagonal boron nitride is 5~10μm.

2. The self-lubricating phenolic laminated composite material according to claim 1, characterized in that, The method for preparing the modified hexagonal boron nitride includes the following steps: Hexagonal boron nitride and a strong alkaline solution were first mixed and then surface hydrolyzed and activated to obtain hydroxylated hexagonal boron nitride. The hydroxylated hexagonal boron nitride, tetraethoxysilane, surfactant, alkaline solution, and solvent are mixed and subjected to a hydrolysis reaction to obtain the modified hexagonal boron nitride.

3. The self-lubricating phenolic laminate composite material according to claim 2, characterized in that, The strong alkali solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and lithium hydroxide solution; the molar concentration of the strong alkali solution is 3~6 mol / L; The mass ratio of the hexagonal boron nitride to the volume ratio of the strong alkaline solution is 1g:10~30mL.

4. The self-lubricating phenolic laminate composite material according to claim 2 or 3, characterized in that, The surface hydrolysis activation temperature is 90~120℃; the surface hydrolysis activation time is 10~36h.

5. The self-lubricating phenolic laminate composite material according to claim 2, characterized in that, The alkaline solution includes one or more of the following: a mixed solution of NH3 and NH4Cl, a mixed solution of NH3 and NH4HCO3, and NH3·H2O; the pH value of the alkaline solution is 8-10. The surfactant includes one or more of decaalkyltrimethylammonium chloride, N-dodecyldimethylamine, fatty acid soap, sodium cis-9-octadecenoate, and sodium laurate soap; The solvent includes an organic solvent and water, wherein the organic solvent includes one or more of ethanol, ethylene glycol, glycerol, tetrahydrofuran, toluene, chlorobenzene and dichlorobenzene; and the volume ratio of the organic solvent to water is 1:4 to 6.

6. The self-lubricating phenolic laminate composite material according to claim 5, characterized in that, The mass ratio of the surface-hydroxylated hexagonal boron nitride to the volume ratio of the solvent is 1g:10~50mL; The volume ratio of the tetraethoxysilane to the solvent is 1:4~30; The mass ratio of the surfactant to the solvent is 1:20~100; The mass ratio of the alkaline solution to the volume ratio of the solvent is 1g:20~35mL; The hydrolysis reaction is carried out at a temperature of 15~35℃ for a time of 12~36h.

7. The self-lubricating phenolic laminate composite material according to claim 1, characterized in that, The fibers in the textile fiber fabric include one or more of polyester fibers, cotton fibers, acrylic fibers, polytetrafluoroethylene fibers, and aramid fibers.

8. A method for preparing the self-lubricating phenolic laminated composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: The lubricant, phenolic resin, and diluent are mixed to obtain a phenolic resin mixed solution; The textile fiber fabric is impregnated with the phenolic resin mixture and then dried to obtain a pre-impregnated textile fiber fabric. The pre-impregnated textile fiber cloth is shaped and then sintered and cured to obtain the self-lubricating phenolic laminate composite material.

9. The preparation method according to claim 8, characterized in that, The sizing amount of textile fiber cloth after impregnation with phenolic resin mixture is 45-65%; The drying temperature is 100~120℃, and the time is 1~10min.

10. The preparation method according to claim 8, characterized in that, The sintering and curing process includes sequentially performing a first sintering and curing, a second sintering and curing, and a third sintering and curing. The first sintering and solidification temperature is 75~85℃, and the first sintering and solidification holding time is 90~120min; The second sintering and curing temperature is 100~120℃, and the second sintering and curing holding time is 90~120min; The third sintering and curing temperature is 140~160℃, and the holding time for the third sintering and curing is 120~240min.

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