A method for producing a low-friction coefficient material

Abstract

The application belongs to the technical field of ecological materials, and particularly relates to a preparation method of a low-friction coefficient material, which comprises the following steps: soaking raw materials in an alkaline solution, adding the raw materials into a mixed solution to remove lignin through a hydrothermal reaction, adding a binder and an additive with lubricating properties, and obtaining the low-friction coefficient material after treatment; the mixed solution is a mixed solution of a reducing agent and an alkaline solution; the mass percentage of the binder in the low-friction coefficient material is 0.1-30%, and the mass percentage of the additive is 0.1-50%. The obtained low-friction coefficient material has higher hardness and lower friction coefficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ecological materials, and particularly relates to a preparation method of a low-friction coefficient material. BACKGROUND

[0002] Wood is the only renewable material among the four major materials (steel, wood, plastic and cement) in the world today. As a natural polymer-based biomass, wood has evolved a complex hierarchical structure over a long period of time to adapt to harsh and variable environments. The hierarchical structure spans multiple orders of magnitude, and each scale structure is arranged in a hierarchical order, which endows wood with different properties and functions. Therefore, when wood is used in production and life scenarios, it exhibits good visibility (natural and beautiful texture), excellent thermal insulation, excellent processability (all types of mechanical processing can be performed), and environmental friendliness, showing great application potential. According to the research on the hierarchical porous microstructure of wood, many wood modification methods have been proposed, such as surface coating, heat treatment, densification treatment, and impregnation treatment to improve the mechanical properties, water resistance, flame retardance, wear resistance, and corrosion resistance of wood. In order to strengthen the performance, the wood is applied to the field of household, civil engineering, aerospace, etc. This is of great significance to economic development and environmental protection.

[0003] In a coordinated mechanical system, the friction between parts is very important. Severe friction between contact surfaces not only wastes energy, but also damages the surface structure of the components, leading to failure of the coordinated system and reducing overall production efficiency. Therefore, in a mechanical coordination system containing wood, the friction between wood and other materials is crucial to the system construction. How to reduce the friction and wear between wood and other materials is a key scientific problem. Currently, wood friction modification methods mainly focus on surface construction, such as spraying a nano coating with a specific texture on the surface to reduce adhesion between contact surfaces, or impregnating a liquid with lubricating properties into wood to penetrate the friction contact interface and play a lubricating role during friction. Surface modification of wood can achieve immediate results, but it has the disadvantages of rapid performance decline and poor long-term stability. The interface between the surface structure and the wood substrate is relatively weak and easy to be damaged and fail under repeated high-intensity friction. With the increasing demand for wood, it is urgent to develop a wood modification method with low friction and high hardness. SUMMARY

[0004] To provide a modification method of wood with low friction and high hardness, the present application provides a preparation method of a low-friction coefficient material.

[0005] A method for preparing a low-friction coefficient material, wherein raw materials are soaked in an alkaline solution, then added to a mixed solution to remove lignin through a hydrothermal reaction, and then a binder and an additive with lubricating properties are added to obtain the low-friction coefficient material after treatment.

[0006] The mixed solution is a mixed solution of a reducing agent and an alkaline solution, and the alkaline solution has a mass concentration of 0.1%-30%.

[0007] The low-friction coefficient material contains 0.1-30% of the binder by mass and 0.1-50% of the additive by mass.

[0008] Preferably, the alkaline solution is one or a composite of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, calcium hydroxide solution, ammonia, sodium carbonate, and sodium bicarbonate.

[0009] Preferably, the mass ratio of the reducing agent to the alkaline solution in the mixed solution is 1:1-5.

[0010] Preferably, the additive is one or more of polytetrafluoroethylene (PTFE) and its derivatives, zirconium oxide ceramic particles, silicon nitride ceramic particles, talc, graphene, and hexagonal boron nitride.

[0011] Preferably, the binder is one or more of sodium alginate, epoxy resin, cyclodextrin and its derivatives, cyanoacrylate and its derivatives, phenolic oligomers, aromatic hydrocarbon derivatives, polymeric cyclic ether derivatives, polyethylene glycol, cellulose and its derivatives, dopamine, and polyvinylidene fluoride.

[0012] The reducing agent is one or more of hydrazine hydrate, sodium borohydride, potassium borohydride, ethanol, iron sulfite, potassium sulfite, sodium bisulfite, tin chloride, sodium sulfite, magnesium, and aluminum.

[0013] Preferably, the raw materials include natural wood, wood chips, and dried herbs.

[0014] Preferably, when the raw material is natural wood, the specific steps for preparation are as follows:

[0015] (7.1) The natural wood is sliced and soaked in an alkaline solution for 1-3 days, then added to the mixed solution and reacted at 50-200 ℃ for 2-10 hours;

[0016] (7.2) The wood from step (7.1) is repeatedly washed until the pH of the solution is about 7, to obtain porous wood.

[0017] (7.3) configuring the additive into an additive solution of 0.1-30 wt%, configuring the binder into a binder solution of 0.1-10 wt%, introducing the additive solution and the binder solution into the porous wood of (7.2) to obtain the composite wood;

[0018] (7.4) treating the composite wood of (7.3) at normal temperature or 40-150 ℃ under a pressure of 20-100 MPa to make the water molecules be uniformly discharged along the direction of the pressure to obtain the low-friction coefficient material.

[0019] Preferably, the ratio of the natural wood to the mixed solution in step (7.1) is 1:2-5.

[0020] Preferably, the pressure of the pressure treatment in step (5.3) is 20-100 MPa.

[0021] Preferably, when the raw material is wood chips, the specific steps for preparation are as follows:

[0022] (9.1) crushing the wood chips to obtain wood chip powder, soaking the wood chip powder in an alkaline solution for 1-3 days, and then adding the wood chip powder into the mixed solution to react at 50-200 ℃ for 2-10 hours;

[0023] The ratio of the wood chip powder to the mixed solution is 1:2-5.

[0024] (9.2) repeatedly washing the wood chips after step (9.1) and then drying to obtain the precursor powder;

[0025] (9.3) mixing and grinding the precursor powder with the binder and the additive, laying the mixed powder flat, and obtaining the low-friction coefficient material under normal temperature and high pressure or hot pressing.

[0026] Preferably, the drying is performed at 30-100 ℃ or freeze-drying.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] 1、The raw material is soaked in an alkaline solution, the natural cellulose on the surface layer is alkalinized to generate alkali cellulose which is easily soluble in the alkaline solution, the cellulose network structure is swelled to have a looser structure and the accessibility is improved, that is, the reaction performance is improved, and the subsequent treatment is facilitated. The wood after alkali treatment is soaked in a certain proportion of sodium sulfite alkaline solution, and a hydrothermal reaction is carried out under high temperature and high pressure, by means of sulfonation of sodium sulfite and catalysis of the solution, temperature and pressure, the lignin which is difficult to dissolve and has higher strength in the cellulose network is converted into water-soluble lignin sulfonate, so that the lignin is removed in the subsequent rinsing, the composition in the cellulose network is more clean and uniform, in the subsequent pressurized treatment process, the cellulose network can be more densely attached together to form a block structure, so that the hardness is improved, and the friction coefficient is not increased due to the particles mixed in the cellulose network in the friction process.

[0029] 2、The low friction coefficient material prepared by the present application has higher hardness and lower friction coefficient, the Brinell hardness of wood is generally about 18, and the Brinell hardness of the optimized low friction coefficient material is close to 30. In addition, the friction coefficient will change greatly, the average friction coefficient of wood under a load of 5 N is 0.25, and the friction coefficient has a growing trend with time, while the average friction coefficient of the optimized low friction coefficient material under a load of 5 N is 0.06 and has higher stability. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The Brinell hardness values of natural wood and the low friction coefficient material of example 1 of the present application;

[0031] Figure 2 The friction curves of natural wood and the low friction coefficient material of example 1 of the present application.

[0032] Note: Figures 1-2 The low-moderate friction coefficient composite wood represents the low friction coefficient material of the present application. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application will be described in detail below, but it should be understood that the protection scope of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the protection scope of the present application. The experimental methods described in the embodiments of the present application are conventional methods unless otherwise specified.

[0034] The natural wood in the raw material refers to block wood, not wood chips.

[0035] Example 1

[0036] A method for preparing a low-friction coefficient material, comprising the following steps:

[0037] (1) Cutting natural basswood into a size of 100x50x25 mm, soaking in a potassium hydroxide solution with a mass concentration of 0.1% for 1 day, and completely immersing the natural basswood in the potassium hydroxide solution; after soaking, adding the natural basswood into a mixed solution of potassium sulfite and potassium hydroxide, the mass concentration of the potassium hydroxide being 0.5%, and performing hydrothermal reaction at 50°C for 10 hours to remove lignin;

[0038] The mass ratio of potassium sulfite to potassium hydroxide in the mixed solution is 1:1, and the mass-volume ratio of the natural basswood to the mixed solution is 1:2.

[0039] (2) Repeatedly washing the basswood after the hydrothermal reaction until the pH is about 7 to obtain porous wood.

[0040] (3) Preparing a PTFE solution with a concentration of 0.1wt% and a sodium alginate solution with a concentration of 0.1wt%, and introducing the PTFE solution and the sodium alginate solution into the porous wood to obtain composite wood.

[0041] (4) Placing the composite wood in a press to press out water at room temperature and under a pressure of 20MPa, so that water molecules are uniformly expelled along the direction of the pressure, and then drying at 60°C to obtain the low-friction coefficient material, the mass percentage of PTFE in the low-friction coefficient material being 30%, and the mass percentage of sodium alginate being 10%.

[0042] Example 2

[0043] A method for preparing a low-friction coefficient material, comprising the following steps:

[0044] (1) Cutting natural basswood into a size of 100x50x25 mm, soaking in a sodium hydroxide solution with a mass concentration of 5% for 2 days, and completely immersing the natural basswood in the sodium hydroxide solution; after soaking, adding the natural basswood into a mixed solution of hydrazine hydrate and lithium hydroxide, the mass concentration of the lithium hydroxide being 0.5%, and performing hydrothermal reaction at 100°C for 2 hours to remove lignin;

[0045] The mass ratio of hydrazine hydrate to lithium hydroxide in the mixed solution is 1:3, and the mass-volume ratio of the natural basswood to the mixed solution is 1:3.

[0046] (2) Repeatedly washing the basswood after the hydrothermal reaction until the pH is about 7 to obtain porous wood.

[0047] (3) Preparing a talc powder solution with a concentration of 10wt% and an epoxy resin solution with a concentration of 5wt%, and introducing the talc powder solution and the epoxy resin solution into the porous wood to obtain composite wood.

[0048] (4) Put the composite wood into the press at 40℃, press out water at 60MPa, so that water molecules are uniformly discharged along the pressure direction, to obtain the low friction coefficient material, the mass ratio of talc in the low friction coefficient material is 0.1%, and the mass ratio of epoxy resin is 0.1%.

[0049] Example 3

[0050] A preparation method of a low friction coefficient material, comprising the following steps:

[0051] (1) Cut natural linden wood into a size of 100×50×25 mm, soak in a calcium hydroxide solution for 3 days, the mass concentration of calcium hydroxide is 10%, and the natural linden wood needs to be completely soaked in the calcium hydroxide solution, after soaking, add the natural linden wood to a mixed solution of sodium borohydride and ammonia water, the mass concentration of ammonia water is 10%, and hydrothermal reaction is carried out at 200℃ for 5 hours to remove lignin;

[0052] The mass ratio of sodium borohydride to ammonia water in the mixed solution is 1:5, and the mass-volume ratio of natural linden wood to the mixed solution is 1:5.

[0053] (2) After the hydrothermal reaction of the linden wood is completed, repeatedly rinse the linden wood until the pH is about 7 to obtain a porous wood.

[0054] (3) Prepare a zirconium oxide ceramic particle solution with a concentration of 30wt% and a polyethylene glycol solution with a concentration of 10wt%, introduce the zirconium oxide ceramic particle solution and the polyethylene glycol solution into the porous wood to obtain a composite wood.

[0055] (4) Put the composite wood into the press at 150℃, press out water at 100MPa, so that water molecules are uniformly discharged along the pressure direction, to obtain the low friction coefficient material, the mass ratio of zirconium oxide ceramic particles in the low friction coefficient material is 50%, and the mass ratio of polyethylene glycol is 30%.

[0056] Example 4

[0057] A preparation method of a low friction coefficient material, comprising the following steps:

[0058] (1) Cut natural linden wood into a size of 100×50×25 mm, soak in a potassium hydroxide solution for 3 days, the mass concentration of potassium hydroxide is 20%, and the natural linden wood needs to be completely soaked in the potassium hydroxide solution, after soaking, add the natural linden wood to a mixed solution of potassium sulfite and potassium hydroxide, the mass concentration of potassium hydroxide is 20%, and hydrothermal reaction is carried out at 100℃ for 4 hours to remove lignin;

[0059] The mass ratio of potassium sulfite to potassium hydroxide in the mixed solution is 1:5, and the mass-volume ratio of natural basswood to the mixed solution is 1:5.

[0060] (2) The basswood after the hydrothermal reaction is repeatedly washed until the pH is about 7 to obtain the porous wood.

[0061] (3) A PTFE solution with a concentration of 30wt% and a sodium alginate solution with a concentration of 10wt% are prepared, and the PTFE solution and the sodium alginate solution are introduced into the porous wood to obtain the composite wood.

[0062] (4) The composite wood is placed in a press at 100°C and pressed at 60MPa to remove water, so that water molecules are uniformly expelled along the pressure direction to obtain the low-friction coefficient material, and the mass fraction of PTFE in the low-friction coefficient material is 30%, and the mass fraction of sodium alginate is 10%.

[0063] Example 5

[0064] A method for preparing a low-friction coefficient material, comprising the following steps:

[0065] (1) Wood chips are placed in a planetary ball mill for ball milling for 10 min, and then the obtained wood chip powder is soaked in a potassium hydroxide solution for 1 day, and the mass concentration of the potassium hydroxide solution is 30%. After soaking, the wood chip powder is added to a mixed solution of potassium hydroxide and sodium sulfite, and the mass concentration of the potassium hydroxide solution is 30%. Ultrasonic mixing and standing for 24 h, and then transferred to a hydrothermal kettle for reaction at a temperature of 100°C for 4 h.

[0066] (2) The wood chip powder-containing solution after complete reaction is centrifuged and washed until the pH is about 7, and the obtained powder is placed in an oven and dried at 80°C for 1 h to obtain a precursor powder.

[0067] (3) 10 g of graphene powder is mixed with the dried precursor powder, 5 mL of epoxy resin is added, and grinding is performed for 10 min, and then it is quickly transferred to a special mold,

[0068] (4) The low-friction coefficient material is obtained by pressing in a press at room temperature and a pressure of 60 MPa for 10 h to completely cure, and finally performing demolding treatment, and the mass fraction of graphene in the low-friction coefficient material is 30%, and the mass fraction of epoxy resin is 10%.

[0069] Example 6

[0070] Example 6 differs from Example 1 in that in step (1), the natural bamboo is cut into a size of 100×50×25mm, and the remaining conditions and steps are the same as in Example 1.

[0071] Comparative Example 1

[0072] The natural basswood was cut into the size of 100x50x25 mm, vacuum dried in a vacuum oven at 60℃ for 1 day to remove as much water as possible in the wood, and used as a comparative sample for subsequent friction experiments.

[0073] Effect verification

[0074] The materials obtained from Comparative Example 1 and Example 4 were subjected to friction performance tests, which were performed on a universal friction and wear tester using a reciprocating module in a ball-on-disc simulation point-to-plane contact mode under an air, normal temperature atmosphere. Before testing, hot melt adhesive was used to firmly fix the material to be tested (the lower friction pair) on the base, and the upper friction pair ball was clamped with a clamp to ensure that the disc and the ball would not move relative to the base or the clamp during reciprocating motion. During testing, the real-time friction coefficient recorded by the friction tester was used as the criterion for lubricating performance.

[0075] The results are shown in Table 1. Figure 1 and Figure 2 The Brinell hardness value and the friction coefficient of Comparative Example 1 were 18.56 and 0.25, respectively, and the Brinell hardness value of Example 4 was 29.35 and 0.06.

[0076] As can be seen from the above, the low friction coefficient material prepared by the present application has higher hardness and lower friction coefficient. The Brinell hardness of unmodified natural wood is generally about 18, while the Brinell hardness of the optimized low friction coefficient material is close to 30. In addition, the friction coefficient will change greatly. The average friction coefficient of wood under a load of 5 N is 0.25, and the friction coefficient has a growing trend with time. The average friction coefficient of the optimized low friction coefficient material under a load of 5 N is 0.06 and has higher stability.

[0077] It should be noted that when the present application claims involve numerical ranges, both endpoints of each numerical range and any number between the two endpoints can be selected. In order to prevent repetition, the present application describes preferred embodiments.

[0078] Although preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they understand the basic inventive concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0079] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A method of producing a low coefficient of friction material, characterized by, The raw material is soaked in the alkaline solution and then added to the mixed solution for heating reaction to remove lignin, and then the binder and the additive with lubricating properties are added, and the low-friction coefficient material is obtained after pressing treatment; The mixed solution is a mixed solution of a reducing agent and an alkaline solution; the mass ratio of the reducing agent to the alkaline solution in the mixed solution is 1:1-5, The mass percentage of the binder in the low-friction coefficient material is 0.1-30%, and the mass percentage of the additive is 0.1-50%; The raw material is natural wood, wood chips, or dried herbal plants; When the raw material is natural wood, the specific steps for preparation are as follows: (7.1) The natural wood is sliced and then soaked in the alkaline solution for 1-3 days, and then added to the mixed solution for reaction at 50-200 ℃ for 2-10 hours; (7.2) The wood prepared in step (7.1) is repeatedly washed until the pH value of the solution is reduced to 7, and porous wood is obtained; (7.3) The additive is configured into an additive solution with a concentration of 0.1-30 wt%, and the binder is configured into a binder solution with a concentration of 0.1-10 wt%, and the additive solution and the binder solution are introduced into the porous wood of (7.2) to obtain composite wood; (7.4) The composite wood of (7.3) is treated at room temperature or at 40-150 ℃ under a pressure of 20-100 MPa, so that water molecules are uniformly discharged along the direction of the pressure to obtain the low-friction coefficient material; When the raw material is wood chips, the specific steps for preparation are as follows: (9.1) The wood chips are crushed to obtain wood chip powder, which is soaked in the alkaline solution for 1-3 days, and then added to the mixed solution for reaction at 50-200 ℃ for 2-10 hours; The solid-liquid ratio of the wood chip powder to the mixed solution is 1:2-5; (9.2) The wood chips prepared in step (9.1) are repeatedly washed and then dried to obtain precursor powder; (9.3) The precursor powder is mixed and ground with the binder and the additive, and the mixed powder is laid flat, and the low-friction coefficient material is obtained under high-pressure conditions at room temperature or hot pressing.

2. The method of claim 1, wherein the low friction coefficient material is prepared by the steps of: The alkaline solution is one or a composite of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, calcium hydroxide solution, ammonia, sodium carbonate, and sodium bicarbonate.

3. The method of claim 1, wherein the low friction coefficient material is prepared by the steps of: The additive is one or more of polytetrafluoroethylene and its derivatives, zirconia ceramic microparticles, silicon nitride ceramic microparticles, talc powder, graphene, and hexagonal boron nitride.

4. The method of claim 3, wherein the low friction coefficient material is prepared by the steps of: The binder is one or more of sodium alginate, epoxy resin, cyclodextrin and its derivatives, cyanoacrylate and its derivatives, phenolic oligomers, aromatic hydrocarbon derivatives, polymeric cyclic ether derivatives, polyethylene glycol, cellulose and its derivatives, dopamine, and polyvinylidene fluoride. The reducing agent is one or more of hydrazine hydrate, sodium borohydride, potassium borohydride, ethanol, iron sulfite, potassium sulfite, sodium bisulfite, tin chloride, sodium sulfite, magnesium, and aluminum.

5. The method of claim 1, wherein the low friction coefficient material is prepared by the steps of: The solid-liquid ratio of the natural wood to the mixed solution in step (7.1) is 1:2-5.

6. The method of claim 1, wherein the low friction coefficient material is prepared by the steps of: The drying is carried out at 30-100 ℃ under drying or freeze-drying conditions.

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