Low friction composite gear, method of making and use thereof

Abstract

The application belongs to the technical field of resin gears, and specifically provides a low-friction composite gear, a preparation method and application thereof, which is prepared by mixing raw materials including the following components by mass: poly(lauryl lactam) 50-60 parts, polyformaldehyde 15-20 parts, a compatilizer 2-3 parts, a heat-conducting fiber 2-3 parts, a coupling agent 0.3-0.4 parts, a crystallization agent 0.1-0.2 parts, and an antioxidant 0.01-0.02 parts; the heat-conducting fiber is obtained by etching and glue-curing poly(ether ether ketone) fiber; and the crystallization agent is obtained by polycondensation reaction of p-dichlorobenzene, sodium sulfide and a biphenyl derivative. The composite gear prepared by using the crystallization agent and the heat-conducting fiber has a gear product crystallinity of 67.9%, a thermal conductivity of 3.34 W·(m·K) ‑1 , and excellent mechanical properties.

Description

Technical Field

[0001] This application belongs to the field of resin gear technology, and in particular relates to a low-friction composite gear, its preparation method and its application. Background Technology

[0002] Resin gears are a type of transmission component made of polymer materials, widely used in automobiles, home appliances, medical devices, office equipment, and other fields. Compared with traditional metal gears, resin gears have advantages such as light weight, corrosion resistance, good self-lubrication, low operating noise, and low cost. They also reduce wear on mating parts and perform excellently in light-load, high-speed, or quiet operation scenarios.

[0003] Based on material type, resin gears can be classified into polyamide, polyoxymethylene, and polycarbonate categories. Among them, polyamide gears have significant application advantages due to their excellent wear resistance, fatigue resistance, and mechanical strength. Within polyamide materials, polylaurolactam, with its low water absorption, good dimensional stability, and chemical resistance, performs better than other polyamide materials in humid or oily environments. Furthermore, its low coefficient of friction and smooth inter-tooth meshing make it more suitable for precision transmission systems. However, the use of polylaurolactam also has certain limitations. Its lower maximum load capacity and poor thermal conductivity make it prone to thermal deformation under high temperature or high load conditions, thus limiting its application in high-power transmission fields.

[0004] Patent application CN119708829A discloses a glass fiber reinforced PA12-PA6T composite material and its preparation method. The method involves introducing a silane-modified glass fiber component into polylaurolamide raw material, and then melt-extruding it with poly(hexamethylene terephthalamide) resin and other additives to obtain the composite material. After silane modification, the glass fiber has good interfacial compatibility with the resin system, and the mechanical properties of the obtained composite material are significantly improved.

[0005] Although the aforementioned application materials enhance the compatibility between the fiber and the matrix and the mechanical properties of the composite system through modification of glass fiber, the poor thermal conductivity of glass fiber itself makes gears made from it prone to shortening their service life due to localized heat accumulation during operation. Therefore, there is a need to develop a low-friction composite gear that combines high load capacity with improved thermal conductivity. Summary of the Invention

[0006] To address the aforementioned issues and further improve the load-bearing capacity of composite gears while enhancing their thermal conductivity, this application provides a low-friction composite gear, its preparation method, and its application.

[0007] In a first aspect, this application provides a low-friction composite gear, which is prepared by mixing raw materials comprising the following parts by weight: 50-60 parts of polylaurolamide, 15-20 parts of polyoxymethylene, 2-3 parts of compatibilizer, 2-3 parts of thermally conductive fiber, 0.3-0.4 parts of coupling agent, 0.1-0.2 parts of crystallizing agent, and 0.01-0.02 parts of antioxidant;

[0008] The preparation steps of the thermally conductive fiber include the following:

[0009] S01. Take polyetheretherketone fiber, place it in an etching solution for treatment, then wash it until neutral, and dry it to obtain etched fiber;

[0010] S02. Mix gelatin, fatty alcohol polyoxyethylene ether and water, heat and stir, then add m-cresol, polyhexamethylene adipamide and nano-alumina, and disperse to obtain a sol solution;

[0011] S03. Take the etched fiber, immerse it in the sol solution and then dry it to obtain the thermally conductive fiber;

[0012] The crystallizing agent is obtained by polycondensation reaction of dichlorobenzene, sodium sulfide and biphenyl derivatives;

[0013] The aspect ratio of the polyetheretherketone fiber is (100-200):1.

[0014] By adopting the above technical solution, the crystallizing agent is a crystalline oligomer with polyphenylene sulfide segments obtained by polycondensation of dichlorobenzene, sodium sulfide, and biphenyl derivatives. This oligomer is then blended and melted with polylaurolactam and polyoxymethylene in the base material. During the cooling crystallization stage, the crystallizing agent crystallizes before the molten resin material and forms a primary crystal nucleus structure. The polylaurolactam and polyoxymethylene, which have crystalline properties, continue to crystallize using the primary crystal nuclei as growth points. After cooling, a highly crystalline composite gear product can be obtained. The high-density crystal arrangement enhances the mechanical properties of the gear material and improves the gear's load-bearing capacity. Polyether ether ketone (PEEK) is also used. The thermally conductive fibers serving as structural supports can suppress the brittle fracture behavior of highly crystalline gear materials through fiber toughening mechanisms. In the sol-gel composition, nano-alumina acts as a thermally conductive medium, and through multiple impregnation and coating processes, a highly thermally conductive skin structure can be coated on the polyether ether ketone surface. During the gear component cooling stage, the thermally conductive fibers with a "skin-core" structure are distributed in the resin matrix between the "island phase" structure composed of crystalline and amorphous regions. They connect adjacent crystalline regions of the resin matrix through bridging, constructing thermally conductive channels, assisting in heat dissipation, and preventing heat accumulation that could damage the gear assembly.

[0015] Furthermore, in step S01, the etching solution is prepared by mixing concentrated nitric acid with a mass concentration of 65%-68% and concentrated sulfuric acid with a mass concentration of 95%-98%, followed by a cold water bath.

[0016] The volume ratio of concentrated nitric acid to concentrated sulfuric acid used is (4-5):1.

[0017] By adopting the above technical solution, the mixed concentrated acid treatment can promote the roughening of the surface of polyetheretherketone (PEEK) fibers. In the subsequent impregnation process with sol solution, the surface of the PEEK fibers can fully contact the sol solution, which facilitates the coating process and improves the adhesion of the skin structure to PEEK.

[0018] Furthermore, in step S02, the ratio of gelatin, fatty alcohol polyoxyethylene ether, water, m-cresol, polyhexamethylene adipamide and nano alumina used is (1-1.2)g:(0.2-0.3)g:5ml:(50-60)ml:(5-7)g:(2-3)g;

[0019] The viscosity of the sol solution is 3.8-5.1 cP.

[0020] By adopting the above technical solution, a sol solution with a certain adhesion to polyether ether ketone can be obtained. In the sol solution, components such as gelatin can improve the viscosity of the sol solution, making the polyether ether ketone coating process easier. The addition of polyhexamethylene adipamide can improve the stability of the thermally conductive fibers in the system and reduce the impact of phase separation on the thermally conductive fibers. The added nano-alumina can promote the formation of a highly thermally conductive skin structure on the surface of the polyether ether ketone fibers after the sol solution is cured.

[0021] Furthermore, the preparation steps of the crystallizing agent include the following: taking p-dichlorobenzene, sodium sulfide and biphenyl derivative, mixing and dispersing, then adding a co-catalyst and heating to react, adding acetic acid to quench and extracting to obtain a precipitate, and then washing and drying to obtain the final product;

[0022] The mass ratio of p-dichlorobenzene, sodium sulfide, biphenyl derivatives, and co-catalyst used is (14.5-15.3):(7.2-7.7):(0.7-0.8):(0.2-0.3).

[0023] The heating reaction is as follows: the temperature is increased to 150-175℃ and maintained for 0.8-1h, then the temperature is further increased to 200-225℃ and maintained for 1.2-1.5h;

[0024] The structural formula of the biphenyl derivative is:

[0025]

[0026] R / R´ is selected from one of chlorine atom, bromine atom and methoxy group;

[0027] The co-catalyst is one of anhydrous sodium acetate or sodium benzoate.

[0028] By adopting the above technical solution, dichlorobenzene, sodium sulfide and biphenyl derivatives undergo nucleophilic substitution reaction under the action of a co-catalyst, and polycondensation is carried out to obtain a polymer structure with polyphenylene sulfide segments. By controlling the reaction conditions, oligomers can be obtained. The biphenyl derivatives introduced in the reaction can promote the ordering of the oligomer molecular chains and the cooling crystallization behavior of the crystallizing agent through their double benzene ring structure effect, so that the crystallizing agent can crystallize faster.

[0029] Secondly, this application provides a method for preparing a low-friction composite gear, comprising the following steps:

[0030] Polyoxymethylene is mixed with crystallizing agent, antioxidant and coupling agent, then polylaurolamide and compatibilizer are added, and the mixture is extruded through a die and injection molded to obtain a crude product. The crude product is then heat-treated to obtain the final product.

[0031] The extrusion die temperature is 210-225℃, the motor speed is 10-15rpm, and the pressure is 50-100bar;

[0032] The injection molding process involves an injection pressure of 80-100 MPa and an extrusion speed of 120-150 mm / s.

[0033] As a general inventive concept, the present invention also provides the application of the low-friction composite gear prepared by the above-described preparation method in resin gears.

[0034] Compared with the prior art, this application has the following beneficial effects:

[0035] 1. This application prepares an oligomer crystallizing agent with polyphenylene sulfide segments, which acts as a primary crystal nucleus during the cooling process of composite gears, promoting the crystallization of polylaurolamide and polyoxymethylene in the raw material components, and finally obtaining a composite gear product with excellent mechanical properties.

[0036] 2. This application also prepares a "skin-core" structure of thermally conductive fiber, which is used in conjunction with a crystallizing agent to improve the problem of brittleness of gear parts caused by high crystallinity modification through fiber toughening; wherein the polyether ether ketone fiber in the core layer serves as the support of the thermally conductive fiber skin structure, and its surface is successively etched and roughened and coated with adhesive to obtain a high thermal conductivity skin structure. When mixed with the other components, it can connect the adjacent resin cooling crystallization crystal zone to construct a thermally conductive channel and avoid heat accumulation in the gear.

[0037] 3. The composite gear prepared using the crystallizing agent of this application in combination with thermally conductive fibers has a crystallinity of up to 67.9% and a thermal conductivity ≥3.34 W·(m·K). -1 It has excellent mechanical strength. Attached Figure Description

[0038] Figure 1The DSC melting curves of the composite gear samples from Examples 1-2 and Comparative Examples 1-2 of this application are for non-isothermal crystallization.

[0039] Figure 2 The crystallinity data are for the composite gear samples of Examples 1-2 and Comparative Examples 1-2 of this application.

[0040] Figure 3 The thermal conductivity data are for the composite gear samples of Examples 1-4 and Comparative Examples 1-2 of this application. Detailed Implementation

[0041] The technical solution of the present invention will be explained in detail below with reference to several representative embodiments.

[0042] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0043] Description of raw materials used in the embodiments and comparative examples of this invention:

[0044] Polyetheretherketone fiber, aspect ratio (100-200):1;

[0045] Gelatin, industrial grade;

[0046] Nano-alumina, Al2O3 wt% ≥ 99.9%, average particle size 200-300 nm;

[0047] Polyhexamethylene adipamide, with an average molecular weight of 12,000-15,000;

[0048] Polyoxymethylene (POM), with an average molecular weight of 30,000-45,000;

[0049] Polylaurolactam, with an average molecular weight of 50,000-75,000.

[0050] Table 1. Injection molding and extrusion process parameters of composite gears in Examples 1-4 and Comparative Examples 1-2

[0051]

[0052] Preparation Example 1

[0053] Take 100 ml of N-methylpyrrolidone, bubble it with nitrogen for 10 min, and then heat it to 75 °C. Then add 14.5 g of p-dichlorobenzene, 7.2 g of sodium sulfide, and 0.7 g of 4,4'-dichlorobiphenyl, followed by 0.2 g of anhydrous sodium acetate. Adjust the magnetic stirring speed to 200 rpm, then raise the system temperature to 150 °C and maintain it for 0.8 h. Then continue to raise the system temperature to 200 °C and maintain it for 1.2 h. Then stop heating, add 0.5 g of acetic acid to quench the reaction, and let it cool naturally to 70 °C. Then extract with acetone to obtain the precipitate. Wash it three times each with 60 °C hot water and ethanol, and then transfer the precipitate to an oven and dry it at 50 °C to obtain the crystallizing agent.

[0054] Mix 40 ml of 65% concentrated nitric acid with 10 ml of 98% concentrated sulfuric acid and place in a cold water bath for later use.

[0055] Take 5g of polyetheretherketone fiber, sonicate it in acetone for 5min, dry it and then immerse it in 50ml of etching solution. Maintain the temperature at 35℃ for 2min, then transfer it to 0.5mol / L sodium hydroxide solution and continue to soak for 5min. Finally, wash it with water until neutral and dry it in an oven at 60℃ for 2h to obtain etched fiber.

[0056] Preparation Example 2

[0057] Take 100 ml of N-methylpyrrolidone, bubble it with nitrogen for 20 min, and then heat it to 80 °C. Then add 15 g of p-dichlorobenzene, 7.5 g of sodium sulfide, and 0.72 g of 4-bromo-4'-methoxybiphenyl, followed by 0.25 g of sodium benzoate. Adjust the magnetic stirring speed to 300 rpm, then raise the system temperature to 175 °C and maintain it for 1 h. Then continue to raise the system temperature to 210 °C and maintain it for 1.2 h. Then stop heating, add 0.5 g of acetic acid to quench the reaction, and let it cool naturally to 70 °C. Then extract with acetone to obtain the precipitate. Wash it three times each with 60 °C hot water and ethanol, and then transfer the precipitate to an oven and dry it at 50 °C to obtain the crystallizing agent.

[0058] Mix 50 ml of 68% concentrated nitric acid with 10 ml of 95% concentrated sulfuric acid and place in a cold water bath for later use.

[0059] Take 5g of polyetheretherketone fiber, sonicate it in acetone for 10min, dry it and then immerse it in 60ml of etching solution. Maintain the temperature at 40℃ for 3min, then transfer it to 0.5mol / l sodium hydroxide solution and continue to soak for 5min. Finally, wash it with water until neutral and dry it in an oven at 60℃ for 2h to obtain etched fiber.

[0060] Preparation Example 3

[0061] Take 100 ml of N-methylpyrrolidone, bubble it with nitrogen for 30 min, and then heat it to 80 °C. Then add 15.3 g of p-dichlorobenzene, 7.7 g of sodium sulfide, and 0.8 g of 4,4'-dibromobiphenyl, followed by 0.3 g of sodium benzoate. Adjust the magnetic stirring speed to 300 rpm, then raise the system temperature to 175 °C and maintain it for 1 h. Then continue to raise the system temperature to 225 °C and maintain it for 1.5 h. Then stop heating, add 0.6 g of acetic acid to quench the reaction, and allow it to cool naturally to 80 °C. Then extract with acetone to obtain the precipitate. Wash it three times each with 60 °C hot water and ethanol, and then transfer the precipitate to an oven and dry it at 50 °C to obtain the crystallizing agent.

[0062] Mix 45 ml of 65% concentrated nitric acid with 10 ml of 98% concentrated sulfuric acid and place in a cold water bath for later use.

[0063] Take 5g of polyetheretherketone fiber, sonicate it in acetone for 10min, dry it and then immerse it in 75ml of etching solution. Maintain the temperature at 40℃ for 3min, then transfer it to 0.5mol / L sodium hydroxide solution and continue to soak for 5min. Finally, wash it with water until neutral and dry it in an oven at 60℃ for 3h to obtain etched fiber.

[0064] Example 1

[0065] The specific steps for preparing the thermally conductive fiber in this embodiment are as follows:

[0066] Mix 1g of gelatin, 0.2g of fatty alcohol polyoxyethylene ether, and 5ml of deionized water. Adjust the magnetic stirring speed to 100rpm and treat at 60℃ for 5min. Then add 50ml of m-cresol and 5g of polyhexamethylene adipamide, followed by 0.5g of Tween 20 and 2g of nano-alumina. Continue stirring at a constant temperature until the system viscosity reaches 3.8cP. Stop heating to obtain a sol solution. Then, take 3g of etching fiber and immerse it in the sol solution for 3s. Remove it and treat it in an oven at 50℃ for 5min. Repeat the operation 5 times and then dry to obtain thermally conductive fiber.

[0067] The specific steps for preparing the low-friction composite gear in this embodiment are as follows:

[0068] Take 1500g of polyoxymethylene, 10g of crystallizing agent, 1g of antioxidant 1010 and 30g of titanate coupling agent (TC-131) and mix them. Place them in a mixer and treat for 5min. Then transfer them to a twin-screw extruder. Add 5000g of polylaurolamide and 200g of compatibilizer (POE-g-MAH) from the main feed port. Mix and treat for 10min. Then add 200g of thermally conductive fiber from the side feed port. Continue to treat for 30min to obtain a melt mixture. Inject the mixture into a rough product. Then heat treat it in an oven at 80℃ for 2h. After deburring and polishing, the product is obtained.

[0069] In this embodiment, the crystallizing agent and etching fiber were prepared in Preparation Example 1.

[0070] Example 2

[0071] The specific steps for preparing the thermally conductive fiber in this embodiment are as follows:

[0072] Mix 1g of gelatin, 0.3g of fatty alcohol polyoxyethylene ether, and 5ml of deionized water. Adjust the magnetic stirring speed to 200rpm and treat at 70℃ for 8min. Then add 55ml of m-cresol and 6g of polyhexamethylene adipamide, followed by 0.6g of Tween 20 and 3g of nano-alumina. Continue stirring at a constant temperature until the system viscosity reaches 4.2cP. Stop heating to obtain a sol solution. Then, take 4g of etching fiber and immerse it in the sol solution for 3s. Remove it and treat it in an oven at 50℃ for 5min. Repeat the operation 5 times and then dry to obtain thermally conductive fiber.

[0073] The specific steps for preparing the low-friction composite gear in this embodiment are as follows:

[0074] Take 1500g of polyoxymethylene, 10g of crystallizing agent, 1g of antioxidant 1010 and 30g of titanate coupling agent (TC-131) and mix them. Place them in a mixer and treat for 5min. Then transfer them to a twin-screw extruder. Add 5000g of polylaurolamide and 200g of compatibilizer (POE-g-MAH) from the main feed port. Mix and treat for 10min. Then add 200g of thermally conductive fiber from the side feed port. Continue to treat for 30min to obtain a melt mixture. Inject the mixture into a rough product. Then heat treat it in an oven at 80℃ for 2h. After deburring and polishing, the product is obtained.

[0075] In this embodiment, the crystallizing agent and etching fiber were prepared in Preparation Example 2.

[0076] Example 3

[0077] The specific steps for preparing the thermally conductive fiber in this embodiment are as follows:

[0078] Mix 1.2g gelatin, 0.3g fatty alcohol polyoxyethylene ether, and 5ml deionized water. Adjust the magnetic stirring speed to 150rpm and treat at 70℃ for 10min. Then add 60ml m-cresol and 7g polyhexamethylene adipamide, followed by 0.6g Tween 20 and 3g nano alumina. Continue stirring at a constant temperature until the system viscosity reaches 5.1cP. Stop heating to obtain a sol solution. Then, take 4g of etching fiber and immerse it in the sol solution for 5s. Remove it and treat it in an oven at 50℃ for 10min. Repeat the operation 5 times and then dry to obtain thermally conductive fiber.

[0079] The specific steps for preparing the low-friction composite gear in this embodiment are as follows:

[0080] Take 2000g of polyoxymethylene, mix it with 15g of crystallizing agent, 2g of antioxidant 1010 and 40g of titanate coupling agent (TC-131), place it in a mixer and treat it for 20min. Then transfer it to a twin-screw extruder, add 5500g of polylaurolamide and 250g of compatibilizer (POE-g-MAH) from the main feed port, mix and treat for 20min, then add 200g of thermally conductive fiber from the side feed port, continue to treat for 40min to obtain a melt mixture. Inject the mixture into a rough product, then heat treat it in a 90℃ oven for 2h, and then remove the burrs and polish it to obtain the final product.

[0081] In this embodiment, the crystallizing agent and etching fiber were prepared in Preparation Example 3.

[0082] Example 4

[0083] The specific steps for preparing the thermally conductive fiber in this embodiment are as follows:

[0084] Mix 1.2g gelatin, 0.3g fatty alcohol polyoxyethylene ether, and 5ml deionized water. Adjust the magnetic stirring speed to 200rpm and treat at 70℃ for 10min. Then add 60ml m-cresol and 7g polyhexamethylene adipamide, followed by 0.6g Tween 20 and 3g nano alumina. Continue stirring at a constant temperature until the system viscosity reaches 4.8cP. Stop heating to obtain a sol solution. Then, take 4g of etching fiber and immerse it in the sol solution for 5s. Remove it and treat it in an oven at 50℃ for 10min. Repeat the operation 6 times and then dry to obtain thermally conductive fiber.

[0085] The specific steps for preparing the low-friction composite gear in this embodiment are as follows:

[0086] Take 2000g of polyoxymethylene, 20g of crystallizing agent, 2g of antioxidant 1010 and 40g of titanate coupling agent (TC-131) and mix them. Place them in a mixer and treat for 20min. Then transfer them to a twin-screw extruder. Add 6000g of polylaurolamide and 300g of compatibilizer (POE-g-MAH) from the main feed port. Mix and treat for 20min. Then add 300g of thermally conductive fiber from the side feed port and continue to treat for 40min to obtain a melt mixture. Inject the mixture into a rough product. Then heat treat it in a 90℃ oven for 3h. After deburring and polishing, the product is obtained.

[0087] In this embodiment, the crystallizing agent was prepared in Preparation Example 2, and the etching fiber was prepared in Preparation Example 3.

[0088] Comparative Example 1

[0089] The only difference between this comparative example and Example 1 is that an equal amount of calcium carbonate micropowder was used instead of a crystallizing agent to prepare a low-friction composite gear.

[0090] Among them, calcium carbonate micro powder has an average particle size of 10-25 micrometers.

[0091] The remaining steps are the same as in Example 1.

[0092] Comparative Example 2

[0093] The only difference between this comparative example and Example 1 is that an equal amount of glass fiber is used instead of thermally conductive fiber to prepare a low-friction composite gear.

[0094] Among them, glass fiber has an aspect ratio of 100:1.

[0095] The remaining steps are the same as in Example 1.

[0096] Performance testing

[0097] 1. Apparent performance test

[0098] Table 2. Test Items for the Apparent Performance of Composite Gears in Examples 1-4 and Comparative Examples 1-2

[0099]

[0100] The test results are shown in Table 3.

[0101] Table 3. Test results of the apparent performance of the composite gears in Examples 1-4 and Comparative Examples 1-2

[0102]

[0103] Analysis of Examples 1-4 and Comparative Examples 1-2, combined with Tables 2 and 3, shows that the test groups of the Examples exhibit better mechanical properties than the Comparative Examples. The composite gears of the Examples have higher strength and modulus, and can withstand higher maximum loads while maintaining a low coefficient of friction, indicating that the prepared composite gear products can still maintain good dimensional stability under higher load torque. Among all the Example groups, Examples 1 and 2 have the best overall performance.

[0104] 2. Crystallinity test

[0105] Referring to the relevant test methods in national standard GB / T19466.3-2004, composite gear samples from Examples 1-2 and Comparative Examples 1-2 were subjected to DSC tests for non-isothermal crystallization. The test results are as follows: Figure 1 As shown, the enthalpy of fusion of polylaurolactam in each group of samples was calculated. According to the formula:

[0106]

[0107] The crystallinity of polylaurolamide in each group of samples was calculated.

[0108] in,

[0109] Crystallinity;

[0110] The enthalpy of melting of polylaurolactam;

[0111] The theoretical enthalpy of polylaurolactam;

[0112] Mass fraction of polylaurolamide.

[0113] Crystallinity test results are as follows Figure 2 As shown.

[0114] Analysis of Examples 1-2 and Comparative Examples 1-2 in conjunction with Figure 1 and Figure 2 It can be concluded that the appearance of the melt peak position in the melt curves of Examples 1-2 lags behind that of Comparative Examples 1-2, indicating that the samples of Examples 1-2 have higher crystalline melting temperatures and more complete crystalline structures. Figure 2 The crystallinity test results can further verify the promoting effect of the combination of crystallizing agent and thermally conductive fiber on the crystallization of polymer in the sample. In contrast, Comparative Example 1 uses calcium carbonate micro powder instead of organic crystallizing agent in the raw material components. Due to potential problems such as dispersibility and compatibility of inorganic components in the system, its promoting effect on the crystallization of polymer components is not good. In Comparative Example 2, the combination of glass fiber and crystallizing agent is not good, resulting in the crystallization performance of the composite gear product not being as good as that of the example scheme.

[0115] 3. Thermal conductivity

[0116] Referring to the relevant test methods in the national standard GB / T3139-2005, the thermal conductivity of composite gear samples from Examples 1-4 and Comparative Examples 1-2 was tested. The test results are as follows: Figure 3 As shown.

[0117] Analysis of Examples 1-4 and Comparative Examples 1-2 in conjunction with Figure 3 It can be concluded that due to the introduction of thermally conductive fibers into the system, the thermal conductivity of the composite gear products in Examples 1 and Comparative Example 2 is greatly improved, showing better performance than Comparative Example 2. Comparative Example 1, due to its low crystallinity and lack of ordered thermally conductive crystalline regions, only slightly improves the thermal conductivity of the product with the addition of thermally conductive fibers. In contrast, Comparative Example 2, by using poorly thermally conductive glass fibers as fiber reinforcement instead of thermally conductive fibers, cannot construct good thermal conductivity channels in the system, resulting in poor thermal conductivity of the product. The composite gears prepared in this way pose a risk of heat accumulation and damage to the gear components during use.

[0118] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this invention.

Claims

1. A low-friction composite gear, characterized in that, It is prepared by mixing the following raw materials in parts by weight: 50-60 parts of polylaurolamide, 15-20 parts of polyoxymethylene, 2-3 parts of compatibilizer, 2-3 parts of thermally conductive fiber, 0.3-0.4 parts of coupling agent, 0.1-0.2 parts of crystallizing agent, and 0.01-0.02 parts of antioxidant; The preparation steps of the thermally conductive fiber include the following: S01. Take polyetheretherketone fiber, place it in an etching solution for treatment, then wash it until neutral, and dry it to obtain etched fiber; S02. Take gelatin, fatty alcohol polyoxyethylene ether and water, heat and stir, then add m-cresol, polyhexamethylene adipamide and nano alumina, and disperse to obtain a sol solution; the ratio of gelatin, fatty alcohol polyoxyethylene ether, water, m-cresol, polyhexamethylene adipamide and nano alumina used is (1-1.2)g:(0.2-0.3)g:5ml:(50-60)ml:(5-7)g:(2-3)g; S03. Take the etched fiber, immerse it in the sol solution and then dry it to obtain the thermally conductive fiber; The preparation steps of the crystallizing agent include the following: A mixture of p-dichlorobenzene, sodium sulfide, and biphenyl derivatives was dispersed, followed by the addition of a co-catalyst and heating to react. Acetic acid was added to quench the reaction, and extraction was performed to obtain a precipitate. The precipitate was then washed and dried to obtain the final product. The mass ratio of p-dichlorobenzene, sodium sulfide, biphenyl derivatives, and co-catalyst used was (14.5-15.3):(7.2-7.7):(0.7-0.8):(0.2-0.3). The structural formula of the biphenyl derivative is: R / R' is selected from one of chlorine atom, bromine atom and methoxy group; The co-catalyst is one of anhydrous sodium acetate or sodium benzoate.

2. The low-friction composite gear according to claim 1, characterized in that, In step S01, the etching solution is prepared by mixing concentrated nitric acid with a mass concentration of 65%-68% and concentrated sulfuric acid with a mass concentration of 95%-98%, and then mixing them in a cold water bath. The volume ratio of concentrated nitric acid to concentrated sulfuric acid used is (4-5):

1.

3. The low-friction composite gear according to claim 1, characterized in that, In step S02, the viscosity of the sol solution is 3.8-5.1 cP.

4. A low-friction composite gear according to claim 1, characterized in that, The heating reaction is as follows: the temperature is increased to 150-175℃ and maintained for 0.8-1h, and then the temperature is further increased to 200-225℃ and maintained for 1.2-1.5h.

5. A method for preparing a low-friction composite gear according to any one of claims 1-4, characterized in that, Includes the following steps: Polyoxymethylene is mixed with crystallizing agent, antioxidant and coupling agent, then polylaurolamide and compatibilizer are added. After mixing and treatment, thermally conductive fiber is added from the side feed port and the process is continued. After extrusion through the die head and injection molding, a crude product is obtained. The crude product is then heat-treated to obtain the final product.

6. The method for preparing a low-friction composite gear according to claim 5, characterized in that, The extrusion die temperature is 210-225℃, the motor speed is 10-15rpm, and the pressure is 50-100bar.

7. The method for preparing a low-friction composite gear according to claim 5, characterized in that, The injection molding process involves an injection pressure of 80-100 MPa and an extrusion speed of 120-150 mm / s.

8. The application of the low-friction composite gear prepared by any one of the preparation methods according to claims 5-7 in resin gears.

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