Preparation method of composite material for PTFE-based sliding bearing with mesh structure

Abstract

A method for preparing a composite material for a PTFE-based sliding bearing having a mesh structure, comprising the following steps: providing a PTFE composite material; mixing the PTFE composite material; providing an auxiliary oil; subjecting the oil-containing mixture to blanking, extrusion, and calendaring to obtain a PTFE oil-containing calendaring film; the compression ratio of blanking extrusion is 20-80, the calendaring speed is 3.5-5.0 m / min, and the thickness of the PTFE oil-containing calendaring film is 0.1-0.5 mm; the PTFE oil-containing calendaring film is degreased, biaxially stretched, and shaped to obtain a PTFE-based sliding bearing fabric having a mesh structure; the composite material is compounded with a metal substrate to obtain a high-strength PTFE-based sliding bearing having a mesh structure. The mesh structure formed by the present preparation method can store grease, and the sliding bearing using the fabric can continuously release grease under conditions of less oil, oil cutoff, and boundary lubrication, thereby obtaining a continuous low-friction operating condition, reducing fabric wear, and extending the service life of the sliding bearing.

Description

Technical Field

[0001] The invention belongs to the technical field of sliding bearings, in particular to a method for manufacturing a composite material for a PTFE-based sliding bearing with a reticular structure. Background Art

[0002] The PTFE-based sliding bearing fabrics produced by existing processes have low matrix strength, and the fabrics are easily worn under conditions of insufficient oil, oil cut-off and boundary lubrication, causing bearing failure. Summary of the invention

[0003] In view of this, the present invention provides a method for manufacturing a composite material for a high PTFE-based sliding bearing having a network structure and capable of storing grease, so as to solve the above problems.

[0004] A method for preparing a composite material for a PTFE-based sliding bearing having a mesh structure comprises the following steps:

[0005] STEP 101: Provide a PTFE composite material, wherein the PTFE composite material is composed of PTFE, a polymer filler, and an inorganic filler, wherein the weight percentage of the PTFE is 50% to 90%, the weight percentage of the polymer filler is 5% to 20%, and the weight percentage of the inorganic filler is 5% to 30%;

[0006] STEP 102: Mix the PTFE composite material to obtain a PTFE mixture;

[0007] STEP 103: providing an auxiliary oil, wherein the auxiliary oil accounts for 15% to 35% of the total weight of the PTFE mixture, and mixing the PTFE mixture with the auxiliary oil to form an oil-containing mixture;

[0008] STEP 104: The oil-containing mixture is subjected to blanking, extrusion and calendering to obtain a PTFE oil-containing calendered film; the compression ratio of the blanking extrusion is 20 to 80, the calendering speed is 3.5 to 5.0 m / min, and the thickness of the PTFE oil-containing calendered film is 0.1 to 0.5 mm;

[0009] STEP 105: Degreasing, biaxially stretching and shaping the PTFE oil-containing calendering film to obtain a PTFE-based sliding bearing fabric with a mesh structure; biaxially stretching is first longitudinally stretched at a temperature of 310-350° C., a stretching ratio of 1.0 to 3.0, and then transversely stretched at a temperature of 320 to 370° C., a stretching ratio of 1.0 to 5.0, and a line speed of 0.5 to 3.0 m / min to obtain the composite material;

[0010] STEP 106: Compound the composite material with a metal substrate to obtain a high-strength PTFE-based sliding bearing with a mesh structure.

[0011] Furthermore, the polymer filler is a mixture of at least one or more of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, perfluoroethylene propylene copolymer, polyphenylene ester, polyimide, and poly(p-phenylene terephthalamide).

[0012] Furthermore, the particle size of the polymer filler is between 0.1 and 100 um.

[0013] Furthermore, the inorganic filler is a mixture of at least one or more of graphite, molybdenum disulfide, silicon dioxide, aluminum oxide, calcium fluoride, and zirconium phosphate.

[0014] Furthermore, the particle size of the inorganic filler is between 0.1 and 20 um.

[0015] Furthermore, the auxiliary oil is any one of petroleum ether, isoparaffin oil, and aviation kerosene.

[0016] Furthermore, in STEP 105, the degreasing temperature is 150 to 200° C., and the line speed is 0.5 to 3 m / min.

[0017] Furthermore, in STEP 105, the setting temperature is 350 to 390°C.

[0018] Furthermore, the fabric porosity of the composite material is 5-35%.

[0019] Compared with the prior art, the method for making a composite material for a PTFE-based sliding bearing with a mesh structure provided by the present invention ensures the strength of the prepared composite material by designing a special PTFE composite material raw material, especially by adding polymer particles and inorganic particles, which provides a premise for setting a mesh structure in the composite material, because if there is no high-strength composite material, the mesh structure cannot be set, that is, a high-strength matrix is ​​a prerequisite for the mesh structure, otherwise it is easy to break during stretching, resulting in defects in the mesh structure. At the same time, the formation of the mesh structure will increase the strength of the matrix formed by the composite material due to the effects of orientation and linking. At the same time, by adding the polymer particles and inorganic particles, the wear resistance of the composite material is also guaranteed. On the premise of ensuring strength and wear resistance, the strength of the prepared PTFE is ensured by first stretching longitudinally and then stretching transversely in the bidirectional stretching process, while controlling the temperature during the longitudinal and transverse stretching. In addition, a network structure is formed by bidirectional stretching, which can store grease. The sliding bearing using this fabric can continuously release grease under conditions of low oil, oil cut-off and boundary lubrication, thereby obtaining continuous low-friction operating conditions, reducing fabric wear and extending the service life of the sliding bearing. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are further described in detail below. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0021] The present invention provides a method for manufacturing a composite material for a PTFE-based sliding bearing having a mesh structure, which comprises the following steps:

[0022] STEP 101: Provide a PTFE composite material, wherein the PTFE composite material is composed of PTFE, a polymer filler, and an inorganic filler, wherein the weight percentage of the PTFE is 50% to 90%, the weight percentage of the polymer filler is 5% to 20%, and the weight percentage of the inorganic filler is 5% to 30%;

[0023] STEP 102: Mix the PTFE composite material to obtain a PTFE mixture;

[0024] STEP 103: providing an auxiliary oil, wherein the auxiliary oil accounts for 15% to 35% of the total weight of the PTFE mixture, and mixing the PTFE mixture with the auxiliary oil to form an oil-containing mixture;

[0025] STEP 104: The oil-containing mixture is subjected to blanking, extrusion and calendering to obtain a PTFE oil-containing calendered film; the compression ratio of the blanking extrusion is 20 to 80, the calendering speed is 3.5 to 5.0 m / min, and the thickness of the PTFE oil-containing calendered film is 0.1 to 0.5 mm;

[0026] STEP105: Degreasing, biaxially stretching and shaping the PTFE oil-containing calendering film to obtain a PTFE-based sliding bearing fabric with a mesh structure; the degreasing temperature is 150-200°C, and the line speed is 0.5-3m / min; biaxially stretching is first longitudinally stretched at a temperature of 310-350°C, a stretching ratio of 1.0-3.0, and then transversely stretched at a temperature of 320-370°C, a stretching ratio of 1.0-5.0, and a line speed of 0.5-3.0m / min; shaping temperature is 350-390°C; the fabric porosity is 5-35% to obtain the composite material;

[0027] STEP 106: Compound the composite material with a metal substrate to obtain a PTFE-based sliding bearing with a network structure.

[0028] In step STEP101, the PTFE can be a PTFE dispersed resin with a molecular weight of 500,000 to 5,000,000 and a particle size of 200-600um. If the molecular weight, particle size and content of the PTFE are too low, it is difficult to form a network structure, which can easily lead to low strength of the network structure. If the content of the PTFE is too high, it will lead to less polymer fillers or inorganic fillers, making it difficult to achieve the rated wear-resistant and friction-reducing effect. In addition, the molecular weight of the PTFE must be greater than 500,000 to complete the following biaxial stretching step, so as to ensure the orientation and network structure formation during biaxial stretching, and also ensure the matrix strength, so that the fabric has high matrix strength.

[0029] The polymer filler can be a mixture of at least one or more of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), perfluoroethylene propylene copolymer (FEP), polyphenylene ester (POB), polyimide (PI), and poly(p-phenylene terephthalamide), with a particle size between 0.1 and 100 um. The polymer filler is used to improve the friction performance of the fabric, increase the strength of the fabric, and improve the wear resistance. It is also used to increase the bonding strength between the fabric and the substrate to ensure that the fabric does not fall off during the use of the sliding bearing. The important percentage of the polymer filler should be set at 5% to 20%. Less than 5% will result in a reduction in the wear resistance and friction reduction effect and will not meet the requirements, while more than 20% will reduce the strength of the matrix and easily increase the friction coefficient.

[0030] The inorganic filler can be a mixture of at least one or more of graphite, molybdenum disulfide, silicon dioxide, aluminum oxide, calcium fluoride, and zirconium phosphate, with a particle size of 0.1 to 20 μm. The inorganic filler is used to reduce the friction coefficient of the fabric and increase the wear resistance of the fabric, thereby promoting the formation and stability of the PTFE transfer film. The important percentage of the inorganic filler is set to 5% to 30%. If it is lower than 5%, the wear-resistant and friction-reducing effect will be reduced, and if it is higher than 30%, the matrix strength will be reduced and the friction coefficient will be easily increased.

[0031] The particle size of the polymer filler and the inorganic filler should be small so as to ensure uniform dispersion in the matrix, so the particle size of the polymer filler should be between 0.1 and 100 um, and the particle size of the inorganic filler should be between 0.1 and 20 um. If the particle size of the polymer filler and the inorganic filler is too large, the network structure formed by the PTFE during biaxial stretching will be destroyed.

[0032] In STEP103, the auxiliary oil can be any one of petroleum ether, isoparaffin oil, and aviation kerosene. The auxiliary oil mainly helps the subsequent molding process. The auxiliary oil accounts for 15% to 35% of the total weight of the PTFE mixture. Too much or too little will cause the PTFE mixture powder to have poor adhesion, and it is easy to fall apart after extrusion and difficult to mold. In addition, after the preparation is completed, by removing the solvent, the prepared blank can be provided with initial pores and an initial network structure, which is conducive to the uniform and stable formation of the subsequent biaxially stretched network structure.

[0033] In STEP 104, by subjecting the oil-containing mixture to blanking, extrusion and calendering, the oil-containing calendered film can be fiberized and provided with initial orientation, thereby facilitating biaxial stretching orientation in subsequent processes.

[0034] In STEP105, longitudinal stretching is first performed at a temperature of 310-350°C, and transverse stretching is then performed at a temperature of 320-370°C to ensure the formation of a network structure. At the same time, to ensure the uniformity of the formed network structure, the temperature and stretching ratio of the transverse stretching are greater than the temperature and stretching ratio of the longitudinal stretching, which can evenly improve the strength and toughness of the PTFE membrane. During stretching, longitudinal stretching is first performed and then transverse stretching. Preliminary orientation has been achieved through longitudinal extrusion and calendering in the early stage. Transverse stretching requires a higher stretching ratio to achieve uniform orientation in both directions, thereby ensuring the uniformity of the entire membrane.

[0035] Through the above-mentioned biaxial stretching, the porosity of the prepared fabric is made to be between 5% and 35%, which is conducive to the subsequent storage of lubricating oil.

[0036] In STEP 106, the method for compounding the above-mentioned fabric with the metal substrate is a prior art and will not be described in detail here. Example 1

[0037] Weigh 7.5 kg of PTFE dispersed resin (molecular weight 1 million, particle size 400 μm), 1.5 kg of polyphenylene ester (particle size 20 μm), and 1.0 kg of calcium fluoride (particle size 5 μm), and mix them evenly using a high-speed mixer to obtain a PTFE mixture;

[0038] Weigh 1.8 kg of isoparaffin oil and mix it evenly with the above PTFE mixture to obtain an oil-containing PTFE mixture;

[0039] The above oil-containing mixture is subjected to blanking, extrusion and calendering to obtain a PTFE oil-containing calendered film with a thickness of 0.20 mm, wherein the compression ratio of blanking extrusion is 35, and the calendering speed is 3.5 m / min;

[0040] After degreasing the PTFE oil-containing calendered film at 190°C, the film was first stretched longitudinally at a temperature of 300°C and a stretch ratio of 2.0, then stretched transversely at a temperature of 320°C and a stretch ratio of 3.0, and finally high-temperature shaped at a setting temperature of 360°C and a line speed of 1.5 m / min to obtain a PTFE-based sliding bearing fabric with a mesh structure;

[0041] The PTFE-based sliding bearing fabric is compounded with a metal substrate to produce a PTFE-based sliding bearing. Example 2

[0042] Weigh 6.5 kg of PTFE dispersed resin (molecular weight 1 million, particle size 400 μm), 1.5 kg of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer (PFA), 1.0 kg of polyphenyl ester (particle size 20 μm), and 1.0 kg of calcium fluoride (particle size 5 μm), and mix them evenly using a high-speed mixer to obtain a PTFE mixture;

[0043] Weigh 1.6 kg of isoparaffin oil and mix it evenly with the above PTFE mixture to obtain an oil-containing PTFE mixture;

[0044] The oil-containing PTFE mixture is subjected to blanking, extrusion and calendering to obtain a PTFE oil-containing calendered film with a thickness of 0.20 mm, wherein the compression ratio of blanking extrusion is 45 and the calendering speed is 3.5 m / min;

[0045] After degreasing the PTFE oil-containing calendered film at 190°C, the film was first stretched longitudinally at 260°C and a stretch ratio of 2.0, then stretched transversely at 330°C and a stretch ratio of 3.0, and finally high-temperature shaped at 360°C and a line speed of 1.5 m / min to obtain a PTFE-based sliding bearing fabric with a mesh structure;

[0046] The fabric is compounded with a metal substrate to produce a PTFE-based sliding bearing.

[0047] Comparative Example 1

[0048] Weigh 7.5 kg of PTFE dispersed resin (molecular weight 1 million, particle size 400 μm), 1.5 kg of polyphenylene ester (particle size 20 μm), and 1.0 kg of calcium fluoride (particle size 5 μm), and mix them evenly using a high-speed mixer to obtain a PTFE mixture;

[0049] Weigh 1.8 kg of isoparaffin oil and mix evenly with the above mixture to obtain a PTFE oil-containing mixture;

[0050] The oil-containing mixture is compounded with a metal substrate to produce a PTFE-based sliding bearing.

[0051] Table 1 shows the tensile test results of the universal testing machine of the embodiment and the comparative example, wherein the sample is a dumbbell-shaped specimen of 115 mm*25 mm. Both ends of the sample are clamped on the universal testing machine, and the test load is applied to the sample steadily and slowly according to the test method specified in GB / T1040.2018.9, and the displacement increment is 20 mm / min until the sample is broken and the test is terminated.

[0052] Table 1 Tensile test results of examples and comparative examples

[0053] Longitudinal tensile strength (MPa) Transverse tensile strength (MPa) Example 1 34 32 Example 2 30 28 Comparative Example 1 12 5

[0054] Table 2 shows the test results of the MRH-3C high-speed ring-block friction tester of the embodiment and the comparative example, wherein the test force is 400N, the linear speed is 0.4m / s, the test time is 2h, and the lubrication condition is one-time grease application.

[0055] Table 2 Friction test results of the embodiments and comparative examples

[0056] Average friction coefficient Wear scar width(mm) Example 1 0.018 1.8 Example 2 0.025 2.2 Comparative Example 1 0.032 2.9

[0057] Table 3 shows the test results of the oil dripping durability of the compressor bushings of the embodiments and comparative examples, wherein the test eccentric force is 10KN, the linear speed is 4.8m / s, the lubrication condition is continuous oil dripping of 20-25 drops / minute, and the test termination condition is temperature ≥125°C.

[0058] Table 3 Compressor bushing oil drip durability bench test results for the embodiments and comparative examples

[0059] Durability time (h) Example 1 1054 Example 2 890 Comparative Example 1 72

[0060] Compared with the prior art, the method for making a composite material for a PTFE-based sliding bearing with a mesh structure provided by the present invention ensures the strength of the prepared composite material by designing a special PTFE composite material raw material, especially by adding polymer particles and inorganic particles, which provides a premise for setting a mesh structure in the composite material, because if there is no high-strength composite material, the mesh structure cannot be set, that is, a high-strength matrix is ​​a prerequisite for the mesh structure, otherwise it is easy to break during stretching, resulting in defects in the mesh structure. At the same time, the formation of the mesh structure will increase the strength of the matrix formed by the composite material due to the effects of orientation and linking. At the same time, by adding the polymer particles and inorganic particles, the wear resistance of the composite material is also guaranteed. On the premise of ensuring strength and wear resistance, the strength of the prepared PTFE is ensured by first stretching longitudinally and then stretching transversely in the bidirectional stretching process, while controlling the temperature during the longitudinal and transverse stretching. In addition, a network structure is formed by bidirectional stretching, which can store grease. The sliding bearing using this fabric can continuously release grease under conditions of low oil, oil cut-off and boundary lubrication, thereby obtaining continuous low-friction operating conditions, reducing fabric wear and extending the service life of the sliding bearing.

[0061] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. A method for preparing a composite material for a PTFE-based sliding bearing having a mesh structure, comprising the following steps: STEP 101: Provide a PTFE composite material, the PTFE composite material consists of PTFE, a polymer filler and an inorganic filler, wherein the weight percentage of the PTFE is 50% to 90%, the weight percentage of the polymer filler is 5% to 20%, the weight percentage of the inorganic filler is 5% to 30%, the molecular weight of the PTFE is 500,000 to 5,000,000, and the particle size of the polymer filler is between 0.1 and 100 um, The inorganic filler has a particle size between 0.1 and 20 μm; STEP 102: Mix the PTFE composite material to obtain a PTFE mixture; STEP 103: providing an auxiliary oil, wherein the auxiliary oil accounts for 15% to 35% of the total weight of the PTFE mixture, and mixing the PTFE mixture with the auxiliary oil to form an oil-containing mixture; STEP 104: The oil-containing mixture is subjected to blanking, extrusion and calendering to obtain a PTFE oil-containing calendered film; the compression ratio of the blanking extrusion is 20 to 80, and the calendering speed is 3.5 to 5.0 m / min to fiberize the calendered film, and the thickness of the PTFE oil-containing calendered film is 0.1 to 0.5 mm; STEP105: Degreasing, biaxially stretching and shaping the PTFE oil-containing calendering film to obtain a PTFE-based sliding bearing fabric with a mesh structure, wherein the temperature and stretching ratio of the transverse stretching are greater than the temperature and stretching ratio of the longitudinal stretching; the biaxial stretching is first longitudinally stretched at a temperature of 310 to 350° C. and a stretching ratio of 1.0 to 3.0, and then transversely stretched at a temperature of 320 to 370° C., a stretching ratio of 1.0 to 5.0, and a line speed of 0.5 to 3.0 m / min to obtain a composite material with a porosity of 5 to 35%, wherein the temperature and stretching ratio of the transverse stretching are respectively greater than the temperature and stretching ratio of the longitudinal stretching; STEP 106: Compound the composite material with a metal substrate to obtain a high-strength PTFE-based sliding bearing with a mesh structure.

2. The method for producing a composite material for a PTFE-based sliding bearing having a network structure according to claim 1, characterized in that: The polymer filler is a mixture of at least one or more of tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer, perfluoroethylene propylene copolymer, polyphenylene ester, polyimide, and poly(p-phenylene terephthalamide).

3. The method for producing a composite material for a PTFE-based sliding bearing having a network structure according to claim 1, characterized in that: The inorganic filler is a mixture of at least one or more of graphite, molybdenum disulfide, silicon dioxide, aluminum oxide, calcium fluoride and zirconium phosphate.

4. The method for producing a composite material for a PTFE-based sliding bearing having a network structure according to claim 1, characterized in that: The auxiliary oil is any one of petroleum ether, isoparaffin oil and aviation kerosene.

5. The method for producing a composite material for a PTFE-based sliding bearing having a network structure according to claim 1, characterized in that: In STEP 105, the degreasing temperature is 150 to 200° C., and the line speed is 0.5 to 3 m / min.

6. The method for producing a composite material for a PTFE-based sliding bearing having a network structure according to claim 1, characterized in that: In STEP 105, the setting temperature is 350 to 390°C.