Vibration-fatigue-resistant enhanced thin-wall polytetrafluoroethylene pipe and preparation method thereof

Abstract

The invention provides a vibration-fatigue-resistant enhanced thin-wall polytetrafluoroethylene pipe and a preparation method thereof, and relates to a material technology. According to the pipe, PTFE dispersion resin serves as a matrix, and performance improvement is achieved through multi-component synergistic modification; 1-3% of aluminum nitride micro powder is added to enhance heat conductivity; 1-5% of potassium hexatitanate fibers subjected to surface treatment with a fluorosilane coupling agent FAS-17 are introduced, interface bonding of the fibers and PTFE is reinforced, interface stripping under long-term vibration is prevented, and the structural stability is improved; 1-3% of polyimide or polyether-ether-ketone micro powder is added as a toughening agent, so that the elongation at break and the vibration and impact resistance are improved; and 0.7-1.2% of a composite polyethylene glycol dispersion regulator is matched, so that the dispersity of the filler and the compactness of the system are improved. The obtained pipe has excellent mechanical property, vibration fatigue resistance and heat-conducting property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene (PTFE) paste extrusion pipe is widely used in complex pipe systems in the fields of aerospace, automobile manufacturing, chemical fluid transportation, etc. due to its excellent chemical inertness, wide temperature resistance range and excellent electrical insulation performance. However, these systems are often inevitably in a long-term or high-frequency mechanical vibration environment, and the anti-fatigue performance of traditional PTFE paste extrusion pipe under such working conditions is poor, and the service life is far lower than expected, which has become a key short board restricting the reliability and safety of equipment.

[0003] The root cause of the vibration fatigue cracking is mainly from two aspects of material nature and manufacturing process:

[0004] Material inherent defects: PTFE resin itself has low modulus and significant high creep (cold flow) property. Under periodic vibration load, the material is prone to plastic deformation and difficult to recover, resulting in continuous stress concentration at micro defects and gradual evolution into a silver line, and finally developing into a macro crack.

[0005] Process-induced defects: In the paste extrusion molding process, the uniformity of PTFE powder and additives, the shear force distribution during extrusion, and the subsequent sintering process jointly determine the microstructure of the pipe. Traditional process is prone to cause micro defects such as pores and uneven fibril orientation in the resin matrix, which become "weak spots" for stress concentration, significantly accelerating the initiation and propagation of fatigue cracks.

[0006] To address this challenge, the industry usually adopts the following improvement schemes, but they all have significant limitations:

[0007] First, fiber reinforced scheme (such as adding glass fiber or carbon fiber).

[0008] This scheme improves the overall hardness and modulus of the composite material by introducing rigid fibers. However, the improvement of its anti-vibration fatigue effect is very limited. The fundamental reason is that micron-sized fibers are difficult to achieve ideal uniform dispersion in the PTFE matrix, and are prone to form new and more severe stress concentration points due to aggregation. Under vibration load, cracks preferentially initiate at the interface between these fiber aggregates and the matrix, resulting in a decrease in the mechanical property stability of the material, and the long-term anti-fatigue protection cannot be achieved.

[0009] Second, optimization of automatic extrusion process.

[0010] By improving the automation and control accuracy of the extrusion equipment, the consistency of the pipe size and the uniformity of extrusion can be improved macroscopically. However, this solution only belongs to the improvement of the process level, and does not touch the essential problem of the insufficient toughness and weak crack propagation resistance of PTFE material from the molecular or microstructure level. Therefore, even if the appearance of the pipe is more uniform, the cracking risk of the pipe in the high-frequency vibration environment still exists.

[0011] Third, chemical copolymerization modification of PTFE.

[0012] By introducing other monomers for copolymerization modification of PTFE (such as PFA, FEP, etc.), the flexibility and impact resistance of the material can indeed be improved. However, this change in molecular chain structure is at the expense of the core performance of PTFE - its chemical corrosion resistance will be weakened, and the upper limit of the long-term use temperature will be reduced. This makes the modified material difficult to meet the complex working conditions with strict requirements for corrosive media and high temperature, and loses the core advantage of PTFE as the "plastic king". SUMMARY

[0013] The purpose of the application is to overcome the problems of high porosity, uneven dispersion of inorganic fillers, low mechanical strength, density and vibration fatigue resistance of traditional PTFE paste extruded pipes. The application provides a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe and a preparation method thereof.

[0014] In a first aspect, the application provides a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, comprising the following preparation steps:

[0015] Pre-treatment: modify potassium hexatitanate fibers with a fluorosilane coupling agent to obtain modified potassium hexatitanate fibers;

[0016] Mixing: mix 80-82 parts by mass of PTFE dispersion resin and 18-20 parts by mass of isoparaffin auxiliary agent, then add 1-5 parts by mass of aluminum nitride powder, 1-5 parts by mass of modified potassium hexatitanate fibers, and 1-4 parts by mass of polyimide or polyether ether ketone powder for further stirring and mixing;

[0017] Then, after aging, preforming, extrusion molding and sintering, a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe is obtained.

[0018] Further, the aluminum nitride powder is 2-3 parts by mass, the modified potassium hexatitanate fibers are 2-3 parts by mass, and the polyimide or polyether ether ketone powder is 1-2 parts by mass.

[0019] Further, the fluorosilane coupling agent accounts for 0.1-0.5 wt% of the weight of the potassium hexatitanate fibers.

[0020] Further, the fluorosilane coupling agent accounts for 0.1-0.3 wt% of the weight of the potassium hexatitanate fibers.

[0021] Further, 0.7-1.2 parts by mass of a dispersing agent polyethylene glycol is added in the mixing step.

[0022] Further, the dispersing agent is innovatively a gradient molecular weight polyethylene glycol compound system, including high molecular weight PEG coated fibers to reduce friction and improve processing fluidity, accounting for 0.2-0.4 wt%; medium molecular weight PEG to adjust interfacial compatibility, accounting for 0.3-0.5 wt%; low molecular weight PEG to block filler surface hydroxyl adsorption, reduce filler agglomeration tendency, and improve filler dispersion uniformity, accounting for 0.2-0.3 wt%; the gradient PEG system ensures that the filler can be highly uniformly dispersed in the form of primary particles, thereby ensuring the uniformity and stability of the final material performance, and the Isopar G extrusion aid reduces the extrusion pressure, avoids pipe cracking, and ensures smooth molding.

[0023] Further, the average particle size of the aluminum nitride powder is 0.1-0.5 μm.

[0024] Further, the temperature in the aging process is 35-50 ℃, and the time is 20-24 h; the pressure in the preforming process is 4-5 MPa, and the time is 10-12 min.

[0025] Further, the barrel temperature in the extrusion molding process is 50-60 ℃, and the die temperature is 70-75 ℃; the drying section temperature in the sintering process is 150-250 ℃, and the sintering section temperature is 270-470 ℃.

[0026] Process control is implemented for full-process optimization: the extrusion speed and pressure are dynamically adjusted through an online monitoring system to ensure uniform orientation and distribution of fibers along the axial direction; an inert gas (nitrogen) circulation system is added in the drying section of the sintering furnace, with a flow rate of 0.5-1 m / s to accelerate the volatilization of Isopar G, reduce the residual amount of the aid, reduce the porosity of the pipe material, and thus improve the mechanical properties, vibration fatigue resistance, and thermal conductivity of the pipe material.

[0027] In a second aspect, the application provides a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe material obtained by the preparation method of the vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe material.

[0028] Beneficial effects: 1. In the aspect of material composite modification, the application adopts a multi-component synergistic optimization strategy: PTFE dispersion resin is used as a base material, 1-3% aluminum nitride powder is added to improve thermal conductivity, 1-5% potassium hexatitanate fibers are introduced, and after a small amount (0.1-0.3 wt%) of fluorosilane coupling agent FAS-17 surface grafting treatment, the siloxane part is combined with the fiber surface, and the fluorine chain segment is compatible with the PTFE molecular chain, so that the interfacial bonding strength is improved, the interfacial peeling under long-term vibration is avoided, and the structural stability of the pipe material is enhanced; 1-3% polyimide or polyether ether ketone is added as a toughening agent to improve the elongation at break and improve the toughness of the material to resist high-frequency vibration impact; the application starts from three aspects of material composite modification, process precise control and structure innovation design, and comprehensively optimizes the density and vibration fatigue resistance of the polytetrafluoroethylene (PTFE) paste extrusion pipe material, thereby endowing the product with excellent mechanical, anti-vibration and thermal conductivity comprehensive performance to meet the harsh requirements of high-frequency vibration environment.

[0029] 2. Further, a gradient molecular weight polyethylene glycol complex system is used as a dispersion medium, and cooperates with potassium hexatitanate fibers treated by fluorosilane coupling agent FAS-17. The modified fibers are uniformly distributed in the PTFE matrix due to their extremely low surface energy and high aspect ratio, forming a supporting three-dimensional fiber network structure, which can effectively inhibit the aggregation of aluminum nitride powder and polyimide powder and other easy-to-agglomerate fillers. The complex system significantly enhances the dispersity, compatibility and structural density of high filling amount aluminum nitride and polyimide in PTFE, thereby synergistically improving the mechanical properties, anti-vibration fatigue performance and thermal conductivity of the pipe material. DETAILED DESCRIPTION

[0030] In order to make the technical scheme of the application clearer, the application will be further described in detail below in combination with specific examples.

[0031] Example 1, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, comprising the following preparation steps:

[0032] (1) Pretreatment: mix potassium hexatitanate fibers (average length 1-8 μm, diameter 0.1-0.3 μm) with 0.1-0.3 wt% of fluorosilane coupling agent FAS-17 based on the weight of the potassium hexatitanate fibers, add 0.7-1.2 parts by mass of anhydrous ethanol as a dispersion medium, stir at 25-40 ℃ for 20-40 min, and then dry at 70-90 ℃ for 1-4 h to remove ethanol, and obtain modified potassium hexatitanate fibers.

[0033] (2) Mixing: 80-82 parts by mass of PTFE dispersion resin and 18-20 parts by mass of isoparaffin (preferably Isopar G manufactured by Exxon Mobil Corporation) are mixed for 10-15 minutes, and then 2-3 parts by mass of aluminum nitride powder (average particle diameter of 0.1-0.5 μm), 2-3 parts by mass of modified potassium hexatitanate fiber, and 1-2 parts by mass of polyimide or polyether ether ketone powder are added and mixed for 0.5-3 hours.

[0034] The isoparaffin preferably has a carbon atom number of 11-14; more preferably, it is Isopar G manufactured by Exxon Mobil Corporation.

[0035] (3) Curing: After mixing, curing is performed at 35-50 °C for 20-24 hours.

[0036] (4) Preforming: Preforming is performed at a pressure of 4-5 MPa, and pressure is maintained for 10-12 minutes.

[0037] (5) Extrusion molding: The preformed body is placed in an extruder, the temperature of the cylinder is 50-60 °C, the temperature of the die is 70-75 °C, and the green pipe is extruded at a speed of 1.6-2 m / min.

[0038] (6) Sintering: The green pipe is passed through a sintering furnace, the temperature of the drying section is 150-250 °C, and the temperature of the sintering section is 270-470 °C.

[0039] (7) Winding: After cooling in air, the product is wound.

[0040] Further, 0.7-1.2 parts by mass of a dispersion regulator, polyethylene glycol, is added in the mixing step.

[0041] Further, the dispersion regulator includes 0.2-0.4 wt% of high molecular weight PEG, 0.3-0.5 wt% of medium molecular weight PEG, and 0.2-0.3 wt% of low molecular weight PEG, and the polyethylene glycol is uniformly dispersed in the paste by stirring at a low speed for 5-10 minutes, and then the aluminum nitride powder, the modified potassium hexatitanate fiber, and the polyimide or polyether ether ketone powder are added and mixed for 0.5-3 hours.

[0042] Preferably, the polyimide powder has a diameter of 3-8 μm.

[0043] Further, the polyethylene glycol can be selected from those manufactured by Shanghai Aladdin Bio-Chemical Corp.

[0044] The average molecular weight Mw of the low molecular weight PEG is 200-999, the average molecular weight Mw of the medium molecular weight PEG is 1,000-5,999, and the average molecular weight Mw of the high molecular weight PEG is 6,000-20,000.

[0045] Embodiment 2, a method for preparing a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, comprising the following preparation steps:

[0046] (1) Pretreatment: mix potassium hexatitanate fibers (average length 5 μm, diameter 0.1 μm, manufactured by Otsuka Chemical Co., Ltd.) with 0.2 wt% fluorosilane coupling agent FAS-17 (manufactured by Suzhou Zhongbo Chemical Co., Ltd.) based on the weight of the potassium hexatitanate fibers, add an appropriate amount of anhydrous ethanol as a dispersion medium, stir at 30°C for 30 min, then dry at 80°C for 2 h, remove the ethanol, and obtain modified potassium hexatitanate fibers.

[0047] (2) Mixing: mix 80 parts by mass of PTFE dispersion resin (F-302, manufactured by Daikin Co., Ltd.) with 20 parts by mass of solvent Isopar G (manufactured by ExxonMobil Co., Ltd.) for 12 min, then add 2 parts by mass of aluminum nitride powder (average particle size 0.3 μm, manufactured by Baigu Co., Ltd.), 3 parts by mass of modified potassium hexatitanate fibers, and 2 parts by mass of polyimide powder (diameter 5 μm, manufactured by Huangshan Jinshi Wood Co., Ltd.) and continue to mix for 1 h.

[0048] (3) Curing: after mixing evenly, cure at 40°C for 20 h.

[0049] (4) Preforming: preform at a pressure of 5 MPa and maintain the pressure for 10 min.

[0050] (5) Extrusion molding: place the preform into an extruder, set the barrel temperature to 60°C and the die temperature to 75°C, and extrude the green pipe at a speed of 1.8 m / min.

[0051] (6) Sintering: pass the green pipe through a 10 m sintering furnace, set the drying section temperature to 200°C and the sintering section temperature to 300°C.

[0052] (7) Winding: after cooling in air, wind up to obtain the finished product.

[0053] Embodiment 3, a method for preparing a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which is different from Embodiment 2 in that 1 part by mass of a dispersion regulator polyethylene glycol complex system (manufactured by Shanghai Aladdin Biochemical Co., Ltd., wherein the dispersion regulator polyethylene glycol comprises 0.3 wt% high molecular weight PEG based on the PTFE dispersion resin, 0.4 wt% medium molecular weight PEG based on the PTFE dispersion resin, and 0.2 wt% low molecular weight PEG based on the PTFE dispersion resin) is added in the mixing step, the polyethylene glycol is uniformly dispersed in the paste by continuing to stir at low speed for 5-10 min, then 2 parts by mass of aluminum nitride powder (average particle size 0.3 μm, manufactured by Baigu Co., Ltd.), 3 parts by mass of modified potassium hexatitanate fibers, and 2 parts by mass of polyimide powder (5 μm, manufactured by Huangshan Jinshi Wood Co., Ltd.) are added and continue to mix for 1 h.

[0054] The average molecular weight Mw of the low molecular weight PEG can be 200-999; the average molecular weight Mw of the medium molecular weight PEG can be 1,000-5999; the average molecular weight Mw of the high molecular weight PEG can be 6,000-20,000; the low molecular weight PEG used in the embodiments of the present application is PEG 400, the medium molecular weight PEG is PEG 2000; and the high molecular weight PEG is PEG 8000.

[0055] Example 4, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which differs from example 3 in that the low molecular weight PEG is not used in the polyethylene glycol compounding system, and the medium molecular weight PEG is used to replace the low molecular weight PEG in equal amount.

[0056] Example 5, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which differs from example 3 in that the high molecular weight PEG is not used in the polyethylene glycol compounding system, and the low molecular weight PEG is used to replace the high molecular weight PEG in equal amount.

[0057] Example 6, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which differs from example 3 in that the low molecular weight PEG is used to replace the high molecular weight PEG and the medium molecular weight PEG in equal amount in the polyethylene glycol compounding system.

[0058] The compactness, anti-fatigue vibration performance and mechanical properties of the pipe of example 3 are obviously superior to those of examples 4-6 and example 2, which can be because the high molecular weight PEG can be well coated on the surface of the potassium hexatitanate fiber to reduce friction; the medium molecular weight PEG can effectively reduce the interfacial energy between the phases and improve the compatibility; and the low molecular weight PEG has strong adsorption capacity and can preferentially occupy the active adsorption sites on the surface of the filler to reduce the agglomeration tendency of the filler. The use of gradient low molecular weight PEG, medium molecular weight PEG and high molecular weight PEG can simultaneously improve the compactness, mechanical properties, anti-fatigue vibration performance and heat conduction effect of the pipe.

[0059] Example 7, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which differs from example 3 in that,

[0060] The fluorosilane coupling agent accounts for 0.5 wt% of the weight of the potassium hexatitanate fiber.

[0061] Comparative example 1, a preparation method of a vibration fatigue resistant reinforced thin-walled polytetrafluoroethylene pipe, which differs from example 3 in that the modified potassium hexatitanate fiber is not used.

[0062] Comparative Example 2, a method for preparing a vibration fatigue resistant reinforced thin-walled PTFE pipe, differs from Example 3 in that the modified potassium hexatitanate fibers are replaced with an equal amount of potassium hexatitanate fibers (average length 5 μm, diameter 0.1 μm, manufactured by Otsuka Chemical Co., Ltd.), and the polyethylene glycol compounding system is not used.

[0063] Comparative Example 3, a method for preparing a vibration fatigue resistant reinforced thin-walled PTFE pipe, differs from Example 3 in that the polyimide micro powder is replaced with an equal amount of modified potassium hexatitanate fibers.

[0064] Performance test: density, thermal conductivity, tensile strength, elongation at break and vibration fatigue resistance of the finished PTFE pipe of the examples and comparative examples, and the test results are shown in Table 1

[0065] Table 1 Performance test results

[0066]

[0067] In Comparative Example 2, the potassium hexatitanate fibers are not surface modified, and the PEG dispersion system is not introduced, resulting in easy agglomeration of the potassium hexatitanate fibers, polyimide and aluminum nitride micro powder, and serious uneven dispersion, forming a large number of structural defects in the material. Therefore, the pipe prepared in Comparative Example 2 has poor performance. Although Comparative Example 3 uses modified potassium hexatitanate fibers and a complete PEG dispersion system to achieve good filler dispersion and strong interfacial bonding, the material lacks an effective toughness adjustment mechanism when under stress because polyimide is not introduced as a toughening phase, resulting in a low elongation at break and exhibiting the typical characteristics of a "high strength and high conductivity" but brittle material. Compared with Comparative Examples 2 and 3, Example 3 exhibits better overall performance. The key is the synergistic use of modified potassium hexatitanate fibers and polyimide toughening agents, supplemented by a complete PEG dispersion system. In this system, the potassium hexatitanate fibers modified by fluorosilane coupling agent form a firm interface with the PTFE matrix, effectively transmitting stress and contributing to higher tensile strength and modulus; at the same time, polyimide as a toughness component can induce plastic deformation, absorb energy and inhibit crack propagation when the material is impacted or stretched. On the basis of good dispersion, the pipe not only maintains high tensile strength and modulus, but also has excellent elongation at break and vibration fatigue resistance. In the examples of the present application, the simultaneous improvement of pipe tensile strength, elongation at break and vibration fatigue resistance is successfully achieved by fiber modification, polymer toughening and gradient dispersion system.

[0068] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the patent scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene (PTFE) pipe, characterized in that, The preparation steps include the following: Pretreatment: Potassium hexatitanate fiber is modified with a fluorosilane coupling agent to obtain modified potassium hexatitanate fiber; Mixing: Mix 80-82 parts by weight of PTFE dispersion resin and 18-20 parts by weight of isoparaffin auxiliaries, then add 1-5 parts by weight of aluminum nitride micro powder, 1-5 parts by weight of modified potassium hexatitanate fiber, and 1-4 parts by weight of polyimide or polyether ether ketone and continue stirring and mixing. Then, after curing, preforming, extrusion molding, and sintering, vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipes are obtained.

2. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 1, characterized in that, The aluminum nitride micro powder is 2-3 parts by weight, the modified potassium hexatitanate fiber is 2-3 parts by weight, and the polyimide or polyether ether ketone is 1-2 parts by weight.

3. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 1 or 2, characterized in that, The fluorosilane coupling agent accounts for 0.1%-0.5 wt% of the potassium hexatitanate fiber.

4. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 1 or 2, characterized in that, The fluorosilane coupling agent accounts for 0.1-0.3 wt% of the potassium hexatitanate fiber.

5. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 4, characterized in that, In the mixing step, 0.7-1.2 parts by weight of polyethylene glycol, a dispersant, are also added.

6. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 5, characterized in that, The dispersant comprises 0.2-0.4% high molecular weight PEG, 0.3-0.5% medium molecular weight PEG, and 0.2-0.3% low molecular weight PEG.

7. A method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene (PTFE) pipe according to any one of claims 1-2, 5-6, characterized in that, The aluminum nitride micro powder has an average particle size of 0.1-0.5 μm.

8. The method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene pipe according to claim 7, characterized in that, The curing process is carried out at a temperature of 35-50 ℃ for 20-24 h; the preforming process is carried out at a pressure of 4-5 MPa for 10-12 min.

9. A method for preparing a vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene (PTFE) pipe according to any one of claims 1-2, 5-6, and 8, characterized in that, During the extrusion molding process, the barrel temperature is 50-60 ℃ and the die temperature is 70-75 ℃; during the sintering process, the drying section temperature is 150-250 ℃ and the sintering section temperature is 270-470 ℃.

10. A vibration fatigue-resistant reinforced thin-walled polytetrafluoroethylene (PTFE) pipe obtained by the preparation method of a vibration fatigue-resistant reinforced thin-walled PTFE pipe according to any one of claims 1-9.

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