High performance polytetrafluoroethylene pipe and method of making same

Abstract

The application discloses a kind of high-performance polytetrafluoroethylene pipe and preparation method thereof, comprising the following steps: step one, high-performance polytetrafluoroethylene raw materials are added to a mixer, stirred and mixed at 50-80 DEG C, 200-750 rpm for 0.5-4 h, to obtain a mixture;Step two, add to a mold, pressure for 30-120 min under 40-95 Mpa, then sintering treatment is carried out;Step three, with the cooling rate of 0.4-0.8 DEG C / min, temperature is reduced to 295-320 DEG C for tempering treatment, and heat preservation is 0.5-2 h, then furnace cooling to room temperature, to obtain high-performance polytetrafluoroethylene pipe.The polytetrafluoroethylene pipe prepared by the application has excellent tensile strength, good thermal conductivity and excellent anti-permeation and corrosion resistance, can be used in high-temperature and strong-corrosion working environment, and can be well used as high-temperature corrosive liquid heat exchange pipe.

Description

Technical Field

[0001] This invention relates to the field of polytetrafluoroethylene (PTFE) materials, and particularly to a high-performance PTFE pipe and its preparation method. Background Technology

[0002] Polytetrafluoroethylene (PTFE) heat exchangers, also known as PTFE heat exchangers, are heat exchangers that use small-diameter PTFE tubes as heat transfer components; they are also called flexible tube heat exchangers. PTFE heat exchangers are mainly used for heat exchange with various highly corrosive media, such as sulfuric acid, highly corrosive chloride solutions, acetic acid, and caustic media for cooling or heating. Examples include a chemical-grade internally and externally corrosion-resistant PTFE heat exchanger disclosed in patent CN216081119U, a PTFE heat exchanger for propionyl chloride production disclosed in patent CN217210484U, and a corrosion-resistant PTFE heat exchanger disclosed in patent CN209524792U.

[0003] Polytetrafluoroethylene (PTFE) possesses extremely stable chemical properties and excellent corrosion resistance. Its smooth tube wall surface is resistant to scaling, and it exhibits moderate flexibility, making it suitable for heat exchange with highly corrosive liquids. However, it also has several drawbacks: PTFE has a low thermal conductivity, and compared to metals, its mechanical properties and high-temperature resistance are inferior. While using small-diameter, thin-walled tubes can compensate for some thermal conductivity issues, the compensation is limited. This affects the effectiveness of PTFE heat exchanger tubes as heat transfer components, limiting its application scenarios. Currently, it is typically only used in lower pressure and lower temperature applications. Furthermore, heat exchanger tubes used with highly corrosive liquids face high-temperature and highly corrosive working environments, thus placing higher demands on PTFE's high-temperature resistance, corrosion resistance, and impermeability.

[0004] Patent CN114230835B discloses a low-permeability polytetrafluoroethylene (PTFE) tube and its preparation method. This method improves the density and thus permeability resistance of PTFE tubes by impregnating or spraying them with PFA emulsion. While it achieves some improvement in permeability resistance, it does not address the high-temperature resistance and thermal conductivity of the PTFE tubes, making it insufficient for applications requiring tubes for highly corrosive liquids.

[0005] Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-performance polytetrafluoroethylene pipe and its preparation method, addressing the shortcomings of the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In its first aspect, the present invention provides a method for preparing high-performance polytetrafluoroethylene (PTFE) tubing, comprising the following steps:

[0008] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 50-80℃ and 200-750rpm for 0.5-4 hours to obtain the mixture.

[0009] Step 2: Add the mixture to the mold, hold under pressure at 40-95 MPa for 30-120 minutes, and then sinter according to the following temperature control procedure:

[0010] Heat to 130-180℃ at a heating rate of 1-3℃ / min, and hold for 0.5-2 hours;

[0011] Heat to 220-280℃ at a heating rate of 0.5-2℃ / min, and hold for 1-3 hours;

[0012] Heat to 360-375℃ at a heating rate of 0.2-1℃ / min, and hold for 1.5-4 hours;

[0013] Step 3: Cool the material to 295-320℃ at a cooling rate of 0.4-0.8℃ / min for tempering treatment, hold for 0.5-2 hours, and then cool it to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0014] Preferably, the method for preparing the high-performance polytetrafluoroethylene pipe includes the following steps:

[0015] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 70℃ and 450rpm for 2 hours to obtain the mixture.

[0016] Step 2: Add the mixture to the mold, hold under pressure at 80 MPa for 45 minutes, and then perform sintering according to the following temperature control procedure:

[0017] Heat to 150℃ at a heating rate of 1.5℃ / min and hold for 1 hour;

[0018] Heat to 250℃ at a heating rate of 1℃ / min and hold for 1.5h;

[0019] Heat to 370℃ at a heating rate of 0.5℃ / min and hold for 2.5 hours;

[0020] Step 3: Cool to 300℃ at a cooling rate of 0.5℃ / min for tempering treatment, hold for 1 hour, and then cool to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0021] Preferably, the high-performance polytetrafluoroethylene raw material comprises the following components in parts by weight:

[0022] 70-95 parts of polytetrafluoroethylene;

[0023] 7.5-20 parts of polyamide-imide;

[0024] 6-23 parts of polyphenylene sulfide;

[0025] Pentaerythritol stearate 0.9-2.4 parts;

[0026] Modified nano-Si3N4, 1.8-3.3 parts;

[0027] Composite reinforcing particles: 9.5-27 parts.

[0028] Preferably, the modified nano-Si3N4 is prepared by the following method:

[0029] S1. Take 0.5-2g of nano Si3N4 and add it to 75-300mL of isopropanol. Disperse it by ultrasonication for 15-60min to obtain Si3N4 dispersion.

[0030] S2. Take 0.06-0.24g of bis(triethanolamine) diisopropyl titanate and add it to 15-60mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 58-65℃ for 1.5-6h, filter, wash the solid product with ethanol, and then vacuum dry at 40-55℃ for 6-24h to obtain modified nano-Si3N4.

[0031] Preferably, the modified nano-Si3N4 is prepared by the following method:

[0032] S1. Take 1g of nano-Si3N4 and add it to 150mL of isopropanol. Disperse it by ultrasonication for 30min to obtain Si3N4 dispersion.

[0033] S2. Take 0.12g of bis(triethanolamine) diisopropyl titanate and add it to 30mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 62℃ for 3h, filter, wash the solid product with ethanol, and then vacuum dry at 50℃ for 12h to obtain modified nano Si3N4.

[0034] Preferably, the composite reinforcing particles are prepared by the following method:

[0035] 1) Modified polytetrafluoroethylene (PTFE) micropowder was prepared by using sodium-naphthalene-tetrahydrofuran solution as an activation treatment solution to modify PTFE micropowder.

[0036] 2) Preparation of boronized graphene oxide;

[0037] 3) Using boronized graphene oxide, graphene oxide-boron nitride composite particles were prepared by hydrothermal method.

[0038] 4) The graphene oxide-boron nitrile composite particles were modified by using carboxyl liquid nitrile rubber to obtain modified graphene oxide-boron nitrile composite particles.

[0039] 5) The modified polytetrafluoroethylene micro powder prepared in step 1) and the modified graphene oxide-boron nitride composite particles prepared in step 4) are mixed to obtain composite reinforced particles.

[0040] Preferably, step 2) specifically includes:

[0041] 2-1) Take 1-4g of graphene oxide and add it to 100-300mL of hydrogen peroxide solution with a mass fraction of 10-20%. Sonicate at 65-80℃ for 1.5-6h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 90-100℃ for 3-8h to obtain pretreated graphene oxide.

[0042] 2-2) Take 0.5-2g of pretreated graphene oxide and add it to 150-400mL of methanol. Disperse it ultrasonically for 30-90min to obtain a pretreated graphene oxide dispersion.

[0043] 2-3) Take 6.5-26.0g of 3-aminophenylboronic acid and add it to 150-600mL of methanol. Stir for 15-60min. Add the resulting mixture to the pretreated graphene oxide dispersion while stirring. Then add 4.2-16g of EDC hydrochloride and sonicate for 10-30min. Then reflux at 60-80℃ for 4-16h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 40-50℃ for 6-24h to obtain boronized graphene oxide.

[0044] Preferably, step 3) specifically includes:

[0045] 3-1) Take 0.5-2g of the boronized graphene oxide prepared in step 2) and add it to 25-75g of deionized water, and ultrasonically disperse it for 15-60min to obtain a boronized graphene oxide dispersion.

[0046] 3-2) Take 0.487-1.95g of sodium azide and add it to 10-40g of deionized water, then add 0.134-0.536g of white phosphorus powder, and then add boronized graphene oxide dispersion under stirring. Stir for 15-60min, transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 10-30min and then seal the stainless steel reactor. Heat to 420-460℃ at a heating rate of 1.5-4℃ / min and react for 24-60h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 80-100℃ for 4-16h to obtain graphene oxide-boron nitride composite particles.

[0047] Preferably, the composite reinforcing particles are prepared by the following method:

[0048] 1) Preparation of modified polytetrafluoroethylene micro powder:

[0049] 1-1) Take 60g of naphthalene and add it to 500mL of tetrahydrofuran. Stir until completely dissolved. Add 10g of sodium metal in portions and stir until the sodium metal is completely dissolved to obtain the activation treatment solution. The whole process is carried out at 2℃ under nitrogen protection.

[0050] 1-2) Under a nitrogen atmosphere, 40g of polytetrafluoroethylene micro powder with a particle size of 0.1-0.5μm was added to the activation treatment solution, stirred at 300rpm for 10min, filtered, the solid product was washed with ethanol, dried at 70℃ for 12h, and ground to obtain modified polytetrafluoroethylene micro powder.

[0051] 2) Preparation of boronized graphene oxide:

[0052] 2-1) Take 2g of graphene oxide and add it to 200mL of hydrogen peroxide solution with a mass fraction of 15%. Sonicate at 70℃ for 3h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 95℃ for 5h to obtain pretreated graphene oxide.

[0053] 2-2) Take 1g of pretreated graphene oxide and add it to 250mL of methanol. Disperse it by ultrasonication for 45min to obtain a dispersion of pretreated graphene oxide.

[0054] 2-3) Take 13.0 g of 3-aminophenylboronic acid and add it to 300 mL of methanol. Stir for 25 min. Add the resulting mixture to the pretreated graphene oxide dispersion under stirring. Then add 9.5 g of EDC hydrochloride. Disperse by ultrasonication for 20 min. Then reflux at 70 °C for 8 h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 45 °C for 12 h to obtain boronized graphene oxide.

[0055] 3) Hydrothermal preparation of graphene oxide-boron nitride composite particles:

[0056] 3-1) Take 1g of the boronized graphene oxide prepared in step 2) and add it to 50g of deionized water. Disperse it ultrasonically for 30min to obtain a boronized graphene oxide dispersion.

[0057] 3-2) Take 0.975g of sodium azide and add it to 20g of deionized water, then add 0.268g of white phosphorus powder, and then add boronized graphene oxide dispersion while stirring. Keep stirring for 30min. Transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 15min and then seal the stainless steel reactor. Heat to 450℃ at a heating rate of 2.5℃ / min and react for 48h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90℃ for 8h to obtain graphene oxide-boron nitride composite particles.

[0058] 4) Modification of graphene oxide-boron nitrile composite particles using carboxyl-based liquid nitrile rubber:

[0059] 2g of graphene oxide-boron nitride composite particles were added to 300mL of toluene, and 3.2g of carboxyl liquid nitrile rubber was added. Under nitrogen protection, the mixture was stirred at 200rpm and 70℃ for 6h. After the reaction was completed, the product was transferred to a Soxhlet extractor and extracted with toluene for 48h. The solid product was vacuum dried at 60℃ for 8h. The product was ground and passed through a 120-mesh sieve to obtain modified graphene oxide-boron nitride composite particles.

[0060] 5) Take 20g of the modified graphene oxide-boron nitride composite particles prepared in step 4) and 30g of the modified polytetrafluoroethylene micro powder prepared in step 1) and add them to a mixer. Mix them at 170℃ and 150rpm for 30min. Cool to room temperature and grind them to a particle size of less than 0.1mm to obtain composite reinforced particles.

[0061] In a second aspect, the present invention provides a high-performance polytetrafluoroethylene (PTFE) pipe, which is prepared by the method described above.

[0062] The beneficial effects of this invention are:

[0063] The polytetrafluoroethylene pipe prepared by this invention has excellent tensile strength, good thermal conductivity, and excellent anti-permeability and corrosion resistance. It can withstand high temperature and strong corrosion working environment and can be well used as a heat exchange pipe for high temperature corrosive liquids.

[0064] In the high-performance polytetrafluoroethylene raw material formulation of this invention, polyamide-imide (PAI) has excellent mechanical properties, heat resistance and chemical stability, and also has good adhesion, which can help improve the bonding strength between the organic substrate and the filler particles, thereby improving the density, corrosion resistance and mechanical strength of the substrate; polyphenylene sulfide is compounded and added to polytetrafluoroethylene material, which can improve the high temperature resistance and corrosion resistance of the substrate.

[0065] This invention employs bis(triethanolamine) diisopropyl titanate to modify the surface of nano-Si3N4. The bis(triethanolamine) diisopropyl titanate molecular chains grafted onto the Si3N4 surface generate mutual repulsion and steric hindrance, which can reduce surface energy, prevent particle aggregation, and improve the compatibility between Si3N4 and polytetrafluoroethylene (PTFE) vinyl materials. This allows Si3N4 to better enhance the high-temperature resistance, density, and corrosion resistance of PTFE vinyl materials.

[0066] The composite reinforcing particles prepared by this invention can further improve the tensile strength, high temperature resistance, thermal conductivity, impermeability, and corrosion resistance of polytetrafluoroethylene (PTFE) pipes. Specifically, the construction of the graphene oxide-boron nitride composite particle structure system, combined with the composite coating of carboxyl liquid nitrile rubber and modified PTFE, can simultaneously overcome the defects of graphene oxide and boron nitride microcrystals being difficult to disperse and prone to agglomeration. It can also solve the problem of boron nitride being difficult to surface modify to improve its dispersion ability in polymers. Ultimately, the reinforcing effect of graphene oxide and boron nitride microcrystals can be fully utilized, producing a synergistic reinforcing effect, resulting in a comprehensive improvement in the mechanical strength, high temperature resistance, corrosion resistance, and impermeability of the prepared PTFE pipes. Attached Figure Description

[0067] Figure 1 This is a flowchart of the preparation method of the high-performance polytetrafluoroethylene pipe of the present invention;

[0068] Figure 2 The infrared absorption spectrum of boronized graphene oxide (B-GO) prepared in Example 1;

[0069] Figure 3 The XRD pattern of the graphene oxide-boron nitride composite particles prepared in Example 1;

[0070] Figure 4 The tensile property test results are for the examples and comparative examples;

[0071] Figure 5 The thermal conductivity test results are for the examples and comparative examples;

[0072] Figure 6 The permeability coefficient test results are for the examples and comparative examples;

[0073] Figure 7 The results of tensile strength tests on the pipe samples of Example 1 after being kept at different temperatures for 2 hours are as follows;

[0074] Figure 8 The tensile strength test results of the pipe sample in Example 1 after being kept at 200°C for different times;

[0075] Figure 9 The results of high-temperature tensile strength tests are for the examples and comparative examples;

[0076] Figure 10 The results of high-temperature permeability tests are shown in the examples and comparative examples. Detailed Implementation

[0077] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0078] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0079] 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. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0080] This invention provides a high-performance polytetrafluoroethylene (PTFE) pipe, the preparation method of which includes the following steps:

[0081] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 50-80℃ and 200-750rpm for 0.5-4 hours to obtain the mixture.

[0082] Step 2: Add the mixture to the mold, hold under pressure at 40-95 MPa for 30-120 minutes, and then sinter according to the following temperature control procedure:

[0083] Heat to 130-180℃ at a heating rate of 1-3℃ / min, and hold for 0.5-2 hours;

[0084] Heat to 220-280℃ at a heating rate of 0.5-2℃ / min, and hold for 1-3 hours;

[0085] Heat to 360-375℃ at a heating rate of 0.2-1℃ / min, and hold for 1.5-4 hours;

[0086] Step 3: Cool the material to 295-320℃ at a cooling rate of 0.4-0.8℃ / min for tempering treatment, hold for 0.5-4 hours, and then cool it to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0087] In a more preferred embodiment, the method for preparing the high-performance polytetrafluoroethylene pipe includes the following steps:

[0088] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 70℃ and 450rpm for 2 hours to obtain the mixture.

[0089] Step 2: Add the mixture to the mold, hold under pressure at 80 MPa for 45 minutes, and then perform sintering according to the following temperature control procedure:

[0090] Heat to 150℃ at a heating rate of 1.5℃ / min and hold for 1 hour;

[0091] Heat to 250℃ at a heating rate of 1℃ / min and hold for 1.5h;

[0092] Heat to 370℃ at a heating rate of 0.5℃ / min and hold for 2.5 hours;

[0093] Step 3: Cool to 300℃ at a cooling rate of 0.5℃ / min for tempering treatment, hold for 1 hour, and then cool to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0094] In this invention, the high-performance polytetrafluoroethylene raw material comprises the following components in parts by weight:

[0095] 70-95 parts of polytetrafluoroethylene;

[0096] 7.5-20 parts of polyamide-imide;

[0097] 6-23 parts of polyphenylene sulfide;

[0098] Pentaerythritol stearate 0.9-2.4 parts;

[0099] Modified nano-Si3N4, 1.8-3.3 parts;

[0100] Composite reinforcing particles: 9.5-27 parts.

[0101] In this invention, modified nano-Si3N4 is prepared by the following method:

[0102] S1. Take 0.5-2g of nano Si3N4 and add it to 75-300mL of isopropanol. Disperse it by ultrasonication for 15-60min to obtain Si3N4 dispersion.

[0103] S2. Take 0.06-0.24g of bis(triethanolamine) diisopropyl titanate and add it to 15-60mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 58-65℃ for 1.5-6h, filter, wash the solid product with ethanol, and then vacuum dry at 40-55℃ for 6-24h to obtain modified nano-Si3N4.

[0104] In this invention, the composite reinforcing particles are prepared by the following method:

[0105] 1) Modified polytetrafluoroethylene (PTFE) micropowder was prepared by using sodium-naphthalene-tetrahydrofuran solution as the activation treatment solution to modify PTFE micropowder:

[0106] 1-1) Take 30-120g of naphthalene and add it to 250-1000mL of tetrahydrofuran. Stir until completely dissolved. Add 5-20g of sodium metal in portions and stir until the sodium metal is completely dissolved to obtain the activation treatment solution. The whole process is carried out at 0-4℃ under nitrogen protection.

[0107] 1-2) Under a nitrogen atmosphere, take 20-80g of polytetrafluoroethylene micro powder with a particle size of 0.1-0.5μm and add it to the activation treatment solution. Stir at 200-400rpm for 5-30min, filter, wash the solid product with ethanol, and then dry at 60-80℃ for 6-24h. Grind to obtain modified polytetrafluoroethylene micro powder.

[0108] 2) Preparation of boronized graphene oxide:

[0109] 2-1) Take 1-4g of graphene oxide and add it to 100-300mL of hydrogen peroxide solution with a mass fraction of 10-20%. Sonicate at 65-80℃ for 1.5-6h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 90-100℃ for 3-8h to obtain pretreated graphene oxide.

[0110] 2-2) Take 0.5-2g of pretreated graphene oxide and add it to 150-400mL of methanol. Disperse it ultrasonically for 30-90min to obtain a pretreated graphene oxide dispersion.

[0111] 2-3) Take 6.5-26.0g of 3-aminophenylboronic acid and add it to 150-600mL of methanol. Stir for 15-60min. Add the resulting mixture to the pretreated graphene oxide dispersion while stirring. Then add 4.2-16g of EDC hydrochloride and sonicate for 10-30min. Then reflux at 60-80℃ for 4-16h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 40-50℃ for 6-24h to obtain boronized graphene oxide.

[0112] 3) Using boronized graphene oxide, graphene oxide-boron nitride composite particles were prepared by a hydrothermal method:

[0113] 3-1) Take 0.5-2g of the boronized graphene oxide prepared in step 2) and add it to 25-75g of deionized water, and ultrasonically disperse it for 15-60min to obtain a boronized graphene oxide dispersion.

[0114] 3-2) Take 0.487-1.95g of sodium azide and add it to 10-40g of deionized water, then add 0.134-0.536g of white phosphorus powder, and then add boronized graphene oxide dispersion under stirring. Stir for 15-60min, transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 10-30min and then seal the stainless steel reactor. Heat to 420-460℃ at a heating rate of 1.5-4℃ / min and react for 24-60h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 80-100℃ for 4-16h to obtain graphene oxide-boron nitride composite particles.

[0115] 4) The graphene oxide-boron nitrile composite particles were modified using carboxyl-based liquid nitrile rubber to obtain modified graphene oxide-boron nitrile composite particles:

[0116] Add 1-4g of graphene oxide-boron nitride composite particles to 150-600mL of toluene, add 1.6-6.4g of carboxyl liquid nitrile rubber, and stir the mixture at 100-400rpm and 60-80℃ for 3-12h under nitrogen protection. After the reaction is complete, transfer the product to a Soxhlet extractor and extract with toluene for 24-60h. Dry the solid product under vacuum at 50-70℃ for 4-12h. Grind the product and pass it through a 120-mesh sieve to obtain modified graphene oxide-boron nitride composite particles.

[0117] 5) The modified polytetrafluoroethylene micropowder prepared in step 1) and the modified graphene oxide-boron nitride composite particles prepared in step 4) are mixed to obtain composite reinforced particles:

[0118] Take 10-40g of the modified graphene oxide-boron nitride composite particles prepared in step 4) and 15-60g of the modified polytetrafluoroethylene micro powder prepared in step 1) and add them to a mixer. Mix them at 160-175℃ and 100-300rpm for 15-45min. Cool to room temperature and grind until the particle size is below 0.1mm to obtain composite reinforced particles.

[0119] In the high-performance polytetrafluoroethylene raw material of this invention, polyamide-imide (PAI) possesses excellent mechanical properties, heat resistance, and chemical stability, while also exhibiting good adhesion, which helps to improve the bonding strength between the organic substrate and the filler particles, thereby improving the substrate's density, corrosion resistance, and mechanical strength. Polyphenylene sulfide (PPS) has high mechanical strength, high temperature resistance, and chemical corrosion resistance; its addition to polytetrafluoroethylene materials can enhance the substrate's high temperature resistance and corrosion resistance. Pentaerythritol stearate acts as a lubricant.

[0120] Modified nano-Si3N4 can improve the high-temperature resistance, density, corrosion resistance, and mechanical strength of the substrate. Furthermore, Si3N4 has a high thermal conductivity, which can improve the thermal conductivity of the polytetrafluoroethylene (PTFE) system. Nano-Si3N4 possesses excellent high-temperature strength, corrosion resistance, and abrasion resistance, making it a commonly used ceramic filler. However, nano-Si3N4 has a high surface energy and poor compatibility with polymers, making it difficult to disperse uniformly in polymer systems. This invention uses a titanate coupling agent, bis(triethanolamine) diisopropyl titanate, to modify the surface of nano-Si3N4. The bis(triethanolamine) diisopropyl titanate molecular chains grafted onto the Si3N4 surface generate mutual repulsion and steric hindrance, which can reduce surface energy, prevent particle agglomeration, and improve the compatibility between Si3N4 and the PTFE system. This allows Si3N4 to better enhance the high-temperature resistance, density, and corrosion resistance of the PTFE material.

[0121] Composite reinforcing particles can further improve the tensile strength, high-temperature resistance, thermal conductivity, impermeability, and corrosion resistance of PTFE pipes. The synthesis mechanism and reinforcing mechanism are explained in detail below.

[0122] Main synthesis mechanism

[0123] 1. The present invention first uses sodium-naphthalene-tetrahydrofuran solution to activate polytetrafluoroethylene to obtain modified polytetrafluoroethylene micro powder Ac-PTFE, which can generate -CH, CH3, -CO and other groups on the surface of polytetrafluoroethylene, making the surface easy to wet and improving adhesion, which is beneficial for subsequent coating modification of modified graphene oxide-boron nitride composite particles.

[0124] 2. Then, through oxidation with hydrogen peroxide, abundant carboxyl functional groups are introduced on the surface of graphene oxide. Then, the amino group on 3-aminophenylboronic acid reacts with the carboxyl group to fix the boric acid group to the graphene oxide in a covalent manner, thus obtaining borated graphene oxide B-GO.

[0125] 3. Then, boronized graphene oxide was mixed with sodium azide and white phosphorus, and a hydrothermal reaction was carried out under high temperature and high pressure to prepare graphene oxide-boron nitride composite particles GO-BN. Based on the principle of coupling effect, the boric acid groups can react with sodium azide in the presence of white phosphorus to generate boron nitride grains in situ on the boronized graphene oxide. This principle is the same as that in the literature "Yu Meiyan, Xu Hongyan, Cui Deliang, et al. Coupling effect in hydrothermal synthesis of boron nitride [C] / / Progress in Nanomaterials and Technology Applications - Proceedings of the Third National Conference on Nanomaterials and Technology Applications (Volume 1). 2003. DOI:ConferenceArticle / 5aa57fabc095d72220dc7d1a." The main reaction process is as follows:

[0126] NaN3→Na+N2+N * ;

[0127] Na + H₂O → NaOH + H₂ * ;

[0128] BO2 - +P(H * → B * +PO4 3- ;

[0129] B * +N * →BN.

[0130] Where, N * H * B * These represent N, H, and B atoms, respectively.

[0131] In the above reaction, the active nitrogen atoms (N) generated by the decomposition of sodium azide at high temperature * If there is not enough time to react with the active boron atoms (B * When combined, boric acid groups can bind with active nitrogen atoms to form N2, leading to a decrease in BN synthesis efficiency. However, in this invention, boric acid groups are uniformly distributed on graphene oxide, which has a high specific surface area. Graphene oxide provides a synthesis carrier, allowing active nitrogen atoms to be easily attracted to the graphene oxide while active boron atoms bind efficiently, thereby improving the synthesis efficiency of BN.

[0132] 4. Next, the surface of the graphene oxide-boron nitrile rubber (GO-BN) composite particles was coated with carboxyl liquid nitrile rubber to obtain modified graphene oxide-boron nitrile rubber (CRBN@GO-BN) composite particles; then, it was mixed with modified polytetrafluoroethylene (PTFE) micro powder to obtain graphene oxide-boron nitrile rubber (CRBN@GO-BN) composite particles coated with carboxyl liquid nitrile rubber and modified PTFE. The polar bonds in carboxyl liquid nitrile rubber can chemically and / or physically bond with the functional groups such as carboxyl and hydroxyl groups on the surface of graphene oxide and / or boron nitride composite particles, thus coating the surface of the composite particles. The modified polytetrafluoroethylene surface has more active functional groups, which can be better bonded by carboxyl liquid nitrile rubber. The molecular chains of carboxyl liquid nitrile rubber and modified polytetrafluoroethylene molecular chains are intertwined and bonded, thereby achieving composite coating of modified graphene oxide-boron nitride composite particles by modified polytetrafluoroethylene and carboxyl liquid nitrile rubber.

[0133] Main enhancement mechanism

[0134] (1) The thermal conductivity of polytetrafluoroethylene is between 0.167 and 0.35 W / (m·K), the thermal conductivity of graphene oxide can reach about 3000 W / (m•K), and the thermal conductivity of boron nitride is about 250-300 W / (m•K).

[0135] Therefore, the thermal conductivity of PTFE can be greatly improved by adding graphene oxide and boron nitride to the PTFE vinyl body. At the same time, graphene oxide has high mechanical strength, excellent high temperature resistance and corrosion resistance, and can form a two-dimensional network structure in the PTFE vinyl body, thereby improving the thermal conductivity, high temperature resistance and tensile strength of the substrate.

[0136] (2) Boron nitride microcrystals generated in situ on graphene oxide can serve as reinforcing nodes in the two-dimensional network structure, enhancing both thermal conductivity and mechanical strength. Furthermore, the formation of the two-dimensional network structure can improve the density of the substrate and enhance its resistance to permeation. Boron nitride possesses excellent high-temperature resistance and corrosion resistance. The boron nitride microcrystals uniformly dispersed in the substrate can also fill the gaps between substrate particles due to their nanoscale characteristics, thus enhancing the substrate's density. Simultaneously, they also improve the substrate's high-temperature resistance and corrosion resistance. On the other hand, the mechanical pulling effect of boron nitride microcrystals on graphene oxide can reduce the curling of graphene oxide, promoting its full unfolding within the substrate to form a two-dimensional network structure.

[0137] (3) The coating modification of modified graphene oxide-boron nitrile rubber with carboxyl liquid nitrile rubber can facilitate the further coating of modified polytetrafluoroethylene (PTFE) onto the composite particles. Further coating of the composite particles with modified PTFE can greatly improve the compatibility between the composite reinforcing particles and the PTFE material. During the mixing and sintering process of high-performance PTFE raw materials, the PTFE-coated composite particles can be uniformly dispersed in the organic components such as PTFE in the raw materials. The structure of the graphene oxide-boron nitride composite particles... The construction of the system, combined with the composite coating of carboxyl liquid nitrile rubber and modified polytetrafluoroethylene, can simultaneously overcome the defects of graphene oxide and boron nitride microcrystals being difficult to disperse and prone to agglomeration. It can also solve the problem that boron nitride is not easy to modify on the surface to improve its dispersion ability in polymers. Ultimately, the reinforcing effect of graphene oxide and boron nitride microcrystals can be fully utilized and a synergistic reinforcing effect can be produced, resulting in a comprehensive improvement in the mechanical strength, high temperature resistance, corrosion resistance and impermeability of the prepared polytetrafluoroethylene pipe.

[0138] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0139] The main sources of raw materials involved in the following examples and comparative examples are as follows:

[0140] Polytetrafluoroethylene (PTFE), powder, average particle size 0.4 μm, specific gravity 2.2 g / cm³, melting point 325~335℃, Guangzhou Songbai Chemical Co., Ltd.

[0141] Polyamide-imide, powder, particle size less than 2μm, brand name Solvay TorlonAI-10, Shanghai Furun Plastics Technology Co., Ltd.;

[0142] Polyphenylene sulfide, brand name Polyplastics 1140A6-HF2000, Suzhou Laurenvis Plastics Co., Ltd.;

[0143] Pentaerythritol stearic acid, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0144] Nano-Si3N4, average particle size 300nm, Jiangsu Qiuzheng New Material Technology Co., Ltd.

[0145] Di(triethanolamine) diisopropyl titanate, also known as di(triethanolamine) titanate diisopropyl ester, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0146] Graphene oxide, thickness 0.6-1.2nm, diameter 0.8-2μm, Guangzhou Hongwu Materials Technology Co., Ltd.

[0147] Cubic boron nitride, hexagonal boron nitride, 2μm, Suzhou Kaifa New Materials Technology Co., Ltd.;

[0148] Carboxylated liquid nitrile rubber, grade SH-820, Dongguan Shengli New Materials Co., Ltd.

[0149] 3-Aminophenylboronic acid, brand: Kramar, Shanghai Ziyi Reagent Factory.

[0150] Example 1

[0151] A method for preparing high-performance polytetrafluoroethylene (PTFE) tubing includes the following steps:

[0152] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 70℃ and 450rpm for 2 hours to obtain the mixture.

[0153] Step 2: Add the mixture to the mold, hold under pressure at 80 MPa for 45 minutes, and then perform sintering according to the following temperature control procedure:

[0154] Heat to 150℃ at a heating rate of 1.5℃ / min and hold for 1 hour;

[0155] Heat to 250℃ at a heating rate of 1℃ / min and hold for 1.5h;

[0156] Heat to 370℃ at a heating rate of 0.5℃ / min and hold for 2.5 hours;

[0157] Step 3: Cool to 300℃ at a cooling rate of 0.5℃ / min for tempering treatment, hold for 1 hour, and then cool to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0158] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0159] 90 parts of polytetrafluoroethylene;

[0160] 15 parts of polyamide-imide;

[0161] 12 parts of polyphenylene sulfide;

[0162] 1.8 parts pentaerythritol stearate;

[0163] 2.6 parts of modified nano-Si3N4;

[0164] 18.5 parts of composite reinforcing particles.

[0165] The modified nano-Si3N4 was prepared by the following method:

[0166] S1. Take 1g of nano-Si3N4 and add it to 150mL of isopropanol. Disperse it by ultrasonication for 30min to obtain Si3N4 dispersion.

[0167] S2. Take 0.12g of bis(triethanolamine) diisopropyl titanate and add it to 30mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 62℃ for 3h, filter, wash the solid product with ethanol, and then vacuum dry at 50℃ for 12h to obtain modified nano Si3N4.

[0168] The composite reinforcing particles were prepared by the following method:

[0169] 1) Preparation of modified polytetrafluoroethylene micro powder:

[0170] 1-1) Take 60g of naphthalene and add it to 500mL of tetrahydrofuran. Stir until completely dissolved. Add 10g of sodium metal in 5 portions and stir until the sodium metal is completely dissolved to obtain the activation treatment solution. The whole process is carried out at 2℃ under nitrogen protection.

[0171] 1-2) Under a nitrogen atmosphere, 40g of polytetrafluoroethylene micro powder with an average particle size of 0.4μm was added to the activation treatment solution, stirred at 300rpm for 10min, filtered, the solid product was washed with ethanol, dried at 70℃ for 12h, and ground to obtain modified polytetrafluoroethylene micro powder.

[0172] 2) Preparation of boronized graphene oxide:

[0173] 2-1) Take 2g of graphene oxide and add it to 200mL of hydrogen peroxide solution with a mass fraction of 15%. Sonicate at 70℃ for 3h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 95℃ for 5h to obtain pretreated graphene oxide.

[0174] 2-2) Take 1g of pretreated graphene oxide and add it to 250mL of methanol. Disperse it by ultrasonication for 45min to obtain a dispersion of pretreated graphene oxide.

[0175] 2-3) Take 13.0 g of 3-aminophenylboronic acid and add it to 300 mL of methanol. Stir for 25 min. Add the resulting mixture to the pretreated graphene oxide dispersion under stirring. Then add 9.5 g of EDC hydrochloride. Disperse by ultrasonication for 20 min. Then reflux at 70 °C for 8 h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 45 °C for 12 h to obtain boronized graphene oxide.

[0176] 3) Hydrothermal preparation of graphene oxide-boron nitride composite particles:

[0177] 3-1) Take 1g of the boronized graphene oxide prepared in step 2) and add it to 50g of deionized water. Disperse it ultrasonically for 30min to obtain a boronized graphene oxide dispersion.

[0178] 3-2) Take 0.975g of sodium azide and add it to 20g of deionized water, then add 0.268g of white phosphorus powder, and then add boronized graphene oxide dispersion while stirring. Keep stirring for 30min. Transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 15min and then seal the stainless steel reactor. Heat to 450℃ at a heating rate of 2.5℃ / min and react for 48h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90℃ for 8h to obtain graphene oxide-boron nitride composite particles.

[0179] 4) Modification of graphene oxide-boron nitrile composite particles using carboxyl-based liquid nitrile rubber:

[0180] 2g of graphene oxide-boron nitride composite particles were added to 300mL of toluene, and 3.2g of carboxyl liquid nitrile rubber was added. Under nitrogen protection, the mixture was stirred at 200rpm and 70℃ for 6h. After the reaction was completed, the product was transferred to a Soxhlet extractor and extracted with toluene for 48h. The solid product was vacuum dried at 60℃ for 8h. The product was ground and passed through a 120-mesh sieve to obtain modified graphene oxide-boron nitride composite particles.

[0181] 5) Take 20g of the modified graphene oxide-boron nitride composite particles prepared in step 4) and 30g of the modified polytetrafluoroethylene micro powder prepared in step 1) and add them to a mixer. Mix them at 170℃ and 150rpm for 30min. Cool to room temperature and grind them to a particle size of less than 0.1mm to obtain composite reinforced particles.

[0182] Example 2

[0183] A method for preparing high-performance polytetrafluoroethylene (PTFE) tubing includes the following steps:

[0184] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 70℃ and 450rpm for 2 hours to obtain the mixture.

[0185] Step 2: Add the mixture to the mold, hold under pressure at 80 MPa for 45 minutes, and then perform sintering according to the following temperature control procedure:

[0186] Heat to 150℃ at a heating rate of 1.5℃ / min and hold for 1 hour;

[0187] Heat to 260℃ at a heating rate of 1℃ / min and hold for 1.5h;

[0188] Heat to 370℃ at a heating rate of 0.5℃ / min and hold for 2.5 hours;

[0189] Step 3: Cool to 300℃ at a cooling rate of 0.5℃ / min for tempering treatment, hold for 1 hour, and then cool to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0190] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0191] 88 parts of polytetrafluoroethylene;

[0192] 17 parts of polyamide-imide;

[0193] 13 parts of polyphenylene sulfide;

[0194] 1.8 parts pentaerythritol stearate;

[0195] 2.5 parts of modified nano-Si3N4;

[0196] 18 parts of composite reinforcing particles.

[0197] The modified nano-Si3N4 was prepared by the following method:

[0198] S1. Take 1g of nano-Si3N4 and add it to 150mL of isopropanol. Disperse it by ultrasonication for 30min to obtain Si3N4 dispersion.

[0199] S2. Take 0.12g of bis(triethanolamine) diisopropyl titanate and add it to 30mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 62℃ for 3h, filter, wash the solid product with ethanol, and then vacuum dry at 50℃ for 12h to obtain modified nano Si3N4.

[0200] The composite reinforcing particles were prepared by the following method:

[0201] 1) Preparation of modified polytetrafluoroethylene micro powder:

[0202] 1-1) Take 60g of naphthalene and add it to 500mL of tetrahydrofuran. Stir until completely dissolved. Add 10g of sodium metal in 5 portions and stir until the sodium metal is completely dissolved to obtain the activation treatment solution. The whole process is carried out at 2℃ under nitrogen protection.

[0203] 1-2) Under a nitrogen atmosphere, 40g of polytetrafluoroethylene micro powder with an average particle size of 0.4μm was added to the activation treatment solution, stirred at 300rpm for 10min, filtered, the solid product was washed with ethanol, dried at 70℃ for 12h, and ground to obtain modified polytetrafluoroethylene micro powder.

[0204] 2) Preparation of boronized graphene oxide:

[0205] 2-1) Take 2g of graphene oxide and add it to 200mL of hydrogen peroxide solution with a mass fraction of 15%. Sonicate at 70℃ for 3h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 95℃ for 5h to obtain pretreated graphene oxide.

[0206] 2-2) Take 1g of pretreated graphene oxide and add it to 250mL of methanol. Disperse it by ultrasonication for 45min to obtain a dispersion of pretreated graphene oxide.

[0207] 2-3) Take 13.0 g of 3-aminophenylboronic acid and add it to 300 mL of methanol. Stir for 25 min. Add the resulting mixture to the pretreated graphene oxide dispersion under stirring. Then add 9.5 g of EDC hydrochloride. Disperse by ultrasonication for 20 min. Then reflux at 70 °C for 8 h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 45 °C for 12 h to obtain boronized graphene oxide.

[0208] 3) Hydrothermal preparation of graphene oxide-boron nitride composite particles:

[0209] 3-1) Take 1g of the boronized graphene oxide prepared in step 2) and add it to 50g of deionized water. Disperse it ultrasonically for 30min to obtain a boronized graphene oxide dispersion.

[0210] 3-2) Take 0.975g of sodium azide and add it to 20g of deionized water, then add 0.268g of white phosphorus powder, and then add boronized graphene oxide dispersion while stirring. Keep stirring for 30min. Transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 15min and then seal the stainless steel reactor. Heat to 450℃ at a heating rate of 2.5℃ / min and react for 48h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90℃ for 8h to obtain graphene oxide-boron nitride composite particles.

[0211] 4) Modification of graphene oxide-boron nitrile composite particles using carboxyl-based liquid nitrile rubber:

[0212] 2g of graphene oxide-boron nitride composite particles were added to 300mL of toluene, and 3.2g of carboxyl liquid nitrile rubber was added. Under nitrogen protection, the mixture was stirred at 200rpm and 70℃ for 6h. After the reaction was completed, the product was transferred to a Soxhlet extractor and extracted with toluene for 48h. The solid product was vacuum dried at 60℃ for 8h. The product was ground and passed through a 120-mesh sieve to obtain modified graphene oxide-boron nitride composite particles.

[0213] 5) Take 20g of the modified graphene oxide-boron nitride composite particles prepared in step 4) and 30g of the modified polytetrafluoroethylene micro powder prepared in step 1) and add them to a mixer. Mix them at 170℃ and 150rpm for 30min. Cool to room temperature and grind them to a particle size of less than 0.1mm to obtain composite reinforced particles.

[0214] Example 3

[0215] A method for preparing high-performance polytetrafluoroethylene (PTFE) tubing includes the following steps:

[0216] Step 1: Add the high-performance polytetrafluoroethylene raw material to the mixer and stir and mix at 70℃ and 450rpm for 2 hours to obtain the mixture.

[0217] Step 2: Add the mixture to the mold, hold under pressure at 80 MPa for 45 minutes, and then perform sintering according to the following temperature control procedure:

[0218] Heat to 150℃ at a heating rate of 1.5℃ / min and hold for 1 hour;

[0219] Heat to 250℃ at a heating rate of 1℃ / min and hold for 2 hours;

[0220] Heat to 370℃ at a heating rate of 0.5℃ / min and hold for 2 hours;

[0221] Step 3: Cool to 310℃ at a cooling rate of 0.5℃ / min for tempering treatment, hold for 1 hour, and then cool to room temperature with the furnace to obtain high-performance polytetrafluoroethylene pipe.

[0222] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0223] 90 parts of polytetrafluoroethylene;

[0224] 16 parts of polyamide-imide;

[0225] 14 parts of polyphenylene sulfide;

[0226] 1.8 parts pentaerythritol stearate;

[0227] 2.8 parts of modified nano-Si3N4;

[0228] 17.5 parts of composite reinforcing particles.

[0229] The modified nano-Si3N4 was prepared by the following method:

[0230] S1. Take 1g of nano-Si3N4 and add it to 150mL of isopropanol. Disperse it by ultrasonication for 30min to obtain Si3N4 dispersion.

[0231] S2. Take 0.12g of bis(triethanolamine) diisopropyl titanate and add it to 30mL of isopropanol and mix well. Add the resulting solution to the Si3N4 dispersion under stirring and nitrogen protection. Stir and reflux at 62℃ for 3h, filter, wash the solid product with ethanol, and then vacuum dry at 50℃ for 12h to obtain modified nano Si3N4.

[0232] The composite reinforcing particles were prepared by the following method:

[0233] 1) Preparation of modified polytetrafluoroethylene micro powder:

[0234] 1-1) Take 60g of naphthalene and add it to 500mL of tetrahydrofuran. Stir until completely dissolved. Add 10g of sodium metal in 5 portions and stir until the sodium metal is completely dissolved to obtain the activation treatment solution. The whole process is carried out at 2℃ under nitrogen protection.

[0235] 1-2) Under a nitrogen atmosphere, 40g of polytetrafluoroethylene micro powder with an average particle size of 0.4μm was added to the activation treatment solution, stirred at 300rpm for 10min, filtered, the solid product was washed with ethanol, dried at 70℃ for 12h, and ground to obtain modified polytetrafluoroethylene micro powder.

[0236] 2) Preparation of boronized graphene oxide:

[0237] 2-1) Take 2g of graphene oxide and add it to 200mL of hydrogen peroxide solution with a mass fraction of 15%. Sonicate at 70℃ for 3h, cool to room temperature, filter, wash with deionized water until neutral, and vacuum dry at 95℃ for 5h to obtain pretreated graphene oxide.

[0238] 2-2) Take 1g of pretreated graphene oxide and add it to 250mL of methanol. Disperse it by ultrasonication for 45min to obtain a dispersion of pretreated graphene oxide.

[0239] 2-3) Take 13.0 g of 3-aminophenylboronic acid and add it to 300 mL of methanol. Stir for 25 min. Add the resulting mixture to the pretreated graphene oxide dispersion under stirring. Then add 9.5 g of EDC hydrochloride. Disperse by ultrasonication for 20 min. Then reflux at 70 °C for 8 h. Cool to room temperature, filter, wash the solid product with deionized water, and vacuum dry at 45 °C for 12 h to obtain boronized graphene oxide.

[0240] 3) Hydrothermal preparation of graphene oxide-boron nitride composite particles:

[0241] 3-1) Take 1g of the boronized graphene oxide prepared in step 2) and add it to 50g of deionized water. Disperse it ultrasonically for 30min to obtain a boronized graphene oxide dispersion.

[0242] 3-2) Take 0.975g of sodium azide and add it to 20g of deionized water, then add 0.268g of white phosphorus powder, and then add boronized graphene oxide dispersion while stirring. Keep stirring for 30min. Transfer the resulting mixture to a stainless steel reactor, purge with nitrogen for 15min and then seal the stainless steel reactor. Heat to 450℃ at a heating rate of 2.5℃ / min and react for 48h. After the reaction is completed, cool to room temperature, filter, wash the solid product with deionized water until neutral, and vacuum dry at 90℃ for 8h to obtain graphene oxide-boron nitride composite particles.

[0243] 4) Modification of graphene oxide-boron nitrile composite particles using carboxyl-based liquid nitrile rubber:

[0244] 2g of graphene oxide-boron nitride composite particles were added to 300mL of toluene, and 3.2g of carboxyl liquid nitrile rubber was added. Under nitrogen protection, the mixture was stirred at 200rpm and 70℃ for 6h. After the reaction was completed, the product was transferred to a Soxhlet extractor and extracted with toluene for 48h. The solid product was vacuum dried at 60℃ for 8h. The product was ground and passed through a 120-mesh sieve to obtain modified graphene oxide-boron nitride composite particles.

[0245] 5) Take 20g of the modified graphene oxide-boron nitride composite particles prepared in step 4) and 30g of the modified polytetrafluoroethylene micro powder prepared in step 1) and add them to a mixer. Mix them at 170℃ and 150rpm for 30min. Cool to room temperature and grind them to a particle size of less than 0.1mm to obtain composite reinforced particles.

[0246] Comparative Example 1

[0247] This example is basically the same as Example 1, except that:

[0248] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0249] 115 parts of polytetrafluoroethylene;

[0250] 1.8 parts pentaerythritol stearate;

[0251] 2.6 parts of modified nano-Si3N4;

[0252] 18.5 parts of composite reinforcing particles.

[0253] Comparative Example 2

[0254] This example is basically the same as Example 1, except that:

[0255] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0256] 90 parts of polytetrafluoroethylene;

[0257] 15 parts of polyamide-imide;

[0258] 12 parts of polyphenylene sulfide;

[0259] 1.8 parts pentaerythritol stearate;

[0260] 2.6 parts of nano-Si3N4;

[0261] 18.5 parts of composite reinforcing particles.

[0262] Comparative Example 3

[0263] This example is basically the same as Example 1, except that:

[0264] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0265] 90 parts of polytetrafluoroethylene;

[0266] 15 parts of polyamide-imide;

[0267] 12 parts of polyphenylene sulfide;

[0268] 1.8 parts pentaerythritol stearate;

[0269] 18.5 parts of composite reinforcing particles.

[0270] Comparative Example 4

[0271] This example is basically the same as Example 1, except that:

[0272] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0273] 90 parts of polytetrafluoroethylene;

[0274] 15 parts of polyamide-imide;

[0275] 12 parts of polyphenylene sulfide;

[0276] 1.8 parts pentaerythritol stearate;

[0277] 2.6 parts of modified nano-Si3N4.

[0278] Comparative Example 5

[0279] This example is basically the same as Example 1, except that:

[0280] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0281] 90 parts of polytetrafluoroethylene;

[0282] 15 parts of polyamide-imide;

[0283] 12 parts of polyphenylene sulfide;

[0284] 1.8 parts pentaerythritol stearate;

[0285] 2.6 parts of modified nano-Si3N4;

[0286] Three portions of graphene oxide-boron nitride composite particles.

[0287] Comparative Example 6

[0288] This example is basically the same as Example 1, except that:

[0289] In this example, the high-performance polytetrafluoroethylene raw material comprises the following components by weight:

[0290] 90 parts of polytetrafluoroethylene;

[0291] 15 parts of polyamide-imide;

[0292] 12 parts of polyphenylene sulfide;

[0293] 1.8 parts pentaerythritol stearate;

[0294] 2.6 parts of modified nano-Si3N4;

[0295] Two parts of graphene oxide;

[0296] 1 part cubic boron nitride;

[0297] 0.5 parts of hexagonal boron nitride.

[0298] I. Performance Characterization

[0299] 1. Reference Figure 2 The infrared absorption spectrum of borate-modified graphene oxide (B-GO) prepared in Example 1 shows that the appearance of characteristic peaks such as BO and Benzene indicates that 3-aminophenylboronic acid was successfully modified onto graphene oxide.

[0300] 2. Reference Figure 3 The image shows the XRD pattern of the graphene oxide-boron nitride composite particles prepared in Example 1. The appearance of characteristic diffraction peaks of graphene oxide and boron nitride indicates the successful synthesis of the composite particles. Furthermore, it can be seen that the synthesized boron nitride crystal forms include cubic boron nitride (cBN) and hexagonal boron nitride (hBN).

[0301] II. Performance Testing

[0302] 1. Tensile property test

[0303] The tests were conducted in accordance with the standards GB / T1040.1-2018 Determination of tensile properties of plastics and QB / T4877-2015 Polytetrafluoroethylene pipes.

[0304] 2. Thermal conductivity

[0305] The thermal conductivity meter was used to test the thermal conductivity of nonmetallic solid materials in accordance with the standard GB / T1029-2015.

[0306] 3. Permeability coefficient

[0307] The test was conducted according to the method provided in patent CN114230835B, "A Low-Permeability Polytetrafluoroethylene Tube and Its Preparation Method," as follows:

[0308] (1) Seal the front end of the polytetrafluoroethylene pipe (diameter 15 mm, length 250 mm, wall thickness 2 mm) prepared in the examples and comparative examples, then inject 45% sulfuric acid, and then seal the end.

[0309] (2) Immerse the polytetrafluoroethylene pipe completely in a container filled with deionized water, control the pure water temperature at 25°C, and seal the container.

[0310] (3) After 10 days, sample the pure water in the container and test the concentration of sulfate ions. Calculate the permeability coefficient using the following formula:

[0311] Permeability coefficient k = (sulfate ion permeation amount μg) ÷ (permeability area cm²) 2 ) ÷ (number of days elapsed) × (thickness of the pipe in cm);

[0312] The sulfate ion permeation rate is calculated by the concentration of sulfate ions in deionized water and the volume of water, and the permeation area is the surface area of ​​the polytetrafluoroethylene pipe.

[0313] The test results of tensile properties, thermal conductivity, and permeability at room temperature are shown in Table 1 below. Figures 4-6 As shown:

[0314] Table 1. Room temperature performance test results

[0315]

[0316] From Table 1 and Figures 4-6 The test results show that the polytetrafluoroethylene pipes prepared in Examples 1-3 have excellent tensile strength, good thermal conductivity, and excellent anti-permeability and corrosion resistance, and are capable of being used as heat exchange pipes for high-temperature corrosive liquids.

[0317] In Comparative Example 1, the absence of polyamide-imide and polyphenylene sulfide resulted in a significant decrease in tensile strength and impermeability. In Comparative Example 2, the decrease in impermeability was attributed to the lack of modification of Si3N4, which affected its dispersion performance. In Comparative Example 3, the absence of Si3N4 led to a decrease in both thermal conductivity and impermeability. In Comparative Example 4, all properties decreased significantly, attributed to the lack of composite reinforcing particles in the high-performance polytetrafluoroethylene raw material. In Comparative Example 5, the lack of organic material coating modification treatment on the graphene oxide-boron nitride composite particles affected the dispersion performance. Comparative Example 6 demonstrates that the physical mixture of graphene and boron nitride provides a significantly weaker reinforcing effect than the composite reinforcing particles used in the examples.

[0318] 4. High temperature resistance test

[0319] 4-1. High-temperature tensile strength

[0320] a. The polytetrafluoroethylene (PTFE) pipe samples prepared in Example 1 were kept at 100℃, 150℃, 200℃, and 250℃ for 2 hours respectively. Then, their tensile strength was measured according to the method described in section 1. The test results are shown in Table 2 below. Figure 7 As shown:

[0321] Table 2 Tensile strength after heat treatment for 2 hours at different temperatures

[0322] 25℃ 100℃ 150℃ 200℃ 250℃ Tensile strength / MPa 56.7 56.1 55 52.9 51.2

[0323] b. Then, following the method in section 1, the tensile strength of the polytetrafluoroethylene pipe samples prepared in Example 1 was measured after being kept at 200°C for different durations. The test results are shown in Table 2 below. Figure 8 As shown:

[0324] Table 3 Tensile strength after heat preservation at 200℃ for different times

[0325] 1h 2h 3h 4h 5h Tensile strength / MPa 55.1 52.9 51.5 50.8 49.7

[0326] c. After incubating the PTFE pipe sample at 200℃ for 3 hours, measure its tensile strength according to the method in section 1. The test results are shown in Table 2 below. Figure 9 As shown:

[0327] Table 4 High-Temperature Performance Test Results

[0328] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Tensile strength / MPa 52.9 52.3 51.5 27.7 46.1 45.9 21.0 41.2 36.3

[0329] Figure 9 The image shows the comparative test results of tensile strength at room temperature and high temperature.

[0330] 4-2. High-temperature permeability coefficient

[0331] Following the permeability test method in section 3, the temperature of the deionized water was controlled at 90°C, and the container was periodically replenished with 90°C deionized water to reach the initial volume. Then, the permeability coefficient at 90°C was tested using the same method.

[0332] The test results are shown in Table 5 below. Figure 10 As shown:

[0333] Table 5. High-Temperature Permeability Coefficient Test Results

[0334] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 <![CDATA[Permeability coefficient (μg·cm) / (cm 2 ·day)]]> 0.012 0.015 0.016 0.059 0.049 0.062 0.097 0.038 0.051

[0335] Figure 10 The image shows the comparative test results of the permeability coefficient at room temperature and high temperature.

[0336] The test results show that the polytetrafluoroethylene pipes prepared in Examples 1-3 have excellent high-temperature resistance under tension, while the high-temperature resistance of each comparative example decreased to varying degrees.

[0337] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for producing a high-performance polytetrafluoroethylene pipe, characterized by, Comprising the following steps: Step one, the high performance polytetrafluoroethylene raw materials into the mixer, 50-80 ℃, 200-750 rpm under stirring mixing 0.5-4 h, the mixture is obtained; Step two, the mixture is added to the mold, 40-95 Mpa under pressure 30-120 min, then according to the following temperature control program sintering treatment: Heating to 130-180 ℃ at a rate of 1-3 ℃ / min, 0.5-2 h; Heating to 220-280 ℃ at a rate of 0.5-2 ℃ / min, 1-3 h; Heating to 360-375 ℃ at a rate of 0.2-1 ℃ / min, 1.5-4 h; Step three, with 0.4-0.8 ℃ / min cooling rate to 295-320 ℃ tempering treatment, 0.5-2 h, then furnace cooling to room temperature, the high performance polytetrafluoroethylene pipe material is obtained; The high performance polytetrafluoroethylene raw material comprises the following components by weight: Polytetrafluoroethylene 70-95 parts; Polyamide-imide 7.5-20 parts; Polyphenylene sulfide 6-23 parts; Pentaerythritol stearate 0.9-2.4 parts; Modified nano Si3N4 1.8-3.3 parts; Composite reinforcing particles 9.5-27 parts; The modified nano Si3N4 is prepared by the following method: S1, take 0.5-2 g of nano Si3N4 and add it to 75-300 mL of isopropyl alcohol, ultrasonic dispersion for 15-60 min, to obtain Si3N4 dispersion liquid; S2, take 0.06-0.24 g of bis-triethanolamine diisopropyl titanate and add it to 15-60 mL of isopropyl alcohol, mix well, the obtained solution is added to the Si3N4 dispersion liquid under stirring and nitrogen protection, stir and reflux at 58-65 ℃ for 1.5-6 h, filter, the solid product is washed with ethanol, then vacuum dried at 40-55 ℃ for 6-24 h, to obtain modified nano Si3N4; The composite reinforcing particles are prepared by the following method: 1) sodium-naphthalene-tetrahydrofuran solution is used as an activation treatment liquid to modify polytetrafluoroethylene powder, to prepare modified polytetrafluoroethylene powder; 2) borated graphene oxide is prepared; 3) using borated graphene oxide, graphene oxide-boron nitride composite particles are prepared by hydrothermal method; 4) carboxyl liquid nitrile rubber is used to modify the graphene oxide-boron nitride composite particles, to obtain modified graphene oxide-boron nitride composite particles; 5) the modified polytetrafluoroethylene powder prepared in step 1) and the modified graphene oxide-boron nitride composite particles prepared in step 4) are mixed, to obtain composite reinforcing particles.

2. The method of producing high performance polytetrafluoroethylene pipe according to claim 1, characterized by, Comprising the following steps: Step one, the high performance polytetrafluoroethylene raw materials into the mixer, 70 ℃, 450 rpm under stirring mixing 2 h, the mixture is obtained; Step two, the mixture is added to the mold, 80 Mpa under pressure 45 min, then according to the following temperature control program sintering treatment: Heating to 150 ℃ at a rate of 1.5 ℃ / min, 1 h; Heating to 250 ℃ at a rate of 1 ℃ / min, 1.5 h; Heating to 370℃ at a heating rate of 0.5℃ / min, holding for 2.5h; Step three, tempering treatment is carried out at a cooling rate of 0.5℃ / min to 300℃, holding for 1h, and then cooling to room temperature with the furnace, to obtain high-performance polytetrafluoroethylene pipe.

3. The method of producing high performance polytetrafluoroethylene pipe according to claim 1, characterized by, The modified nano-Si3N4 is prepared by the following method: S1, 1g of nano-Si3N4 is added to 150mL of isopropanol, and ultrasonic dispersion is carried out for 30min to obtain a Si3N4 dispersion liquid; S2, 0.12g of bis-triethanolamine diisopropyl titanate is added to 30mL of isopropanol and mixed uniformly, and the obtained solution is added to the Si3N4 dispersion liquid under stirring and nitrogen protection, and stirred and refluxed at 62℃ for 3h, then filtered, and the solid product is washed with ethanol, and then vacuum dried at 50℃ for 12h to obtain the modified nano-Si3N4.

4. The method of producing high performance polytetrafluoroethylene pipe according to claim 1, characterized by, Step 2) specifically includes: 2-1) 1-4g of graphene oxide is added to 100-300mL of 10-20% mass fraction hydrogen peroxide solution, ultrasonic treatment is carried out at 65-80℃ for 1.5-6h, cooled to room temperature, filtered, washed with deionized water until neutral, and vacuum dried at 90-100℃ for 3-8h to obtain pretreated graphene oxide; 2-2) 0.5-2g of pretreated graphene oxide is added to 150-400mL of methanol, ultrasonic dispersion is carried out for 30-90min to obtain a pretreated graphene oxide dispersion liquid; 2-3) 6.5-26.0g of 3-aminobenzene boronic acid is added to 150-600mL of methanol, stirred for 15-60min, and the obtained mixture is added to the pretreated graphene oxide dispersion liquid under stirring, and then 4.2-16g of EDC hydrochloride is added, ultrasonic dispersion is carried out for 10-30min, and then refluxed at 60-80℃ for 4-16h, cooled to room temperature, filtered, and the solid product is washed with deionized water, and vacuum dried at 40-50℃ for 6-24h to obtain boronated graphene oxide.

5. The method of producing high performance polytetrafluoroethylene pipe according to claim 1, characterized by, Step 3) specifically includes: 3-1) 0.5-2g of boronated graphene oxide prepared in step 2) is added to 25-75g of deionized water, ultrasonic dispersion is carried out for 15-60min to obtain a boronated graphene oxide dispersion liquid; 3-2) 0.487-1.95g of sodium azide is added to 10-40g of deionized water, then 0.134-0.536g of white phosphorus powder is added, and then the boronated graphene oxide dispersion liquid is added under stirring, and stirred for 15-60min, and the obtained mixture is transferred to a stainless steel reaction kettle, nitrogen is introduced for 10-30min, and then the stainless steel reaction kettle is sealed, heated to 420-460℃ at a heating rate of 1.5-4℃ / min, and reacted for 24-60h, and after the reaction is completed, cooled to room temperature, filtered, and the solid product is washed with deionized water until neutral, and vacuum dried at 80-100℃ for 4-16h to obtain graphene oxide-boron nitride composite particles.

6. The method of producing high performance polytetrafluoroethylene pipe according to claim 1, characterized by, The composite reinforcing particles are prepared by the following method: 1) Preparation of modified polytetrafluoroethylene micro powder: 1-1) 60 g of naphthalene was added to 500 mL of tetrahydrofuran, stirred until completely dissolved, 10 g of sodium metal was added in portions, and stirred until the sodium metal was completely dissolved, to obtain an activation treatment solution, the whole process was operated at 2℃ under nitrogen protection; 1-2) Under nitrogen atmosphere, 40 g of polytetrafluoroethylene powder with a particle size of 0.1-0.5 μm was added to the activation treatment solution, stirred at 300 rpm for 10 min, filtered, the solid product was washed with ethanol, then dried at 70℃ for 12 h, ground, to obtain modified polytetrafluoroethylene powder; 2) Preparation of boronated graphene oxide: 2-1) 2 g of graphene oxide was added to 200 mL of 15% mass fraction hydrogen peroxide solution, ultrasonic treated at 70℃ for 3 h, cooled to room temperature, filtered, washed with deionized water until neutral, vacuum dried at 95℃ for 5 h, to obtain pretreated graphene oxide; 2-2) 1 g of pretreated graphene oxide was added to 250 mL of methanol, ultrasonic dispersed for 45 min, to obtain pretreated graphene oxide dispersion; 2-3) 13.0 g of 3-aminobenzoic acid was added to 300 mL of methanol, stirred for 25 min, the obtained mixture was added to the pretreated graphene oxide dispersion under stirring, then 9.5 g of EDC hydrochloride was added, ultrasonic dispersed for 20 min, then refluxed at 70℃ for 8 h, cooled to room temperature, filtered, the solid product was washed with deionized water, vacuum dried at 45℃ for 12 h, to obtain boronated graphene oxide; 3) Preparation of graphene oxide-boron nitride composite particles by hydrothermal method: 3-1) 1 g of boronated graphene oxide prepared in step 2) was added to 50 g of deionized water, ultrasonic dispersed for 30 min, to obtain boronated graphene oxide dispersion; 3-2) 0.975 g of sodium azide was added to 20 g of deionized water, then 0.268 g of white phosphorus powder was added, then the boronated graphene oxide dispersion was added under stirring, kept stirring for 30 min, the obtained mixture was transferred to a stainless steel reaction kettle, after nitrogen was introduced for 15 min, the stainless steel reaction kettle was sealed, heated to 450℃ at a heating rate of 2.5℃ / min, reacted for 48 h, after the reaction was completed, cooled to room temperature, suction filtered, the solid product was washed with deionized water until neutral, vacuum dried at 90℃ for 8 h, to obtain graphene oxide-boron nitride composite particles; 4) Modification of graphene oxide-boron nitride composite particles with carboxyl liquid nitrile rubber: 2 g of graphene oxide-boron nitride composite particles was added to 300 mL of toluene, 3.2 g of carboxyl liquid nitrile rubber was added, under nitrogen protection, stirred at 200 rpm, 70℃ for 6 h, after the reaction was completed, the product was transferred to a Soxhlet extractor, extracted with toluene for 48 h, the solid product was vacuum dried at 60℃ for 8 h, the product was ground, passed through a 120 mesh sieve, to obtain modified graphene oxide-boron nitride composite particles; 5) 20 g of the modified graphene oxide-boron nitride composite particles prepared in step 4), 30 g of the modified polytetrafluoroethylene micro powder prepared in step 1) were added into an internal mixer, and mixed at 170 °C and 150 rpm for 30 min. After cooling to room temperature, the mixture was ground to a particle size of 0.1 mm or less to obtain the composite reinforcing particles.

7. A high performance polytetrafluoroethylene tubing characterized by, The modified graphene oxide-boron nitride composite particles are prepared by the method according to any one of claims 1-6.

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