Acid and alkali resistant polytetrafluoroethylene composite material, preparation method and application thereof

Abstract

The application belongs to the technical field of functional polymer materials, and particularly relates to an acid and alkali resistant polytetrafluoroethylene composite material and a preparation method and application thereof, wherein the polytetrafluoroethylene composite material comprises the following raw materials in parts by weight: PFA 89 parts, plasticizer 1-4.5 parts, coupling agent 0.5-2 parts, weathering agent 0.5 part and functional additive 4-9 parts; the functional additive prepared from flake graphite, polyamide acid and PFPE-DMA is uniformly coated on the surface of the PFA and the like in the form of a polar dispersion liquid, can play a role of filling structure and thermal self-polymerization in the PFA melt extrusion molding process, construct a rigid-flexible polymer anti-permeation acid and alkali resistant network, and is suitable for manufacturing complex corrosion prevention parts under extreme working conditions.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials technology, specifically relating to an acid and alkali resistant polytetrafluoroethylene composite material, its preparation method, and its application. Background Technology

[0002] In extreme industrial environments such as petrochemicals, semiconductor cleaning, and new energy smelting, valves, pump bodies, pipe linings, and seals are exposed to harsh media such as high pressure and strong acids and alkalis for extended periods. Polytetrafluoroethylene (PTFE), due to its extremely strong chemical inertness, is widely used in corrosion-resistant components in these fields. However, pure PTFE is highly susceptible to cold creep under long-term pressure, leading to seal failure. Existing improvement technologies typically involve physically blending inorganic fillers (such as glass fiber, carbon powder, and graphite) into fluoropolymers. While this can improve creep resistance to some extent, the inherent polar repulsion between the inorganic fillers and the polymer matrix results in numerous microscopic gaps at the phase interface. Under dynamic pressure, strong acids and alkalis readily penetrate these interfacial gaps via capillary action, ultimately causing the composite material to disintegrate and severely corrode the equipment. Furthermore, the extremely high melt viscosity of conventional PTFE makes it impossible to process complex parts through injection molding or extrusion. Even when PFA (fusible polytetrafluoroethylene) with excellent processing properties is used instead, the aforementioned interfacial penetration and high-pressure deformation problems are still difficult to fundamentally solve through traditional dry blending. Summary of the Invention

[0003] In view of the above situation, the present invention provides an acid and alkali resistant polytetrafluoroethylene composite material, its preparation method and application. Based on the technical concept of liquid phase coating combined with dynamic reaction melt extrusion, the polyamic acid precursor and flexible perfluorinated macromonomer are pre-adsorbed and coated on the surface of PFA particles. Then, the excellent melt processing characteristics of PFA are utilized to induce in-situ thermal self-polymerization and thermal imidization ring closure, thereby obtaining a composite material with high strength and compressive strength, acid and alkali resistance and easy injection molding.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides an acid and alkali resistant polytetrafluoroethylene composite material, which comprises the following raw materials in parts by weight: 89 parts of PFA (fusible polytetrafluoroethylene), 1-4.5 parts of plasticizer, 0.5-2 parts of coupling agent, 0.5 parts of weather resistant agent, and 4-9 parts of functional additives.

[0005] Furthermore, the plasticizer is selected from FEP (perfluoroethylene propylene) or PTFE ultrafine powder.

[0006] Furthermore, the coupling agent is selected from titanate coupling agent NDZ-311w or aluminate coupling agent DL-411.

[0007] Furthermore, the weathering agent is selected from any one of the following: UV-360 ultraviolet light absorber, nano titanium dioxide, and carbon black.

[0008] Furthermore, the functional additive is composed of flake graphite, polyamic acid, PFPE-DMA (double-terminated methacrylate perfluoropolyether), and DMF (N,N-dimethylformamide) in a mass ratio of 12.8:2.8:4.4:80.

[0009] Furthermore, the preparation method of the functional additive is as follows: S1: Polyamic acid, PFPE-DMA and DMF are mixed and ultrasonically treated. The hydrophobic perfluorinated macromolecules are emulsified and dispersed in a polar solvent system by utilizing the ultrasonic cavitation effect to obtain a polymer microemulsion. S2: The polymer microemulsion and flake graphite were mixed and continuously sheared at 6000 rpm for 1.5 h using a high-shear emulsification disperser to obtain the functional additive.

[0010] This invention also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite materials, the specific steps of which are as follows: Step 1: Place PFA, plasticizer, coupling agent and weathering agent in a mixer and mix them evenly at low speed. Add functional additives and continue mixing for 30 minutes. Utilize the strong wetting properties of DMF to make the flake graphite, polyamic acid and PFPE-DMA uniformly coated and adsorbed on the PFA surface. The coupling agent plays a bridging and adhesion role to ensure that the materials are mixed evenly and obtain a slurry. Step 2: Transfer the slurry to a vacuum dryer and evaporate the DMF at 70°C. The polyamic acid will precipitate and form a film on the particle surface. At the same time, the liquid PFPE-DMA and graphite powder will be further adhered to the PFA surface for subsequent melt extrusion to obtain wet material. Step 3: Place the wet material in a twin-screw extruder for melt extrusion. Set the temperature to 300℃ for preheating. At this time, the PFPE-DMA coated on the surface of PFA undergoes thermal self-polymerization to become flexible fluororubber. Raise the temperature to 350℃. Under the extrusion action, PFPE-DMA and graphite powder permeate and disperse together in the continuous molten phase of PFA, playing a filling and supporting role. Meanwhile, the polyamic acid part undergoes thermal imidization reaction to generate rigid polyimide, which improves the deformation problem of polytetrafluoroethylene under high pressure acid and alkali environment. After extrusion, it is cooled by water and pelletized to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0011] The present invention also provides an application of an acid and alkali resistant polytetrafluoroethylene composite material, which is used to prepare special engineering plastics.

[0012] Furthermore, the special engineering plastics include the following products: pneumatic diaphragm valves for semiconductor equipment, CMP (chemical mechanical planarization) retaining rings, high-frequency antenna substrates, radomes that transmit light, cable insulation layers, electrolyte battery encapsulation shells, and electronic water pump impellers.

[0013] The beneficial effects achieved by this invention are as follows: The polytetrafluoroethylene composite material provided by this invention uses fusible polytetrafluoroethylene as the continuous phase matrix, which not only inherits the extreme corrosion resistance of perfluorinated polymers, but also endows the material with the ability to injection mold / extrude complex parts. The introduced FEP or special fluorinated wax as a plasticizing and lubricating phase effectively improves the dispersion and flowability of the filler. The coupling agent, with its hydrolysis resistance, is beneficial to the interfacial bonding between inorganic graphite and polar polymers, reducing the risk of delamination. It abandons the traditional inactive filler mixing and adopts a PAA and PFPE-DMA dual precursor system. In the high-temperature melt extrusion stage, PAA undergoes thermal imidization in the melt, generating a rigid polyimide microframework in situ. PFPE-DMA forms a flexible perfluorinated elastomer network in the melt through the thermal self-polymerization of the end groups, effectively sealing the nanoscale stress microcracks at the filler-resin interface and cutting off the penetration channels of acid and alkali ions. The resulting composite material has good resistance to high-temperature deformation and can meet the material performance requirements under extreme working conditions such as high salt, strong acid and alkali, and high pressure alternating load. It can be used for the production of high-value precision parts and has high industrial value and application prospects. Attached Figure Description

[0014] Figure 1 The appearance examination results are for the acid and alkali resistant polytetrafluoroethylene product prepared in Example 6. Figure 2 The results of the compression deformation rate investigation of the polytetrafluoroethylene materials prepared in Examples 1-5 and Comparative Examples 1-2; Figure 3 The results of the acid and alkali resistance mass change rate investigation of the polytetrafluoroethylene materials prepared in Examples 1-5 and Comparative Examples 1-2; Figure 4 The results of the acid and alkali resistance tensile strength retention rate of the polytetrafluoroethylene materials prepared in Examples 1-5 and Comparative Examples 1-2 are presented. Figure 5 The tensile strength test results are for the polytetrafluoroethylene materials prepared in Examples 1-5 and Comparative Examples 1-2. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0017] Unless otherwise specified, all methods used in the following examples are conventional. Unless otherwise specified, all raw materials used in the following examples are new materials purchased from the market, and all parts are parts by weight. In the following examples and comparative examples, the PFA used is fusible polytetrafluoroethylene granules, model DS700, with a melt index of 6.1-12 g / min; the FEP used is Lichang high-strength series, with a melting point of 270±5℃; the flake graphite used is high-purity graphite with a particle size of 45 μm and a carbon content of 90%; and the PFPE-DMA used has an average molecular weight of 2000 Da and a content of ≥98%.

[0018] In the following examples and comparative examples, the functional additives were prepared from the following raw materials in parts by weight: 64 parts flake graphite, 14 parts polyamic acid, 22 parts PFPE-DMA, and 400 parts DMF. The specific preparation method is as follows: S1: Mix 14 parts of polyamic acid, 22 parts of PFPE-DMA and 400 parts of DMF, and sonicate at 800 W and 20 Hz for 30 min to obtain a polymer microemulsion; S2: Mix 64 parts of polymer microemulsion and flake graphite, and continuously shear at 6000 rpm for 1.5 h using a high-shear emulsifying disperser while controlling the temperature at 45℃ to obtain the functional additive.

[0019] Example 1: This example provides an acid and alkali resistant polytetrafluoroethylene composite material, which includes the following raw materials in parts by weight: 89 parts PFA, 1 part FEP, 0.5 parts titanate coupling agent NDZ-311w, 0.5 parts ultraviolet light absorber UV-360, and 9 parts functional additives.

[0020] This embodiment also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite material, the specific steps of which are as follows: Step 1: Take 89 parts of PFA, 1 part of FEP, 0.5 parts of titanate coupling agent NDZ-311w and 0.5 parts of UV absorber UV-360 and place them in a mixer. Stir at 150 rpm for 5 minutes to mix evenly. Add 9 parts of functional additives and continue stirring for 30 minutes to obtain the slurry. Step 2: Transfer the slurry to a vacuum dryer, evaporate the DMF at a jacket temperature of 70℃, and dry for 4 hours to obtain a wet material; Step 3: Place the wet material in a twin-screw extruder for melt extrusion. The feeding zone is set at 260°C, the melting zone at 300°C, and the temperature is increased to 350°C. The screw speed is 350 rpm. After extrusion, the material is cooled by water and pelletized. The pellets are 2.5 mm in diameter and 3 mm in length to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0021] Example 2: This example provides an acid and alkali resistant polytetrafluoroethylene composite material, which includes the following raw materials in parts by weight: 89 parts PFA, 3 parts FEP, 1 part titanate coupling agent NDZ-311w, 0.5 parts nano titanium dioxide, and 6.5 parts functional additives.

[0022] This embodiment also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite material, the specific steps of which are as follows: Step 1: Take 89 parts of PFA, 3 parts of FEP, 1 part of titanate coupling agent NDZ-311w and 0.5 parts of nano titanium dioxide and put them into a mixer. Stir at 150 rpm for 5 minutes to mix evenly. Add 6.5 parts of functional additives and continue stirring for 30 minutes to obtain slurry. Step 2: Transfer the slurry to a vacuum dryer, evaporate the DMF at a jacket temperature of 70℃, and dry for 4 hours to obtain a wet material; Step 3: Place the wet material in a twin-screw extruder for melt extrusion. The feeding zone is set at 260°C, the melting zone at 300°C, and the temperature is increased to 350°C. The screw speed is 350 rpm. After extrusion, the material is cooled by water and pelletized. The pellets are 2.5 mm in diameter and 3 mm in length to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0023] Example 3: This example provides an acid and alkali resistant polytetrafluoroethylene composite material, which includes the following raw materials in parts by weight: 89 parts PFA, 4.5 parts FEP, 2 parts aluminate coupling agent DL-411, 0.5 parts carbon black, and 4 parts functional additives.

[0024] This embodiment also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite material, the specific steps of which are as follows: Step 1: Take 89 parts of PFA, 4.5 parts of FEP, 2 parts of aluminate coupling agent DL-411 and 0.5 parts of carbon black and put them into a mixer. Mix them evenly at 150 rpm for 5 minutes. Add 4 parts of functional additives and continue mixing for 30 minutes to obtain the slurry. Step 2: Transfer the slurry to a vacuum dryer, evaporate the DMF at a jacket temperature of 70℃, and dry for 4 hours to obtain a wet material; Step 3: Place the wet material in a twin-screw extruder for melt extrusion. The feeding zone is set at 260°C, the melting zone at 300°C, and the temperature is increased to 350°C. The screw speed is 350 rpm. After extrusion, the material is cooled by water and pelletized. The pellets are 2.5 mm in diameter and 3 mm in length to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0025] Example 4: This example provides an acid and alkali resistant polytetrafluoroethylene composite material, which includes the following raw materials in parts by weight: 89 parts of PFA, 1 part of PTFE ultrafine powder, 2 parts of titanate coupling agent NDZ-311w, 0.5 parts of nano titanium dioxide, and 7.5 parts of functional additives.

[0026] This embodiment also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite material, the specific steps of which are as follows: Step 1: Take 89 parts of PFA, 1 part of PTFE ultrafine powder, 2 parts of titanate coupling agent NDZ-311w and 0.5 parts of nano titanium dioxide and put them into a mixer. Mix them evenly at 150 rpm for 5 minutes. Add 7.5 parts of functional additives and continue to stir for 30 minutes to obtain a slurry. Step 2: Transfer the slurry to a vacuum dryer, evaporate the DMF at a jacket temperature of 70℃, and dry for 4 hours to obtain a wet material; Step 3: Place the wet material in a twin-screw extruder for melt extrusion. The feeding zone is set at 260°C, the melting zone at 300°C, and the temperature is increased to 350°C. The screw speed is 350 rpm. After extrusion, the material is cooled by water and pelletized. The pellets are 2.5 mm in diameter and 3 mm in length to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0027] Example 5: This example provides an acid and alkali resistant polytetrafluoroethylene composite material, which includes the following raw materials in parts by weight: 89 parts PFA, 4 parts PTFE ultrafine powder, 0.5 parts aluminate coupling agent DL-411, 0.5 parts carbon black, and 6 parts functional additives.

[0028] This embodiment also provides a method for preparing acid and alkali resistant polytetrafluoroethylene composite material, the specific steps of which are as follows: Step 1: Take 89 parts of PFA, 4 parts of PTFE ultrafine powder, 0.5 parts of aluminate coupling agent DL-411 and 0.5 parts of carbon black and put them into a mixer. Mix them evenly at 150 rpm for 5 minutes. Add 6 parts of functional additives and continue mixing for 30 minutes to obtain a slurry. Step 2: Transfer the slurry to a vacuum dryer, evaporate the DMF at a jacket temperature of 70℃, and dry for 4 hours to obtain a wet material; Step 3: Place the wet material in a twin-screw extruder for melt extrusion. The feeding zone is set at 260°C, the melting zone at 300°C, and the temperature is increased to 350°C. The screw speed is 350 rpm. After extrusion, the material is cooled by water and pelletized. The pellets are 2.5 mm in diameter and 3 mm in length to obtain acid and alkali resistant polytetrafluoroethylene composite material.

[0029] Example 6: This example provides an application of the acid and alkali resistant polytetrafluoroethylene (PTFE) composite material prepared in Example 2, used to prepare PTFE sheets and PTFE tubes. The preparation method is as follows: The continuous extrusion molding process was adopted: the acid and alkali resistant polytetrafluoroethylene composite material prepared in Example 2 was placed in a twin-screw extruder, the temperature was set to 340°C, and after extrusion, it was placed in a three-roll calender for cooling and shaping. The temperature of the three rolls was 180°C to obtain polytetrafluoroethylene sheets.

[0030] Using injection molding, the acid and alkali resistant polytetrafluoroethylene composite material prepared in Example 2 was placed in an injection molding machine. The barrel nozzle was set to a high temperature of 360°C for melting, and the mold temperature was set to 220°C. The material was then injected slowly at a high pressure of 80 MPa into the valve mold and the connecting pipe mold to form polytetrafluoroethylene valves and polytetrafluoroethylene pipes, respectively.

[0031] The difference between Comparative Example 1 and Example 2 is that no functional additives were added; the rest is the same as Example 2.

[0032] Comparative Example 2 consists of commercially available polytetrafluoroethylene (PTFE) particles.

[0033] Appearance inspection: Polytetrafluoroethylene (PTFE) sheets, valves, and pipes prepared from the acid- and alkali-resistant PTFE composite material prepared in Example 2 were photographed and recorded. The results are shown in the table below. Figure 1 .

[0034] High-temperature and high-pressure resistance test: Polytetrafluoroethylene (PTFE) composite materials prepared in Examples 1-5 and Comparative Example 1 were injection molded, while the PTFE material in Comparative Example 2 was cold-pressed and sintered to form cylinders with a diameter of 10 mm and a height of 10 mm. These were used as samples for testing. Following the method in GB / T 1041-2008 "Determination of Compression Properties of Plastics", the high-pressure compression deformation rate was investigated at 150℃ and 15 MPa. The results are shown in [Figure number missing]. Figure 2.

[0035] Acid and alkali resistance tests: Polytetrafluoroethylene (PTFE) composite materials prepared in Examples 1-5 and Comparative Example 1 were injection molded, while the PTFE material in Comparative Example 2 was cold-pressed and sintered to form dumbbell-shaped specimens. Following the method in GB / T 11547-2008 "Determination of Resistance to Liquid Chemical Reagents in Plastics", acid and alkali resistance tests were conducted on each specimen. The acidic agent was a 75% sulfuric acid solution, and the alkali agent was a 40% sodium hydroxide solution. Each specimen was immersed in the acidic and alkali agents for 7 days, respectively. The mass change rate and tensile strength retention rate before and after immersion were recorded. The results are shown in [Figure number missing]. Figure 3 and Figure 4 .

[0036] Tensile strength testing: Polytetrafluoroethylene (PTFE) composite materials prepared in Examples 1-5 and Comparative Example 1 were injection molded, while the PTFE material in Comparative Example 2 was cold-pressed and sintered to form dumbbell-shaped specimens. The tests were conducted according to GB / T 1040.2-2006 "Determination of Tensile Properties of Plastics". The results are shown in the table below. Figure 5 .

[0037] Figure 2 The results showed that the high-temperature and high-pressure compression deformation rate of Examples 1, 2, 4 and 5 was well controlled, while the deformation rate of the materials in Comparative Examples 1-2 was higher. This indicates that the prepared acid and alkali resistant polytetrafluoroethylene composite material has better compressive deformation resistance, i.e., resistance to high-temperature cold flow creep, and the material structure is more rigid and dense.

[0038] Figure 3 The results showed that the mass change rates of Examples 1-5 in both solutions were at a low level, around 2%, while Comparative Example 2 exceeded 11%, and Comparative Example 1 approached 9%. The change rate of the comparative examples in strong alkali was also significantly higher, between 5% and 7%, indicating that the acid and alkali resistant polytetrafluoroethylene composite material has good chemical stability and resistance to chemical corrosion. However, Comparative Example 1, due to the lack of a dense network formed by functional additives, allowed liquid to easily penetrate into the interior through capillary penetration along the interface, resulting in severe corrosion and poor chemical stability, especially reduced resistance to strong acid corrosion.

[0039] Figure 4 The results showed that Examples 1, 2, 4, and 5 exhibited extremely high tensile strength retention rates, all above 90%. Example 3 was slightly lower, at about 80%. Comparative Examples 1 and 2 showed significantly reduced tensile strength retention rates, indicating low acid and alkali adaptability and poor material tolerance under extreme conditions.

[0040] Figure 5The results showed that the composite materials of Examples 1-5 and Comparative Examples 1-2 all had good tensile strength. Among them, the tensile strength of Examples 1-5 was significantly higher than that of the polytetrafluoroethylene materials of Comparative Examples 1-2 due to the multiple rigid-flexible cross-linked network structure and the supporting adhesion effect of the filler, demonstrating good mechanical strength and high pressure adaptability.

[0041] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. An acid and alkali resistant polytetrafluoroethylene composite material, characterized in that, The polytetrafluoroethylene composite material comprises the following raw materials in parts by weight: 89 parts PFA, 1-4.5 parts plasticizer, 0.5-2 parts coupling agent, 0.5 parts weather resistant agent, and 4-9 parts functional additives; The functional additive is composed of flake graphite, polyamic acid, PFPE-DMA, and DMF in a mass ratio of 12.8:2.8:4.4:

80. The preparation method of the functional additive is as follows: S1: Polyamic acid, PFPE-DMA and DMF are mixed and ultrasonically treated to obtain a polymer microemulsion; S2: Mix polymer microemulsion and flake graphite, and shear emulsify to obtain functional additives.

2. The acid and alkali resistant polytetrafluoroethylene composite material according to claim 1, characterized in that, The plasticizer is selected from FEP or PTFE ultrafine powder.

3. The acid and alkali resistant polytetrafluoroethylene composite material according to claim 2, characterized in that, The coupling agent is selected from either titanate coupling agent NDZ-311w or aluminate coupling agent DL-411.

4. The acid and alkali resistant polytetrafluoroethylene composite material according to claim 2, characterized in that, The weathering agent is selected from any one of the following: UV-360 ultraviolet light absorber, nano titanium dioxide, and carbon black.

5. A method for preparing an acid and alkali resistant polytetrafluoroethylene composite material according to any one of claims 1-4, characterized in that, The specific steps are as follows: Step 1: Take PFA, plasticizer, coupling agent and weathering agent and stir to mix. Add functional additives and continue stirring to obtain slurry; Step 2: Volatilize the DMF in the slurry to obtain a wet material; Step 3: The wet material is melt-extruded, preheated to 300℃, and then the temperature is increased to 350℃. After extrusion, it is cooled with water and pelletized to obtain acid and alkali resistant polytetrafluoroethylene composite material.

6. The application of an acid and alkali resistant polytetrafluoroethylene composite material according to any one of claims 1-4, characterized in that, The polytetrafluoroethylene composite material is used to prepare special engineering plastics; The special engineering plastics include the following products: pneumatic diaphragm valves for semiconductor equipment, CMP retaining rings, high-frequency antenna substrates, transparent radar radomes, cable insulation layers, electrolyte battery encapsulation shells, and electronic water pump impellers.

Images