Polytetrafluoroethylene / polyphenylene sulfide composite coating with micro-nano-pore structure and preparation method of polytetrafluoroethylene / polyphenylene sulfide composite coating

Abstract

The invention discloses a polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro-nano pore structure and a preparation method of the polytetrafluoroethylene / polyphenylene sulfide composite coating. The method comprises the following steps: dispersing PTFE powder in an ethanol / water / surfactant mixed solvent, and dispersing PPS resin powder in ethanol to respectively prepare dispersion liquids; mixing in proportion and spraying on a metal substrate to form a wet film; freezing the wet film at the temperature of 0 DEG C to-30 DEG C for hole casting; heating and curing at 100-200 DEG C and 370-390 DEG C to promote sublimation of ice crystals and emulsification and expansion of the surfactant to synergistically expand pores; and finally, cooling and crystallizing to obtain the coating with the micro-nano composite pore structure. The method is simple in process, green, environmentally friendly and controllable in pore structure, and the optimal pore structure (the micron pore diameter is about 51.49 microns, and the nano pore diameter is about 215 nm) can be obtained at the temperature of-10 DEG C. The coating is stable in structure, the dry friction coefficient is 0.155, good mechanical durability is shown, and the specific micro-nano porous structure of the coating has wide application prospects in the fields of icing prevention, oil-water separation, oil storage and lubrication and the like.

Description

Technical Field

[0001] This invention belongs to the field of coating polymers, and specifically relates to a polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro-nanoporous structure and its preparation method. Background Technology

[0002] Polymer-based functional coatings have attracted widespread attention in the field of surface engineering due to their lightweight, corrosion resistance, and high designability. Among these, constructing micro / nano porous structures within coatings can endow material surfaces with unique wettability, adhesion, and load-bearing capacity, thereby expanding their applications in areas such as anti-icing, oil-water separation, photothermal processes, material loading, and slow release. The composite system of polytetrafluoroethylene (PTFE) and polyphenylene sulfide (PPS) is considered an ideal material matrix for constructing high-performance porous coatings due to its synergistically enhanced mechanical properties and excellent engineering durability.

[0003] Currently, various methods for constructing porous structures in polymers have been disclosed in existing technologies. For example, the chemical foaming method (CN 120923767 A) suffers from complex decomposition processes, harsh reaction conditions (high pressure and high temperature), and residues that may affect the long-term performance of the coating; the phase separation method (CN 120310396 A) often involves highly corrosive solvents, has high requirements for equipment and process safety, and requires cumbersome subsequent cleaning; the block copolymer self-assembly method (CN 114678515 B) has high raw material costs and complex film formation processes, making it difficult to achieve economical and uniform preparation on the surfaces of large or complex components; while the high-temperature-centrifugation method (CN 116790164 B) is complex and energy-intensive. Therefore, developing a general method for preparing porous coatings that matches the excellent matrix properties of PTFE / PPS, is simple in process, and has controllable pore structure is of vital importance for promoting the application of this type of high-performance material on multifunctional surfaces. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a simple process for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide (PTFE / PPS) composite coating with controllable pore structure, as well as its preparation method. Inspired by the formation principle of "frozen tofu," this invention utilizes a low-temperature freezing-heating curing process to biomimetically construct a micro / nanoporous structure in the PTFE / PPS composite coating.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating is presented. The core of this method lies in controlling the solvent system and freezing temperature, utilizing the water-ice phase transition as the pore-forming driving force, combining the emulsifying and expanding effect of surfactants, and the cooling and crystallization behavior of PTFE / PPS, to synergistically construct and stabilize the micro / nanoporous structure of the coating.

[0006] A micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating is prepared by the following steps: S1. Preparation of polytetrafluoroethylene dispersion: PTFE powder with an average particle size of 3-5 μm is dispersed in a mixed solvent composed of ethanol, water and surfactant, and ground and dispersed for 65-80 h to obtain a PTFE dispersion with a solid content of 20-30%. S2. Preparation of polyphenylene sulfide dispersion: PPS resin powder with an average particle size of 4-10 μm is dispersed in ethanol and ball-milled to obtain PPS dispersion. S3. Preparation of mixed coating: The PTFE dispersion from step S1 and the PPS dispersion from step S2 are mixed, and the volume fraction of PTFE in the solid components of the coating is controlled to be 35-45%. The mixture is stirred evenly to obtain a PTFE / PPS coating. S4. Spraying to form a film: Using compressed air spraying technology, the PTFE / PPS coating prepared in step S3 is sprayed onto the surface of the substrate to form a wet coating film. S5. Freezing and casting holes: Freeze the wet coating film obtained in step S4 at a temperature of 0°C to -30°C for 0.5-2 hours. S6. Quickly place the frozen sample into an oven, keep it at 100-200℃ for 0.5 hours, and then raise the temperature to 380-390℃ at 10℃ / min and keep it at 1-2 hours. S7. Cooling and crystallization: The furnace is naturally cooled to room temperature to obtain a polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro-nano porous structure.

[0007] Preferably, in the above-mentioned micro-nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating: in step S1, the surfactant is a cationic surfactant, anionic surfactant, amphoteric surfactant or nonionic surfactant, and its mass concentration added in the mixed solvent is 5-15%.

[0008] Preferably, in the above-mentioned micro-nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating: in step S1, the volume ratio of ethanol, water and surfactant is 1:1:1.

[0009] Preferably, in the above-mentioned micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating: in step S5, the freezing temperature is -10℃. Experimental results show that when the freezing temperature is -10℃ and the solvent system is ethanol / water / surfactant, the prepared coating has the optimal pore structure, with an average micron-sized pore diameter of approximately 51.49 μm and an average nano-sized pore diameter of approximately 215 nm.

[0010] Preferably, in the above-mentioned micro-nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating: in step S4, the substrate is a metal substrate, which needs to be sanded with sandpaper and ultrasonically cleaned with petroleum ether or acetone before spraying.

[0011] Preferably, the stable coefficient of friction of the micro / nanoporous PTFE / PPS composite coating under dry friction conditions is 0.155.

[0012] The polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro-nano porous structure has a honeycomb-like micro-nano composite porous structure on its surface, with an average micron pore size of 20-50 μm and an average nanopore size of 100-300 nm. The dry friction coefficient of the coating is 0.13-0.16.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide (PTFE / PPS) composite coating provided by this invention combines the biomimetic pore-forming principle of "frozen tofu" with the preparation process of polymer coatings. Utilizing ice crystals as a green pore-forming agent, the method directly constructs a micro / nano hierarchical pore structure in the coating through the synergistic effects of freeze casting, heating to expand pores, and cooling to solidify pores. Compared with traditional pore-forming methods such as adding chemical foaming agents or high-temperature centrifugation, this invention's process is simple and environmentally friendly, and the resulting pore structure is more uniform and has better connectivity. This method achieves controllable construction of the coating's pore structure through a simple and environmentally friendly freezing process, and the prepared coating possesses both structural and mechanical stability.

[0014] (2) The present invention involves mixing materials in a specific ratio and spraying them onto a metal substrate to form a wet film; freezing the wet film at 0°C to -30°C to create pores; then heating it to 100-200°C and 370-390°C to solidify it, promoting the sublimation of ice crystals and the synergistic expansion of the pores through emulsification and expansion of surfactants; finally, cooling and crystallization to obtain a coating with a micro-nano composite pore structure. The present invention has a simple, environmentally friendly, and controllable pore structure, and can obtain the optimal pore structure (micron pore size approximately 51.49 μm, nano pore size approximately 215 nm) at -10°C. The coating structure is stable, with a dry friction coefficient of 0.155, exhibiting good mechanical durability. Its unique micro-nano porous structure has broad application prospects in fields such as anti-icing, oil-water separation, and oil storage and lubrication. The present invention can obtain the optimal micro-nano porous structure at -10°C, and can also form an effective porous structure with a pore size of approximately 37-48 μm at 0°C and -20°C. This proves that the preparation method has good process tolerance and controllability, and is easy to implement and promote in actual production. Attached Figure Description

[0015] Figure 1Surface structure and tribological properties of the ethanol / water / surfactant coating system at -10°C: microstructure (a, b); XPS structure analysis of the coating surface (c, d); FT-IR structure analysis of the coating surface (e); dry friction coefficient (f).

[0016] Figure 2 Microstructure of the ethanol / water / surfactant coating system at -20°C: SEM at 200X (a); SEM at 10Kx (b).

[0017] Figure 3 Microstructure of the ethanol / water coating system at 0℃ freezing temperature: SEM at 200X (a); SEM at 10Kx (b).

[0018] Figure 4 Microstructure of the ethanol / water coating system at -10℃ freezing temperature: SEM at 200X (a); SEM at 10Kx (b). Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0021] Example 1: A method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating includes the following steps: (1) Preparation of polytetrafluoroethylene dispersion: PTFE powder (average particle size 5μm) is added to a mixed solvent composed of ethanol, water and nonionic surfactant octylphenol polyoxyethylene ether (volume ratio 1:1:1), wherein the surfactant concentration is 10 wt%. After 4-5 cycles of conical milling, a PTFE dispersion with a solid content of 40% is obtained.

[0022] (2) Preparation of polyphenylene sulfide dispersion: PPS resin powder (average particle size 4μm) was added to ethanol and ball-milled for 72 hours to obtain a uniform PPS dispersion.

[0023] (3) Preparation of mixed coating: Take an appropriate amount of PTFE dispersion and PPS dispersion according to the ratio of PTFE volume fraction of 40% in steps (1) and (2), mix them, stir evenly, and obtain PTFE / PPS coating.

[0024] (4) Spraying film: Spray the PTFE / PPS coating mixed in step (3) onto the 316L stainless steel substrate that has been sanded with 320 grit sandpaper and ultrasonically cleaned with petroleum ether.

[0025] (5) Freeze casting: The wet film coating prepared in step (4) is quickly transferred to a low temperature environment of -10℃ and frozen for 1 hour.

[0026] (6) Heating and curing: Quickly place the coating sample from step (5) into an oven and keep it at 150°C for 0.5 hours, then raise the temperature to 380°C at 10°C / min and keep it at 1 hour.

[0027] (7) Cooling and crystallization: Cool the coating sample from step (6) to room temperature in the furnace to obtain a porous PTFE / PPS coating.

[0028] The surface SEM image of the micro-nanoporous structure prepared in Example 1 of this invention is shown in Figure 1. Figure 1 ,Depend on Figure 1 (ab) shows that the coating has an average pore size of 51.49 μm and an average pore size of 215 nm. XPS and FT-IR analyses indicate that the PTFE / PPS structure is intact. Figure 1 (ce). The constructed porous polymer coating was tested for tribological properties on a heavy-duty tribological testing machine (load 5.5 MPa, rotation speed 800 r / min, time 1 h). See Figure 1 (f) The prepared porous oil-storing coating exhibits a stable friction coefficient of 0.155 under dry friction. This result demonstrates that the coating maintains good mechanical stability despite its porous structure.

[0029] Example 2: A method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating includes the following steps: (1) Preparation of polytetrafluoroethylene dispersion: PTFE powder (average particle size 5μm) is added to a mixed solvent composed of ethanol, water and nonionic surfactant octylphenol polyoxyethylene ether (volume ratio 1:1:1), wherein the surfactant concentration is 10 wt%. After 4-5 cycles of conical milling, a PTFE dispersion with a solid content of 40% is obtained.

[0030] (2) Preparation of polyphenylene sulfide dispersion: PPS resin powder (average particle size 4μm) was added to ethanol and ball-milled for 72 hours to obtain a uniform PPS dispersion.

[0031] (3) Preparation of mixed coating: Take an appropriate amount of PTFE dispersion and PPS dispersion according to the ratio of PTFE volume fraction of 40% in steps (1) and (2), mix them, stir evenly, and obtain PTFE / PPS coating.

[0032] (4) Spraying film: Spray the PTFE / PPS coating mixed in step (3) onto the 316L stainless steel substrate that has been sanded with 320 grit sandpaper and ultrasonically cleaned with petroleum ether.

[0033] (5) Freeze casting: Quickly transfer the wet film coating prepared in step (4) to a low temperature environment of -20°C and freeze for 1 hour.

[0034] (6) Heating and curing: Quickly place the coating sample from step (5) into an oven and keep it at 150°C for 0.5 hours, then raise the temperature to 380°C at 10°C / min and keep it at 1 hour.

[0035] (7) Cooling and crystallization: Cool the coating sample from step (6) to room temperature in the furnace to obtain a porous PTFE / PPS coating.

[0036] The surface SEM image of the micro-nanoporous structure prepared in Example 2 of this invention is shown in Figure 2. Figure 2 ,Depend on Figure 2 (ab) shows that the average pore size of the coating is 37 μm in micrometers and 235 nm in nanometers.

[0037] Example 3: A method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating includes the following steps: (1) Preparation of polytetrafluoroethylene dispersion: PTFE powder (average particle size 5μm) is added to a mixed solvent composed of ethanol and water (volume ratio 1:1), and ground by a conical mill for 4-5 cycles to obtain a PTFE dispersion with a solid content of 40%.

[0038] (2) Preparation of polyphenylene sulfide dispersion: PPS resin powder (average particle size 4μm) was added to ethanol and ball-milled for 72 hours to obtain a uniform PPS dispersion.

[0039] (3) Preparation of mixed coating: Take an appropriate amount of PTFE dispersion and PPS dispersion according to the ratio of PTFE volume fraction of 40% in steps (1) and (2), mix them, stir evenly, and obtain PTFE / PPS coating.

[0040] (4) Spraying film: Spray the PTFE / PPS coating mixed in step (3) onto the 316L stainless steel substrate that has been sanded with 320 grit sandpaper and ultrasonically cleaned with petroleum ether.

[0041] (5) Freeze casting: Quickly transfer the wet film coating prepared in step (4) to a low temperature environment of 0°C and freeze for 1 hour.

[0042] (6) Heating and curing: Quickly place the coating sample from step (5) into an oven and keep it at 150°C for 0.5 hours, then raise the temperature to 380°C at 10°C / min and keep it at 1 hour.

[0043] (7) Cooling and crystallization: Cool the coating sample from step (6) to room temperature in the furnace to obtain a porous PTFE / PPS coating.

[0044] The surface SEM image of the micro-nanoporous structure prepared in Example 3 of this invention is shown in Figure 3. Figure 3 ,Depend on Figure 3 (ab) shows that the average pore size of the coating is 48 μm in micrometers and 245 nm in nanometers.

[0045] Example 4: A method for preparing a micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating includes the following steps: (1) Preparation of polytetrafluoroethylene dispersion: PTFE powder (average particle size 5μm) is added to a mixed solvent composed of ethanol and water (volume ratio 1:1), and ground by a conical mill for 4-5 cycles to obtain a PTFE dispersion with a solid content of 40%.

[0046] (2) Preparation of polyphenylene sulfide dispersion: PPS resin powder (average particle size 4μm) was added to ethanol and ball-milled for 72 hours to obtain a uniform PPS dispersion.

[0047] (3) Preparation of mixed coating: Take an appropriate amount of PTFE dispersion and PPS dispersion according to the ratio of PTFE volume fraction of 40% in steps (1) and (2), mix them, stir evenly, and obtain PTFE / PPS coating.

[0048] (4) Spraying film: Spray the PTFE / PPS coating mixed in step (3) onto the 316L stainless steel substrate that has been sanded with 320 grit sandpaper and ultrasonically cleaned with petroleum ether.

[0049] (5) Freeze casting: The wet film coating prepared in step (4) is quickly transferred to a low temperature environment of -10℃ and frozen for 1 hour.

[0050] (6) Heating and curing: Quickly place the coating sample from step (5) into an oven and keep it at 150°C for 0.5 hours, then raise the temperature to 380°C at 10°C / min and keep it at 1 hour.

[0051] (7) Cooling and crystallization: Cool the coating sample from step (6) to room temperature in the furnace to obtain a porous PTFE / PPS coating.

[0052] The surface SEM image of the micro-nanoporous structure prepared in Example 4 of this invention is shown in Figure 4. Figure 4 ,Depend on Figure 4(ab) shows that the average pore size of the coating is 37.2 μm in micrometers and 180 nm in nanometers.

Claims

1. A micro / nanoporous polytetrafluoroethylene / polyphenylene sulfide composite coating, characterized in that... It is made by the following steps: S1. Preparation of polytetrafluoroethylene dispersion: PTFE powder with an average particle size of 3-5 μm is dispersed in a mixed solvent composed of ethanol, water and surfactant, and ground and dispersed for 65-80 h to obtain a PTFE dispersion with a solid content of 20-30%. S2. Preparation of polyphenylene sulfide dispersion: PPS resin powder with an average particle size of 4-10 μm is dispersed in ethanol and ball-milled to obtain PPS dispersion. S3. Preparation of mixed coating: The PTFE dispersion from step S1 and the PPS dispersion from step S2 are mixed, and the volume fraction of PTFE in the solid components of the coating is controlled to be 35-45%. The mixture is stirred evenly to obtain a PTFE / PPS coating. S4. Spraying to form a film: Using compressed air spraying technology, the PTFE / PPS coating prepared in step S3 is sprayed onto the surface of the substrate to form a wet coating film. S5. Freezing and casting holes: Freeze the wet coating film obtained in step S4 at a temperature of 0°C to -30°C for 0.5-2 hours. S6. Quickly place the frozen sample into an oven, keep it at 100-200℃ for 0.5 hours, and then raise the temperature to 380-390℃ at 10℃ / min and keep it at 1-2 hours. S7. Cooling and crystallization: The furnace is naturally cooled to room temperature to obtain a polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro-nano porous structure.

2. The polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro / nanoporous structure according to claim 1, characterized in that: In step S1, the surfactant is a cationic surfactant, anionic surfactant, amphoteric surfactant, or nonionic surfactant, and its mass concentration added to the mixed solvent is 5-15%.

3. The polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro / nanoporous structure according to claim 2, characterized in that: In step S1, the volume ratio of ethanol, water and surfactant is 1:1:

1.

4. The polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro / nanoporous structure according to claim 1, characterized in that: In step S5, the freezing temperature is -10°C.

5. The polytetrafluoroethylene / polyphenylene sulfide composite coating with a micro / nanoporous structure according to claim 1, characterized in that: In step S4, the substrate is a metal substrate, which needs to be sanded with sandpaper and ultrasonically cleaned with petroleum ether or acetone before spraying.

6. The application of the polytetrafluoroethylene / polyphenylene sulfide composite coating with micro-nanoporous structure as described in claim 1 in the fields of solid-liquid composite lubrication, anti-icing, or oil-water separation.

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