Preparation method of high-temperature-resistant durable super-hydrophobic powder coating and application of coating to heat distribution pipeline

Abstract

According to the preparation method of the high-temperature-resistant durable super-hydrophobic powder coating, integrated powder coating particles are prepared by mixing through a tabletting-crushing-sieving technology, and finally, one end of a solid nano-material in the integrated powder coating particles is embedded into a bottom layer, and the other end of the solid nano-material protrudes out of the surface of the coating, so that a nano-fiber bridging interface strengthening structure is formed. According to the invention, the low surface energy material, the solid nano material and the thermoplastic film-forming resin are effectively combined together to construct firm and stable integrated powder coating particles, so that the overall performance is synergistically enhanced, and the protection capability of a micron-scale structure to a nano-scale structure is greatly improved; the solvent-free durable super-hydrophobic powder coating is directly prepared through electrostatic spraying, so that the technological process is simplified; the solid, solvent-free and environment-friendly super-hydrophobic powder coating is prepared, has excellent high-temperature resistance and super-hydrophobic performance, and has potential advantages in the aspect of anti-corrosion and anti-drag application of a heat distribution pipeline.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of superhydrophobic powder coating, in particular to a preparation method of a solvent-free durable superhydrophobic powder coating. BACKGROUND

[0002] Superhydrophobic coatings typically have a contact angle greater than 150° and a sliding angle less than 10°, which can effectively prevent water droplet adhesion and retention, exhibit self-cleaning, waterproof, corrosion-resistant and other characteristics, and are widely used in many fields such as aerospace, automotive, construction, optoelectronics, etc. Through the organic combination of micro-nano surface structure and low surface energy material, superhydrophobic coatings can be efficiently constructed. Micro-nano structure provides surface roughness, increases gas-liquid interface, and thus improves hydrophobicity; low surface energy material reduces the adhesion of liquid to the surface, further enhancing the hydrophobic effect. The combination of multiple technologies can achieve more excellent superhydrophobic performance and improve the stability and durability of the coating. Currently, the common method for constructing superhydrophobic coatings is to introduce hydrophobically modified organic, inorganic or organic-inorganic composite solid nanomaterials into the film-forming resin system to achieve the micro-nano structure and low surface energy characteristics on the surface of the coating. However, this nano-scale surface structure is usually fragile and easily damaged by external forces such as scratching and impact, which can cause surface structure damage, thus reducing hydrophobicity and weakening the superhydrophobic performance of the coating.

[0003] In the application of heat pipes, coating the inner wall of the pipe with a high-temperature-resistant superhydrophobic coating can reduce maintenance frequency and replacement costs, and ensure long-term stable operation of the heating system. However, current traditional coating technology faces many challenges in practical application. The insufficient high-temperature resistance and superhydrophobicity of traditional coatings result in insufficient corrosion resistance and drag reduction, making it difficult to meet the needs of long-term operation and improved efficiency of heat pipes.

[0004] There is an urgent need in the art for a preparation method of a solvent-free durable superhydrophobic powder coating. SUMMARY

[0005] To solve the above technical problems, the present application discloses a preparation method of a solvent-free durable superhydrophobic powder coating, comprising the following steps:

[0006] (a) dry mixing solid nanomaterials, solid low surface energy materials, and thermoplastic film-forming resins to obtain uniformly mixed powders;

[0007] (b) forming block-shaped materials from the uniformly mixed powders through a tabletting process, wherein the pressure of the tabletting process is 1-30 tons;

[0008] (c) crushing and sieving the blocky material to obtain solid low surface energy material, solid nanomaterial and thermoplastic film-forming resin integrated powder coating particles with a median particle size of 25-50 microns;

[0009] (d) applying electrostatic spraying technology to spray thermoplastic film-forming resin powder coating particles on the surface of the substrate to form a primer layer, the primer layer has a film thickness of 10-30 microns and is greater than the length of the solid nanomaterial;

[0010] (e) applying electrostatic spraying technology to spray the integrated powder coating particles on the surface of the primer layer and performing high-temperature curing treatment to form a solvent-free durable super-hydrophobic powder coating layer, wherein the high-temperature curing temperature is higher than the melting point of the thermoplastic film-forming resin, so that one end of the solid nanomaterial in the integrated powder coating particles is embedded in the primer layer and the other end protrudes from the surface of the coating layer to form a nanofiber bridging interface strengthening structure.

[0011] Preferably,

[0012] The solid nanomaterial includes any one of the following: oxide nanofiber, carbon-based solid nanofiber, metal solid nanofiber, polymer solid nanomaterial.

[0013] Preferably,

[0014] The oxide nanofiber includes any one of the following: silicon dioxide (SiO2), titanium dioxide (TiO2), zinc oxide (ZnO), aluminum oxide (Al2O3), iron oxide (Fe2O3).

[0015] Preferably,

[0016] The carbon-based solid nanofiber includes any one of the following: carbon nanotube, carbon nanowire, wherein,

[0017] The carbon nanotube includes multi-walled carbon nanotubes (MWCNTs).

[0018] Preferably,

[0019] The metal solid nanofiber includes any one of the following: gold (Au), silver (Ag), copper (Cu) nanofiber.

[0020] Preferably,

[0021] The polymer solid nanomaterial includes any one of the following: polystyrene (PS) nanofiber, polyacrylonitrile (PAN) nanofiber, polyaniline (PANI) nanotube.

[0022] Preferably,

[0023] The solid low surface energy material includes any one of the following: polytetrafluoroethylene (PTFE), polytetrafluoroethylene (PFA), fluorinated polymer, silicone resin.

[0024] Preferably,

[0025] The fluorinated polymer includes any one of the following: polytetrafluoroethylene (FEP), ethylene-tetrafluoroethylene copolymer (ETFE).

[0026] Preferably,

[0027] The thermoplastic film-forming resin includes a special engineering thermoplastic resin.

[0028] Preferably,

[0029] The special engineering thermoplastic resin includes any one of the following: polytetrafluoroethylene (PTFE), polysulfone (PSU), polyether ether ketone (PEEK), polyamide (PA), polyimide (PI).

[0030] The application also discloses a high-temperature-resistant and durable super-hydrophobic powder coating.

[0031] The high-temperature-resistant and durable super-hydrophobic powder coating is prepared by any one of the methods.

[0032] The application also discloses an application of the powder coating to a heat pipe.

[0033] The powder coating adopts the high-temperature-resistant and durable super-hydrophobic powder coating.

[0034] The application includes an application of the high-temperature-resistant and durable super-hydrophobic powder coating as an inner wall coating of the heat pipe, and the heat pipe includes a heat pipe of a water supply section and / or a water return section.

[0035] Compared with the prior art, the application has the following beneficial effects:

[0036] The application effectively combines the low surface energy material, the solid nanomaterial and the thermoplastic film-forming resin together, constructs a solid and stable integrated powder coating particle, realizes synergistic enhancement in overall performance, greatly improves the protection capability of the micron-scale structure on the nanometer-scale structure, and simplifies the process flow by directly preparing the solvent-free durable super-hydrophobic powder coating through electrostatic spraying.

[0037] The description is only a summary of the technical scheme of the application, in order to make the technical means of the application more clear and understandable, to the extent that the person skilled in the art can implement the content of the description, and in order to make the application and other purposes, features and advantages more obvious and easy to understand, the application will be described below with reference to the drawings. Attached Figure Description

[0038] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings:

[0039] Figure 1 The diagram shows the surface morphology of PEEK, PTFE, and MWCNTs materials and MPP particles (i.e., integrated MWCNTs / PTFE / PEEK powder coating particles) in Example 1, indicating that PTFE, PEEK, and MWCNTs particles are effectively combined to form a tightly interwoven MWCNTs / PTFE / PEEK network, and have the roughened structure required for a superhydrophobic coating.

[0040] Figure 2 This indicates the effect of different mass fractions of MWCNTs on the wettability of P-MPP composite coatings. The results show that when the amount of MWCNTs added is above 3%, the contact angle of the coating is above 160 degrees, and when the amount added is above 4%, the sliding angle is below 10 degrees, achieving superhydrophobicity.

[0041] Figure 3 The image shows the surface morphology of a P-MPP composite coating with a MWCNT content of 4 wt%. The P-MPP coating surface has numerous micron-sized protrusions, forming a multi-level micro / nanoporous coating. Furthermore, the presence of MWCNTs hinders the melt flow and leveling of PTFE and PEEK resins during high-temperature processes, leading to the formation of micron-sized protrusions. These two effects endow the coating with the micro / nano roughened structure required for a superhydrophobic coating.

[0042] Figure 4 This indicates the self-cleaning and water-repellent properties of the P-4%MPP composite coating, demonstrating that the P-4%MPP superhydrophobic coating exhibits significant anti-sticking and water-repellent properties.

[0043] Figure 5 The data represents the relationship between the wettability and film thickness of the P-4%MPP superhydrophobic coating with and without a PEEK underlayer as a function of wear cycles. After friction, the hydrophobic properties of both coatings with and without a PEEK underlayer decreased to a similar degree, and both still exhibited superhydrophobic properties after 800 cycles, indicating excellent mechanical durability. Furthermore, the superhydrophobic coating with a PEEK underlayer showed a lower film thickness decrease rate under the same wear conditions, suggesting that the PEEK underlayer plays a crucial role in achieving high durability for the P-4%MPP superhydrophobic coating.

[0044] Figure 6represents the high-temperature resistance of the P-4% MPP super-hydrophobic coating, which shows that the P-4% MPP super-hydrophobic coating exhibits excellent super-hydrophobicity at high temperature (400 ℃, 12 h), and the high-temperature resistance is much higher than that of traditional organic coatings;

[0045] Figure 7 represents the chemical stability of the P-4% MPP super-hydrophobic coating, which shows that the P-4% MPP super-hydrophobic coating has excellent resistance to strong acid / strong base solution, UV radiation, alcohol and butanone and other organic solvents, and is very suitable for application in harsh environments;

[0046] Figure 8 represents that in a comparative example of the application, when no roughening material carbon nanotube MWCNTs is added, the coating surface only changes slightly, and the contact angle is below 120 degrees, and super-hydrophobicity is not achieved;

[0047] Figure 9 represents that in another comparative example of the application, SiO2 nanoparticles with a non-fiber structure are used as a nano-roughening material and introduced into a 10% PTFE / PEEK resin matrix, and the coating is prepared by the same treatment method as in Example 1; when the SiO2 nanoparticle loading is 1 wt%, the coating contact angle is 118.8°; when the SiO2 nanoparticle content is increased to 3%, the coating exhibits super-hydrophobic properties; however, due to the poor connectivity between inorganic nanoparticles, the nanoparticles cannot be combined into the resin matrix as well and completely as fibers, so that the coating does not have mechanical durability; through several simple finger rubbings, the loose cluster structure is destroyed, and even the particles are detached, the contact angle (WCA) value rapidly decreases to below 150°, and the coating loses hydrophobicity;

[0048] Figure 10 represents that in another comparative example of the application, without the action of a low-surface-energy resin (such as PTFE), the coating hydrophobic angle is below 110 degrees, and super-hydrophobicity is not exhibited, and the results show that the coating super-hydrophobicity cannot be achieved only by relying on a film-forming resin and a roughening material;

[0049] Figure 11 represents that in another comparative example of the application, the material is not pressed into a tablet and crushed in advance, but is directly sprayed after dry mixing; from the surface morphology of the super-hydrophobic coating prepared by the direct dry mixing method, it can be seen that part of the MWCNTs is embedded in the resin, and more MWCNTs clusters are loosely and independently distributed on the coating surface, and are easily mechanically abraded and damaged. The evaluation of the wear resistance of the coating shows that after 80 wear cycles, the WCA value of the super-hydrophobic coating decreases to below 150°, indicating that the wear resistance of the coating is very poor;

[0050] Figure 12The high-temperature and high-pressure boiling resistance of the coating prepared by the present application and the coating of the prior art are shown in the following figures.

[0051] The present application will be further explained in conjunction with the accompanying drawings and examples. DETAILED DESCRIPTION

[0052] Specific embodiments of the present application will be described in greater detail below with reference to the accompanying drawings. While the present application is illustrated with reference to specific embodiments, it will be appreciated that it can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0053] Throughout the specification and claims, the term "comprising" or "including" is used in the sense of "including but not limited to". The description that follows is intended to be a more complete description of the preferred embodiments of the application, and is not intended to limit the application. The scope of the application is defined by the appended claims.

[0054] In one embodiment, the present application discloses a method for preparing a solvent-free durable superhydrophobic powder coating, comprising the following steps:

[0055] (a) dry mixing solid nanomaterials, solid low-surface energy materials and thermoplastic film-forming resins to obtain uniformly mixed powders;

[0056] (b) forming a block material from the uniformly mixed powders by a tabletting process, wherein the pressure of the tabletting process is 1-30 tons;

[0057] (c) crushing and sieving the block material to obtain integrated powder coating particles of solid low-surface energy materials, solid nanomaterials and thermoplastic film-forming resins with a median particle size of 25-50 microns;

[0058] (d) spraying the thermoplastic film-forming resin powder coating particles onto the surface of a substrate by electrostatic spraying technology to form a primer layer, wherein the film thickness of the primer layer is 10-30 microns and greater than the length of the solid nanomaterials;

[0059] (e) spraying the integrated powder coating particles onto the surface of the primer layer by electrostatic spraying technology and performing high-temperature curing treatment to form a solvent-free durable superhydrophobic powder coating, wherein the high-temperature curing temperature is higher than the melting point of the thermoplastic film-forming resin, so that one end of the solid nanomaterials in the integrated powder coating particles is embedded in the primer layer and the other end protrudes from the surface of the coating to form a nanofiber bridging interface strengthening structure.

[0060] It should be noted that:

[0061] The thickness of the bottom layer is greater than the length of the solid nanomaterial, which is intended to ensure that the solid nanomaterial is embedded in the bottom layer while also protruding from the top of the coating to ensure that the premise of effective bridging of the nanofiber is ensured, which is a key to improving the adhesion and wear resistance of the coating;

[0062] High-temperature curing causes the solid low-surface-energy material to interface with the thermoplastic film-forming resin and form a homogeneous structure with molecular-level dispersion, and during high-temperature curing, the thermoplastic film-forming resin softens, allowing one end of the solid nanomaterial to be embedded in the bottom layer and the other end to protrude from the top of the coating to form a bridging structure; in addition, high-temperature curing causes the thermoplastic film-forming resin to be uniformly dispersed throughout the coating system, avoiding the problem of rapid surface energy increase after wear caused by the migration of the thermoplastic film-forming resin to the surface in traditional coatings, ensuring long-term durability;

[0063] In addition, in the above embodiments, the substrate, the bottom layer, and the solid nanomaterial protruding from the top layer together form a "sandwich" structure, and high-temperature curing promotes the stable formation of the "sandwich" structure.

[0064] For the above embodiments, the present application effectively combines low-surface-energy materials, solid nanomaterials, and thermoplastic film-forming resins together to construct a solid and stable integrated powder coating particle, achieving synergistic enhancement in overall performance and greatly improving the protection capability of micron-scale structures for nanoscale structures; and since the solvent-free durable superhydrophobic powder coating is directly prepared by electrostatic spraying, the present application also simplifies the process flow; thus, the present application can prepare a solid, solvent-free, and environmentally friendly superhydrophobic powder coating.

[0065] Preferably,

[0066] The solid nanomaterials include any of the following: oxide nanofibers, carbon-based solid nanofibers, metal solid nanofibers, and polymer solid nanomaterials.

[0067] Preferably,

[0068] The oxide nanofibers include any of the following: silicon dioxide (SiO2), titanium dioxide (TiO2), zinc oxide (ZnO), aluminum oxide (Al2O3), and iron oxide (Fe2O3).

[0069] Preferably,

[0070] The carbon-based solid nanofibers include any of the following: carbon nanotubes and carbon nanowires, wherein,

[0071] The carbon nanotubes include multi-walled carbon nanotubes (MWCNTs).

[0072] Preferably,

[0073] Metallic solid nanofiber includes any one of the following: gold (Au), silver (Ag), copper (Cu) nanofiber.

[0074] Preferably,

[0075] Polymer solid nanomaterial includes any one of the following: polystyrene (PS) nanofiber, polyacrylonitrile (PAN) nanofiber, polyaniline (PANI) nanotube.

[0076] Preferably,

[0077] Solid low surface energy material includes any one of the following: polytetrafluoroethylene (PTFE), polyperfluoroalkoxyethylene (PFA), fluorinated polymer, silicone resin.

[0078] Preferably,

[0079] Fluorinated polymer includes any one of the following: polyperfluoroethylene-propylene (FEP), ethylene-tetrafluoroethylene copolymer (ETFE).

[0080] Preferably,

[0081] Thermoplastic film-forming resin includes special engineering thermoplastic resin.

[0082] Preferably,

[0083] The special engineering thermoplastic resin includes any one of the following: polytetrafluoroethylene (PTFE), polysulfone (PSU), polyether ether ketone (PEEK), polyamide (PA), polyimide (PI).

[0084] In another embodiment, the preparation method of the solvent-free durable super-hydrophobic powder coating includes the following steps:

[0085] S1, using a laboratory high-shear mixer to dry mix solid nanomaterials, solid low surface energy materials and thermoplastic film-forming resin in different mass ratios to obtain a uniformly mixed powder;

[0086] S2, placing the uniformly mixed powder in a mold, and using a tablet press to press the uniformly mixed powder at an appropriate pressure to form a block material with an appropriate diameter;

[0087] S3, crushing and sieving the block material by a grinding machine to form solid low surface energy material, solid nanomaterial and thermoplastic film-forming resin integrated powder coating particles with an appropriate median particle size;

[0088] S4, using electrostatic spraying method to spray the thermoplastic film-forming resin powder coating particles on the surface of the substrate, and pre-curing at an appropriate temperature to form a thin layer as a bottom layer;

[0089] S5, spray the integrated powder coating particles on the surface of the primer layer, and high-temperature curing to obtain a solvent-free durable super-hydrophobic powder coating, wherein the high-temperature curing temperature is higher than the melting point of the thermoplastic film-forming resin, so that one end of the solid nanomaterial in the integrated powder coating particles is embedded in the primer layer, and the other end protrudes from the surface of the coating layer to form a nano-fiber bridging interface reinforcement structure.

[0090] In another embodiment,

[0091] The mass fraction of the solid nanomaterial in the integrated particles is 1-30%, the mass fraction of the low-surface-energy material in the integrated powder coating particles is 1-30%, and the mass fraction of the thermoplastic film-forming resin in the integrated powder coating particles is 50%-90%.

[0092] In another embodiment,

[0093] When the solid low-surface-energy material (such as hydrophobic resin) has a melting point close to that of the thermoplastic film-forming resin, under the curing temperature condition higher than the melting point, the hydrophobic resin and the thermoplastic resin melt and flow together to form a solid and stable composite film-forming resin.

[0094] In another embodiment,

[0095] When the solid low-surface-energy material is consistent with the solid nanomaterial (such as hydrophobic SiO2), only one of them can be selected to be combined with the thermoplastic film-forming resin for the preparation of the super-hydrophobic powder coating.

[0096] In another embodiment,

[0097] In step S4, the temperature is set to be higher than the melting point of the thermoplastic film-forming resin, and the baking time is sufficient to make the thermoplastic film-forming resin powder coating particles begin to melt and form a film.

[0098] In another embodiment,

[0099] In step S4, the thickness of the primer layer is between 10-30 microns, and the film thickness is higher than the length of the solid nanomaterial.

[0100] In another embodiment,

[0101] In step S5, the temperature is set to be higher than the melting point of the thermoplastic film-forming resin, and the baking time is sufficient to completely cure the integrated powder coating particles.

[0102] In embodiment 1, the preparation method of the solvent-free durable super-hydrophobic powder coating comprises the following steps:

[0103] S10, using a laboratory high shear mixer, 1, 3, 4, 5, 7 wt% of nano-MWCNTs particles, 1, 5, 10, 20, 30 wt% of low surface energy material PTFE particles are dry mixed into PEEK film-forming resin particles respectively, and after uniform mixing, a plurality of groups of MWCNTs / PTFE / PEEK mixed particles are obtained;

[0104] S20, the plurality of groups of MWCNTs / PTFE / PEEK mixed particles are respectively placed into a cylindrical mold with a diameter of 5 centimeters, and an electric tablet press is used to press at a force of 20 tons for 30 seconds to form a cylindrical block-shaped material with a diameter of 5 centimeters;

[0105] S30, the cylindrical block-shaped material is crushed by a grinding machine, and after passing through a 180-mesh sieve, MWCNTs / PTFE / PEEK (MPP) integrated particles with a median particle size of 25-50 microns are obtained;

[0106] S40, PEEK film-forming resin particles are sprayed on the surface of the substrate by electrostatic spraying, and are pre-cured at 380 ℃ for 2 minutes to form a PEEK bottom layer;

[0107] S50, MPP nano-particles are directly sprayed as a powder coating on the PEEK bottom layer by electrostatic spraying, and after baking and curing at 380 ℃ for 10 minutes, a plurality of groups of PEEK-MWCNTs / PTFE / PEEK (P-MPP) super-hydrophobic powder coatings are prepared.

[0108] In this embodiment, the combination of micro / nano-level hierarchical structure features and low surface energy is crucial for the preparation of super-hydrophobic coatings. Among them, polyether ether ketone (PEEK) is used as the film-forming matrix material, which has biocompatibility, mechanical strength and long-term heat resistance to ensure the stability of the coating structure. Experiments show that it still maintains stable super-hydrophobic performance in a high temperature environment of 400 ℃. PTFE resin (melting point 325-335 ℃) as a low surface energy functional phase, through the strong bond energy of C-F bond, gives the coating the characteristics of chemical inertness and low friction coefficient. MWCNTs (length 10 μm, diameter 5-20 nm) as an inorganic reinforcing phase, through the nano-level protrusions, a micro-nano hierarchical structure is constructed, and the toughness of the coating is improved. The MWCNTs / PTFE / PEEK composite powder particles are prepared by tabletting, crushing and sieving.

[0109] Further, the influence of different mass fractions of nano-MWCNTs particles and low-surface-energy material PTFE particles on the superhydrophobicity and durability of the prepared coating is studied to explore the optimal conditions for achieving superhydrophobicity and durability of the coating. The research and development found that when the proportion of MWCNTs particles in MWCNTs / PTFE / PEEK (MPP) nano-micropowder coating particles is 4 wt%, the proportion of PTFE resin particles is 10 wt%, and the proportion of PEEK resin particles is 86 wt%, the superhydrophobicity and durability of the prepared PEEK-MWCNTs / PTFE / PEEK (P-4%MPP) coating reach the best, the contact angle is ~163.78°, and the sliding angle is ~1.3°. After 800 times of abrasion at a pressure of 19.2 Kpa, the contact angle decreases to below 150°. Through experiments, the PEEK-MWCNTs / PTFE / PEEK superhydrophobic coating can still have a film thickness of 13.2 μm after 100000 times of abrasion cycle, providing protection performance for the coating foundation.

[0110] In Example 2, the preparation method of the solvent-free durable superhydrophobic powder coating includes the following steps:

[0111] S10, use a laboratory high-shear mixer to dry mix 2, 4, 6, 8 wt% nano-zinc oxide fiber particles and 10, 20, 30 wt% low-surface-energy material PFA particles in PES film-forming resin particles, respectively, and mix uniformly to obtain multiple groups of MWCNTs / PTFE / PES mixed particles;

[0112] S20, place the MWCNTs / PTFE / PES mixed particles into a cylindrical mold with a diameter of 2.5 centimeters, and use an electric tablet press to press at a force of 10 tons for 20 seconds to form a cylindrical block-shaped material with a diameter of 2.5 centimeters;

[0113] S30, use a grinder to crush the cylindrical block-shaped material, and after passing through a 180-mesh sieve, obtain ZnO / PFA / PES integrated particles with a median particle size of 25-40 microns;

[0114] S40, use electrostatic spraying to spray PES film-forming resin particles on the surface of the substrate, and pre-cure at 300 ℃ for 2 minutes to form a PES bottom layer;

[0115] S50, use electrostatic spraying to spray ZnO / PFA / PES nano-particles directly as a powder coating on the PES bottom layer, and bake and cure at 320 ℃ for 10 minutes to prepare a PES-ZnO / PFA / PES superhydrophobic powder coating.

[0116] In this embodiment, nano-zinc oxide is used as the roughening material, PFA as the low surface energy resin, and PES as the film-forming resin, which endows the coating with micro-nano rough structure and low surface property. The contact angle of the coating is between 155-162 degrees, and the rolling angle is between 5-10 degrees, realizing super-hydrophobic property. Meanwhile, the bridging effect of zinc oxide fibers and the strong bonding force between the bottom layer and the substrate make the coating have excellent mechanical durability. After 1000 times (19.2 Kpa, CS-10F Taber) of strong friction, the coating still has a contact angle of 150°, and the adhesion reaches the highest level of 5B. In addition, the high temperature resistance, chemical stability, ultraviolet resistance of the selected film-forming resin and low surface energy resin, and the chemical stability of nano-zinc oxide make the coating maintain super-hydrophobic property after 45 days of continuous high temperature and high pressure (150℃, 2.5Mpa) treatment, 50 times (standard specified number) of butanone wiping test, and 100 days of ultraviolet radiation, with a contact angle of 150 degrees or more.

[0117] Further referring to Figures 1 to 12 ,

[0118] Figure 1 The surface morphology of PEEK, PTFE and MWCNTs materials and MPP particles (i.e. MWCNTs / PTFE / PEEK integrated powder coating particles) in Example 1 is shown, which shows that PTFE, PEEK and MWCNTs particles are effectively combined together to form a tightly interwoven MWCNTs / PTFE / PEEK network, and have the roughening structure required for super-hydrophobic coating;

[0119] Figure 2 The effect of different mass fractions of MWCNTs on the wettability of P-MPP composite coating is shown, and the results show that when the addition amount of MWCNTs is more than 3%, the contact angle of the coating is more than 160 degrees, and when the addition amount is more than 4%, the sliding angle is less than 10 degrees, reaching super-hydrophobicity;

[0120] Figure 3 The surface morphology of P-MPP composite coating with 4wt% MWCNTs content is shown, and the P-MPP coating surface has numerous micron-sized protrusions, forming a multi-level micro / nano-porous coating. In addition, the presence of MWCNTs hinders the melting and leveling of PTFE and PEEK resins during high temperature process, leading to the formation of micron-sized protrusions. The two effects make the coating have the micro-nano roughening structure required for super-hydrophobic coating;

[0121] Figure 4 The self-cleaning performance and water bouncing performance of P-4%MPP composite coating are shown, which shows that the P-4%MPP super-hydrophobic coating has significant anti-sticking and bouncing performance;

[0122] Figure 5 The figure shows the change of the wettability and film thickness of P-4%MPP superhydrophobic coating with / without PEEK primer with the abrasion cycles; the hydrophobicity of the two coatings with / without PEEK primer is reduced to a similar degree after rubbing, and both still show superhydrophobicity after 800 rubs, indicating that the coating has excellent mechanical durability; meanwhile, the superhydrophobic coating with a PEEK primer has a lower film thickness reduction rate under the same abrasion conditions, indicating that the PEEK primer plays an important role in achieving high durability of the P-4%MPP superhydrophobic coating;

[0123] Figure 6 The figure shows the high-temperature resistance of the P-4%MPP superhydrophobic coating, which indicates that the P-4%MPP superhydrophobic coating shows excellent superhydrophobicity at high temperatures (400 ℃, 12 h), and its high-temperature resistance is much higher than that of traditional organic coatings;

[0124] Figure 7 The figure shows the chemical stability of the P-4%MPP superhydrophobic coating, which indicates that the P-4%MPP superhydrophobic coating shows excellent resistance to strong acid / strong base solutions, UV radiation, alcohol, and butanone organic solvents, making it very suitable for application in harsh environments;

[0125] Figure 8 The figure shows that in a comparative example of the present application, when no roughening material carbon nanotubes MWCNTs is added, the coating surface only changes slightly, and the contact angle is below 120 degrees, which does not reach superhydrophobicity;

[0126] Figure 9 The figure shows that in a comparative example of the present application, SiO2 nanoparticles with a non-fiber structure are used as a nano-roughening material and introduced into a 10% PTFE / PEEK resin matrix, and the coating is prepared by the same treatment method as in Example 1; when the SiO2 nanoparticle loading is 1 wt%, the coating contact angle is 118.8°; increasing the SiO2 nanoparticle content to 3% makes the coating show superhydrophobic properties; however, due to the poor connectivity between inorganic nanoparticles, they cannot be combined into the resin matrix as well and completely as fibers, making the coating not have mechanical durability; through a few simple finger rubs, this loose cluster structure is destroyed, and even causes the particles to fall off, the contact angle (WCA) value rapidly decreases to below 150°, making the coating lose hydrophobicity;

[0127] Figure 10 The figure shows that in another comparative example of the present application, without the action of a low-surface-energy resin (such as PTFE), the coating hydrophobicity angle is below 110 degrees, and does not show superhydrophobicity, indicating that relying only on the film-forming resin and the roughening material cannot achieve superhydrophobicity of the coating;

[0128] Figure 11 For another comparative example of the present application, the material was not pressed into tablets and crushed in advance, but was directly sprayed after dry mixing of the particles. The surface morphology of the super-hydrophobic coating prepared by direct dry mixing method can be seen that in addition to a part of MWCNTs embedded in the resin, more MWCNTs clusters are loosely and independently distributed on the surface of the coating, which is easy to be mechanically abraded and damaged. The evaluation of the abrasion resistance of the coating shows that after 80 cycles of abrasion, the WCA value of the super-hydrophobic coating is reduced to below 150°, indicating that the abrasion resistance of the coating is very poor.

[0129] To verify the application of the coating in heat pipe, the coating was also tested for high temperature and high pressure boiling resistance. After continuous high temperature and high pressure (150℃, 2.5Mpa) boiling in deionized water, the damage degree of the coating was checked. Referring to Figure 12 , the left graph is the coating of the present application (Example 2: 4wt% nano-zinc oxide fiber particles and 10wt% PFA), the upper left is the initial sample, and the lower left is the sample after boiling in high temperature and high pressure for 35 days. It can be seen from the figure that the coating has no peeling, cracking and blistering; the upper and lower middle graphs are the initial sample and the sample after boiling in high temperature and high pressure for 12 days of pure PFA coating, respectively. It can be seen that the sample after boiling has serious blistering; the right graph is an epoxy coating, which is a traditional commercial product commonly used for pipe coating, and the lower right graph is the sample after boiling in high temperature and high pressure for 6 days. It can be seen from the figure that the sample has a large number of damage and blistering. Through comparison, it can be seen that the product of the present application has excellent high temperature and high pressure boiling resistance, and has good application prospect in heat pipe.

[0130] The above description has been given for the purpose of illustration and description. Furthermore, this description is not intended to limit embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof.

Claims

1. A method for preparing a high-temperature resistant, durable, superhydrophobic powder coating, characterized in that, The method includes the following steps: (a) Solid nanomaterials, solid low surface energy materials and thermoplastic film-forming resins are dry-mixed to obtain a uniformly mixed powder; (b) The uniformly mixed powder is formed into a block material by a tableting process, wherein the pressure of the tableting process is 1-30 tons; (c) The block material is crushed and sieved to obtain solid low surface energy material, solid nanomaterial and thermoplastic film-forming resin integrated powder coating particles with a median particle size of 25-50 micrometers. (d) Thermoplastic film-forming resin powder coating particles are sprayed onto the surface of a substrate using electrostatic spraying technology, and then pre-cured to form an underlayer. The thickness of the underlayer film is 10-30 micrometers and is greater than the length of the solid nanomaterial. (e) The integrated powder coating particles are sprayed onto the surface of the substrate using electrostatic spraying technology and cured at high temperature to form a solvent-free, durable, superhydrophobic powder coating. The high temperature curing temperature is higher than the melting point of the thermoplastic film-forming resin, so that one end of the solid nanomaterial in the integrated powder coating particles is embedded in the substrate and the other end protrudes from the coating surface, forming a nanofiber bridging interface reinforcement structure.

2. The method according to claim 1, wherein, The solid nanomaterials include any of the following: oxide nanofibers, carbon-based solid nanofibers, metal solid nanofibers, and polymer solid nanomaterials.

3. The method according to claim 2, wherein, Oxide nanofibers include any of the following: silicon dioxide (SiO2), titanium dioxide (TiO2), zinc oxide (ZnO), aluminum oxide (Al2O3), and iron oxide (Fe2O3).

4. The method according to claim 2, wherein, Carbon-based solid nanofibers include any of the following: carbon nanotubes and carbon nanowires, wherein... Carbon nanotubes include multi-walled carbon nanotubes (MWCNTs).

5. The method according to claim 2, wherein, Metal solid nanofibers include any of the following: gold (Au), silver (Ag), and copper (Cu) nanofibers.

6. The method according to claim 2, wherein, Polymer solid nanomaterials include any of the following: polystyrene (PS) nanofibers, polyacrylonitrile (PAN) nanofibers, and polyaniline (PANI) nanotubes.

7. The method according to claim 1, wherein, Solid low surface energy materials include any of the following: polytetrafluoroethylene (PTFE), perfluoroalkoxyethylene (PFA), fluorinated polymers, and silicone resins; Fluorinated polymers include any of the following: perfluoroethylene propylene (FEP) and ethylene-tetrafluoroethylene copolymer (ETFE).

8. The method according to claim 1, wherein, Thermoplastic film-forming resins include special engineering thermoplastic resins, which include any of the following: polytetrafluoroethylene (PTFE), polysulfone (PSU), polyetheretherketone (PEEK), polyamide (PA), and polyimide (PI).

9. A high-temperature resistant, durable, superhydrophobic powder coating, characterized in that: The high-temperature resistant, durable, superhydrophobic powder coating is prepared by the method described in any one of claims 1 to 8.

10. The application of powder coating in thermal pipelines, characterized in that, The powder coating is the high-temperature resistant, durable, superhydrophobic powder coating as described in claim 9; The application includes the use of the high-temperature resistant, durable, superhydrophobic powder coating as an inner wall coating for a thermal pipeline, which includes a water supply section and / or a water return section.

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