Preparation and application of fluorine-free super-hydrophobic coating with excellent flame retardant properties

Abstract

The present invention belongs to the field of super hydrophobic coatings, and provides the preparation and application of fluorine-free super hydrophobic coatings with excellent flame retardancy. The extensive use of fluorine-containing chemicals, low durability, cumbersome preparation process, and difficulty in having a wide range of functions are all the main bottlenecks of currently artificially preparing super hydrophobic materials, which restricts its large-scale production and practical application. The present invention adopts a simple, fluorine-free spraying strategy, and the novel branched thiol (T-SMA and T-noSMA) prepared by ultraviolet-assisted click reaction is mixed with particles of different scales to obtain a super hydrophobic layer. Phenylphosphonic acid is added to glycidyl ether oxypropyl cage-type polyhexyloxyoxyethane (GPOSS) to achieve flame retardant effect. The coating WCA=165° has excellent self-cleaning, antifouling properties. To strong alkali, ultraviolet rays, cold and hot treatments, there is very high stability and coating also shows excellent flame retardancy, and the technology can provide a new strategy for designing durable, scalable super hydrophobic materials with special properties.

Description

Technical Field

[0001] The present invention belongs to the field of super hydrophobic coatings, and in particular relates to the preparation of a fluorine-free super hydrophobic coating with excellent flame retardant properties. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] As a medium between materials and the external environment, coatings often require regular maintenance and upkeep, but this will cause a lot of energy consumption. In order to achieve low energy consumption, the surface of the material has high requirements for self-cleaning, chemical inertness, long durability and safety. Interestingly, superhydrophobic surfaces have attracted great attention from academia and various industries in the fields of self-cleaning, oil-water separation, corrosion resistance, anti-icing, drag reduction, etc. Generally, in order to achieve low surface energy, fluorocarbon functional groups are mostly used as an important candidate material. Ma et al. proposed an efficient polyfluorination strategy to prepare superhydrophobic nanocomposites by long-chain perfluoroepoxy resin (PFEP) and tetrafluorophenyl epoxy resin (FEP). This new strategy provides an effective guide for the large-scale preparation of robust, multi-responsive, superhydrophobic and oleophobic materials. Unfortunately, due to the toxicity, bioaccumulation and persistence of long-chain fluorocarbon functional groups, they may cause a series of human health and environmental problems. Therefore, it is very ideal and necessary to use fluorine-free chemical reagents to achieve superhydrophobic coatings. In recent years, organosilanes have become a hot topic for constructing fluorine-free superhydrophobic materials due to their low cost, unique polyhedral molecular structure, and low surface energy. Zhang et al. used organosilane / Al2O3 nanoparticles (POS / Al2O3 NPs) to prepare a simple, scalable, fluorine-free, and sprayable superhydrophobic and superoleophobic coating, which has great application prospects in various fields such as self-cleaning, corrosion resistance, and scald prevention. Although fluorine-free superhydrophobic coatings can solve some problems such as self-cleaning and durability, in order to enhance the safety of the material and extend its service life, how to integrate superphobicity and flame retardancy into one is still an unresolved problem.

[0004] To date, the most effective and widely used flame retardants contain halogens and formaldehyde, but they are gradually being phased out due to their harmful effects on humans and the environment. Organophosphorus flame retardants have become an alternative due to their low smoke, low halogen, and halogen-free properties. Gu et al. deposited dopamine (PDA) onto flame-retardant cotton fabric grafted with ammonium vinylphosphonate (AMVP). The reducing activity of catechol in PDA then led to the in situ growth of antibacterial silver nanoparticles (AgNPs) on the fabric surface. Subsequently, the fabric was coated with PDMS to achieve excellent flame retardant, antibacterial, superhydrophobic, and self-cleaning properties. Barthwal et al. prepared a MWCNTs / ZnO composite using a sol-gel method, dispersing it in a PDMS solution and forming a durable coating on a substrate after PDMS polymerization. The resulting coating exhibited superhydrophobicity (WCA: 156°) and flame retardant properties, but the mechanical properties of the coating remain to be improved. Despite extensive progress in developing coatings combining superhydrophobicity and flame retardancy, most use long-chain fluorocarbons or have inherently rough substrates, such as cotton. This severely limits the safety and applicability of these coatings, and their robustness should be improved. Therefore, developing a collaborative design strategy that combines superior robustness with a broad range of functionalities, including mechanochemical strength, long-term durability, self-cleaning properties, and flame retardancy, has been a challenge to date. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a kind of preparation and application of the fluorine-free super hydrophobic coating with excellent flame retardant properties.The present invention utilizes pentaerythritol tetrakis (3-mercaptopropionic acid) ester (PETMP), glycidyl methacrylate (GMA) and octadecyl methacrylate (SMA) to introduce epoxide and long carbon hydrophobic group in same molecule by mercapto-alkene click reaction.Long alkyl chain provides lower surface energy, and after curing, epoxy group forms very strong cross-linked network, improves the bonding strength between substrate and coating, thus improves the mechanical property of coating.Phenylphosphonic acid is joined in glycidyl ether oxygen propyl cage type polyhexyloxyoxy alkane (GPOSS) and reaches flame retardant effect, and the epoxy group in GPOSS can improve the bonding strength with substrate layer and hydrophobic layer after curing.The coating has excellent antifouling performance, durability, chemical stability, anti-icing performance and flame retardant properties, can be for designing the durable, scalable super hydrophobic material with special properties to provide a new strategy.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a fluorine-free super-hydrophobic coating with excellent flame retardant properties, comprising: solvent A, solvent B, and solvent C;

[0008] The preparation method of the solvent A comprises:

[0009] GPOSS is mixed with phenylphosphonic acid and AS in a solvent and heated in a water bath for a certain period of time to obtain the product;

[0010] The preparation method of the solvent B comprises:

[0011] GMA and PETMP are mixed evenly in a solvent and cured by ultraviolet light in the presence of a photoinitiator to obtain T-noSMA;

[0012] The T-noSMA is uniformly mixed with SiO2, TiO2 and a curing agent in a solvent to obtain the product;

[0013] The preparation method of the solvent C comprises:

[0014] GMA, PETMP and SMA are mixed evenly in a solvent and cured by ultraviolet light in the presence of a photoinitiator to obtain T-SMA;

[0015] The T-SMA is uniformly mixed with hydrophobically modified SiO2 and TiO2 particles in a solvent to obtain the product.

[0016] In some embodiments, the mass ratio of GPOSS to phenylphosphonic acid is 0.16:0.24-0.28.

[0017] In some embodiments, the mass volume ratio of GPOSS to AS is 0.16 g:0.07-0.08 mL.

[0018] In some embodiments, the molar ratio of GMA to PETMP is 4:1-1.2.

[0019] In some embodiments, the mass ratio of the T-noSMA to SiO2 and TiO2 is 1:2.5-3:2.5-3.

[0020] In some embodiments, the molar ratio of GMA, PETMP, and SMA is 3:1-1.2:1-1.2.

[0021] In some embodiments, the mass ratio of the T-SMA to the hydrophobically modified SiO2 and TiO2 particles is 1.25:0.8-0.9.

[0022] In some embodiments, the photoinitiator is DMPA;

[0023] In some embodiments, the curing agent is 2-methylimidazole.

[0024] A second aspect of the present invention provides a fluorine-free super-hydrophobic coating having excellent flame retardant properties prepared from the above-mentioned fluorine-free super-hydrophobic coating, comprising, from bottom to top:

[0025] The bottom layer is solidified from solvent A;

[0026] The middle layer is obtained by solidification of solvent B;

[0027] The top layer is solidified from solvent C.

[0028] In some embodiments, the substrate material is selected from copper sheet, aluminum sheet, cardboard, wood, and glass.

[0029] The third aspect of the present invention provides the use of the above-mentioned fluorine-free super-hydrophobic coating in improving the mechanical properties, corrosion resistance, flame retardancy, anti-icing / de-icing properties, thermal insulation properties, and durability in extreme environments of the substrate.

[0030] Beneficial effects of the present invention

[0031] (1) The present invention uses PETMP, GMA and SMA to trigger a click reaction under ultraviolet irradiation, and successfully prepares T-SMA and T-noSMA. Due to the addition of micro-nanoparticles, the coating has excellent superhydrophobic properties, and its maximum contact angle is 165°. The addition of phosphorus-containing substances in GPOSS makes it have outstanding flame retardant properties. The two interact with each other, and a multifunctional coating that combines fluorine-free superhydrophobicity and flame retardancy is successfully prepared by a simple spraying method. The coating can act on different substrates and shows good self-cleaning properties in a series of anti-fouling experiments. In addition, the coating still has excellent durability after a series of mechanical stresses (up to 4000 sand insertion tests; 600 tape peelings; 250 Taber wear tests; 7 hours of ultrasonic cycles). The chemical stability of the coating was demonstrated by immersion in different pH solutions and organic solutions and corrosion under harsh acetate mist conditions. The coating also shows excellent performance in de-icing / anti-icing. The present invention can provide a new strategy for designing durable and scalable superhydrophobic materials with special properties.

[0032] (2) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 .(a) Infrared spectrum of T-noSMA; (b) 1H-NMR spectrum of T-noSMA; (c) SEM image of the coating surface; (d) SEM image and energy spectrum of the coating cross section.

[0035] Figure 2.(a) Schematic diagram of the contact angle of water droplets on different substrates; (b) Contact angles of water droplets on different substrates; (c) Schematic diagram of the contact angles of different liquids on the same substrate; (d) Contact angles of different liquids on the same substrate; (e) Bouncing of droplets on a superhydrophobic surface; (f) Schematic diagram of self-cleaning; (g) Schematic diagram of immersion cleaning.

[0036] Figure 3 .(a) Adhesion test on different substrates; (b) Sand insertion test; (c) Tape peeling test; (d) Taber abrasion test; (e) Ultrasonic test; (f) Schematic diagram of contact angles after immersion in different solvents.

[0037] Figure 4 (a) Ice adhesion test on different substrates; (b) Anti-icing test on original and coated aluminum sheets; (c) Schematic diagram of the anti-icing test on original and coated aluminum sheets; (d) Time-lapse image of the freezing process of droplets on original and coated aluminum sheets.

[0038] Figure 5 .(a) Heat release rate of original PU and coated PU; (b) Total released heat of original PU and coated PU; (c) Effective combustion heat of original PU and coated PU; (d) Specific extinction area of ​​original PU and coated PU; (e) Schematic diagram of combustion of wooden house model and coated wooden house.

[0039] Figure 6 .(a) Temperature difference during heating; (b) Schematic diagram of contact angle under different external environments; (c) Actual photos of the original copper sheet and the coated copper sheet after 100 hours of CASS test; (d) Tafel polarization curve of CASS corrosion experiment; (e) EIS curve of CASS corrosion experiment.

[0040] Figure 7 .Schematic diagram of the preparation process of the super hydrophobic coating of the present invention.

[0041] Figure 8 .Infrared spectra of hydrolyzed SiO2 before and after modification.

[0042] Figure 9 .(a) Infrared spectrum of T-SMA; (b) 1H NMR spectrum of T-SMA; (c) Structural formulas of reactants and products (GMA; PETMP; SMA; T-noSMA; T-SMA).

[0043] Figure 10 .Schematic diagram of handheld thrust gauge de-icing.

[0044] Figure 11 WCA (a) and WSA (b) of the coating after immersion in different pH environments for 45 h. DETAILED DESCRIPTION

[0045] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0046] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0047] In the following examples, the materials and reagents used are as follows:

[0048] Titanium dioxide (0.1-0.3 μm), phenylphosphonic acid, tetraethyl orthosilicate (TEOS), octadecyl methacrylate (SMA), hexadecyltrimethoxysilane (HDTMS), glycidyl methacrylate (GMA), 2-methylimidazole, dimethyl benzoate (DMPA), N-aminoethyl-γ-aminopropyltrimethoxysilane (AS), and pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) were provided by Shanghai MacLean Biochemical Co., Ltd. Nanosized titanium dioxide (10-25 nm, 100 nm) and silicon dioxide (5 μm) were purchased from Aladdin Reagent Co., Ltd. Glycidyloxypropyl caged polysilsesquioxane (GPOSS) was purchased from Guangzhou Yixin Technology Co., Ltd. Anhydrous ethanol (EtOH), ammonia, sodium hydroxide, and tetrahydrofuran were provided by Sinopharm Chemical Reagent Co., Ltd. Sand and the wooden house model were purchased from a local store. All chemicals were of analytical grade and used as received without further purification.

[0049] Example 1 Hydrophobic modification of particles

[0050] In a round-bottom flask, EtOH (8.33 mL), TEOS (0.3 mL), HDTMS (3.6 mL), ammonia water (0.75 g) and deionized water (0.33 g) were mixed evenly, and TiO2 of different particle sizes (mass ratio of 1:1) was added. The mixture was stirred at room temperature for 11 h, and the hydrophobically modified particles were obtained after centrifugal drying and grinding.

[0051] Example 2 Preparation of novel branched thiols (T-noSMA) and alkylated thiols (T-SMA).

[0052] GMA and PETMP were mixed in a molar ratio of 4:1, and tetrahydrofuran (THF) with the same mass as the reactants was added. The mixture was ultrasonicated for 10 min, and 0.001 mol of initiator DMPA was added. The mixture was UV-cured for 1 h to obtain T-noSMA.

[0053] GMA, PETMP, and SMA were mixed in a molar ratio of 3:1:1, and tetrahydrofuran (with the same mass as the reactants) was added. The mixture was ultrasonicated for 10 min, and 0.001 mol DMPA was added. The mixture was UV-cured for 1 h to obtain T-SMA.

[0054] Example 3 Preparation of superphobic flame retardant coating

[0055] Bottom layer: 0.16 g GPOSS was dissolved in 1 mL EtOH by ultrasonication. After 10 min, 0.24 g phenylphosphonic acid and 0.07 mL AS were added. The mixture was incubated in a water bath at 60°C for 30 min to obtain the final uniform solution A.

[0056] Middle layer: 0.1 g T-noSMA and THF were ultrasonically mixed at a mass ratio of 1:4, 0.25 g SiO2, 0.25 g TiO2 and 0.0005 g curing agent 2-methylimidazole were added, ultrasonicated for 10 min, and stirred for 30 min to obtain the final uniform solution B.

[0057] Top layer: 1.25 g T-SMA and 5 g THF were ultrasonically mixed, and then 0.8 g hydrophobically modified particles were added and stirred for 30 min to obtain the final uniform solution C.

[0058] Use a spray gun to spray the coating onto horizontal substrates such as glass slides, aluminum sheets, and wood. First, apply 3 mL of the A solution and cure at 45°C for 1 hour. Similarly, apply 5 mL of the B solution and cure at 80°C for 30 minutes. Remove the coating and apply 5 mL of the L solution. Dry in a 120°C oven for 8 hours to obtain the final coating.

[0059] Example 4 Characterization

[0060] 1 Mechanical properties characterization

[0061] Taber abrasion test: Robustness evaluation was performed using a Taber abrasion tester according to ASTM standard test (D4060). The grinding wheel was subjected to a 250g load and the wear test was performed on a coated glass substrate with a diameter of 10cm.

[0062] Strong tape peel test: Attach strong tape to the coating surface, roll a 200g weight back and forth, then grasp one end of the tape and quickly pull it apart. This process constitutes one cycle, and the tape is replaced every 10 times. The coating is then tested for contact angle.

[0063] Gravel drop test: Using 30g of sand particles with a diameter of 0.2-0.6mm, the prepared super-hydrophobic coating was subjected to a falling sand test from a height of 20-100cm. The substrate was held at a 45° angle to the horizontal surface, and the falling sand time was controlled to less than 1 minute. The durability of the coating depends on the volume of sand particles per unit area of ​​the impact surface, the impact time, the particle size, and the free fall height. The impact energy of sand particles (0.2-0.6mm) on super-hydrophobic coatings at different heights can be calculated as:

[0064]

[0065]

[0066] Put1into2

[0067]

[0068] Where m is the mass of the sand grain (kg). ρ is the density of the sand grain (1600 kg / m³). v is the velocity of the falling sand grain (m / s). D is the diameter of the sand grain (m). g is the acceleration due to gravity (9.8 m / s²). h is the height of the sand grain from the coating. In this paper, we use an average value of D of 0.4 mm to calculate the impact energy of the sand on the coating.

[0069] 2 Corrosion resistance test

[0070] Copper accelerated acetic acid salt spray (CASS) test: First, prepare a neutral corrosion solution containing 5wt% NaCl, add an appropriate amount of glacial acetic acid to adjust the pH value to about 3, and add an appropriate amount of anhydrous copper chloride (concentration: 0.26g·L -1 (ASTM B368) induced strong corrosion. The test temperature was 50 ± 1°C. The coating and the control coating were placed in a salt spray corrosion tester (Dongguan Lester Equipment Co., Ltd.) and their corrosion status was observed after different time periods.

[0071] Electrochemical measurements: Electrochemical measurements of the coatings were performed in a copper-accelerated acetate mist environment. Electrochemical measurements were performed using a CHI660D electrochemical workstation (Chenhua, Shanghai, China) at a stable open-circuit voltage. The working electrode was a 10 cm × 10 cm sample of the coated metal. The counter electrode was platinum, and the reference electrode was a Hg / Hg2SO4 electrode. The polarization curve scan rate was 1 × 10 -3 V / s, frequency range is 10 -2 Hz-10 5 Hz, the sinusoidal signal perturbation is 5×10 -3 mV. Each test was repeated three times or more to ensure the accuracy of the experimental results.

[0072] 3 Characterization of flame retardant properties

[0073] The limiting oxygen index experiment was conducted using a British FTT0077 oxygen index meter. The sample size was 80 mm × 10 mm × 4 mm, and the test standard was ASTM D2863.

[0074] The cone calorimeter test used a British FTT0007 cone calorimeter with a sample size of 100 mm × 100 mm × 4 mm and a radiation intensity of 25 kW·m -2 , in accordance with ISO5660 standard.

[0075] 4. Characterization of anti-icing / de-icing performance

[0076] Anti-icing: The entire test was conducted in a refrigerated cycler. Both pristine and coated aluminum sheets were placed in the refrigerated cycler at a 3° inclination. The initial temperature was 0°C. 2 ml of water was dripped onto the sample for each 10°C decrease until the temperature reached -70°C. Each temperature was maintained for 30 minutes to allow the deionized water to completely freeze, and the ice on the surface was then weighed.

[0077] De-icing: Fill the PDMS mold (1cm×1cm) on the surface to be tested with water and freeze it in a -20°C low-temperature chamber for more than 5 hours to ensure complete freezing. After removing the soft PDMS mold, place a square flat surface (1cm diameter) force probe parallel to the surface to be tested. During the test, continue to apply external force until the ice cube is completely moved, thereby obtaining the peak force required to remove the ice cube. The ice adhesion force is calculated as follows:

[0078]

[0079] Where τ is the adhesion force of ice (Pa), F is the force required to remove ice (N), and A is the contact area between ice and the measured surface (m 2 ).

[0080] 5 Characterization of thermal insulation performance

[0081] The invention uses an alcohol burner as a flame source, places the coated aluminum sheet and the original aluminum sheet on an iron ring respectively, and contacts the outer flame. During the heating process, the invention uses a thermocouple thermometer to measure the temperature, and finally uses infrared thermal imaging to observe the final temperature.

[0082] 6 Other performance characteristics

[0083] The surface wettability of different samples at room temperature was determined using a KRüSS SDSA25S (KRüSS, Germany) contact angle system. Static contact angle / rolling angle measurements were performed using a ~4 μL water droplet. Each sample was tested three times at different locations, and the average was calculated. SEM observations were performed using a SUPRA TM55 Thermal Field Emission Scanning Electron Microscopy (Zeiss, Germany). After spraying and curing on a glass substrate, the sample was quenched with liquid nitrogen and characterized on different surfaces and cross sections. Fourier transform infrared (FTIR) spectroscopy was performed using a Thermo Scientific Nicoleti S20 for infrared characterization, and each test was repeated 3 times to ensure the accuracy of the experimental results. Infrared thermal imaging observations were performed using a handheld UT1160H thermal infrared imager (UNI-T, China). Thermal infrared images were all taken continuously at a fixed distance. The droplet bouncing was captured using a WDW-02 high-speed camera (Ametek Corporation).

[0084] Experimental Example 1

[0085] Based on the coatings prepared in the above embodiments and the related performance test results, it can be seen that low surface energy materials and rough micro-nano structures are two necessary conditions for preparing super-hydrophobic materials. In the present invention, the bottom layer, middle layer and top layer respectively use GPOSS, T-noSMA and T-SMA as the matrix, octadecyltrimethoxysilane (SMA) long alkyl chain to provide low surface energy, SiO2 and TiO2 particles of different particle sizes are used as fillers to construct a rough micro-nano structure. By regulating the chemical composition of the three layers, different functions are concentrated in one. Figure 7 shown.

[0086] 1 Chemical characterization and surface morphology analysis of coatings

[0087] 1.1. Characterization of hydrophobic modification of silica

[0088] FTIR was used to analyze the functional group changes of hydrolyzed SiO2 before and after modification. The results are as follows: Figure 8 As shown. nano-SiO2, HDTMS and HDTMS-nano-SiO2 at 800cm -1 and 1100cm -1 There are absorption peaks at 3450cm, which are the antisymmetric and symmetric contraction vibration peaks of Si-O-Si bond. -1 At 1467 cm, both HDTMS-nano-SiO2 and nano-SiO2 have absorption peaks. These peaks are attributed to the stretching vibration peaks of the silanol groups on the surface of SiO2 particles. The absorption peak of HDTMS-nano-SiO2 is slightly weaker than that of hydrolyzed SiO2, which proves that the surface hydroxyl groups of HDTMS-nano-SiO2 are relatively reduced and have been successfully modified. Compared with the unmodified hydrolyzed SiO2, the absorption peaks at 2925, 2854 and 1467 cm -1Three new absorption peaks appeared at , representing the stretching vibrations of -CH3, -CH2 and CO bonds, indicating that the HDTMS hydrophobic alkyl chain was successfully grafted onto the hydrolyzed SiO2 surface.

[0089] 1.2. Characterization of novel branched thiols (T-noSMA) and alkylated thiols (T-SMA)

[0090] T-noSMA and T-SMA are prepared via thiol-ene click chemistry. The initiator DMPA cleaves under UV light to form free radicals, which then abstract hydrogen atoms from thiol groups, generating thiol radicals. These thiol radicals attack the carbon-carbon double bond, shifting the active center and generating alkyl radicals. These alkyl radicals then abstract hydrogen atoms from thiol compounds, generating further thiol radicals, thus entering the cycle. The thiol radicals generated in this second step can either initiate chain growth or react with free radicals to terminate the chain.

[0091] like Figure 1 As shown in a, in the infrared spectrum of T-noSMA, 1730 cm -1 The peak at 2574cm is the C=O stretching vibration of the ester group. -1 The absorption peak of the product is weaker than that of PETMP. In addition, the peak of C=C bond in GMA is at 1636cm -1 disappeared at 907 cm -1 There is a relatively weak absorption peak at , which is caused by the epoxy group, which indicates that it is successfully grafted. For the infrared spectrum of T-SMA, such as Figure 9 As shown in a, 1636cm -1 The characteristic peak of C=C double bond belonging to SMA disappears, which also proves that SMA has successfully modified PETMP.

[0092] Figure 1 Figure b shows a typical reaction between the reactants and T-noSMA. 1 H-NMR spectrum. In the GMA spectrum, signals for vinyl end groups were observed at 5.6-6.2 ppm. After the reaction, the 5.6-6.2 ppm signal disappeared, while the peak intensity of the methylene protons at 2.5-2.9 ppm increased. Furthermore, the signal for the methyl protons near the terminal double bond of GMA, previously observed at 2.0 ppm, changed quantitatively at 1.2 ppm, indicating a change in the chemical state of the methyl protons.

[0093] In the GMA spectrum, two proton peaks of vinyl end groups were observed at 5.6 and 6.2 ppm. After the reaction, the proton peak disappeared, indicating that GMA and PETMP reacted successfully. At the same time, in the nuclear magnetic resonance spectrum of the product, it was found that the methylene proton peak at 2.5-2.9 ppm increased in number compared to GMA and PETMA. This is because a large number of methylene groups are formed after the double bond reaction, further indicating that the reaction was successful. In addition, by comparing the proton peak (Hm) of the product and GMA at 2.0 ppm, it can be found that the proton peak of the product moves to a high field compared to GMA. This is because in GMA, the methyl group where Hm is located is next to the double bond. After the successful reaction, the double bond next to Hm disappears, resulting in an increase in the electron cloud density of the methyl group where Hm is located, and the proton peak of the methyl group moves to a high field. These changes in proton peaks indicate the successful reaction of GMA and PETMP.

[0094] exist Figure 9 Representative 1H-NMR spectra of the reactants and T-SMA are shown in panel b. In the SMA spectrum, a signal indicating a vinyl end group is observed at 5.4-6.1 ppm, which disappears after the reaction. These data demonstrate that GMA and SMA modified PETMP via a thiol-ene click reaction, successfully synthesizing the designed T-noSMA and T-SMA.

[0095] 1.3. Superhydrophobic surface morphology and structure analysis

[0096] The key to constructing a super-hydrophobic coating lies in the multi-scale structure of the surface. In the process of design and preparation, the top layer uses alkylated particles to provide roughness, and the alkylated T-SMA is coated on the surface of the rough structure, providing protection for it and adhesion to the middle layer. The middle layer of the present invention uses nano-scale SiO2 and micron-scale TiO2 as fillers, so that it plays the role of a rough substrate. The filler ratio of its particles affects the size of the contact angle of the top layer, as shown in Table 1. When the particle content is 40% and 50%, the coating reaches super-hydrophobicity, but at 50%, it can withstand 250 wears (Taber wear machine 250g load), and when the particle content increases, it affects the spraying effect, so the particle content of 50% is finally selected. The surface morphology of the coating under different magnifications is shown in Figure 1. Figure 1 As shown in Figure c, the SEM image shows that a large number of coating particles cover the substrate and it is very rough.

[0097] Table 1. Effect of middle layer particle filler on super hydrophobicity of coating

[0098]

[0099] Overall, the present invention adopts a step-by-step and layered preparation strategy to construct a three-layer super-hydrophobic structure. The present invention performs SEM and EDS energy spectrum analysis on its cross section, as shown in FIG. Figure 1As shown in (d), the cross-section of the coating clearly reveals its layered structure, with a bottom layer, middle layer, and top layer. Because both the top and middle layers contain significant amounts of SiO₂ and TiO₂, and both T-noSMA and T-SMA are essentially composed of C, S, and O, there's no clear boundary between the top and middle layers. However, phosphorus, a key component of phenylphosphonic acid, is concentrated in the bottom layer, allowing the present invention to clearly identify the boundary between the bottom and middle layers. However, due to solvent evaporation, a small amount of phosphorus may have been carried over and migrated to the middle and upper layers, resulting in some distribution in the upper layer.

[0100] Because the present invention utilizes a three-layer design, interlayer adhesion is crucial. The base layer utilizes GPOSS as its primary component, with AS as its curing agent. Because the coating contains numerous epoxy groups, a highly cross-linked network is formed through a ring-opening reaction with -NH2. Furthermore, -NH- and other groups can form multiple hydrogen bonds with the substrate. Furthermore, the active Si-OH groups, generated by the hydrolysis of Si-O-CH3 in AS, can condense with -OH groups on the substrate surface to form -Si-OM (where M represents the surface of the substrate). This dual effect ensures the coating's high adhesion to a variety of substrates. The middle layer utilizes T-noSMA as its primary matrix, also containing numerous epoxy groups. This layer forms a highly cross-linked network through a ring-opening reaction with 2-methylimidazole, forming numerous hydrogen bonds with the base layer. Furthermore, since T-noSMA itself possesses a certain degree of adhesiveness, a certain degree of physical cross-linking is also present. The top layer exhibits the same adhesion properties as the middle layer, except that long alkyl chains are grafted onto it to provide a low surface energy. This analysis demonstrates the coating's excellent mechanical durability.

[0101] 2 Superhydrophobicity of coating

[0102] The above analysis proves that the super-hydrophobic coating was successfully prepared. Due to the advantages of its spraying and the specially designed chemical structure, the present invention has the potential for large-scale production and the general ability of the substrate. The reported composite coating is applicable to various material surfaces, including copper sheets, aluminum sheets, cardboard, wood, glass, etc., and all sample surfaces are converted from hydrophilic to super-hydrophobic (such as Figure 2 The present invention explores the applicability of the coating, as shown in a and b. Figure 2 As shown in c and d, six different liquid droplets, including acid, alkali, coffee, tea, milk, and juice, were dropped on the substrate respectively. The results showed that all liquids remained spherical on the surface, exhibiting excellent hydrophobic properties.

[0103] Droplet bouncing is also an important indicator of superhydrophobic performance. Traditional droplet bouncing behavior mainly includes four stages: impact, spreading, contraction and bouncing. The present invention releases a 6μL droplet from a height of 6cm, t s is the spreading time, tr is the retraction time, and the gravitational potential energy of the droplet is gradually converted into kinetic energy during the falling process, such as Figure 2 As shown in Figure e, at t = 0ms, the droplet hits the surface. At this time, the kinetic energy stored in the droplet overcomes the viscous force and spreads. s =8ms, the droplet reaches its maximum spreading state, at which time the droplet diameter is the maximum spreading diameter Dmax. Subsequently, the surface energy released by the superhydrophobic droplet is converted into kinetic energy, overcoming the surface adhesion effect to induce the droplet to retract and bounce, and the droplet finally reaches t r =Leave the contact surface at 33ms.

[0104] Generally, superhydrophobic surfaces have excellent antifouling properties, which is one of the most critical properties of a material. Figure 2 Figure f simulates the process of water droplets washing away dirt. When the droplets roll down the inclined superphobic surface, they carry away the dirt particles. Compared to glass, the dirt remains on the surface. In addition, the coating was soaked in a mud-water mixture for a few seconds and then removed. The surface of the sample remained clean after soaking ( Figure 2 (g) This is because the hierarchical micro-nanostructure of the superhydrophobic surface creates a stable air layer between the coating surface and the droplets, which can reduce the actual contact area and adhesion between the liquid and the coating surface.

[0105] 3 Mechanical / chemical durability

[0106] Although superhydrophobic materials have been widely reported, their poor mechanical / chemical durability has always been a key obstacle to their further development. Therefore, it is necessary to evaluate the durability of coating samples to ensure their stability in various application scenarios. Here, the present invention tests the mechanical durability and chemical stability. First, good adhesion of the coating to the substrate contributes to durability and stability, so the adhesion strength between the coating and the substrate is accurately measured by a pull-out adhesion tester. Figure 3 In a, the adhesion of the test sample on glass can reach 2.23MPa, on wood it is 1.872MPa, and on aluminum sheet it is 0.673MPa. These data results prove that the super hydrophobic coating can adhere well to the substrate. In terms of mechanical durability, the present invention carried out sand insertion experiment, tape peeling test, Taber test and falling sand experiment. Due to the stable chemical bonding between the components of the coating system, and the strong adhesion of T-SMA and T-noSMA, the test sample has good mechanical durability. The present invention inserts the coating into sand particles with an average diameter of 0.4mm at a speed of 500mm / min on a universal mechanical testing instrument and then pulls it out, and cycles it, such as Figure 3In b, the super hydrophobicity of the test sample is still maintained above 150° after 3500 cycles, and water droplets can still stand stably on the surface after 4000 cycles. The present invention selects a 200g load to conduct a tape peeling test on the coating. Figure 3 In Figure c, the coating still has good water repellency after 600 peeling cycles. According to the American Society for Testing and Materials (ASTM) standard, the mechanical properties of the coating were characterized using a Taber abrasion tester. Figure 3 As shown in Figure d, the coating remains above 150° after 200 cycles under a load of 250g. After 250 cycles, the WCA is 149.377°, and water droplets can still roll off the coating. The present invention uses sand particles weighing 30 grams and with a diameter of 0.2-0.6mm to conduct a falling sand test on the prepared super-hydrophobic coating from a height of 20-100cm. The substrate is kept at 45° relative to the horizontal surface, and the falling sand time is controlled within 1min. When the falling sand impact height is 100cm, the WCA of water in the coating is 155.532°, and the impact energy of the sand on the coating is 5.25×10 -7 J, indicating that the coating still exhibits excellent superhydrophobic properties.

[0107] The chemical stability of the coating was studied by ultrasonic tests and solution immersion tests. Figure 3 As shown in Figure e, the coating still has excellent superhydrophobicity after 7 hours of ultrasonic treatment. Solution immersion experiments show that the coating still has excellent superhydrophobicity after being immersed in various organic solvents for 10 days ( Figure 3 (f) The excellent chemical stability can be attributed to the highly cross-linked network formed by the ring-opening reaction of T-noSMA and T-SMA, which helps to maintain the stability of the structure.

[0108] 4. De-icing / anti-icing performance

[0109] Superhydrophobic surfaces, characterized by high contact angles and low sliding angles, have broad application prospects in deicing and anti-icing. The deicing and anti-icing properties of the prepared superhydrophobic coating were evaluated through three experimental phases: ice adhesion strength testing, frozen water repellency testing, and icing delay time testing.

[0110] For materials that are exposed to low temperature environments for a long time, ice accumulation on their surfaces is inevitable. Therefore, whether the accumulated ice can be removed quickly and easily from the surface is one of the indicators to measure whether the coating material is suitable for use in low temperature environments. Here, the present invention uses the adhesion of ice on the surface of the material to measure. The present invention uses a PDMS mold to freeze ice cubes of a specific size on the surface of the coated and untreated substrate, and measures the peak force required to remove the ice cubes using a handheld thrust meter, such as Figure 10 .

[0111] And the adhesion force of ice cubes on different samples is calculated according to the formula, such as Figure 4 In Figure a, for the untreated aluminum sheet, ice adheres tightly to the surface, with an adhesion strength of nearly 353.3 kPa. In contrast, the ice adhesion strength of the coated sheet is only 51.6 kPa, which is only 1 / 7 of the adhesion strength. Similarly, other coated substrates (wood, glass, and copper) also show lower ice adhesion strength compared to untreated substrates. In particular, for the wood substrate, the adhesion of the coated ice is much lower than that of the untreated substrate. This can be attributed to the air pockets between the micro-nanostructures of the superhydrophobic surface. When force is applied to remove ice, these air pockets act as stress concentration points, reducing the adhesion strength.

[0112] For coatings that are placed in low temperature environments for a period of time, anti-icing performance is particularly important. The freezing water repellency test is a good indicator of the anti-icing effect of the coating. Figure 4 As shown in b and c, the present invention uses aluminum sheets as the base material, and both the coated and untreated aluminum sheets are placed in a refrigeration cycler at an inclination angle of 3°. The test temperature range is set to 0°C to -70°C, and the mass of ice accumulated on the sample surface by 2mL of water is recorded every time the set temperature drops by 10°C to explore the anti-icing performance of the coating at different temperatures. It can be seen that there is almost no ice on the surface of the coating before -20°C, but compared with the aluminum sheet, ice gradually forms on the surface within a few minutes. As the temperature decreases, the mass of ice continues to increase, and 2.1384g of ice accumulates on the ordinary aluminum sheet. In contrast, under the same conditions, only 0.5633g of ice accumulates on the surface of the coating. This is because some water can detach from the surface of the coating before the heat at the contact interface is completely dissipated. The freezing water repellent experiment confirms that the superhydrophobic coating can repel dynamic water droplets and prevent freezing.

[0113] It is well known that when a coating is placed horizontally in a low-temperature environment, water droplets stay on the surface and eventually turn into ice. Therefore, the ability to delay the freezing time is also an important evaluation criterion for anti-icing materials. Using an Al sheet as the substrate, the ambient temperature was set to -20°C, and 5μL water droplets were placed on the surface of the untreated and coated Al sheet and monitored. Figure 4 As shown in middle d, initially, the water droplet remains transparent. Subsequently, the nucleation process begins, and the droplet gradually changes from transparent to a translucent ice-water mixture. Finally, the water droplet completely solidifies and turns white. The water droplet on the coating is completely frozen after 277s, and the freezing time is delayed by about 3 times compared with the untreated Al plate. This result is mainly attributed to the heat transfer process between the coating and the water droplet. Due to the layered micro-nanostructure of the superhydrophobic surface, a large number of air pockets are formed between the surface and the water droplet, which not only reduces the contact area between the liquid and the solid, but also acts as a heat transfer barrier, slowing down heat transfer and prolonging the freezing time.

[0114] 5. Flame retardant properties

[0115] In addition to excellent removal / icing performance, the super hydrophobic coating prepared by the present invention also has good flame retardant properties. This is necessary to ensure safety in extremely hot and dry conditions, and can also reduce the severity of the fire or give people more time to escape the fire. In order to study the flame retardancy of the coating, the limiting oxygen index (LOI) of the original polyurethane (PU) and the coated PU was measured by cone calorimeter and quantitatively characterized. The limiting oxygen index of the original PU is about 22.5%, and the limiting oxygen index of the coated PU is about 26.8%, both higher than the original PU. It is almost flame retardant. From Figure 5 As can be seen in Figure a, the peak heat release rate (pkHRR) of PU after coating is about 143.77kW·m -2 , compared with the original PU’s 205.98kW·m -2 Compared with the pkHRR, the pkHRR decreased by 30.2%. At the same time, the heat release rate (HRR) of the coated PU is generally at a low level, proving that the coated PU can effectively inhibit heat release. Figure 5 As shown in Figure b, the total heat release (THR) data also shows that the THR of the coated PU is only 1 / 4 of the original PU, and has good flame retardant properties.

[0116] In addition, the effective heat of combustion (EHC), specific extinction area (SEA) and toxic gas release of CO and CO2 were measured. Figure 5 As can be seen in Figure c, the peak EHC of the coated PU is 44.68MJ / kg, which is 47.04% lower than the 84.38MJ / kg of the original PU, indicating that the combustion degree of volatile gases in the gas phase flame is reduced. As a data parameter to measure the amount of smoke generated during the combustion process, the extinction area is compared for monitoring. Figure 5 It can be seen from Figure d that the amount of smoke produced by the coated PU is reduced by 45.53% compared with the original PU. During the combustion process, the release rates of CO and CO2 of the coated PU reach the highest at around 25s and 35s, and then gradually decrease. Compared with the original PU, the CO and CO2 release rates of the coated PU are reduced by about 45.66% and 39.59%, respectively. In order to observe the flame retardant effect more directly, the present invention sprayed the cabin model (18.1cm×13.1cm×13.5cm) and ignited it with a spray gun. Figure 5As can be seen in Figure e, the original cabin model was quickly and completely consumed, gradually reducing to ash. Apparently, the coated cabin was difficult to ignite and quickly extinguished after ignition, leaving behind a complete charred layer. The improved flame retardancy of the prepared coating is primarily due to the inclusion of a flame retardant in its base layer. Phenylphosphonic acid decomposes upon heating to form orthophosphoric acid, which generates phosphorus oxide radicals (PO·) and benzene radicals in the gas phase. The released phosphorus radicals are more effective at capturing H· and HO· radicals, inhibiting the combustion reaction. The orthophosphoric acid, upon dehydration, forms a char layer that isolates oxygen and improves the thermal stability of the coating.

[0117] 6Durability in extreme environments

[0118] The practical application of coatings involves various operating environments. An ideal super-hydrophobic coating should be able to withstand harsh operating conditions, such as extreme temperatures, corrosive liquid environments, and ultraviolet radiation. First, a heat insulation test is performed. After heating the original Al sheet and the coated Al sheet for 5 minutes, the temperature of the coated Al sheet is always lower than that of the Al sheet. Figure 6 As shown in (a), the prepared coating has good thermal insulation properties. In addition, after immersion in different pH environments for 45 hours, the WCA of the coating sample only slightly decreased, and the WSA slightly increased. ( Figure 11 In addition, the durability under various external environments was evaluated, such as exposure to extreme temperatures (-40°C and 400°C), UV radiation, Figure 6 Figure b shows that the WCA and WSA of the coating material remained almost unchanged after 12 h of exposure.

[0119] In order to simulate a more severe corrosion environment, the present invention combines the copper ion accelerated acetate spray (CASS) test to evaluate the corrosion resistance of the coating. Figure 6 As shown in Figure c, after 100 hours, the original copper sheet was partially corroded, while the coated copper sheet remained in good condition, indicating its protective effect on the base material. Combined with electrochemical testing, the Tafel polarization curve and Nyquist curve were used to further evaluate the corrosion resistance of the coating. Tafel polarization is a commonly used electrochemical method in corrosion systems. Generally speaking, the greater the corrosion potential (Ecorr), the more difficult it is for corrosion to occur. The lower the corrosion current density (Icorr), the slower the surface corrosion rate. Figure 6 As shown in middle d, after spraying the coating on the original Cu sheet, Ecorr increased from -0.63V to -0.243V, and Icorr increased from 0.001841A / cm 2 Down to 0.000719cm 2 This shows that the copper sheet protected by the coating has stronger corrosion resistance. After 100 hours of CASS test, the copper sheet Ecorr dropped to -1.02V and Icorr increased to 0.003943A / cm 2, while the Ecorr of the coated copper sheet dropped to -0.534V and Icorr increased to 0.001087A / cm 2 , indicating that the coating can effectively prevent metal surface corrosion. Figure 6 From the Nyquist curve in Figure f, we can see that the arc radius of the coated copper is much larger than that of the original copper, indicating that the corrosion resistance of the coated copper is higher than that of the original copper. After 100 hours of corrosion, the impedance of the original copper sheet dropped to 2.31Ω·cm -2 , and the impedance of the coated copper sheet is 23.2Ω·cm -2 , which is significantly higher than that of the original copper sheet, indicating that the coating has good corrosion resistance.

[0120] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A fluorine-free super hydrophobic coating with excellent flame retardant properties, characterized in that, include: Solvent A, solvent B, solvent C; The preparation method of the solvent A comprises: Glycidyl ether oxypropyl cage-type polyhexyloxyoxyethane GPOSS is mixed with phenylphosphonic acid and N-aminoethyl-γ-aminopropyltrimethoxysilane AS in a solvent and heated in a water bath for a certain period of time to obtain; The preparation method of the solvent B comprises: Glycidyl methacrylate (GMA) and pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) were mixed evenly in a solvent and cured by ultraviolet light in the presence of a photoinitiator to obtain T-noSMA. The T-noSMA is uniformly mixed with silicon dioxide SiO2, titanium dioxide TiO2 and a curing agent in a solvent to obtain; The preparation method of the solvent C comprises: Glycidyl methacrylate (GMA), pentaerythritol tetrakis (3-mercaptopropionate) PETMP and octadecyl methacrylate (SMA) are mixed uniformly in a solvent and cured by ultraviolet light in the presence of a photoinitiator to obtain T-SMA. The T-SMA is uniformly mixed with hydrophobically modified silicon dioxide SiO2 and hydrophobically modified titanium dioxide TiO2 particles in a solvent to obtain; In the coating prepared by the fluorine-free super-hydrophobic coating with excellent flame retardant properties, solvent A is cured to form a bottom layer, solvent B is cured to form a middle layer, and solvent C is cured to form a top layer.

2. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The mass ratio of the glycidyl ether oxypropyl cage-type polyhexyloxyoxyethane GPOSS to phenylphosphonic acid is 0.16:0.24-0.

28.

3. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The mass volume ratio of the glycidyl ether oxypropyl cage-type polyhexyloxysilane GPOSS to N-aminoethyl-γ-aminopropyltrimethoxysilane AS is 0.16 g:0.07-0.08 mL.

4. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The molar ratio of glycidyl methacrylate (GMA) to pentaerythritol tetrakis (3-mercaptopropionate) PETMP is 4:1-1.

2.

5. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The mass ratio of the T-noSMA to silicon dioxide SiO2 and titanium dioxide TiO2 is 1:2.5-3:2.5-3.

6. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The molar ratio of glycidyl methacrylate (GMA), pentaerythritol tetrakis (3-mercaptopropionate) PETMP, and octadecyl methacrylate (SMA) is 3:1-1.2:1-1.

2.

7. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The mass ratio of the T-SMA to the hydrophobically modified silicon dioxide SiO2 and hydrophobically modified titanium dioxide TiO2 particles is 1.25:0.8-0.

9.

8. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The photoinitiator is dimethyl benzoate DMPA.

9. the fluorine-free super hydrophobic coating with excellent flame retardant properties as claimed in claim 1, is characterized in that, The curing agent is 2-methylimidazole.

10. The fluorine-free super-hydrophobic coating with excellent flame retardant properties prepared from the fluorine-free super-hydrophobic coating according to any one of claims 1 to 9, characterized in that From bottom to top, it includes: The bottom layer is solidified from solvent A; The middle layer is obtained by solidification of solvent B; The top layer is solidified from solvent C.

11. The fluorine-free super-hydrophobic coating with excellent flame retardant properties according to claim 10, characterized in that: The base material is selected from copper sheet, aluminum sheet, cardboard, wood, and glass.

12. Application of the fluorine-free super-hydrophobic coating according to any one of claims 1 to 9 in improving the mechanical properties, corrosion resistance, flame retardancy, anti-icing / de-icing properties, thermal insulation properties, and durability in extreme environments of a substrate.

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