A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating and preparation method thereof

Abstract

The invention discloses a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating and a preparation method thereof, and belongs to the technical field of composite coating materials. It is prepared by preparing low surface energy polyurea and modified silicon dioxide, and compounding the two, wherein, in the molecular structure of the low surface energy polyurea, only part of the molecular chain contains a group of terminal hydroxyl fluorinated polysiloxane, and through its preparation method, the PDSF group is close to the central core. The prepared polyurea composite coating has extremely high wear resistance and impact resistance under the condition of meeting super-hydrophobic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite coating materials, and in particular relates to a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating and a preparation method thereof. Background Art

[0002] In the practical application of super-hydrophobic coatings, durability (including mechanical stability, chemical corrosion resistance, etc.) is the core indicator for evaluating its engineering practicality, which directly determines the service life and performance reliability of the coating under complex working conditions. In order to improve the durability of super-hydrophobic coatings, many attempts have been made. For example, for super-hydrophobic coatings, low surface energy and microstructure play a key role in the wettability of their surfaces. In order to construct the rough structure of super-hydrophobic surfaces, people have tried to use inorganic particles such as SiO2, TiO2, and ZnO as fillers embedded in matrix materials. However, the poor interfacial bonding between these inorganic particles and the matrix material makes the prepared super-hydrophobic coating unable to meet the growing durability requirements. In addition, people have also tried self-healing strategies, optimized adhesives, and armor protection. For example, self-healing surface hydrophobicity through wax-based materials, or using femtosecond laser etching inverted pyramid microframes to protect internal nanostructures, but these methods rely on complex processes or expensive equipment.

[0003] In recent years, polyurea has been used in the field of super-hydrophobic coatings. Polyurea coatings have gradually become a research hotspot in the field of super-hydrophobic coatings due to their excellent mechanical properties and chemical stability. For example, by combining polyurea with low surface energy substances (such as fluorides), the durability and hydrophobicity of the coating can be significantly improved. Although polyurea-based super-hydrophobic coatings have made important progress in performance, they still face some challenges. For example, under high mechanical stress or long-term friction, the micro-nano structure of the coating is easily destroyed, resulting in a decrease in hydrophobic properties; in complex environments (such as high humidity, strong acidity and alkali or high temperature), the chemical stability and hydrophobic properties of the coating gradually deteriorate. These problems limit the further promotion and application of polyurea-based super-hydrophobic coatings.

[0004] In view of this, the prior art needs to be further improved. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating and a preparation method thereof, the purpose of which is to solve at least one of the above problems.

[0006] The present invention achieves its technical purpose through the following technical solutions:

[0007] A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating, the composite coating is made of low surface energy polyurea and modified silica, wherein:

[0008] The low surface energy polyurea is prepared by reacting polytetrahydrofuran diol, benzene-1,2,4,5-tetrol, dimethylsilane diol, terminal hydroxyl fluorinated polysiloxane, diphenylmethane diisocyanate and a polyamine chain extender;

[0009] The modified silica is prepared by modifying silica with a fluorosilane coupling agent;

[0010] The molecular structure of the low surface energy polyurea is based on benzene-1,2,4,5-tetrol as the central core, and only part of the molecular chains connected to the central core contain terminal hydroxyl fluorinated polysiloxane groups.

[0011] Compared with the prior art, the present invention has at least the following advantages:

[0012] The present invention uses polytetrahydrofuran diol, benzene-1,2,4,5-tetrol, dimethylsilane diol, terminal hydroxyl fluorinated polysiloxane, diphenylmethane diisocyanate and polyamine chain extender to react and prepare low surface energy polyurea. By controlling the usage amount of PDSF, only part of the molecular chains in the molecular structure contain terminal hydroxyl fluorinated polysiloxane groups. The primary polymerization and prepolymerization are carried out step by step, so that on the molecular chain containing terminal hydroxyl fluorinated polysiloxane groups, the PDSF group is closer to the central core. This structure is conducive to the low surface energy polyurea to embed silicon dioxide deep into the molecular structure of the low surface energy polyurea when compounding silicon dioxide (especially silicon dioxide modified by a fluorosilane coupling agent). At the same time, the introduced PDSF and the like also ensure its super hydrophobic property. This structure enables the composite prepared super hydrophobic polyurea composite coating to have higher wear resistance and impact resistance than the existing polyurea / SiO2 composite coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the main flow chart of the present invention for preparing the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating;

[0014] Figure 2 It is a reaction principle diagram of the prepolymerization reaction of the present invention;

[0015] Figure 3 yes Figure 2 A schematic diagram of the structure of the first molecular chain and the second molecular chain in the molecular structure of the prepolymer obtained by the prepolymerization reaction;

[0016] Figure 4 This is a reaction principle diagram of the present invention for synthesizing low surface energy polyurea by chain extension reaction;

[0017] Figure 5 It is an X-ray photoelectron spectrum curve diagram of the modified polyurea synthesized by the present invention and the common unmodified polyurea;

[0018] Figure 6is a Fourier transform infrared spectrum of the SiO2 nanoparticles of the present invention before and after modification;

[0019] Figure 7 is a curve diagram of the change of water contact angle of the super hydrophobic polyurea composite coating prepared in Example 1 of the present invention and the polyurea composite coating of Comparative Example 2 when subjected to friction;

[0020] Figure 8 The present invention is a comparison diagram of the effects of the super-hydrophobic polyurea composite coating prepared in Example 1 of the present invention and the composite coating prepared in Comparative Example 4 without polyurea modification and silica modification during self-cleaning tests, wherein group (a) corresponds to a self-cleaning test effect diagram of the composite coating prepared in Comparative Example 4 without polyurea modification and silica modification, which is immersed in an aqueous solution of ferric chloride; group (b) corresponds to a self-cleaning test effect diagram of the super-hydrophobic polyurea composite coating prepared in Example 1 of the present invention, which is immersed in an aqueous solution of ferric chloride; group (c) corresponds to a self-cleaning test effect diagram of the super-hydrophobic polyurea composite coating prepared in Example 1 of the present invention, which is immersed in a carbon black suspension (prepared with carbon black particles having a particle size of less than 40 μm). DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] like Figures 1 to 8 As shown, the present invention provides a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating, which is made of low surface energy polyurea and modified silica, wherein:

[0023] The low surface energy polyurea is prepared by reacting polytetramethylene glycol (PTMG), benzene-1,2,4,5-tetrol (Btt), dimethylsilanediol (DMSD), terminal hydroxyl fluorinated polysiloxane (PDSF), diphenylmethane diisocyanate (MDI) and a polyamine chain extender;

[0024] The modified silica is prepared by modifying silica with a fluorosilane coupling agent (e.g., tridecafluorooctyltrimethoxysilane. Unless otherwise specified, tridecafluorooctyltrimethoxysilane is used in the modification of silica in the following text);

[0025] The molecular structure of the low surface energy polyurea is based on benzene-1,2,4,5-tetrol as the central core, and only part of the molecular chains connected to the central core contain terminal hydroxyl fluorinated polysiloxane (PDSF) groups.

[0026] Preferably, in the process of preparing the low surface energy polyurea, the usage of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetramethylene glycol (PTMG) and diphenylmethane diisocyanate (MDI) is controlled in a molar ratio of 1:(1.5-2.2):(4-4.5):(4-4.5):(18-20), and this molar ratio is hereinafter referred to as the predetermined molar ratio usage.

[0027] Preferably, the polyamine chain extender is WANALINK®6200 chain extender produced by Wanhua Chemical Group Co., Ltd., which is a diamine chain extender.

[0028] More specifically, the low surface energy polyurea is prepared by the following method:

[0029] Step S1, raw material pretreatment:

[0030] Prepare raw materials according to production needs; vacuum dry benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD) and polytetrahydrofurandiol (PTMG) in a vacuum drying oven at 60°C for at least 8 hours (the vacuum degree is controlled at 0.1 mbar) to remove moisture;

[0031] During the drying process, the moisture content is tested starting from the 8th hour (e.g., by Karl Fischer method, infrared spectroscopy, etc.), and then the test is repeated every 1 to 2 hours until the moisture content of the raw material is less than 0.05wt%, and the drying process is terminated;

[0032] Step S2, primary polymer synthesis:

[0033] Under nitrogen protection, add the dried Btt and PDSF into the reactor in a predetermined molar ratio [Btt:PDSF=1:(1.5-2.2)], and stir the mixture with a mechanical stirrer at a speed of 200 rpm until a uniform solution is formed; then, gradually add MDI to react the mixture, thereby connecting PDSF to the Btt molecule to obtain a primary polymer; in this process, the amount of MDI added is 5 to 6 times the molar amount of Btt, that is, Btt:MDI=1:(5-6), and continue stirring (200 rpm) during the addition of MDI, and use a temperature controller to maintain the reaction temperature at 80-85°C. After the addition of MDI is completed, continue stirring (200 rpm) and react for 30 minutes;

[0034] Step S3, prepolymer synthesis:

[0035] The temperature of the reactor was maintained at 80-85°C, and stirring was continued (200 rpm) under nitrogen protection. Then, the pretreated DMSD and PTMG were added to the reactor in a predetermined molar ratio and stirred to form a uniform solution. Then, MDI was gradually added to react the mixture, thereby connecting DMSD and PTMG to the molecules of the primary polymer to generate a prepolymer with -NCO groups at the ends.

[0036] The total amount of MDI added is added according to a predetermined molar ratio. Since a portion of MDI has been added in step S2, in this step S3, the total amount added minus the amount added in step S2 is the molar amount of MDI added in this step S3.

[0037] Although the synthesis of the prepolymer consists of two steps, step S2 and step S3, the overall reaction principle can be referred to Figure 2 and Figure 3 ; The reason why it is completed in two steps is that the PDSF group is closer to the central core than the DMSD and PTMG groups on the molecular chain containing the PDSF group; its role will be described later and will not be repeated here;

[0038] Step S4, synthesis of low surface energy polyurea:

[0039] The temperature in the reactor was lowered to 55-60°C. While maintaining stirring, the polyamine chain extender WANALINK® 6200 was gradually added. The amount of 6200 chain extender was about 0.5 times the total amount of MDI added (calculated in molar amount, for example, if the total amount of MDI added was 20 mol, then 6200 chain extender was added in an amount of 10 mol). The reaction was continued for 1-2 hours to obtain a mixed product containing low surface energy polyurea. It should be noted that the reaction principle of the synthesis of low surface energy polyurea is as follows: Figure 4 As shown, in Figure 4 In the molecular structure of the prepolymer shown, except for the -NCO group, the rest is represented by " " indicates; it should also be noted that the low surface energy polyurea in the present invention is a modified polyurea, in which some H atoms in the urea structure are replaced; see Figure 5 It can be seen from the XPS test spectrum that the modified polyurea (low surface energy polyurea) of the present invention is successfully modified, and elements such as fluorine and silicon are successfully grafted onto the polyurea. Compared with ordinary unmodified polyurea (pure polyurea PUA), it has a lower surface energy, indicating that it may have significant advantages in hydrophobicity, oleophobicity, wear resistance, chemical resistance, etc. This will be discussed later and will not be repeated here;

[0040] Preferably, in step S4, the stirring is performed in a stepwise decreasing manner, and the initial stirring speed is 150 rpm, which can ensure that the chain extender is evenly dispersed in the system. As the reaction proceeds, the stirring speed can be gradually reduced, for example, by 50 rpm every 30 minutes until the stirring speed is reduced to 50 rpm, which helps to reduce the generation of bubbles and ensure the uniformity of the reaction, while avoiding excessive shearing that affects the performance of the final product;

[0041] Step S5, polyurea purification:

[0042] After the chain extension reaction is completed, slowly add an appropriate amount of terminator (such as methanol or ethanol, the volume is 1% to 2% of the volume of the reaction solution) to the reactor, and stir for 10 minutes to terminate the reaction of the residual -NCO group; then, transfer the reaction solution to a precipitation container, add 3 to 5 times the volume of a polyurea poor solvent (such as a mixture of methanol and water, the volume ratio is 1:1), and stir at a speed of 100 rpm until the polyurea is completely precipitated as a flocculent precipitate; then, collect the precipitate by a vacuum filtration device, and repeatedly wash it with a poor solvent for 3 times (each time the amount is twice the volume of the precipitate) to remove unreacted MDI, chain extender and small molecule by-products. Finally, transfer the filter cake to a vacuum drying oven and dry it at 60 to 80°C for 12 to 24 hours until constant weight is obtained to obtain a purified low surface energy polyurea.

[0043] Furthermore, the modified silicon dioxide is prepared by the following steps:

[0044] Step A, heating silicon dioxide powder (particle size in the range of 10 to 200 nanometers) to 100 to 150° C. in a vacuum drying oven and drying for at least 2 hours to remove moisture adsorbed on the surface; then cooling to room temperature and storing in a vacuum drying oven for later use;

[0045] Step B, weigh an appropriate amount of tridecafluorooctyltrimethoxysilane (abbreviated as PFOTS here, English alias Perfluorooctyltrimethoxysilane, purity ≥ 95%), dissolve it in anhydrous ethanol to form a PFOTS solution, then slowly add the dried silica powder to the PFOTS solution, stir (300 rpm) at 50°C for 2 to 4 hours to ensure that PFOTS is evenly covered on the silica surface; the mass ratio of silica, PFOTS and anhydrous ethanol is controlled at 100:3:1500 (it should be understood that this is only a preferred ratio, which can be adjusted as needed during actual preparation);

[0046] Step C: After the reaction is completed, the modified silica is washed with ethanol to remove unreacted PFOTS and possible by-products; the modified silica is then separated by centrifugation (e.g., 3000 rpm, 10 minutes) and decantation, and dried in a vacuum oven at 60-80°C for at least 12 hours until constant weight is reached. Figure 6 It can be seen from the infrared spectrum that silica has a lower transmittance after being modified by PFOTS, indicating that new chemical groups or structures have been successfully introduced into the nano-silica particles during the modification process. These changes may give silica new properties, such as lower surface energy, better hydrophobicity, and enhanced chemical stability.

[0047] Next, a method for preparing a super-hydrophobic polyurea composite coating by using the prepared low surface energy polyurea and modified silica comprises the following steps:

[0048] Step SS1, mixing the prepared modified silica nanoparticles with benzyl alcohol, a defoamer and a dispersant, and during the mixing process, using an ultrasonic dispersing device (power 500W) to treat the mixture for 1 to 2 hours to ensure that the silica nanoparticles are uniformly dispersed in the solution; wherein the defoamer is an organosilicon defoamer such as polydimethylsiloxane, and the dispersant is a polyacrylate dispersant such as poly(acrylic acid-co-maleic acid) sodium salt; when polydimethylsiloxane is used as the defoamer and poly(acrylic acid-co-maleic acid) sodium salt is used as the dispersant, the amount ratio of the modified silica nanoparticles, benzyl alcohol, defoamer and dispersant is controlled at 10:100:0.05:1 by weight (it should be understood that this is only a preferred ratio and can be adjusted as needed during actual preparation);

[0049] Step SS2, transfer the solution obtained in step SS1 to a magnetic stirrer, set the speed of magnetic stirring to 150 rpm, heat the solution to about 80°C while magnetic stirring, and set the stirring time to 1 hour (the purpose of stirring is to ensure uniform mixing of materials, and the purpose of heating is to activate modified silica nanoparticles, etc., which is conducive to compounding with low surface energy polyurea, and the heating temperature will not cause decomposition of the material); during the stirring process, gradually add the low surface energy polyurea to the magnetic stirrer until it is completely mixed. After the low surface energy polyurea is added, the viscosity gradually increases. The target viscosity range is 200 to 1000 mPa·s by monitoring with a rotational viscometer; in parts by weight, the low surface energy polyurea is added in an amount of modified silica nanoparticles / low surface energy polyurea = 6% to 14% (this ratio is hereinafter referred to as SiO2 proportion);

[0050] Step SS3, coating the mixture of the low surface energy polyurea obtained in step SS2 and modified silica nanoparticles on the substrate (brushing, spraying or dipping can be used, and a suitable coating method is selected according to the required coating thickness and uniformity), and then moving it into an oven and heating it at 50° C. for two days to obtain the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating.

[0051] Embodiment 1

[0052] A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating, the composite coating is made of low surface energy polyurea and modified silica, wherein:

[0053] The low surface energy polyurea is prepared by reacting polytetramethylene glycol (PTMG), benzene-1,2,4,5-tetrol (Btt), dimethylsilanediol (DMSD), terminal hydroxyl fluorinated polysiloxane (PDSF), diphenylmethane diisocyanate (MDI) and a polyamine chain extender;

[0054] The modified silicon dioxide is prepared by modifying silicon dioxide with tridecafluorooctyltrimethoxysilane;

[0055] And wherein, the molecular structure of the low surface energy polyurea is based on benzene-1,2,4,5-tetrol as the central core, and among the molecular chains connected to the central core, only some of the molecular chains contain terminal hydroxyl fluorinated polysiloxane (PDSF) groups;

[0056] In the process of preparing the low surface energy polyurea, the usage of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetramethylene glycol (PTMG) and diphenylmethane diisocyanate (MDI) is controlled in a molar ratio of 1:1.5:4:4:18;

[0057] The preparation methods of the low surface energy polyurea, the modified silica and the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating are described above and will not be repeated here; in addition, in this embodiment 1, the proportion of SiO2 is 10%.

[0058] Embodiment 2

[0059] The only difference between Example 2 and Example 1 is that the usage of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetramethylene glycol (PTMG) and diphenylmethane diisocyanate (MDI) is controlled within a molar ratio of 1:2:4:4:18.

[0060] Embodiment 3

[0061] The only difference between Example 3 and Example 1 is that the usage of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetramethylene glycol (PTMG) and diphenylmethane diisocyanate (MDI) is controlled at a molar ratio of 1:2.2:4.5:4.5:20.

[0062] Embodiment 4

[0063] The only difference between the fourth embodiment and the first embodiment is that in the fourth embodiment, the proportion of SiO2 is 6%.

[0064] Embodiment 5

[0065] The only difference between the fifth embodiment and the first embodiment is that in the fifth embodiment, the proportion of SiO2 is 14%.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that the usage of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetrahydrofurandiol (PTMG) and diphenylmethane diisocyanate (MDI) is controlled at a molar ratio of 1:1:4:4:18.

[0068] Comparative Example 2

[0069] The only difference between Comparative Example 2 and Example 1 is that the usage amounts of benzene-1,2,4,5-tetrol (Btt), terminal hydroxyl fluorinated polysiloxane (PDSF), dimethylsilanediol (DMSD), polytetramethylene glycol (PTMG) and diphenylmethane diisocyanate (MDI) are controlled within a molar ratio of 1:4:4:4:18.

[0070] Comparative Example 3

[0071] In Comparative Example 3, low surface energy polyurea is prepared according to the molar ratio and dosage of Example 1, and the proportion of SiO2 is also the same. The difference is that there is no primary polymer synthesis step in Comparative Example 3, that is, in Comparative Example 3, the dried Btt, PDSF, DMSD and PTMG are directly added to the reactor according to the predetermined molar ratio and stirred to form a uniform solution; then MDI is gradually added to react the mixture to generate a prepolymer with -NCO groups at the ends; the remaining preparation steps, dosages, etc. are the same as the preparation method of Example 1.

[0072] Comparative Example 4

[0073] Comparative Example 4 prepares a composite coating with reference to Example 1 (referring to the method for preparing a super-hydrophobic polyurea composite coating using low surface energy polyurea and modified silica), except that it uses the common amino-terminated polyaspartic acid ester polyurea PUA on the market and composites it with unmodified SiO2 nanoparticles.

[0074] Comparative Example 5

[0075] The only difference between Comparative Example 5 and Example 1 is that in Example 5, the proportion of SiO2 is 3%.

[0076] Comparative Example 6

[0077] The only difference between Comparative Example 6 and Example 1 is that in this Example 6, the proportion of SiO2 is 20%.

[0078] Performance Test:

[0079] In order to verify the comprehensive performance of the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating of the present invention, we conducted the following tests:

[0080] Hydrophobic performance test:

[0081] According to ASTM D7334-08 standard, a contact angle meter (model OCA20, DataPhysics, Germany) was used to measure the static water contact angle (WCA) and sliding angle (SA). The test conditions were: room temperature (25°C) and relative humidity 50%. The following test results were obtained:

[0082]

[0083] It can be seen from the test results that the samples of Examples 1 to 5 all exhibit excellent super-hydrophobic properties, with water contact angles all higher than 150° and rolling angles all lower than 5°, meeting the standards of super-hydrophobic coatings.

[0084] In addition, it can be seen from Examples 1 to 3 that when SiO2 accounts for the same proportion, as the molar ratio of PDSF to Btt increases, the water contact angle gradually increases and the rolling angle gradually decreases. Specifically, the molar ratio of PDSF to Btt in Example 3 is the highest (2.2: 1), and its water contact angle reaches 160°, and the rolling angle is only 2°, showing excellent super-hydrophobic performance, which shows that within a certain range, the introduction of PDSF and the increase in its proportion have a promoting effect on the super-hydrophobic performance of the coating. The SiO2 proportions of Comparative Examples 1 and 2 are the same as those of Example 1, but the molar ratios of PDSF to Btt are 1: 1 and 4: 1, respectively. It can be seen from the test results that the water contact angle of Comparative Example 1 is 146°, and the rolling angle is 7°, which fails to meet the requirements of the super-hydrophobic coating. The water contact angle of Comparative Example 2 is 158°, and the rolling angle is 3°, which meets the standard of the super-hydrophobic coating, which further shows that the increase in the proportion of PDSF has a promoting effect on the super-hydrophobic performance of the coating. The water contact angle of comparative example three is 140°, and the rolling angle is 10°, which is lower than the standard of super-hydrophobic coating. Although it uses the same raw materials as in Example 1, it lacks the initial polymer synthesis step in the synthesis of low surface energy polyurea, which may lead to insufficient ordered arrangement and structural optimization of molecular chains, thereby affecting the surface energy of the coating and the formation of micro-nano structure. In addition, comparative example four uses unmodified SiO2 nanoparticles and ordinary polyurea PUA, and the water contact angle is only 109°, and the rolling angle is 22°, which is much lower than the performance of the embodiment sample, which further proves the importance of modifying SiO2 nanoparticles with fluorosilane coupling agents and obtaining modified low surface energy polyurea in the present invention. The modified SiO2 nanoparticles can better combine with low surface energy polyurea to form a more optimized micro-nano structure, thereby significantly improving the super-hydrophobic performance of the coating. The difference between Comparative Examples 5 and 6 and Example 1 is that the proportion of SiO2 is 3% for Comparative Example 5 and 20% for Comparative Example 6. The water contact angle of Comparative Example 5 is 130° and the rolling angle is 11°, which is far below the super-hydrophobic standard, indicating that too low SiO2 content cannot form an effective micro-nano structure, resulting in insufficient hydrophobic performance. The water contact angle of Comparative Example 6 is 142° and the rolling angle is 8°. Although the water contact angle has increased, the rolling angle is still high, indicating that too high SiO2 content may cause the internal structure of the coating to be too crowded, affecting the uniformity of the micro-nano structure, and thus failing to achieve the ideal super-hydrophobic performance.

[0085] Abrasion resistance test:

[0086] Since Comparative Example 1 and Comparative Examples 3 to 6 did not meet the super-hydrophobic standard, they were no longer tested during the wear resistance test.

[0087] During the test, the sandpaper drag test method was used. The polyurea composite coating sample to be tested was fixed on the test platform, and the P400 sandpaper (400 mesh) was fixed on the sliding device. Make sure that the sandpaper is flat and wrinkle-free. Place a 500g weight on the sandpaper, and then start the test platform to drag the sandpaper along the fixed track for friction. Each stroke is 20cm, and one round trip is counted as one friction. Perform 40 frictions under the above conditions. After the friction is completed, use a contact angle meter to re-measure the water contact angle and rolling angle of the coating. Use an optical microscope or scanning electron microscope (SEM) to observe the microstructural changes on the coating surface and record the wear conditions. Finally, the following wear test results were obtained:

[0088]

[0089] From the wear test results, it can be seen that the coating of embodiment one to five is still maintained at more than 150 ° of water contact angle after 40 times of sandpaper dragging friction, and the rolling angle is less than or equal to 6 °, which meets the standard of super-hydrophobic coating, which shows that these coatings can still maintain good super-hydrophobic performance under mechanical friction conditions. The coating of comparative example two has a water contact angle of 145 ° after friction, and a rolling angle of 10 °, which no longer meets the super-hydrophobic standard, and it can be seen by comparison that the change of its water contact angle and rolling angle before and after friction is relatively large (compared to embodiment one to five), indicating that its wear resistance is obviously inferior to the sample of embodiment one to five. Due to the SiO2 of comparative example two, the proportion is the same as that of embodiment one to three, so it can be inferred that this difference is caused by low surface energy polyurea, and the molar ratio of PDSF in comparative example two is relatively large, so that in the molecular chain of synthetic polyurea, almost every molecular chain connected to the central core Btt includes a group of PDSF, which may be unfavorable for modified silica to be embedded in the depth of synthetic polyurea structure, thereby causing its wear resistance to be insufficient. In Examples 1 to 5, since the usage of benzene-1,2,4,5-tetraol, terminal hydroxyl fluorinated polysiloxane, dimethylsilanediol, polytetrahydrofurandiol and diphenylmethane diisocyanate is controlled within a predetermined molar ratio range, only part of the molecular chain of the synthesized low surface energy polyurea contains the terminal hydroxyl fluorinated polysiloxane group, thereby ensuring the wear resistance of the composite coating. In addition, the enhancement of the wear resistance may also be affected by the position of PDSF in the molecular chain.

[0090] In order to further highlight the difference between the super-hydrophobic polyurea composite coating of the embodiment of the present application and the comparative example 2, the super-hydrophobic polyurea composite coating of the embodiment 1 and the super-hydrophobic polyurea composite coating of the comparative example 2 are tested and compared, and the effect is as follows: Figure 7 As shown by Figure 7It can be clearly seen that the water contact angle of the super hydrophobic polyurea composite coating of Example 1 changes slowly when it is rubbed, and still has a water contact angle close to 150° after 80 wears, while the water contact angle of the coating of Comparative Example 2 changes rapidly when it is rubbed, and its water contact angle quickly drops below 150° as the number of wears increases (see Figure 7 After 20 times of wear, the water contact angle of comparative example 2 is significantly lower than that of example 1. The above tests show that the super-hydrophobic polyurea composite coating provided by the embodiments of the present invention has good wear resistance.

[0091] In addition, we also tested the impact resistance of Examples 1 to 5 and Comparative Examples 1 to 6. Specifically, a standard drop hammer impact tester was used to impact the composite coating in a free drop hammer impact mode. The drop hammer mass was 10kg, the drop hammer height was 0.5m, and the impact was 5 times. The impact resistance of the coating was reflected by testing the changes in the water contact angle and the rolling angle, as well as the damage area. It was found through testing that the coatings of Examples 1 to 5 still maintained a water contact angle of more than 148° after 5 impacts, and the rolling angle was less than 6°, which basically met the standard of super-hydrophobic coatings, and its damaged area was relatively small, all less than 15mm²; Comparative Examples 1 to 3, 5 and 6 had relatively small changes in their water contact angle and rolling angle after 5 impacts, especially Comparative Example 2. After 5 impacts, the water contact angle remained above 153°, the rolling angle was 4°, and its damaged area was only 6mm², indicating that the use of sufficient PDSF helps to maintain the impact resistance of the coating. In addition, after 5 impacts, the damage area of ​​Comparative Example 4 is relatively large (the measured value is 42 mm²), indicating that its impact resistance is significantly inferior to that of the superhydrophobic polyurea composite coating of the embodiment of the present invention.

[0092] Self-cleaning test

[0093] In order to verify the self-cleaning effect of the super-hydrophobic polyurea composite coating of the present invention, we conducted pollution tests on the coatings of Examples 1 to 5 and Comparative Examples 1 to 6, respectively, using ferric chloride aqueous solution (concentration of 0.1 mol / L) and carbon black suspension (prepared with carbon black particles with a particle size of less than 40 μm) at room temperature 25 ° C for 24 hours, and then rinsed the coating surface with deionized water at a flow rate of 1 L / min for 5 minutes to observe its self-cleaning effect. Among them, Examples 1 to 5, Comparative Examples 1 to 3, and Comparative Examples 5 to 6 all showed good self-cleaning effects, which may be due to the fact that the low surface energy polyurea prepared by the present invention is used in the schemes of these embodiments or comparative examples, while the self-cleaning effect of Comparative Example 4 is relatively poor.

[0094] Figure 8 1 is a rendering of a self-cleaning test of a super-hydrophobic polyurea composite coating prepared in Example 1 and a composite coating of Comparative Example 4; Figure 8 In the figure, the (a) group corresponds to the self-cleaning test effect diagram of the composite coating of comparative example 4 after being soaked in an aqueous solution of ferric chloride. It can be seen that after being soaked in an aqueous solution of ferric chloride for 24 hours, a large amount of substances such as ferric chloride are attached to its surface. Even after rinsing, there are still obvious pollutant residues on its surface, indicating that its self-cleaning effect is poor. The (b) group corresponds to the super-hydrophobic polyurea composite coating prepared by soaking Example 1 in the same aqueous solution of ferric chloride. After the coating surface is rinsed, its coating surface is almost completely restored to its initial state, and almost no pollutant residues can be seen. At this time, the water contact angle tested is 150° and the rolling angle is 4°, which shows that it has excellent self-cleaning ability. The (c) group corresponds to the super-hydrophobic polyurea composite coating of Example 1 soaked in a carbon black suspension. After being soaked in a carbon black suspension for 24 hours, after rinsing, its coating surface also shows a good self-cleaning effect. Although there is a certain amount of carbon black residue on the surface, its water contact angle is measured to be 148° and the rolling angle is 5°, which is basically close to the initial super-hydrophobic coating state, which further proves its self-cleaning ability under different pollution conditions.

[0095] It should be understood that "comprising" as used herein with respect to the acid generator composition and the environmentally friendly autogenous acid includes the approach of "consisting of".

[0096] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating, which is made of low surface energy polyurea and modified silica nanoparticles, characterized in that: The low surface energy polyurea is prepared by reacting polytetrahydrofuran diol, benzene-1,2,4,5-tetrol, dimethylsilane diol, terminal hydroxyl fluorinated polysiloxane, diphenylmethane diisocyanate and a polyamine chain extender; The modified silicon dioxide nanoparticles are prepared by modifying silicon dioxide with a fluorosilane coupling agent; The molecular structure of the low surface energy polyurea is based on benzene-1,2,4,5-tetrol as the central core, and only some of the molecular chains connected to the central core contain terminal hydroxyl fluorinated polysiloxane groups; In the preparation process of the low surface energy polyurea, benzene-1,2,4,5-tetrol and terminal hydroxyl fluorinated polysiloxane are first mixed, then diphenylmethane diisocyanate is added for primary polymerization to prepare a primary polymer, then polytetrahydrofuran diol and dimethylsilane diol are added, and then diphenylmethane diisocyanate is added for reaction to obtain a prepolymer, and then a polyamine chain extender is added to obtain the low surface energy polyurea; the primary polymerization and the prepolymerization are carried out step by step, so that on the molecular chain containing the terminal hydroxyl fluorinated polysiloxane group, the terminal hydroxyl fluorinated polysiloxane group is closer to the central core than the dimethylsilane diol group and the polytetrahydrofuran diol group; And wherein, by weight, the modified silicon dioxide nanoparticles / low surface energy polyurea = 6% to 14%.

2. A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating as claimed in claim 1, characterized in that: In the process of preparing the low surface energy polyurea, the usage of benzene-1,2,4,5-tetrol, terminal hydroxyl fluorinated polysiloxane, dimethylsilanediol, polytetrahydrofurandiol and diphenylmethane diisocyanate is controlled in a molar ratio of 1:(1.5-2.2):(4-4.5):(4-4.5):(18-20).

3. A wear-resistant and impact-resistant super-hydrophobic polyurea composite coating as claimed in claim 2, characterized in that: The polyamine chain extender is a diamine chain extender.

4. A method for preparing a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating, which is used to prepare the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating according to any one of claims 1 to 3, characterized in that: The preparation method includes the preparation of low surface energy polyurea, which comprises the following steps: Step S1, raw material pretreatment: Prepare raw materials according to production needs; vacuum dry benzene-1,2,4,5-tetrol, terminal hydroxyl fluorinated polysiloxane, dimethylsilanediol and polytetrahydrofurandiol in a vacuum drying oven at 60° C. for at least 8 hours to remove moisture; Step S2, primary polymer synthesis: Under nitrogen protection, the dried benzene-1,2,4,5-tetrol and the terminal hydroxyl fluorinated polysiloxane are added into the reaction kettle in a predetermined molar ratio, and the mixture is stirred at a speed of 200 rpm with a mechanical stirrer until a uniform solution is formed; then, the reaction temperature is maintained at 80-85° C., and diphenylmethane diisocyanate is gradually added to react the mixture to obtain a primary polymer; Step S3, prepolymer synthesis: The temperature of the reaction kettle is maintained at 80-85° C., and stirring is continued under nitrogen protection. Then, pretreated dimethylsilanediol and polytetrahydrofurandiol are added to the reaction kettle in a predetermined molar ratio and stirred to form a uniform solution. Then, diphenylmethane diisocyanate is gradually added to react the mixture to generate a prepolymer having -NCO groups at the ends. Step S4, synthesis of low surface energy polyurea: The temperature in the reaction kettle is lowered to 55-60° C., and a polyamine chain extender is gradually added under stirring, and the reaction is carried out for 1-2 hours to obtain a mixed product containing low surface energy polyurea; Step S5, polyurea purification: After the chain extension reaction is completed, a terminator is slowly added to the reactor and stirred for 10 minutes to terminate the reaction of the residual -NCO groups; then, the purified low surface energy polyurea is obtained through precipitation, collection, washing and drying.

5. The method for preparing a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating according to claim 4, characterized in that: In step S4, the stirring is performed in a step-wise decreasing manner, with the initial stirring speed being 150 rpm. As the reaction proceeds, the stirring speed is gradually reduced until it is reduced to 50 rpm.

6. A method for preparing a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating as claimed in claim 4 or 5, characterized in that: The preparation method also includes modifying silicon dioxide with a fluorosilane coupling agent, and compounding the modified silicon dioxide with low surface energy polyurea.

7. The method for preparing a wear-resistant and impact-resistant super-hydrophobic polyurea composite coating according to claim 6, characterized in that: The preparation method further comprises the following steps: Step SS1, mixing the prepared modified silica nanoparticles with benzyl alcohol, a defoaming agent and a dispersant, and during the mixing process, treating the mixture with an ultrasonic dispersion device for 1 to 2 hours to ensure that the silica nanoparticles are uniformly dispersed in the solution; Step SS2, transferring the solution obtained in step SS1 to a magnetic stirrer, heating the solution to 80° C. while magnetically stirring, and setting the stirring time to 1 hour; during the stirring process, gradually adding the prepared low surface energy polyurea to the magnetic stirrer until it is completely mixed and its viscosity reaches the predetermined requirement; Step SS3: coating the mixture obtained in step SS2 on a substrate, and then placing it in an oven and heating it at 50° C. for two days to obtain the wear-resistant and impact-resistant super-hydrophobic polyurea composite coating.

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