Secondary surface mirror based on hydrotalcite coating modified polymer and its preparation method and application

Abstract

The present application relates to a secondary surface mirror based on hydrotalcite coating modified polymer and its preparation method and application. The secondary surface mirror based on hydrotalcite coating modified polymer comprises a polymer matrix and an antistatic layer, and a hydrotalcite modified layer distributed between the polymer matrix and the antistatic layer; the hydrotalcite modified layer comprises a porous coating formed by cross-linking at least one of hydrotalcite nanosheet or hydrotalcite-like nanosheet and a silane coupling agent; preferably, the silane coupling agent can be bonded by reacting with the polymer matrix or the hydrotalcite coating, such as the polymer matrix is a polymer matrix containing hydroxyl, carboxyl or a polymer matrix which can be modified to generate hydroxyl, carboxyl, and the silane coupling agent is an aminoalkylsilane having amino group.

Description

Technical Field

[0001] This invention relates to a secondary surface mirror based on a surface-modified polymer film, its preparation method and application, belonging to the technical field of polymer film surface modification and spacecraft thermal control coating. Background Technology

[0002] Polymer materials possess advantages such as good flexibility, light weight, low cost, and ease of processing, making them an important component in various fields including home appliances, electronics, automotive, and aerospace. As a crucial material closely related to the national economy, high-tech, and modern life, they have played a significant role in various sectors. For example, polyimide (PI) and fluoroplastic films (F46, etc.) are commonly used substrates for flexible film secondary surface mirrors, and secondary surface mirrors prepared using PI or F46 as substrates are an important class of thermal control materials.

[0003] However, antistatic indium tin oxide (ITO) films exhibit poor adhesion to polymer substrates. Furthermore, due to the brittleness of ITO, the organic-inorganic interface mismatch leads to easy detachment and cracking of the ITO film, resulting in compromised antistatic properties during subsequent use and in the alternating hot and cold environments of orbit, hindering further processing and use. Particularly during low-orbit operation, atomic oxygen in the low-orbit environment can further corrode the fluoroplastic substrate through cracks and other defects, affecting thermal control functionality. Therefore, it is essential to address these issues and seek alternative thermal control materials that are resistant to atomic oxygen and have good film adhesion. Summary of the Invention

[0004] To address the current issues of processing, use, and low-orbit space environment tolerance of thin-film secondary surface mirrors, this invention aims to provide a secondary surface mirror based on a polymer modified with hydrotalcite coating, its preparation method, and its application.

[0005] On one hand, the present invention provides a secondary surface mirror based on a hydrotalcite-coated modified polymer, comprising: a polymer matrix and an antistatic layer, and a hydrotalcite-modified layer distributed between the polymer matrix and the antistatic layer; The hydrotalcite-modified layer comprises a porous coating formed by crosslinking at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets with a silane coupling agent. Preferably, the silane coupling agent is capable of reactively bonding with the polymer matrix or the hydrotalcite coating. For example, the polymer matrix is ​​a polymer matrix containing hydroxyl and carboxyl groups or a polymer matrix that can be modified to generate hydroxyl and carboxyl groups, and the silane coupling agent is an aminoalkylsilane. In this invention, the hydroxyl groups on the surface of the hydrotalcite nanosheets or hydrotalcite-like nanosheets dehydrate and bond with the hydroxyl groups generated by the hydrolysis of the aminoalkylsilane coupling agent, thereby improving the mechanical strength of the hydrotalcite nanosheet or hydrotalcite-like nanosheet coating. Simultaneously, the hydroxyl and carboxyl groups on the surface of the selected polymer matrix dehydrate and bond with the terminal amino groups of the silane coupling agent, improving the bonding strength between the hydrotalcite nanosheet or hydrotalcite-like nanosheet coating and the polymer matrix. Most importantly, the highly oriented stacked structure formed by cross-linking at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets with a silane coupling agent greatly extends the erosion path of atomic oxygen and increases the resistance along the erosion path, resulting in extremely excellent anti-atomic oxygen erosion performance and very low mass loss of the coating. At the same time, the structure has a certain amount of porosity, which allows for appropriate cross-slip movement between nanosheets to absorb and release stress, so the flexibility of the coating is significantly improved and the resistance to peeling and cracking is excellent.

[0006] Preferably, the chemical composition of the hydrotalcite nanosheets or hydrotalcite-like nanosheets is [M 2+ 1-x M 3+ x (OH)2] x+ A n- x / n ·mH2O, where M 2+ It is a divalent metal cation, preferably selected from Mg. 2+ Ni 2+ Co 2+ Zn 2+ Cu 2+ At least one of them; M 3+ It is a trivalent metal cation, preferably selected from Al. 3+ Cr 3+ Fe 3+ ,Sc 3+ At least one of them; A n- It is an anion, preferably selected from CO3. 2- NO3 - Cl - OH - SO4 2- PO4 3- C6H4(COO)2 2-At least one of the following; x ranges from 0.1 to 0.5, preferably from 0.2 to 0.33; more preferably, the divalent metal cation is Mg. 2+ The trivalent metal cation is Al 3+ The optimal choice is Mg 2+ :Al 3+ =2:1.

[0007] Preferably, the hydrotalcite nanosheets or hydrotalcite-like nanosheets are nearly hexagonal or circular; the diameter of the circumscribed circle of the circular or nearly hexagonal nanosheets is between 100 and 500 nm, and the diameter-to-thickness ratio is 15 to 40.

[0008] Preferably, it further comprises a silane coupling agent modified layer distributed between the polymer matrix and the hydrotalcite modified layer; the thickness of the silane coupling agent modified layer is 20 nm to 1000 nm.

[0009] Preferably, the silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and 3-aminopropylmethyldiethoxysilane, and is preferably 3-aminopropyltriethoxysilane.

[0010] Preferably, the ratio of at least one hydrotalcite nanosheet or hydrotalcite-like nanosheet to the silane coupling agent in the porous coating is (5-40) mg:(5-20) μL. That is, the ratio of at least one hydrotalcite nanosheet or hydrotalcite-like nanosheet to the silane coupling agent is 1 mg:6 μL to 8 mg:1 μL.

[0011] Preferably, the hydroxyl-containing polymer matrix is ​​prepared by a two-step alkaline / acid treatment of a polymer containing an imide ring or / and an ester group; more preferably, the polymer containing an imide ring or / and an ester group is polyimide, polyester, or polyethylene terephthalate; the two-step alkaline / acid treatment includes: first reacting and modifying the polymer matrix in an alkaline solution at room temperature for 0.5 to 3 hours, and then reacting and modifying it in an acetic acid solution for 0.5 to 3 hours; preferably, the alkaline solution is a sodium hydroxide solution with a concentration of 0.5 to 2 mol / L, and the acid solution is an acetic acid solution with a concentration of 0.5 to 2 mol / L.

[0012] Preferably, the composition of the antistatic layer is selected from at least one of transparent conductive oxides such as ITO film, indium oxide, tin oxide, zinc oxide and cadmium oxide; the thickness of the antistatic layer does not exceed 100 μm.

[0013] Preferably, a reflective layer is also included on the side of the hydrotalcite-modified layer away from the fluoroplastic film; the reflective layer includes a metal reflective film, a fully dielectric reflective film, a metal-dielectric reflective film, etc.; the thickness of the reflective layer does not exceed 100 μm. For example, a metal reflective film is selected, and the metal composition is selected from at least one of silver film, aluminum film, gold film, and copper. The metal reflective layer is metallic silver or aluminum, which has high visible light reflectivity. In addition, a protective film layer is added to the outer surface of the metal reflective layer to prevent the silver layer from oxidizing. In this case, the secondary surface mirror has a four-layer structure, consisting of an antistatic layer, a hydrotalcite-modified layer, a fluoroplastic film, and a reflective layer. The antistatic layer faces the space environment. The hydrotalcite-modified layer serves as a transition layer to increase the strength of the antistatic layer, and also has excellent space environment tolerance, giving the secondary surface mirror excellent space environment resistance and tolerance for subsequent processing and use. In this case, if there is no need for antistatic properties, the antistatic layer can be omitted, and it can be used as a non-antistatic secondary surface mirror.

[0014] Furthermore, the antistatic layer is preferably an indium tin oxide (ITO) film, which has excellent conductivity, high visible light transmittance, and excellent spatial environmental stability.

[0015] Preferably, the hydrotalcite-modified film is an antigenic oxygen-protective UV-modified film to provide better adaptability to different space environments such as low-Earth orbit, high-Earth orbit, and orbital changes.

[0016] Preferably, the thickness of the polymer matrix does not exceed 1000 μm.

[0017] On the other hand, the present invention also provides a method for preparing a secondary surface mirror based on a hydrotalcite-coated modified polymer, comprising: (1) Add a silane coupling agent to an aqueous dispersion containing at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets and mix them. Then coat the mixture onto the surface of a polymer matrix containing hydroxyl groups. After drying, heat treat it at 80-250°C for 3-12 hours to obtain a hydrotalcite modified coating. (2) An antistatic layer is prepared on the surface of the hydrotalcite modified coating by vacuum coating or chemical method; (3) A metal reflective layer is prepared on the other side of the polymer matrix by vacuum coating or chemical method to obtain a secondary surface mirror of the surface-modified polymer matrix.

[0018] Preferably, the concentration of the aqueous dispersion containing at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets is 5–40 mg / mL, more preferably 18 mg / mL; the mixing method is stirring, and the stirring speed is 200–400 rpm.

[0019] Preferably, the coating is applied at least once; the coating includes spin coating, drip coating, spray coating, scraping coating, or static lifting coating; preferably, the spin coating speed is 600-1400 rpm, and the spin coating time is 6-18 seconds per application.

[0020] Preferably, the drying process is performed at least once, at a temperature of 60–120°C, and for each drying session lasting 10–30 seconds.

[0021] Furthermore, the present invention also provides an application of a secondary surface mirror based on a hydrotalcite-coated modified polymer in the field of space environment.

[0022] Unlike conventional dense anti-proton oxygen coatings, the coating of this invention is composed of inorganic magnesium-aluminum hydrotalcite nanosheets as protective units and an aminohydrosilane coupling agent. It possesses a non-dense micro / nano structure formed by a highly uniformly oriented stacked arrangement of nanosheets, preventing cracking due to internal stress. Simultaneously, the aminohydrosilane coupling agent enhances the interfacial adhesion between the coating and the substrate, preventing peeling. The main body of this coating is an inorganic magnesium-aluminum hydrotalcite nanosheet layer, which is inexpensive, has a simple process, is easy to operate, and exhibits excellent anti-proton oxygen / anti-peeling and cracking performance, making it widely applicable in the aerospace field. Furthermore, this secondary surface mirror based on a hydrotalcite-modified polymer can be used as a spacecraft thermal control material, exhibiting excellent space environment tolerance and suitable for high, medium, and low Earth orbit environments. Especially in low Earth orbit environments, it also demonstrates excellent anti-proton oxygen performance.

[0023] Beneficial effects: 1) The fish-scale-like, non-dense structure hydrotalcite modified layer provided by the present invention has excellent antigenic oxygen properties because its main body is an oriented, densely packed inorganic hydrotalcite-like nanosheet material. (2) Unlike existing dense inorganic coatings that are prone to peeling and cracking, this coating material has a nanosheet stacked structure with highly consistent orientation, and the sheets can slide appropriately in an alternating manner, so its flexibility is significantly improved, which can prevent cracking during hot and cold cycles and bending. The coating and the polyimide matrix are bonded by a modified layer, resulting in high bonding strength and excellent anti-peeling performance. (3) The raw materials for this coating are inexpensive, the process is simple, and the operation is convenient; (4) The secondary surface mirror based on the hydrotalcite coating modified polymer in this invention can solve the problems in the processing and use of existing thin-film secondary surface mirrors. It has excellent anti-ionic oxygen UV protection properties and can withstand multiple thermal cycles without cracks or other defects. Its tensile properties and optical transmittance change very little, and its film adhesion and thermal cycling resistance are good. It can be widely used in high, medium and low orbit space environments. In addition, the method of this invention theoretically does not limit the raw materials for its large-scale production. The solution can be stored for a long time, and the required equipment can be purchased or developed. In principle, there are no factors that limit its large-scale production, which is conducive to its practical application. Attached Figure Description

[0024] Figure 1 The image shows a bonding test diagram of the enhanced adhesion of the ITO film layer after adding a hydrotalcite coating in Example 1, and a comparison diagram of the ITO coating directly on the substrate surface. Figure 2 The images show optical microscopy and bending direction diagrams of the ITO / hydrotalcite composite coating in Example 1 after being bent 500 times on a cylinder with a radius of 1 mm. It can be seen from the images that no obvious cracks were generated in the modified film. Figure 3 for Figure 3 The ITO / hydrotalcite composite coating has a thickness of 5.22×10. 21 atoms / cm 2 The light micrograph after the dose atomic oxygen test shows that there is no significant change in the morphology of the film. Detailed Implementation

[0025] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0026] In this disclosure, the secondary surface mirror based on the hydrotalcite-modified polymer has a four-layer structure, consisting of an ITO antistatic layer, a hydrotalcite-modified layer, an F40 thin film, and a metallic Ag reflective layer. The antistatic layer faces the space environment.

[0027] The hydrotalcite-modified layer comprises a porous coating consisting of a stacked structure formed by hydrotalcite nanosheets or hydrotalcite-like nanosheets with a certain sheet size and a small amount of silane coupling agent. The surface morphology of the hydrotalcite-modified layer is a fish-scale-like sheet structure with a non-dense structure of a certain pore size. Furthermore, the hydrotalcite-modified layer adheres to the surface of a polymer matrix containing hydroxyl groups. At this point, the coating and the matrix are primarily bonded through the amino groups of the silane coupling agent to the carboxyl groups generated by the matrix modification, resulting in an imidization reaction that enhances the interfacial bonding.

[0028] In an optional embodiment, the chemical composition of the hydrotalcite nanosheets or hydrotalcite-like nanosheets of a certain size can be expressed as [M 2+1-x M 3+ x (OH)2] x+ A n- x / n ·mH2O. Where M 2+ It is a divalent metal cation, such as Mg 2+ Ni 2+ Co 2+ Zn 2+ Cu 2+ etc.; M 3+ It is a trivalent metal cation, such as Al 3+ Cr 3+ Fe 3+ ,Sc 3+ etc.; A n- It is an anion, such as CO3. 2- NO3 - Cl - OH - SO4 2- PO4 3- C6H4(COO)2 2- Inorganic and organic ions, as well as complex ions, are preferred; the value of x is preferably between 0.1 and 0.5, and between 0.2 and 0.33. A preferred composition is hydrotalcite-like nanosheets with a magnesium-to-aluminum ratio of 2:1, wherein the divalent metal cation, trivalent metal cation, and anion are Mg... 2+ Al 3+ Cl - And Mg 2+ Al 3+ =2:1.

[0029] In an optional embodiment, the hydrotalcite or hydrotalcite-like nanosheets of a certain size can be prepared in large quantities by a two-step method of co-precipitation and hydrothermal treatment. Meanwhile, the sheets are nearly hexagonal or circular, with the diameter of the circle or the circumscribed circle of the hexagon in the range of 100 nm to 500 nm and the radial-axial ratio of 15 to 40.

[0030] In an optional embodiment, the polymer matrix containing hydroxyl groups can be a polymer containing an imide ring or ester group, such as polyimide, polyester, or polyethylene terephthalate, which is a type of polymer that easily generates carboxyl groups on its surface after two-step alkali and acid treatment.

[0031] In an optional embodiment, the thickness of the porous coating can be 200 nm to 10 μm.

[0032] This invention also provides a method for preparing a secondary surface mirror based on a polymer modified with a hydrotalcite coating. The method is flexible and easy to implement on a large scale. The following exemplarily illustrates the method for preparing a secondary surface mirror based on a polymer modified with a hydrotalcite coating.

[0033] Alkali / acid modification of polymer matrices. Polyimide, polyester, and polyethylene terephthalate matrices were placed in 0.5–2 mol / L (e.g., 1 mol / L) sodium hydroxide solution and 0.5–2 mol / L (e.g., 1 mol / L) acetic acid solution, respectively, and reacted for 0.5–3 hours (e.g., 1 h) to obtain alkali / acid modified polymer matrices. During solution replacement and after modification, the matrices were repeatedly washed with deionized water and anhydrous ethanol to remove residual modification solution. After drying at room temperature, subsequent coating processes were carried out.

[0034] Preparation of an aqueous dispersion containing hydrotalcite nanosheets or / and hydrotalcite-like nanosheets. Preferably, it is prepared by a two-step method of co-precipitation and hydrothermal treatment. Taking magnesium-aluminum hydrotalcite-like nanosheets as an example, the two-step method of co-precipitation and hydrothermal treatment for preparing hydrotalcite-like nanosheets includes: preparing a solution by mixing magnesium chloride hexahydrate, aluminum chloride hexahydrate, and water in a molar ratio of (3-x):3x:350 (where x ranges from 0.1 to 0.5, preferably from 0.2 to 0.33); rapidly adding ammonia water within 5 seconds and stirring to adjust the pH to 9-10; stirring for 15 minutes and then allowing it to stand for 1 hour to age; centrifuging the obtained white suspension and washing the precipitate repeatedly with deionized water until the pH reaches 8-9; after washing, adding a certain amount of deionized water to the precipitate and stirring evenly, and then placing it in an oven at 80-200°C for hydrothermal treatment for 24 hours.

[0035] A certain amount of aminohydrosilane is added as a crosslinking agent to an aqueous dispersion containing hydrotalcite nanosheets or / and hydrotalcite-like nanosheets. After stirring for a certain period of time, the mixture is coated onto a polymer matrix that has undergone two-step alkali / acid modification to form a wet film. The stirring speed is 200-400 rpm, and the stirring time is 30-90 minutes (e.g., 60 min).

[0036] After each wet film is initially dried, it is coated again, and after multiple coatings, it is heat-treated in an air atmosphere. The final product is a hydrotalcite-modified layer with a fish-scale-like, non-dense structure. For example, the initial drying process of the wet film involves treatment in an oven at 80°C for 20 seconds.

[0037] In optional embodiments, the coating method is any one of spin coating, drop coating, spray coating, blade coating, or static dip coating. Multiple coating processes are performed, with the number of processes ranging from 3 to 9. Preferably, the number of coating processes is 6.

[0038] In an optional embodiment, the heat treatment temperature can be a single temperature value or a gradient of several temperature values ​​within the range of 80 to 250°C. The total heat treatment time can be 3 to 12 hours. Preferably, the heat treatment process involves treating at 80°C, 110°C, and 150°C for 1 hour, 1 hour, and 3 hours, respectively.

[0039] Specifically, a method for preparing a fish-scale-like, non-dense hydrotalcite modified layer is illustrated by using magnesium chloride hexahydrate, aluminum chloride hexahydrate, 3-aminopropyltriethoxysilane, and alkali / acid / aminohydrosilane modified polyimide films, spin coating as magnesium and aluminum sources, crosslinking agents, polymer matrix, and coating methods, respectively, to prepare magnesium-aluminum hydrotalcite nanosheets.

[0040] Preparation of magnesium-aluminum layered double hydroxide (TLH) nanosheet dispersions: 0.6449 g of magnesium chloride hexahydrate and 1.9314 g of aluminum chloride hexahydrate were dissolved in 50 mL of deionized water to prepare a precursor solution. Ammonia was rapidly added within 5 seconds, and the pH was adjusted to 9–10 with stirring. After stirring for 15 min, the solution was allowed to stand for 1 h for aging. The resulting white suspension was centrifuged, and the precipitate was washed repeatedly with deionized water until the pH reached 8–9. After washing, a certain amount of deionized water was added to the precipitate and stirred until homogeneous, obtaining a dispersion with a mass concentration of 5–40 mg / mL (e.g., 18 mg / mL). The dispersion was then placed in an oven at 80–150 °C (e.g., 80 °C) for hydrothermal treatment for 24 h. Finally, a near-hexagonal magnesium-aluminum LDH nanosheet dispersion with a circumscribed circle diameter in the range of 100–500 nm (e.g., 120 nm) and a radial-axial ratio of 15–40 (e.g., 18) was obtained.

[0041] Preparation of a fish-scale-like, non-dense hydrotalcite modified layer. 3-Aminopropyltriethoxysilane was added to the above-mentioned magnesium-aluminum hydrotalcite nanosheet dispersion to a concentration of 5–20 μL / mL (e.g., 10 μL / mL). After stirring for 30 min, 6 drops of the solution were added dropwise at 1000 rpm and spin-coated onto a 20 × 20 mm alkali / acid modified polyimide film substrate for 12 s. The resulting wet film was preliminarily dried in an 80°C aminopropylsilane oven for 20 s, followed by spin-coating and drying again, for a total of 6 coatings. Subsequently, it was heat-treated in air at 80, 110, and 150°C for 1 h, 1 h, and 3 h, respectively. Finally, the above-mentioned fish-scale-like, non-dense hydrotalcite modified layer was obtained.

[0042] Preparation of the antistatic ITO layer. A 30-100 nm ITO layer is deposited on the surface of the hydrotalcite modified layer by magnetron sputtering, or a 30-1000 nm ITO coating can be applied by spin coating.

[0043] Preparation of the metal reflective layer. A 30–100 nm Ag layer was deposited on the other side surface using magnetron sputtering.

[0044] Preparation of protective film on Ag surface. A protective film layer was deposited on the Ag surface using magnetron sputtering.

[0045] In a preferred embodiment of the present invention, the hydrotalcite modified layer can react and diffuse on the surface of the polymer film to form a gradient transition layer, which has excellent bonding strength and bending resistance.

[0046] The advantages of the method described in this invention are as follows: it uses commercially available metal chloride salts as raw materials, which are inexpensive; the precursor and coating are prepared by a wet chemical method, which requires low equipment and is simple and easy to operate; the prepared magnesium-aluminum hydrotalcite nanosheet coating is uniform in film formation and free from agglomeration, exhibiting excellent antigenic oxygen properties; the use of an aminohydrosilane coupling agent not only enhances the degree of cross-linking between magnesium-aluminum hydrotalcite sheets, significantly improving the flexibility of the coating, but also enables the coating to form a strong bond with the surface-modified polyimide surface, significantly improving the adhesion of the coating.

[0047] Testing: Ground-based atomic oxygen simulation test equipment was used to characterize the atomic oxygen erosion performance of the samples, and a precision balance was used to measure the mass loss; a space thermal cycling simulation test equipment was used to characterize the thermal stress cracking resistance of the samples; a QTY-10A bending tester was used to test the bending stress cracking resistance of the samples; a cross-cut test was used to characterize the bonding strength between the coating and the substrate; and a scanning electron microscope was used to observe the surface morphology and coating thickness of the samples.

[0048] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0049] Example 1 (1) Preparation of an aqueous dispersion of magnesium-aluminum layered double hydroxide nanosheets (circumscribed circle diameter 140 nm) with a concentration of 18 mg / mL. 0.6449 g of magnesium chloride hexahydrate and 1.9314 g of aluminum chloride hexahydrate were dissolved in 50 mL of deionized water to prepare a precursor solution. Ammonia was rapidly added within 5 s, and the pH was adjusted to 9–10 by stirring. After stirring for 15 min, the solution was allowed to stand for 1 h for aging. The resulting white suspension was centrifuged and the precipitate was washed repeatedly with deionized water until the pH reached 8–9. After washing, a certain amount of deionized water was added to the precipitate and stirred until homogeneous, obtaining a dispersion with a mass concentration of 18 mg / mL. The dispersion was then placed in an oven at 80 °C for hydrothermal treatment for 24 h. Finally, a dispersion of magnesium-aluminum layered double hydroxide nanosheets with a near-hexagonal shape, a circumscribed circle diameter of approximately 120 nm, and a diameter-to-thickness ratio of approximately 18 was obtained. (2) 3-Aminopropyltriethoxysilane (50 μL) was added to the above magnesium-aluminum hydrotalcite nanosheet dispersion (5 mL) (wherein the ratio of at least one of the talc nanosheets or hydrotalcite-like nanosheets to the silane coupling agent was 9 mg: 5 μL). After stirring for 60 min, 6 drops of the solution were added dropwise at 1000 rpm and spin-coated onto a 20 × 20 mm alkali / acid modified polyimide film substrate for 12 s. The formed wet film was preliminarily dried in an oven at 80 °C for 20 s, and then spin-coated and dried again, for a total of 6 coatings. Subsequently, it was heat-treated in air atmosphere at 80, 110, and 150 °C for 1 h, 1 h, and 3 h, respectively. Finally, the above-mentioned fish-scale-like, non-dense antigenic hydrotalcite coating was obtained; (3) Preparation of antistatic ITO layer. A 100-1000 nm ITO layer was deposited on the surface of the hydrotalcite modified layer by spin coating; (4) Preparation of the metal reflective layer. A 30-100 nm Ag layer was deposited on the other side surface by magnetron sputtering; (5) Preparation of protective film on Ag surface. A protective film layer was deposited on the Ag surface by magnetron sputtering.

[0050] The absorptivity and emissivity of the secondary surface mirror based on the hydrotalcite-coated modified polymer were tested, showing a low absorptivity-emissivity ratio. Furthermore, after applying the antistatic ITO layer with 3M 610 tape, no obvious peeling was observed on the surface, and it did not detach or crack after being bent 20 times with a radius of 2.5 mm, indicating a significant increase in the ITO layer's adhesion.

[0051] Furthermore, the space environment tolerance of the secondary surface mirror based on the hydrotalcite-coated modified polymer was further tested, after 5.22 × 10⁻⁶ days. 21 atoms / cm 2 The mass loss after AO irradiation was -0.01 mg / cm³. 2 No obvious erosion was observed, significantly improving the antigen oxygen performance, and the absorption-emission ratio changed little after UV, AO, and thermal cycling tests.

[0052] Example 2 The preparation process of the secondary surface mirror based on the hydrotalcite coating modified polymer in this Example 2 is the same as that in Example 1, except that the hydrothermal temperature in step (1) is 110℃.

[0053] Example 3 The preparation process of the secondary surface mirror based on the hydrotalcite coating modified polymer in Example 3 is the same as that in Example 1, except that the hydrothermal temperature in step (1) is 130°C.

[0054] Example 4 The preparation process of the secondary surface mirror based on the hydrotalcite-coated modified polymer in Example 4 is the same as in Example 1, except that the hydrothermal temperature in step (1) is 150°C. In this example, the diameter of the hydrotalcite nanosheets is too large, which significantly reduces the bending strength of the bonding layer at the interface between the coating and the substrate, and the crack size is significantly larger than in other examples with lower hydrothermal temperatures.

[0055] Example 5 The preparation process of the secondary surface mirror based on the hydrotalcite coating modified polymer in Example 5 is the same as in Example 1, except that 3-aminopropyltriethoxysilane is not added in step (2). In this example, the adhesion between the coating and the substrate decreases without the addition of a crosslinking agent, and the cross-cut test rating is reduced to level 1.

[0056] Example 6 The preparation process of the secondary surface mirror based on the hydrotalcite coating modified polymer in Example 6 is the same as in Example 1, except that the content of 3-aminopropyltriethoxysilane added in step (2) is 150 μL (where the ratio of at least one of the talc nanosheets or hydrotalcite-like nanosheets to the silane coupling agent is 3 mg: 5 μL).

[0057] Example 7 In Example 7, the preparation process of the secondary surface mirror based on the hydrotalcite-coated modified polymer is the same as in Example 1, except that the content of 3-aminopropyltriethoxysilane added in step (2) is 300 μL (where the ratio of at least one of the talc nanosheets or hydrotalcite-like nanosheets to the silane coupling agent is 3 mg: 10 μL). In this example, the excessive crosslinking agent significantly increases the quality loss of the coating and significantly reduces the antigen oxygen performance.

[0058] Comparative Example 1 The preparation process of the antistatic film and reflective film in Comparative Example 1 is the same as in Example 1, except that the hydrotalcite-modified layer is not included. The adhesion, bending, and other properties of the secondary surface mirrors based on the hydrotalcite-coated modified polymer are compared.

[0059] All the raw materials listed in this invention, as well as the upper and lower limits and ranges of the raw materials and the upper and lower limits and ranges of the process parameters, can achieve this invention. Examples are not listed here individually. Before preparing the antistatic layer, the metal reflective layer, and the protective film, the antigenic oxygen content and adhesion of the alkali / acid modified polyimide film substrate / fish-scale-like, non-dense antigenic oxygen hydrotalcite coating prepared in the above examples are first tested, as shown in Table 1. .

[0060] Finally, it is necessary to state that the above embodiments are only used to further illustrate the technical solution of the present invention in detail, and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A secondary surface mirror based on a polymer modified with a hydrotalcite coating, characterized in that, include: The polymer matrix and the antistatic layer, the hydrotalcite modified layer distributed between the polymer matrix and the antistatic layer, and the silane coupling agent modified layer distributed between the polymer matrix and the hydrotalcite modified layer. The hydrotalcite-modified layer comprises a porous coating formed by crosslinking at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets with a silane coupling agent; the silane coupling agent is capable of reactively bonding with the polymer matrix or the hydrotalcite coating, wherein the polymer matrix is ​​a polymer matrix containing hydroxyl and carboxyl groups, and the silane coupling agent is an aminoalkylsilane having an amino group; the ratio of at least one of the hydrotalcite nanosheets or hydrotalcite-like nanosheets to the silane coupling agent in the porous coating is (5-40) mg: (5-20) μL; The hydrotalcite nanosheets or hydrotalcite-like nanosheets are nearly hexagonal or circular in shape with a diameter between 100 and 380 nm.

2. The secondary surface mirror based on a hydrotalcite-coated modified polymer according to claim 1, characterized in that, The chemical composition of the hydrotalcite nanosheets or hydrotalcite-like nanosheets is [M 2+ 1-x M 3+ x (OH)2] x+ A n- x / n ·mH2O, where M 2+ It is a divalent metal cation, M 3+ A is a trivalent metal cation. n- It is an anion; x ranges from 0.1 to 0.

5.

3. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to claim 2, characterized in that, The divalent metal cation is selected from Mg. 2+ Ni 2+ Co 2+ Zn 2+ Cu 2+ At least one of the following; the trivalent metal cation is selected from Al 3 + Cr 3+ Fe 3+ ,Sc 3+ At least one of them; the A n- Anions are selected from CO3 2- NO3 - Cl - OH - SO4 2- PO4 3- C6H4(COO)2 2- At least one of them.

4. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to claim 3, characterized in that, The divalent metal cation is Mg. 2+ The trivalent metal cation is Al 3+ Mg 2+ :Al 3+ =2:

1.

5. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to claim 1, characterized in that, The ratio of the diameter to the thickness of the circumcircle of the circular or near-hexagonal shape is 15 to 40.

6. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The thickness of the silane coupling agent modified layer is 20 nm to 1000 nm.

7. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The silane coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and 3-aminopropylmethyldiethoxysilane.

8. The secondary surface mirror based on a hydrotalcite-coated modified polymer according to claim 7, characterized in that, The silane coupling agent is 3-aminopropyltriethoxysilane.

9. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The polymer matrix containing hydroxyl and carboxyl groups is prepared by a two-step alkaline / acid treatment of polymers containing imide rings and / or ester groups.

10. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to claim 9, characterized in that, Polymers containing imide rings and / or ester groups are polyimides or polyesters.

11. The secondary surface mirror based on a hydrotalcite-coated modified polymer according to claim 9, characterized in that, The two-step alkaline / acid treatment includes: first reacting and modifying the polymer matrix in an alkaline solution at room temperature for 0.5 to 3 hours, and then reacting and modifying it in an acetic acid solution for 0.5 to 3 hours.

12. The secondary surface mirror based on a hydrotalcite-coated modified polymer according to claim 11, characterized in that, The alkaline solution is a sodium hydroxide solution with a concentration of 0.5–2 mol / L, and the acetic acid solution is an acetic acid solution with a concentration of 0.5–2 mol / L.

13. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The antistatic layer is selected from at least one of ITO film, indium oxide, tin oxide, zinc oxide and cadmium oxide.

14. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The thickness of the antistatic layer does not exceed 100 μm.

15. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The thickness of the polymer matrix does not exceed 1000 μm.

16. The secondary surface mirror based on a polymer modified with a hydrotalcite coating according to any one of claims 1-5, characterized in that, The side of the hydrotalcite modified layer away from the polymer matrix also includes a reflective layer; the reflective layer includes a metal reflective film, a fully dielectric reflective film, or a metal dielectric reflective film; the thickness of the reflective layer does not exceed 100 μm.

17. A method for preparing a secondary surface mirror based on a polymer modified with a hydrotalcite coating as described in any one of claims 1-16, characterized in that, include: (1) Add silane coupling agent to an aqueous dispersion containing at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets and mix, then coat it on the surface of a polymer matrix containing hydroxyl and carboxyl groups, and after drying, heat treat it at 80-250°C for 3-12 hours to obtain a hydrotalcite modified coating. (2) An antistatic layer is prepared on the surface of the hydrotalcite modified coating by vacuum coating or chemical method; (3) A metal reflective layer is prepared on the other side of the polymer matrix by vacuum deposition or chemical method to obtain a secondary surface mirror of the surface-modified polymer matrix.

18. The preparation method according to claim 17, characterized in that, The concentration of the aqueous dispersion containing at least one of hydrotalcite nanosheets or hydrotalcite-like nanosheets is 5–40 mg / mL; the mixing method is stirring, and the stirring speed is 200–400 rpm.

19. The preparation method according to claim 17 or 18, characterized in that, The coating is applied at least once; the coating includes spin coating, drip coating, spray coating, or scraping coating.

20. The preparation method according to claim 19, characterized in that, The spin coating speed is 600-1400 rpm, and the spin coating time is 6-18 seconds per coat.

21. The preparation method according to claim 17, characterized in that, The drying process is performed at least once, at a temperature of 60–120°C, with each drying session lasting 10–30 seconds.

22. The application of a secondary surface mirror based on a hydrotalcite-coated modified polymer as described in any one of claims 1-16 in the field of space environment.

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