Polyimide fiber membrane for radiation refrigeration as well as preparation method and application of polyimide fiber membrane

Abstract

The invention relates to the technical field of radiation refrigeration materials, in particular to a polyimide fiber membrane for radiation refrigeration and a preparation method and application thereof. The polyimide fiber membrane for radiation refrigeration comprises polyimide-containing resin and inorganic particles, the polyimide-containing resin is prepared from diamine and dianhydride, the diamine is selected from a combination of diamine A and other diamines, and the diamine A comprises at least one of 4-aminobenzene-2, 5-pyridine diamine and 4, 4 '-diaminodiphenylamine; the dianhydride at least comprises dianhydride B, and the dianhydride B is selected from at least one of 1, 2, 4, 5-hydrogenated pyromellitic dianhydride, 3, 3 ', 4, 4'-dicyclohexyltetracarboxylic dianhydride and 4, 4 '-(hexafluoroisopropylidene) diphthalic anhydride. The invention has the advantages of high whiteness, high temperature resistance, ultraviolet resistance, high relative refractive index and higher infrared absorptivity.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation refrigeration materials, and in particular to a polyimide fiber membrane for radiation refrigeration and a preparation method and application thereof. Background Art

[0002] Radiative cooling is a new type of passive, energy-free cooling method based on the thermal radiation behavior of an object at absolute zero, which radiates its own heat to the low-temperature outer space through an atmospheric transparent window (8-13μm). In order to achieve a true radiative cooling effect, the selected radiative cooling material or structure must have a high reflectivity in the visible light band and a high absorptivity (emissivity) in the atmospheric transparent window, that is, to resist the temperature rise caused by the absorption of sunlight while strengthening the radiative cooling of its own heat.

[0003] Polymers stand out in the field of radiation cooling because of their high absorptivity (emissivity) in the atmospheric transparent window and their easy production and low cost. For example, PDMS, PMMA, PVDF, PE, etc. However, they face two problems at the same time. First, most polymers are transparent in the visible light band, that is, the reflectivity is almost 0. The solutions adopted include using a highly reflective metal film substrate or using Mie scattering to prepare a microporous structure in the structure, which leads to problems such as high cost, heavy weight and weakened mechanical strength. Secondly, since radiation cooling materials need to be exposed to sunlight for a long time, they are easily aged by high temperature and ultraviolet radiation, resulting in reduced radiation cooling performance. In addition, the above materials have poor high temperature resistance, which is not conducive to large-scale practical applications. Efficient radiation cooling materials need to have weather-resistant characteristics such as high temperature resistance, UV resistance, and stable thermal performance, and they must be lightweight, flexible, and have high strength properties to be applicable to a wider range of application scenarios.

[0004] Polyimide (PI) has the characteristics of high strength, high heat resistance, and low dielectric constant, and is widely used in flexible printed circuits, flexible optoelectronic displays, aerospace and other fields. The unique chemical structure of PI gives it a higher absorption rate in the infrared band, providing a new way to prepare radiation refrigeration materials with both high temperature resistance and UV resistance. In particular, the emergence of PI electrospun fiber membranes has attracted widespread attention in the research and application of cooling fabrics. PI electrospun fiber membranes mainly improve the reflection of sunlight by forming Mie scattering through the diameter distribution of the fiber membrane. No metal substrate is required, and light weight and flexibility can be achieved. Therefore, PI can be used as one of the preferred materials for efficient radiation refrigeration.

[0005] At present, there are two main problems that restrict the use of polyimide in radiation refrigeration materials. First, due to the formation of intermolecular or intramolecular charge transfer complexes (CTCs), traditional polyimide films have a brown or yellow appearance. This has an adverse effect on the reflectivity of sunlight, limiting its application in the field of radiation refrigeration materials. Although the introduction of fluorine-containing groups can inhibit the formation of CTCs, reduce the yellowness index of the fiber membrane, and enhance the reflection of sunlight, the fluorine-containing groups are not environmentally friendly and are not conducive to their large-scale application. At the same time, the refractive index of PI in the sunlight band is generally around 1.4, and the relative refractive index with air is only about 0.4, so the reflectivity of sunlight in the scattering of the fiber membrane structure is relatively low. Secondly, the absorption rate of PI in the mid-infrared band of 9-11μm is low, which needs to be further improved.

[0006] Therefore, in response to the current urgent application demand for high-performance radiative cooling fabric materials, it is urgently necessary to develop PI fiber membranes that have high whiteness, high temperature resistance, UV resistance, high relative refractive index and higher infrared absorption rate. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a polyimide fiber membrane for radiation refrigeration having high whiteness, high temperature resistance, ultraviolet resistance, high relative refractive index and higher infrared absorptivity, as well as a preparation method and application thereof.

[0008] The present invention is achieved through the following technical solutions:

[0009] A first aspect of the present invention provides a polyimide fiber membrane for radiative refrigeration, comprising a resin containing polyimide and inorganic particles, wherein the resin containing polyimide is prepared from a diamine and a dianhydride, wherein the diamine is selected from a combination of diamine A and other diamines, wherein the diamine A comprises at least one of 4-aminobenzene-2,5-pyridinediamine (PIDA) and 4,4'-diaminodiphenylamine (DADPA); and the dianhydride comprises at least one of dianhydride B, wherein the dianhydride B is selected from at least one of 1,2,4,5-hydrogenated pyromellitic dianhydride (HPMDA), 3,3',4,4'-dicyclohexyltetracarboxylic dianhydride (HBPDA) and 4,4'-(hexafluoroisopropyl)diphthalic anhydride (6FDA).

[0010] In some embodiments of the present invention, the content of diamine A in diamine is 0.5-5 mol%.

[0011] In some embodiments of the present invention, the content of the dianhydride B in the dianhydride is 60-100 mol %.

[0012] In some embodiments of the present invention, the dianhydride further includes other dianhydrides, and the other dianhydrides are selected from one or more of pyromellitic anhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic anhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic anhydride (a-BPDA), 4,4'-biphenyl ether dianhydride (ODPA), p-phenylene-trimellitic anhydride (TAHQ), 3,3',4,4'-benzophenone tetracarboxylic anhydride (BTDA) and ethylene glycol trimellitic anhydride (TMEG).

[0013] In some embodiments of the present invention, the other diamine is selected from 4,4'-diaminodiphenyl ether (ODA), phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), 4,4-diamino-2,2-dimethylbiphenyl, 1,4-bis(4-amino-benzoate)benzene, bis(4-aminophenyl)terephthalate, 4,4'-diaminobenzanilide (DABA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), 1,3-bis(4-aminophenoxy)benzene (1,3,4-APB), 1,4-bis(4-aminophenyl)terephthalate. One or more of 1,4-bis(4-(4-aminophenoxy)phenyl)propane (BAPP), 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (HFBAPP) and diaminodiphenylmethane (DDM).

[0014] In some embodiments of the present invention, the molar ratio of the diamine to the dianhydride is 1:0.97-1:1.

[0015] In some embodiments of the present invention, the inorganic particles include at least one of core-shell composite particles and hollow particles.

[0016] Preferably, the core-shell composite particles include at least one of silicon oxide / titanium oxide, silicon oxide / zinc sulfide, silicon oxide / zinc oxide, and silicon oxide / aluminum oxide core-shell composite particles.

[0017] Preferably, the hollow particles include at least one of hollow zinc sulfide particles, hollow silica particles, and hollow titanium oxide particles.

[0018] In some embodiments of the present invention, the amount of the inorganic particles added is 0.1-50 wt % of the amount of the resin containing polyimide.

[0019] In some embodiments of the present invention, the size of the inorganic particles is 0.2-5 μm.

[0020] In some embodiments of the present invention, the resin containing polyimide further contains the following structure:

[0021]

[0022] The second aspect of the present invention provides a method for preparing the above-mentioned polyimide fiber membrane for radiant cooling, comprising the following steps:

[0023] (1) preparing a resin solution containing polyimide by reacting diamine and dianhydride in a solvent;

[0024] (2) adding inorganic particles into a resin solution containing polyimide to obtain a spinning solution;

[0025] (3) The spinning solution is subjected to electrospinning to obtain a polyimide fiber membrane for radiant refrigeration.

[0026] In step (2), inorganic particles are added to the polyimide solution, mixed and stirred by a ball mill to obtain a spinning solution.

[0027] In some embodiments of the present invention, the solvent in step (1) is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, γ-caprolactone, xylene and toluene.

[0028] Preferably, the solvent in step (1) is selected from one or more of N,N-dimethylacetamide and γ-caprolactone.

[0029] In some embodiments of the present invention, in addition to adding dianhydride and diamine in step (1), an imidization catalyst is also required to be added. The imidization catalyst includes but is not limited to triethylamine.

[0030] Preferably, step (1) further comprises adding an azeotropic agent, which includes but is not limited to a toluene solution.

[0031] In some embodiments of the present invention, after the reaction in step (1) is completed, ethanol may be added, and the precipitate may be dried and then dissolved in a solvent to obtain a resin solution containing polyimide.

[0032] In some embodiments of the present invention, the solid content of the spinning solution in step (2) is 15-30%, and the viscosity is 10-1000 poise.

[0033] While improving the performance of polyimide fiber membrane, optimizing the solid content of spinning solution and resin viscosity is also the key to improving the processability of polyimide fiber membrane. Generally speaking, when the viscosity is too low, a beaded structure will be formed, which will affect the reflectivity of sunlight, while when the viscosity is too high, the needle will be blocked during the spinning process, which is not conducive to processing and molding.

[0034] In some embodiments of the present invention, the thickness of the polyimide fiber membrane for radiative cooling obtained by electrospinning in step (3) is 50-500 μm.

[0035] In some embodiments of the present invention, the dianhydride in step (1) is added in batches, and the amount of the first batch added is 90-95 wt % of the total amount.

[0036] In some embodiments of the present invention, the reaction in step (1) is divided into three stages, the temperature of the first stage is 30-70°C, and the time is 0.5-2 hours; the temperature of the second stage is 80-150°C, and the time is 5-8 hours; the temperature of the third stage is 150-200°C, and the time is 1-3 hours.

[0037] The third aspect of the present invention provides the use of the above-mentioned polyimide fiber membrane for radiant cooling or the polyimide fiber membrane for radiant cooling prepared by the above-mentioned preparation method in the preparation of high-temperature resistant cooling fabrics, which can be applied to human thermal management, building energy saving and cooling, electronic equipment temperature control, automobile sun protection clothing and other fields.

[0038] Preferably, the polyimide fiber membrane is used by covering the human body, building or vehicle with the polyimide fiber membrane. When the polyimide fiber membrane is left to stand for 2-4 hours under sunlight, the membrane will be a cooling fiber membrane with a temperature significantly lower than the ambient temperature. Meanwhile, after being heated at 300°C for 3 minutes, the cooling effect remains unchanged.

[0039] The beneficial effects of the present invention are:

[0040] (1) The average reflectivity of the polyimide fiber film for radiant cooling of the present invention to sunlight can reach 95%. Due to the use of a diamine with a special structure, the fiber diameter is evenly distributed, which is conducive to enhancing the Mie scattering of sunlight by the fiber structure. At the same time, the addition of inorganic particles with a high refractive index contrast further improves the reflectivity to sunlight, and the average reflectivity at 0.4-0.8μm reaches 95%.

[0041] (2) The polyimide fiber membrane for radiant cooling of the present invention has a high emissivity in the infrared band, and the average emissivity in the 8-13 μm band is as high as 92%, which has a significant cooling effect. -2 When the temperature is lower than the ambient temperature, a cooling temperature of 9°C below the ambient temperature can be achieved.

[0042] (3) The glass transition temperature of the polyimide fiber membrane for radiant cooling of the present invention is greater than 290°C, and it has excellent high temperature resistance. After being heated at 300°C for 3 minutes, its refrigeration performance is almost unchanged compared with the sample before heating. Its contact angle is greater than 130°, and it has high hydrophobicity and can achieve self-cleaning function. It can be used in the fields of building energy saving, vehicles and other outdoor articles, especially passive radiant cooling fabrics and covers in high temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The schematic diagram of the structure of the polyimide fiber membrane for radiant cooling of the present invention is shown in FIG.

[0044] Figure 2 This is a schematic diagram of the structure of the outdoor experimental temperature measurement device. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0046] Example 1

[0047] 4,4'-diaminodiphenyl ether (ODA) (19.5235 g, 0.0975 mol) and 4-aminobenzene-2,5-pyridinediamine (PIDA) (0.5006 g, 0.0025 mol) and 90.0 g N,N-dimethylacetamide (DMAc) were added to a 1000 mL round-bottom three-necked flask equipped with a mechanical stirrer, a thermometer, a reflux condenser, a Dean-Stark separator, and a nitrogen inlet and outlet. Nitrogen was introduced, and 1,2,4,5-hydrogenated pyromellitic dianhydride (HPMDA) (22.4170 g, 0.1 mol) was added at one time, and the residual dianhydride monomer was washed with 9.0 g DMAc. After stirring at room temperature for 0.5 hours, a light yellow viscous solution was obtained, and the reaction was accompanied by heat release, and the system temperature could reach about 60°C. 0.5 g triethylamine and 150 mL toluene solution were added to the reaction system as an imidization catalyst and an azeotropic agent, respectively. Under nitrogen protection, the system temperature was raised to 140°C and the reaction was carried out for 6 hours. During the reaction, the azeotrope of toluene and water was distilled out of the system and collected by the Dean-Stark separator until the water in the system was completely discharged. The system temperature was then further raised to 180°C and the reaction was carried out for 3 hours. After the reaction was completed, it was naturally cooled to room temperature, and the obtained viscous polyimide solution was slowly poured into excess ethanol to precipitate white filaments, which were the resin containing polyimide (PI resin). The obtained filamentous PI resin was collected and dried in a vacuum oven at 80°C for 24 hours to obtain the target PI resin mixture.

[0048] 51.00 g of the above dried target PI resin mixture was dissolved in 153 g of N,N-dimethylacetamide (DMAc) at room temperature with a solid content of 25% to obtain a solution containing PI resin. 10 g of DMAc was added to 1.2494 g (accounting for 20 wt% of the target PI resin mixture) of silicon oxide / alumina core-shell composite particles and ball-milled for 2 h to make them uniformly mixed, and 20 g of the above solution containing PI resin was added and ball-milled for 2 h to obtain a spinning solution, and a 21# metal needle with an inner diameter of 0.5 mm was used as a spinneret for the spinning solution, and the polymer solution was extruded at a speed of 0.15 mL / h through a syringe pump. A roller-type receiving device (diameter: 10 cm; length: 30 cm) was used, with aluminum foil as the receiving substrate, the distance between the needle and the receiving device was 16 cm, and a voltage of 15 kV was applied between the syringe and the receiving device, so that the spinning solution was extruded from the stainless steel needle under the action of the electric field, and the randomly arranged PI fibers were deposited on the uniformly rotating aluminum foil (rotation speed: 4 rpm), and a composite fiber membrane of polyimide and silicon oxide / alumina core-shell composite particles was obtained, which was a polyimide fiber membrane for radiation cooling. During the electrospinning process, the temperature was controlled at 25 ± 5 ° C and the relative humidity was controlled at 40 ± 10 RH. Then its radiation cooling effect and heat resistance were tested.

[0049] The preparation process of Examples 2-6 and Comparative Examples 1-4 is the same as that of Example 1, the only difference being the composition of the added raw materials. Specific data are shown in Table 1.

[0050] Table 1 Raw material composition of the embodiments and comparative examples

[0051]

[0052] Table 2 shows the optical properties of the polyimide fiber membrane for radiation cooling in the wavelength range of 0.25-2.5μm and 2.5-25μm tested by UV-visible-near infrared spectrophotometer and Fourier infrared spectrometer. The average reflectivity (i.e., UV resistance) of the polyimide fiber membrane for radiation cooling in the 0.25-0.4μm band reaches 78%, the average reflectivity of 0.4-0.8μm can reach 95%, the reflectivity at 457nm (the higher this value, the higher the whiteness value of the sample) reaches 92%, and the average emissivity in the atmospheric transparent window (8-13μm) can reach more than 92%, indicating that heat can be efficiently radiated into space.

[0053] Table 2 Properties of polyimide fiber membrane for radiant cooling

[0054]

[0055] Figure 2 This is a schematic diagram of a self-designed outdoor experimental temperature measurement device. The device is mainly composed of polyurethane foam wrapped with aluminum foil, a thermal couple, a polyethylene film, and a sample stage. The outermost layer of the polyurethane foam is wrapped with aluminum foil. The aluminum foil and polyurethane foam can reduce heat transfer, and the polyethylene film can reduce heat convection between the test area and the outside world. The device is placed in an outdoor environment and directly exposed to sunlight. The solar irradiance is recorded by an all-weather light radiation data recorder, and the thermocouple records the real-time temperature of different samples.

[0056] Table 3 shows the maximum cooling effect of the polyimide fiber membrane for radiant cooling compared with the ambient temperature, and the comparison of the cooling effect before and after heat treatment at 300°C for 3 minutes (the difference in the maximum cooling temperature before and after the heat treatment).

[0057] Table 3 Comparison of the maximum cooling temperature below ambient temperature and the cooling effect before and after heat treatment

[0058] Maximum cooling temperature (℃) Comparison of cooling effect before and after heat treatment (℃) Example 1 9.0 0.3 Example 2 9.2 0.3 Example 3 9.1 0.3 Example 4 9.1 0.3 Example 5 9.2 0.3 Example 6 9.4 0.3 Comparative Example 1 7.6 0.4 Comparative Example 2 3.0 0.4 Comparative Example 3 7.0 0.4 Comparative Example 4 3.0 0.4

[0059] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A polyimide fiber membrane for radiant cooling, characterized in that: The invention comprises a resin containing polyimide and inorganic particles. The resin containing polyimide is prepared from diamine and dianhydride. The diamine is selected from a combination of diamine A and other diamines. The diamine A comprises at least one of 4-aminobenzene-2,5-pyridinediamine and 4,4'-diaminodiphenylamine. The dianhydride comprises at least one of dianhydride B, and the dianhydride B is selected from at least one of 1,2,4,5-hydrogenated pyromellitic dianhydride, 3,3',4,4'-dicyclohexyltetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride.

2. The polyimide fiber membrane for radiant cooling according to claim 1, characterized in that: The molar ratio of the diamine to the dianhydride is 1:0.97-1:1, and / or the content of the diamine A in the diamine is 0.5-5 mol %, and / or the content of the dianhydride B in the dianhydride is 60-100 mol %.

3. The polyimide fiber membrane for radiant cooling according to claim 1, characterized in that: The dianhydride also includes one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, p-phenylene-diphenyltrimellitate dianhydride, 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride and ethylene glycol diphenyltrimellitate anhydride.

4. The polyimide fiber membrane for radiant cooling according to claim 1, characterized in that: The other diamines are selected from one or more of 4,4'-diaminodiphenyl ether, phenylenediamine, m-phenylenediamine, 4,4-diamino-2,2-dimethylbiphenyl, 1,4-bis(4-amino-benzoate)benzene, bis(4-aminophenyl)terephthalate, 4,4'-diaminobenzanilide, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, 4,4'-diamino-2,2'-bistrifluoromethylbiphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and diaminodiphenylmethane.

5. The polyimide fiber membrane for radiant cooling according to claim 1, characterized in that: The inorganic particles include at least one of core-shell composite particles and hollow particles. The core-shell composite particles include at least one of silicon oxide / titanium oxide, silicon oxide / zinc sulfide, silicon oxide / zinc oxide, and silicon oxide / aluminum oxide core-shell composite particles. The hollow particles include at least one of hollow zinc sulfide particles, hollow silica particles, and hollow titanium oxide particles. The amount of the inorganic particles added is 0.1-50wt% of the amount of the resin containing polyimide added.

6. The polyimide fiber membrane for radiant cooling according to claim 1, characterized in that: The polyimide-containing resin also contains the following structure:

7. The method for preparing a polyimide fiber membrane for radiant cooling according to any one of claims 1 to 6, characterized in that: The steps include: (1) preparing a resin solution containing polyimide by reacting diamine and dianhydride in a solvent; (2) adding inorganic particles into a resin solution containing polyimide to obtain a spinning solution; (3) The spinning solution is subjected to electrospinning to obtain a polyimide fiber membrane for radiant refrigeration.

8. The preparation method according to claim 7, characterized in that: The solvent in step (1) is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, γ-caprolactone, xylene and toluene; the dianhydride is fed in batches, and the amount of the first batch is 90-95wt% of the total amount; the reaction is divided into three stages, the temperature of the first stage is 30-70°C, and the time is 0.5-2 hours; the temperature of the second stage is 80-150°C, and the time is 5-8 hours; the temperature of the third stage is 150-200°C, and the time is 1-3 hours.

9. The preparation method according to claim 7, characterized in that: The solid content of the spinning solution in step (2) is 15-30%, and the viscosity is 10-1000 poise.

10. Use of the polyimide fiber membrane for radiant cooling according to any one of claims 1 to 6 or the polyimide fiber membrane for radiant cooling prepared by the preparation method according to any one of claims 7 to 9 in preparing high temperature resistant cooling fabrics.

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