A radiative cooling film containing polymer microspheres and its preparation and application

Abstract

The invention discloses a radiation cooling film containing polymer microspheres and its preparation and application. The method comprises: dissolving cage-type silsesquioxane in a water-insoluble ester solvent, adding water and stirring to react to obtain a pre-emulsion; taking part of the pre-emulsion as a seed, adding part of the initiator to react to obtain a seed emulsion, and then uniformly dropping the remaining pre-emulsion and initiator into the seed emulsion to continue the reaction to obtain polymer microspheres; dissolving an electrospun polymer in a solvent to obtain a mixed solution, taking the polymer microspheres in the mixed solution and stirring to obtain a spinning solution, and then electrostatic spinning to obtain the result. The radiation cooling film containing polymer microspheres of the invention comprises electrospun nanofibers and polymer microspheres with selective radiation. The combination of polymer microspheres of different particle sizes and fibers of different diameters can optimize the reflection performance of the obtained film in the visible light to near-infrared band and the radiation performance at the atmospheric window.

Description

Technical Field

[0001] The invention belongs to the technical field of radiation refrigeration materials, and in particular relates to a radiation refrigeration film containing polymer microspheres and a preparation method and application thereof. Background Art

[0002] In recent years, climate change has caused rising temperatures and frequent natural disasters around the world. Traditional cooling methods, represented by air conditioning, account for a large proportion of energy consumption. In addition, many common refrigerants in air conditioning systems also have a strong greenhouse effect, further exacerbating CO 2 Therefore, efficient cooling is particularly important for achieving sustainable development and solving the problem of climate change.

[0003] Radiative cooling materials can reflect most of the sunlight (0.3-2.5 μm) while radiating heat to the outside space through the atmosphere's long-wave infrared transparent window (8-13 μm), thereby causing spontaneous cooling of the surface without consuming any energy. It relies on the material's own characteristics to achieve cooling and has potential application prospects in many fields.

[0004] According to Kirchhoff's law, the radiation capacity of a material is equal to its absorption capacity in the mid-infrared region. 2 The particles enhance the radiation performance of the material, and the Si-O bond is only in the mid-infrared region of 1120cm -1 The Si-O-Si skeleton of polyhedral oligomericsilsesquioxane (POSS) has a strong absorption peak at 800-1200 cm -1 There is a strong absorption peak at the top corner, and the R group at the top corner can be acryloxy, vinyl, phenyl and other groups. The characteristic absorption of these groups brings it the ability of selective radiation. The reflection and radiation performance of the material is not only related to the chemical composition of the material, but also has a great relationship with the size of the material. At present, there is no report on the use of cage-type silsesquioxane to construct polymer microspheres as radiation cooling materials. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a radiative cooling film containing polymer microspheres. The present invention uses cage-type silsesquioxane as a monomer to prepare polymer microspheres with controllable particle size as a radiation device of radiative cooling materials through Pickering emulsion polymerization, and then combines electrospun nanofibers to improve the reflective performance of the film through the controllable fiber diameter of the fiber membrane and the abundant pores between the fibers, so that the material has a high reflectivity in the visible light to near-infrared band, and a high emissivity in the mid-infrared band.

[0006] Another object of the present invention is to provide a radiative cooling film prepared by the above method.

[0007] Another object of the present invention is to provide applications of the above-mentioned radiation cooling film.

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

[0009] A method for preparing a radiative cooling film containing polymer microspheres comprises the following steps:

[0010] (1) dissolving cage-type silsesquioxane in a water-insoluble ester solvent, then adding water and stirring at room temperature to react to obtain a pre-emulsion;

[0011] (2) taking part of the pre-emulsion as a seed, adding part of the initiator thereto, reacting at 75-80° C. for 0.5-1 h under a nitrogen or inert gas atmosphere to obtain a seed emulsion, and then evenly dropping the remaining pre-emulsion and initiator into the seed emulsion, raising the temperature to 80-85° C. after the dropping is complete, and continuing the reaction for 3-6 h to obtain polymer microspheres;

[0012] (3) The electrospinning polymer is dissolved in a solvent to obtain a mixed solution, polymer microspheres are taken into the mixed solution and stirred evenly to obtain a spinning solution, and then electrostatic spinning is performed to obtain a radiant cooling film containing polymer microspheres.

[0013] Preferably, the cage-type silsesquioxane is a pentahedral silsesquioxane (T 6 -POSS), hexahedral silsesquioxane (T 8 -POSS), heptahedral silsesquioxane (T 10 -POSS), octahedral silsesquioxane (T 12 -POSS), wherein the R group at the top angle is at least one of methacryloyloxypropyl, vinyl, and phenyl.

[0014] Preferably, the water-insoluble ester solvent is at least one of isoamyl acetate, butyl acetate, n-hexyl acetate and xylene.

[0015] Preferably, the mass ratio of the cage-type silsesquioxane to the water-insoluble ester solvent and water is 1:(5-15):(30-40).

[0016] Preferably, the stirring reaction is carried out at a speed of 500 to 800 r / min and for a time of 0.5 to 1 h.

[0017] Preferably, the mass ratio of the total amount of pre-emulsion to the total amount of initiator in step (2) is (720-1120):1, and the amount of pre-emulsion and the amount of initiator used to prepare the seed emulsion are both 1 / 4-1 / 6 of their respective total amounts.

[0018] Preferably, the initiator is at least one of ammonium persulfate and potassium persulfate.

[0019] Preferably, the electrospun polymer in step (3) is at least one of polyvinylidene fluoride-co-hexafluoropropylene and polystyrene.

[0020] Preferably, the solvent in step (3) is at least one of acetone, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone and toluene.

[0021] Preferably, the mass ratio of the electrospinning polymer to the solvent in the mixed solution is 1:(4-7).

[0022] Preferably, the mass ratio of the electrospinning polymer to the polymer microspheres in the spinning solution is 10:(0.5-1).

[0023] Preferably, the spinning rate of the electrospinning is 1-3 ml / h, the spinning voltage is 14-15 kV, and the distance between the receiver and the needle is 10-15 cm.

[0024] The radiative cooling film containing polymer microspheres prepared by the present invention can be applied to radiative cooling.

[0025] Compared with the prior art, the present invention achieves the following technical effects:

[0026] (1) The radiative cooling film containing polymer microspheres prepared by the present invention comprises electrospun nanofibers and polymer microspheres with selective radiation, wherein the electrospun nanofiber framework is composed of polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP) and / or polystyrene (PS), which itself has a certain radiative cooling capacity, and the fiber diameter range in the film covers the entire visible light to near-infrared range, which is conducive to light reflection according to Mie scattering, and the controllable fiber diameter and abundant pores between the fibers make the material have excellent reflective performance; in addition, the polymer microspheres with controllable particle size prepared by cage-type silsesquioxane have a selective radiation ability that brings good radiation performance of the film at the atmospheric window (8-13 μm). By matching polymer microspheres of different particle sizes with fibers of different diameters, the reflective performance of the prepared film in the visible light to near-infrared band and its radiation performance at the atmospheric window can be optimized.

[0027] (2) The present invention adopts Pickering emulsion polymerization method when preparing polymer microspheres, which does not require emulsifiers, saves costs, and is far less toxic to the human body than surfactants, and is environmentally friendly; the prepared emulsion has strong stability and is not easily affected by factors such as system pH value, concentration, temperature and oil phase composition. In addition, the present invention uses electrospinning technology to directly and continuously prepare nanofibers, which is simple, efficient and low-cost.

[0028] (3) The present invention can adjust the particle size of the prepared polymer microspheres by changing the ratio of the cage-type silsesquioxane monomer to the non-water-soluble ester solvent in the pre-emulsion. The preparation process is simple and the obtained polymer microspheres have high thermal stability. The application of cage-type silsesquioxane in preparing radiant cooling films is further expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is the structural formula of the cage-type silsesquioxane used in the embodiments of the present invention.

[0031] Figure 2 This is a thermal SEM image of the polymer microspheres prepared in Example 1 of the present invention.

[0032] Figure 3 This is the thermogravimetric analysis spectrum of the polymer microspheres prepared in Example 1 of the present invention.

[0033] Figure 4 This is the emissivity spectrum of the polymer microspheres prepared in Example 1 of the present invention at the atmospheric window (8-13 μm).

[0034] Figure 5 This is the EDS spectrum of the radiative cooling film containing polymer microspheres prepared in Example 1 of the present invention. Figure 6 This is the distribution of the four elements C, O, F, and Si in the film.

[0035] Figure 7 This is a reflectivity spectrum of the radiative cooling film containing polymer microspheres prepared in Example 1 of the present invention in the solar spectrum region (0.3-2.5 μm).

[0036] Figure 8 This is the emissivity spectrum of the radiative cooling film containing polymer microspheres prepared in Example 1 of the present invention at the atmospheric window (8-13 μm).

[0037] Fig. 9 This is the emissivity spectrum of the radiative cooling film containing polymer microspheres prepared in Example 4 of the present invention at the atmospheric window (8-13 μm). DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0039] Unless otherwise specified, the technical solutions described in the present invention are all conventional technologies in the art.

[0040] Octamethacryloxypropyl cage silsesquioxane (MASQ-T 8 ) has a CAS number of 160185-24-0; the tetravinyl hexaphenyl cage silsesquioxane HFSQ-T used 10 It has been disclosed in the Chinese invention patent application "CN202210276055.X A tetraethylene hexaphenyl bifunctional T10 cage-shaped silsesquioxane and its preparation method".

[0041] Example 1

[0042] (1) 1g MASQ-T 8Dissolve in 10 g of isoamyl acetate (PEA), add 30 g of deionized water, and pre-emulsify by mechanical stirring at room temperature at a stirring speed of 500 r / min. After stirring for 1 hour, a white pre-emulsion is obtained.

[0043] (2) Take 1 / 5 (mass) of the pre-emulsion obtained in step (1) in a flask as a seed, prepare 2 g of a 2.5% ammonium persulfate (APS) solution as an initiator, add 1 / 5 (mass) to the flask through a constant flow pump, the reaction temperature is 75° C., and the reaction is carried out under nitrogen atmosphere for 30 min to obtain a seed emulsion with blue light; then the remaining initiator and pre-emulsion are evenly added to the obtained seed emulsion through a constant flow pump, and the addition is completed within two hours, then the reaction temperature is increased to 80° C., and the reaction is carried out under nitrogen atmosphere for 5 h to obtain a white emulsion, which is washed with ethanol and centrifuged to obtain polymer microspheres, which are recorded as P MASQ .

[0044] (3) 2.55 g of PVDF-HFP was dissolved in 12.45 g of a mixed solvent of acetone (ACE) and N,N-dimethylacetamide (DMAC) (v / v=3 / 7) and stirred to obtain a mixed solution. 0.255 g of the polymer microspheres obtained in step (2) was added to the mixed solution. After magnetic stirring for 6 h, the mixture was spun in an electrospinning machine at a spinning rate of 2 ml / h, a spinning voltage of 15 kV, and a distance of 15 cm from the receiver to the needle. The obtained fiber membrane was soaked in ethanol for 0.5 h and then dried to obtain a radiative cooling film containing polymer microspheres, denoted as NM@P MASQ .

[0045] The SEM image of the polymer microspheres prepared in this example is as follows Figure 2 As shown in the figure, it can be seen that the particle size of the polymer microspheres is between 0.3 and 3 μm, and the average particle size is about 1.3 μm.

[0046] The thermogravimetric analysis spectrum of the polymer microspheres prepared in this example is as follows Figure 3 As shown in the figure, it can be seen that the polymer microspheres have excellent thermal stability.

[0047] The emissivity spectrum of the polymer microspheres prepared in this example at the atmospheric window (8-13 μm) is as follows: Figure 4 As shown in the figure, it can be seen that the average emissivity of the polymer microspheres at the atmospheric window can reach 83%.

[0048] The EDS spectrum of the radiative cooling film containing polymer microspheres prepared in this example is as follows: Figure 5 and Figure 6As shown in the figure, it can be seen that the fiber diameter in the film is between 0.2 and 2.5 μm, the fiber diameter range covers the entire visible light to near-infrared range (0.3 to 2.5 μm), and the four elements C, O, F, and Si are evenly distributed in the film. It can be seen that the polymer microspheres are evenly distributed in the fiber membrane.

[0049] The reflectivity spectrum of the radiative cooling film containing polymer microspheres prepared in this embodiment in the solar spectrum region (0.3-2.5 μm) is as follows: Figure 7 As shown in the figure, it can be seen that the average reflectivity of the film in the solar spectrum region is above 97%.

[0050] The emissivity spectrum of the radiative cooling film containing polymer microspheres prepared in this embodiment at the atmospheric window (8-13 μm) is as follows: Figure 8 As shown, it can be seen from the figure that the average emissivity of the film at the atmospheric window reaches 84%.

[0051] Example 2

[0052] (1) 1g MASQ-T 8 Dissolve in 5 g of isoamyl acetate (PEA), add 30 g of deionized water, and pre-emulsify by mechanical stirring at room temperature at a stirring speed of 500 r / min. After stirring for 1 hour, a white pre-emulsion is obtained.

[0053] (2) Take 1 / 5 (mass) of the pre-emulsion obtained in step (1) in a flask as a seed, prepare 2 g of ammonium persulfate (APS) solution with a mass concentration of 2.5% as an initiator, add 1 / 5 (mass) into the flask through a constant flow pump, the reaction temperature is 75° C., and react for 30 minutes under nitrogen atmosphere to obtain a seed emulsion with blue light; then, the remaining initiator and pre-emulsion are evenly added to the obtained seed emulsion through a constant flow pump, and the addition is completed within two hours. Then, the reaction temperature is increased to 80° C., and the reaction is carried out for 5 hours under nitrogen atmosphere to obtain a white emulsion, which is washed with ethanol and centrifuged to obtain polymer microspheres.

[0054] (3) 2.55 g of PVDF-HFP was dissolved in 12.45 g of a mixed solvent of acetone (ACE) and N,N-dimethylacetamide (DMAC) (v / v=3 / 7) and stirred to obtain a mixed solution. 0.255 g of the polymer microspheres obtained in step (2) was added to the mixed solution. After magnetic stirring for 6 h, the mixture was spun in an electrospinning machine at a spinning rate of 2 ml / h, a spinning voltage of 15 kV, and a distance of 15 cm from the receiver to the needle. The obtained fiber membrane was soaked in ethanol for 0.5 h and then dried to obtain a radiant cooling film containing polymer microspheres.

[0055] Example 3

[0056] (1) 1g MASQ-T 8Dissolve in 15 g of isoamyl acetate (PEA), add 30 g of deionized water, and pre-emulsify by mechanical stirring at room temperature at a stirring speed of 500 r / min. After stirring for 1 hour, a white pre-emulsion is obtained.

[0057] (2) Take 1 / 5 (mass) of the pre-emulsion obtained in step (1) in a flask as a seed, prepare 2 g of a 2.5% ammonium persulfate (APS) solution as an initiator, add 1 / 5 (mass) to the flask through a constant flow pump, the reaction temperature is 80° C., and react for 30 minutes under an inert atmosphere to obtain a seed emulsion with blue light; then, the remaining initiator and pre-emulsion are evenly added to the obtained seed emulsion through a constant flow pump, and the addition is completed within two hours. Then, the reaction temperature is increased to 85° C., and the reaction is carried out for 5 hours under a nitrogen atmosphere to obtain a white emulsion, which is washed with ethanol and centrifuged to obtain polymer microspheres.

[0058] (3) 2.55 g of PVDF-HFP was dissolved in 12.45 g of a mixed solvent of acetone (ACE) and N,N-dimethylacetamide (DMAC) (v / v=3 / 7) and stirred to obtain a mixed solution. 0.255 g of the polymer microspheres obtained in step (2) was added to the mixed solution. After magnetic stirring for 6 h, the mixture was spun in an electrospinning machine at a spinning rate of 1 ml / h, a spinning voltage of 15 kV, and a distance of 15 cm from the receiver to the needle. The obtained fiber membrane was soaked in ethanol for 0.5 h and then dried to obtain a radiant cooling film containing polymer microspheres.

[0059] Example 4

[0060] (1) 1g HFSQ-T 10 Dissolve in 15 g of isoamyl acetate (PEA), add 30 g of deionized water, and pre-emulsify by mechanical stirring at room temperature at a stirring speed of 800 r / min. After stirring for 1 hour, a white pre-emulsion is obtained.

[0061] (2) 1 / 5 (mass) of the pre-emulsion obtained in step (1) was taken into a flask as a seed, 2 g of a 2.5% ammonium persulfate (APS) solution was prepared as an initiator, and 1 / 5 (mass) was added to the flask through a constant flow pump. The reaction temperature was 80° C., and the reaction was carried out under an inert atmosphere for 30 min to obtain a seed emulsion with blue light; then the remaining initiator and pre-emulsion were evenly added to the obtained seed emulsion through a constant flow pump, and the addition was completed within two hours. Then the reaction temperature was increased to 85° C., and the reaction was carried out under a nitrogen atmosphere for 6 h to obtain a white emulsion, which was washed with ethanol and centrifuged to obtain polymer microspheres with an average particle size of about 0.5 μm, denoted as P. HFSQ-0.5 .

[0062] (3) 2.55 g of PVDF-HFP was dissolved in 12.45 g of a mixed solvent of acetone (ACE) and N,N-dimethylacetamide (DMAC) (v / v=3 / 7) and stirred to obtain a mixed solution. 0.255 g of the polymer microspheres obtained in step (2) was added to the mixed solution, and after magnetic stirring for 6 h, the mixture was spun in an electrospinning machine at a spinning rate of 3 ml / h, a spinning voltage of 15 kV, and a distance of 15 cm from the receiver to the needle. The obtained fiber membrane was soaked in ethanol for 0.5 h and then dried to obtain a radiation cooling film containing polymer microspheres, which was denoted as NM@P HFSQ-0.5 .

[0063] The emissivity spectrum of the radiative cooling film containing polymer microspheres prepared in this embodiment at the atmospheric window (8-13 μm) is as follows: Fig. 9 As shown, it can be seen from the figure that the average emissivity of the film at the atmospheric window reaches 92%.

[0064] Example 5

[0065] (1) 1g HFSQ-T 10 Dissolve in 20 g of isoamyl acetate (PEA), add 30 g of deionized water, and pre-emulsify by mechanical stirring at room temperature at a stirring speed of 800 r / min. After stirring for 1 hour, a white pre-emulsion is obtained.

[0066] (2) Take 1 / 5 (mass) of the pre-emulsion obtained in step (1) in a flask as a seed, prepare 2 g of a 2.5% ammonium persulfate (APS) solution as an initiator, add 1 / 5 (mass) to the flask through a constant flow pump, the reaction temperature is 75° C., and react for 30 minutes under an inert atmosphere to obtain a seed emulsion with blue light; then, the remaining initiator and pre-emulsion are evenly added to the obtained seed emulsion through a constant flow pump, and the addition is completed within two hours. Then, the reaction temperature is increased to 80° C., and a white emulsion is obtained after reacting for 6 hours under a nitrogen atmosphere. The polymer microspheres are washed with ethanol and centrifuged to obtain polymer microspheres.

[0067] (3) 2.55 g of PVDF-HFP was dissolved in 12.45 g of a mixed solvent of acetone (ACE) and N,N-dimethylacetamide (DMAC) (v / v=3 / 7) and stirred to obtain a mixed solution. 0.255 g of the polymer microspheres obtained in step (2) was added to the mixed solution. After magnetic stirring for 6 h, the mixture was spun in an electrospinning machine at a spinning rate of 3 ml / h, a spinning voltage of 15 kV, and a distance of 15 cm from the receiver to the needle. The obtained fiber membrane was soaked in ethanol for 0.5 h and then dried to obtain a radiative cooling film containing polymer microspheres.

[0068] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a radiative cooling film containing polymer microspheres, characterized in that: The following steps are involved: (1) dissolving a cage-type silsesquioxane in a water-insoluble ester solvent, then adding water and stirring the mixture at room temperature to obtain a pre-emulsion; the cage-type silsesquioxane is T6-POSS, T8-POSS, T 10 -POSS, T 12 - at least one of POSS, wherein the R group at the vertex is at least one of methacryloxypropyl, vinyl, and phenyl; (2) Take part of the pre-emulsion as a seed, add part of the initiator thereto, react at 75-80°C for 0.5-1 h under a nitrogen or inert gas atmosphere to obtain a seed emulsion, then evenly drop the remaining pre-emulsion and initiator into the seed emulsion, raise the temperature to 80-85°C after the addition is complete, and continue to react for 3-6 h to obtain polymer microspheres; (3) dissolving the electrospinning polymer in a solvent to obtain a mixed solution, taking polymer microspheres into the mixed solution and stirring them evenly to obtain a spinning solution, and then electrospinning is performed to obtain a radiant cooling film containing polymer microspheres; The electrospun polymer is polyvinylidene fluoride co-hexafluoropropylene; The water-insoluble ester solvent is at least one of isoamyl acetate, butyl acetate, n-hexyl acetate, and xylene; the mass ratio of the cage-type silsesquioxane to the water-insoluble ester solvent and water is 1:(5-15):(30-40).

2. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The stirring reaction is carried out at a speed of 500-800 r / min and a time of 0.5-1 h.

3. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The mass ratio of the total amount of pre-emulsion to the total amount of initiator in step (2) is (720-1120):1, and the amount of pre-emulsion and the amount of initiator used to prepare the seed emulsion are both 1 / 4-1 / 6 of their respective total amounts; the initiator is at least one of ammonium persulfate and potassium persulfate.

4. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The solvent in step (3) is at least one of acetone, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone and toluene.

5. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The mass ratio of the electrospinning polymer to the solvent in the mixed solution is 1:(4-7).

6. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The mass ratio of the electrospinning polymer to the polymer microspheres in the spinning solution is 10:(0.5-1).

7. The method for preparing a radiative cooling film containing polymer microspheres according to claim 1, characterized in that: The spinning rate of the electrospinning is 1-3 ml / h, the spinning voltage is 14-15 kV, and the distance between the receiver and the needle is 10-15 cm.

8. The radiative cooling film containing polymer microspheres prepared by the method for preparing the radiative cooling film containing polymer microspheres according to any one of claims 1 to 7.

9. Use of the radiative cooling film containing polymer microspheres as claimed in claim 8 in radiative cooling.

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