Insulating high-thermal-conductivity EVA packaging adhesive film for photovoltaic module and preparation method of insulating high-thermal-conductivity EVA packaging adhesive film

Abstract

The invention belongs to the technical field of solar photovoltaic packaging materials, and discloses an insulating high-thermal-conductivity EVA packaging adhesive film for a photovoltaic module and a preparation method of the insulating high-thermal-conductivity EVA packaging adhesive film. The insulating high-thermal-conductivity EVA packaging adhesive film comprises an ethylene-vinyl acetate copolymer and a three-dimensional composite filler uniformly distributed in the ethylene-vinyl acetate copolymer, wherein the three-dimensional composite filler accounts for 1wt.%-10wt.% of the total mass of the insulating high-thermal-conductivity EVA packaging adhesive film; the three-dimensional composite filler is prepared by compounding and gelatinizing modified boron nitride and reduced graphene oxide; the modified boron nitride is hexagonal boron nitride or spherical boron nitride with active groups on the surface; the active group is amino or carboxyl. The three-dimensional composite filler is used for replacing traditional insulating ceramic or metal oxide, the three-dimensional composite filler is introduced into the ethylene-vinyl acetate copolymer, an interconnected three-dimensional filler network is constructed in the composite adhesive film, and the heat-conducting property of the EVA adhesive film is remarkably improved on the premise that good electric insulation is kept.

Description

Technical Field

[0001] The invention relates to the technical field of solar photovoltaic packaging materials, and in particular to an insulating and highly thermally conductive EVA packaging adhesive film for photovoltaic components and a preparation method thereof. Background Art

[0002] Photovoltaic cells are exposed to solar radiation and the large amount of heat accumulated during operation will seriously inhibit the photoelectric conversion efficiency of the cells. Studies have shown that for every 10°C increase in the temperature of photovoltaic cells, their photoelectric conversion efficiency will decrease by 5%. Related research on existing technologies has shown that effectively reducing the temperature of photovoltaic modules is the key to improving the heat dissipation of cells.

[0003] Ethylene-vinyl acetate copolymer, or EVA, has become a typical polymer material for photovoltaic module packaging due to its significant advantages in sealing, adhesion, durability, optical properties, etc. According to statistics, more than 80% of photovoltaic modules in the existing technology are encapsulated with EVA film. The classic photovoltaic cell module is generally composed of a glass cover-upper EVA film-cell-lower EVA film-TPT backplane. However, the thermal conductivity of EVA is <0.4W / m·K. Its extremely low thermal conductivity is not conducive to the heat dissipation of photovoltaic modules, which will shorten the service life of photovoltaic modules and reduce the efficiency of photovoltaic power generation.

[0004] Those skilled in the art have proposed that the EVA film located at the bottom layer of the photovoltaic module has no requirements for light transmittance, so the thermal conductivity of the EVA film can be improved by filling and modifying the EVA film located at the bottom layer of the photovoltaic module, thereby achieving the purpose of improving the heat dissipation of the battery and improving the efficiency of photovoltaic power generation. For photovoltaic encapsulation films, in addition to requiring them to have good thermal conductivity to promote the heat dissipation of photovoltaic modules and ensure the efficiency of photovoltaic power generation, considering their practical applications, they should also have good electrical insulation and mechanical properties.

[0005] In order to solve the above technical problems, the current existing technology mainly attempts to improve the electrical insulation performance of EVA film by adding insulating ceramics or metal oxides as thermal conductive fillers in EVA film. However, such fillers need to be added in an amount of >30wt.% to significantly improve the thermal conductivity of EVA film. In addition, a high amount of fillers is not conducive to maintaining the flexibility of EVA film. Although carbon materials and metals have high thermal conductivity, it is difficult to ensure good electrical insulation performance of EVA composite films prepared with them as fillers, which seriously limits their application in photovoltaic cells. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides an insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules and a preparation method thereof. The present invention is based on the self-assembly of EVA molecular surfaces to regulate the film structure, replaces traditional insulating ceramics or metal oxides with three-dimensional composite fillers, and introduces three-dimensional composite fillers into ethylene-vinyl acetate copolymers to construct an interconnected three-dimensional filler network inside the composite film, thereby significantly improving the thermal conductivity of the EVA film while maintaining good electrical insulation.

[0007] The insulating high thermal conductivity EVA packaging film for photovoltaic modules and the preparation method thereof of the present invention are realized by the following technical scheme:

[0008] The first object of the present invention is to provide an insulating and highly thermally conductive EVA packaging film for photovoltaic modules, comprising a film matrix and fillers uniformly distributed in the matrix.

[0009] In the present invention, the film matrix is ​​ethylene-vinyl acetate copolymer.

[0010] The filler is a three-dimensional composite filler, and the three-dimensional composite filler accounts for 1wt.% to 10wt.% of the total mass of the insulating high thermal conductive EVA packaging film, and the rest is ethylene-vinyl acetate copolymer.

[0011] It should be noted that the present invention is based on the theory of thermal conduction pathways, and considering that constructing a three-dimensional filler network in a polymer matrix can provide a complete and effective path for carrier heat transfer, significantly improve the thermal conductivity of the polymer at a lower filler content, and protect the mechanical properties of the polymer composite material to the maximum extent. Therefore, the present invention replaces traditional insulating ceramics or metal oxides with three-dimensional composite fillers, and introduces three-dimensional composite fillers into ethylene-vinyl acetate copolymers to construct an interconnected three-dimensional filler network inside the composite film, thereby significantly improving the thermal conductivity of the EVA film while maintaining good electrical insulation.

[0012] The three-dimensional composite filler of the present invention is prepared by compounding and gelling modified boron nitride and reduced graphene oxide; the modified boron nitride is hexagonal boron nitride or spherical boron nitride with active groups on the surface; wherein the active groups are amino groups or carboxyl groups.

[0013] In some preferred embodiments of the present invention, the three-dimensional composite filler is prepared by the following steps:

[0014] Step 1, preparation of modified boron nitride:

[0015] The boron nitride raw material is dispersed in a solvent, and then a surface modifier is added and stirred at room temperature to introduce active groups on the surface of the boron nitride raw material through the surface modifier to obtain modified boron nitride; wherein the boron nitride raw material is hexagonal boron nitride or spherical boron nitride.

[0016] Step 2, preparing a modified boron nitride solution:

[0017] The modified boron nitride is dispersed in water to obtain a modified boron nitride solution.

[0018] Step 3, composite modified boron nitride and graphene oxide:

[0019] The graphene oxide dispersion is dispersed in the modified boron nitride solution, and then a reducing agent is added to mix and heat treatment is performed, so that during the gelation of the graphene oxide and the modified boron nitride, the reducing agent in situ reduces the graphene oxide to reduced graphene oxide, thereby obtaining a reduced graphene oxide / boron nitride composite filler with a three-dimensional structure. After washing, freeze drying is performed to obtain a reduced graphene oxide / modified boron nitride aerogel with a three-dimensional structure, and the reduced graphene oxide / modified boron nitride aerogel is used as a three-dimensional composite filler.

[0020] It should be noted that in the above step 1 of the present invention, hexagonal boron nitride or spherical boron nitride is used as the first thermal conductive filler raw material to optimize the carrier heat transfer path. And considering the factor of interface thermal resistance, the present invention introduces amino or carboxyl groups on the surface of hexagonal boron nitride or spherical boron nitride by introducing a surface modifier, so that the obtained modified boron nitride can form a good interface with graphene oxide and the polymer matrix, reduce the interface thermal resistance, and then improve the thermal conductivity of the composite film.

[0021] In some preferred embodiments of the present invention, the surface modifier is one or more of tannic acid, dopamine and silane coupling agent; 3 mol to 34 mol of the surface modifier is added for every 1 g of boron nitride raw material.

[0022] In the above step 2 of the present invention, graphene oxide is used as the second thermal conductive filler raw material, and after mixing it with the modified boron nitride solution, a reducing agent is added to achieve the successful compounding of the first thermal conductive filler modified boron nitride and the second thermal conductive filler reduced graphene oxide, and a reduced graphene oxide / modified boron nitride aerogel with a three-dimensional structure is obtained. It should be noted that in the process of exploration, the present invention also tried to prepare reduced graphene oxide first, and then compound the obtained prepared reduced graphene oxide with modified boron nitride, but the composite effect was not good, and it was difficult to form a three-dimensional filler with stable performance. Therefore, the present invention adopts the method of first compounding graphene oxide with modified boron nitride and then reducing it in situ, and compared with first preparing reduced graphene oxide and then mixing it with modified boron nitride, graphene oxide has more active groups on the surface than reduced graphene oxide, and can better compound with modified boron nitride to form a three-dimensional filler.

[0023] In some preferred embodiments of the present invention, the mass concentration of the graphene oxide dispersion is 0.7wt.% to 1.6wt.%, so as to promote uniform dispersion of the filler and prevent filler agglomeration.

[0024] In some preferred embodiments of the present invention, the mass ratio of graphene oxide in the graphene oxide dispersion to modified boron nitride in the modified boron nitride solution is 3.5-4.5:1, so as to achieve the purpose of constructing a good three-dimensional filler thermal conductive network.

[0025] In some preferred embodiments of the present invention, the reducing agent is one or more of hydroiodic acid, hydrazine hydrate and ascorbic acid to ensure that the graphene oxide can be reduced, thereby improving the thermal conductivity of the filler.

[0026] In some preferred embodiments of the present invention, the reducing agent is added according to the mass of graphene oxide in the graphene oxide dispersion, and 70 mol to 245 mol of the reducing agent is added for every 1 g of graphene oxide, so as to achieve the purpose of complete reduction of the graphene oxide.

[0027] In some preferred embodiments of the present invention, the solvent is a mixed solvent of ethanol and water in a volume ratio of 8:1.5 to 2.5, so as to achieve hydroxylation of the surface of boron nitride and hydrolyze the surface modifier to promote modification of boron nitride.

[0028] In some preferred embodiments of the present invention, the stirring treatment time is 12 hours to 36 hours to promote the dispersion and uniform mixing of the filler.

[0029] In some preferred embodiments of the present invention, the ethylene-vinyl acetate copolymer is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 25 wt.% and a melt index of 19 g / 10 min, so that the prepared insulating and highly thermally conductive EVA packaging film has good flexibility.

[0030] In some preferred embodiments of the present invention, when hexagonal boron nitride is used as the boron nitride raw material, the hexagonal boron nitride has a sheet diameter of 1 μm to 2 μm and a sheet thickness of 1 nm to 2 nm, so as to optimize the carrier heat transfer path.

[0031] In the above step 3, the temperature of the heating treatment is 70° C. to 85° C., and the heating time is 2 to 6 hours, so that the graphene oxide is reduced to reduced graphene oxide.

[0032] The second object of the present invention is to provide a method for preparing the above-mentioned insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules, comprising the following steps:

[0033] Step 1: Prepare filler dispersion:

[0034] The three-dimensional composite filler is dispersed in an organic solvent to obtain a filler dispersion.

[0035] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0036] The ethylene-vinyl acetate copolymer is dispersed in an organic solvent to obtain an ethylene-vinyl acetate copolymer solution.

[0037] Step 3: Prepare the film-forming solution:

[0038] The ethylene-vinyl acetate copolymer solution and the filler dispersion are mixed to obtain a film-forming solution.

[0039] Step 4: Solution pouring:

[0040] The film-forming liquid is made into a composite film by a solution casting method, and the obtained composite film is used as an insulating and highly thermally conductive EVA packaging adhesive film.

[0041] It should be noted that the present invention preferably adopts a solution casting method to prepare an insulating and highly thermally conductive EVA encapsulation film. In the process of preparing the insulating and highly thermally conductive EVA encapsulation film by the solution casting method, a three-dimensional composite filler is introduced, and the film structure is regulated based on the self-assembly of the EVA molecular surface. At the same time, an interconnected three-dimensional filler network is constructed inside the composite film, so that the thermal conductivity of the EVA film is significantly improved while maintaining good electrical insulation. In the preparation process, the polymer molecules will self-assemble on the surface of the composite film due to the action of surface tension, so that it maintains good electrical insulation properties.

[0042] The organic solvent used in the present invention is any one of ethyl acetate, tetrahydrofuran and xylene. In view of environmental friendliness and cost issues, the organic solvent used in the present invention is more preferably ethyl acetate.

[0043] In some preferred embodiments of the present invention, the mass ratio of the three-dimensional composite filler in the filler dispersion to the ethylene-vinyl acetate copolymer in the ethylene-vinyl acetate copolymer solution is 0.01-0.1:1.

[0044] In some preferred embodiments of the present invention, when the insulating high thermal conductive EVA packaging film is prepared by the solution casting method, the following steps are performed:

[0045] The film-forming liquid is poured into a container, sealed with plastic wrap, and left to stand for heating and drying to obtain an insulating and highly thermally conductive EVA packaging film.

[0046] In some preferred embodiments of the present invention, the static heating drying includes a first heating stage and a second heating stage performed sequentially, wherein the temperature of the first heating stage is 25°C to 40°C and the time is 2h to 5h; the temperature of the second heating stage is 40°C to 60°C and the time is 4h to 8h.

[0047] In some preferred embodiments of the present invention,

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention replaces traditional insulating ceramics or metal oxides with three-dimensional composite fillers. By introducing three-dimensional composite fillers into ethylene-vinyl acetate copolymer, an interconnected three-dimensional filler network is constructed inside the composite film, thereby significantly improving the thermal conductivity of the EVA film while maintaining good electrical insulation.

[0050] The present invention adopts a solution casting method to prepare an insulating high-thermal conductive EVA encapsulation film. During the process of preparing the insulating high-thermal conductive EVA encapsulation film by the solution casting method, a three-dimensional composite filler is introduced, and the film structure is regulated based on the self-assembly of the EVA molecular surface. At the same time, an interconnected three-dimensional filler network is constructed inside the composite film, so that the thermal conductivity of the EVA film is significantly improved while maintaining good electrical insulation. In addition, during the preparation process, the polymer molecules are self-assembled on the surface of the composite film due to the effect of surface tension, so that the composite film maintains good electrical insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The figure is a schematic diagram of the preparation process of the insulating and highly thermally conductive EVA packaging film of the present invention.

[0052] Figure 2 This is a diagram showing the modification mechanism of the surface modification of boron nitride in Example 1.

[0053] Figure 3 The three-dimensional composite filler-NH of Example 1 2 SEM image of .

[0054] Figure 4 The volume resistivity test results of Examples 1 to 5 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0055] The technical scheme in the embodiments of the present invention will be described clearly and completely below. It should be noted that in the following embodiments of the present invention, the ethylene-vinyl acetate copolymer used is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 25wt.% and a melt index of 19g / 10min. And the boron nitride raw materials used are all hexagonal boron nitride, referred to as hBN, and the sheet diameter of hBN is 1μm to 2μm, and the sheet thickness is 1nm to 2nm.

[0056] Example 1

[0057] This embodiment provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps, and its preparation process can be found in Figure 1 :

[0058] Step 1: Prepare filler dispersion:

[0059] (I) Preparation of three-dimensional composite fillers:

[0060] 1) Preparation of modified boron nitride:

[0061] 1 g hBN was added to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2 and stirred for 6 h. Subsequently, 2 g of KH550 silane coupling agent was added and magnetically stirred at room temperature for 24 h. The solution was then filtered to obtain modified boron nitride, which was recorded as hBN-NH 2 In this embodiment, the mechanism of amination modification of boron nitride is as follows: Figure 2 As shown, it can be seen that boron nitride is first hydroxylated in an alcohol-water mixed solution, and then amino-modified under the action of KH550 silane coupling agent to obtain modified boron nitride.

[0062] 2) Preparation of modified boron nitride solution:

[0063] The obtained 0.08 g hBN-NH 2 The modified boron nitride solution was obtained by mixing with 100 g of distilled water and magnetically stirring at room temperature for 20 min, which was recorded as hBN-NH 2 Solution.

[0064] 3) Composite modified boron nitride and graphene oxide:

[0065] 3.1) 32 g of a graphene oxide dispersion having a solid content of 1 wt.% and 100 g of distilled water were mixed by high-frequency ultrasound for 10 min to obtain a graphene oxide solution.

[0066] 3.2) The obtained graphene oxide solution and the obtained hBN-NH 2 The solutions were mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0067] 3.3) According to the mass ratio of GO to ascorbic acid being 1:6, the obtained first mixed solution and ascorbic acid were stirred at room temperature with a glass rod for 3 min to be evenly mixed to obtain a second mixed solution.

[0068] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 80°C for 4 h to reduce the graphene oxide to reduced graphene oxide. The solvent was removed, and the obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler, which was recorded as rGO / hBN-NH 2 .

[0069] (ii) Dispersed three-dimensional composite fillers:

[0070] 0.12 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred for 10 min at room temperature, and ultrasonically dispersed for 10 min under high-frequency ultrasound to obtain a filler dispersion.

[0071] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0072] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0073] Step 3: Prepare the film-forming solution:

[0074] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0075] Step 4: Solution pouring:

[0076] The above-mentioned film-forming liquid was poured into a culture dish and sealed with plastic wrap, then placed in a fume hood at room temperature for 4 hours, and then transferred to a 50° C. oven for drying for 6 hours. The insulating and highly thermally conductive EVA packaging film obtained in this example was recorded as 3wt.% filler.

[0077] Example 2

[0078] This embodiment provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps:

[0079] Step 1: Prepare filler dispersion:

[0080] (I) Preparation of three-dimensional composite fillers:

[0081] 1) Preparation of modified boron nitride:

[0082] 1 g hBN was added to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2 and stirred for 6 h. Subsequently, 2 g of KH550 silane coupling agent was added and magnetically stirred at room temperature for 24 h. The solution was then filtered to obtain modified boron nitride, which was recorded as hBN-NH 2 .

[0083] 2) Preparation of modified boron nitride solution:

[0084] The obtained 0.08 g hBN-NH 2The modified boron nitride solution was obtained by mixing with 100 g of distilled water and magnetically stirring at room temperature for 20 min, which was recorded as hBN-NH 2 Solution.

[0085] 3) Composite modified boron nitride and graphene oxide:

[0086] 3.1) 32 g of a graphene oxide dispersion having a solid content of 1 wt.% and 100 g of distilled water were mixed by high-frequency ultrasound for 10 min to obtain a graphene oxide solution.

[0087] 3.2) The obtained graphene oxide solution and the obtained hBN-NH 2 The solutions were mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0088] 3.3) According to the mass ratio of GO to ascorbic acid being 1:6, the obtained first mixed solution and ascorbic acid were stirred at room temperature with a glass rod for 3 min to be evenly mixed to obtain a second mixed solution.

[0089] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 80° C. for 4 h to reduce the graphene oxide to reduced graphene oxide, and the solvent was removed. The obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler.

[0090] (ii) Dispersed three-dimensional composite fillers:

[0091] 0.04 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred for 10 min at room temperature, and ultrasonically dispersed for 10 min under high-frequency ultrasound to obtain a filler dispersion.

[0092] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0093] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0094] Step 3: Prepare the film-forming solution:

[0095] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0096] Step 4: Solution pouring:

[0097] Pour the above-mentioned film-forming solution into a petri dish, seal it with plastic wrap, then place it in a fume hood at room temperature for 4 h, and then transfer it to an oven at 50 °C for drying for 6 h to obtain an insulating EVA / rGO / hBN-NH with a filler content of 1 wt%. 2 Composite thermal conductive film.

[0098] That is, the difference between Example 2 and Example 1 lies in:

[0099] In this example, the addition amount of the three-dimensional composite filler is 0.04 g, and the insulating high thermal conductivity EVA encapsulation adhesive film obtained in this example is denoted as 1 wt.% filler.

[0100] Example 3

[0101] This example provides an insulating high thermal conductivity EVA encapsulation adhesive film for photovoltaic modules, which is prepared by the following steps:

[0102] Step 1, prepare a filler dispersion:

[0103] (1) Prepare a three-dimensional composite filler:

[0104] 1) Prepare modified boron nitride:

[0105] Add 1 g of hBN to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2, stir for 6 h, then add 2 g of KH550 silane coupling agent, magnetically stir at room temperature for 24 h, and then perform suction filtration to obtain modified boron nitride, denoted as hBN-NH 2 .

[0106] 2) Prepare a modified boron nitride solution:

[0107] Mix the obtained 0.08 g of hBN-NH 2 and 100 g of distilled water, and magnetically stir at room temperature for 20 min to obtain a modified boron nitride solution, denoted as hBN-NH 2 solution.

[0108] 3) Compound modified boron nitride and graphene oxide:

[0109] 3.1) Mix 32 g of a graphene oxide dispersion with a solid content of 1 wt.% and 100 g of distilled water, and ultrasonically agitate at high frequency for 10 min to obtain a graphene oxide solution.

[0110] 3.2) Mix the obtained graphene oxide solution and the obtained hBN-NH 2 solution, magnetically stir at room temperature for 20 min, and ultrasonically disperse under high-frequency ultrasound for 10 min, and then magnetically stir at room temperature for 12 h to obtain a uniformly dispersed first mixed solution.

[0111] 3.3) According to the mass ratio of GO to ascorbic acid being 1:6, the obtained first mixed solution and ascorbic acid were stirred at room temperature with a glass rod for 3 min to be evenly mixed to obtain a second mixed solution.

[0112] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 80°C for 4 h to reduce the graphene oxide to reduced graphene oxide. The solvent was removed, and the obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler, which was recorded as rGO / hBN-NH 2 .

[0113] (ii) Dispersed three-dimensional composite fillers:

[0114] 0.20 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred for 10 min at room temperature, and ultrasonically dispersed for 10 min under high-frequency ultrasound to obtain a filler dispersion.

[0115] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0116] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0117] Step 3: Prepare the film-forming solution:

[0118] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0119] Step 4: Solution pouring:

[0120] The above film-forming solution was poured into a culture dish and sealed with plastic wrap, then placed in a fume hood at room temperature for 4 h, and then transferred to a 50 °C oven for drying for 6 h to obtain an insulating EVA / rGO / hBN-NH with a filler content of 3 wt%. 2 Composite thermal conductive film.

[0121] That is, the difference between Example 3 and Example 1 is:

[0122] In this embodiment, the addition amount of the three-dimensional composite filler is 0.20 g, and the insulating and highly thermally conductive EVA packaging film obtained in this embodiment is recorded as 5 wt. % filler.

[0123] Example 4

[0124] This embodiment provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps:

[0125] Step 1: Prepare filler dispersion:

[0126] (I) Preparation of three-dimensional composite fillers:

[0127] 1) Preparation of modified boron nitride:

[0128] 1 g hBN was added to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2 and stirred for 6 h. Subsequently, 2 g of KH550 silane coupling agent was added and magnetically stirred at room temperature for 24 h. The solution was then filtered to obtain modified boron nitride, which was recorded as hBN-NH 2 .

[0129] 2) Preparation of modified boron nitride solution:

[0130] The obtained 0.08 g hBN-NH 2 The modified boron nitride solution was obtained by mixing with 100 g of distilled water and magnetically stirring at room temperature for 20 min, which was recorded as hBN-NH 2 Solution.

[0131] 3) Composite modified boron nitride and graphene oxide:

[0132] 3.1) 32 g of a graphene oxide dispersion having a solid content of 1 wt.% and 100 g of distilled water were mixed by high-frequency ultrasound for 10 min to obtain a graphene oxide solution.

[0133] 3.2) The obtained graphene oxide solution and the obtained hBN-NH 2 The solutions were mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0134] 3.3) According to the mass ratio of GO to ascorbic acid being 1:6, the obtained first mixed solution and ascorbic acid were stirred at room temperature with a glass rod for 3 min to be evenly mixed to obtain a second mixed solution.

[0135] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 80°C for 4 h to reduce the graphene oxide to reduced graphene oxide. The solvent was removed, and the obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler, which was recorded as rGO / hBN-NH 2 .

[0136] (ii) Dispersed three-dimensional composite fillers:

[0137] 0.28 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred at room temperature for 10 min, and ultrasonically dispersed under high-frequency ultrasound for 10 min to obtain a filler dispersion.

[0138] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0139] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0140] Step 3: Prepare the film-forming solution:

[0141] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0142] Step 4: Solution pouring:

[0143] The above film-forming solution was poured into a culture dish and sealed with plastic wrap, then placed in a fume hood at room temperature for 4 h, and then transferred to a 50 °C oven for drying for 6 h to obtain an insulating EVA / rGO / hBN-NH with a filler content of 3 wt%. 2 Composite thermal conductive film.

[0144] That is, the difference between Example 4 and Example 1 is:

[0145] In this embodiment, the addition amount of the three-dimensional composite filler is 0.28 g, and the insulating and highly thermally conductive EVA packaging film obtained in this embodiment is recorded as 7 wt. % filler.

[0146] Example 5

[0147] This embodiment provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps:

[0148] Step 1: Prepare filler dispersion:

[0149] (I) Preparation of three-dimensional composite fillers:

[0150] 1) Preparation of modified boron nitride:

[0151] 1 g hBN was added to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2 and stirred for 6 h. Subsequently, 2 g of KH550 silane coupling agent was added and magnetically stirred at room temperature for 24 h. The solution was then filtered to obtain modified boron nitride, which was recorded as hBN-NH 2 .

[0152] 2) Preparation of modified boron nitride solution:

[0153] The obtained 0.08 g hBN-NH 2 The modified boron nitride solution was obtained by mixing with 100 g of distilled water and magnetically stirring at room temperature for 20 min, which was recorded as hBN-NH 2 Solution.

[0154] 3) Composite modified boron nitride and graphene oxide:

[0155] 3.1) 32 g of a graphene oxide dispersion having a solid content of 1 wt.% and 100 g of distilled water were mixed by high-frequency ultrasound for 10 min to obtain a graphene oxide solution.

[0156] 3.2) The obtained graphene oxide solution and the obtained hBN-NH 2 The solutions were mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0157] 3.3) According to the mass ratio of GO to ascorbic acid being 1:6, the obtained first mixed solution and ascorbic acid were stirred at room temperature with a glass rod for 3 min to be evenly mixed to obtain a second mixed solution.

[0158] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 80° C. for 4 h to reduce the graphene oxide to reduced graphene oxide, and the solvent was removed. The obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler.

[0159] (ii) Dispersed three-dimensional composite fillers:

[0160] 0.37 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred at room temperature for 10 min, and ultrasonically dispersed under high-frequency ultrasound for 10 min to obtain a filler dispersion.

[0161] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0162] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0163] Step 3: Prepare the film-forming solution:

[0164] After mixing the obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion, magnetically stir for 20 min at room temperature to mix evenly, and ultrasonically disperse for 10 min under high-frequency ultrasound, and then magnetically stir for 12 h at room temperature to obtain a film-forming solution.

[0165] Step Four, solution casting:

[0166] Pour the above film-forming solution into a petri dish, seal it with plastic wrap, then place it in a fume hood at room temperature for 4 h, and then transfer it to an oven at 50 °C to dry for 6 h to obtain an insulating EVA / rGO / hBN-NH 2 composite thermally conductive film with a filler content of 3 wt%.

[0167] That is, the difference between Example 5 and Example 1 is that:

[0168] In this example, the addition amount of the three-dimensional composite filler is 0.37 g, and the insulating high thermal conductivity EVA encapsulation film obtained in this example is denoted as 9 wt.% filler.

[0169] Example 6

[0170] This example provides an insulating high thermal conductivity EVA encapsulation film for photovoltaic modules, which is prepared by the following steps:

[0171] Step One, prepare a filler dispersion:

[0172] (1) Prepare a three-dimensional composite filler:

[0173] 1) Prepare modified boron nitride:

[0174] Add 1 g of hBN to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:1.5, stir for 4 h, then add 3 mol of tannic acid, magnetically stir at room temperature for 12 h, and then perform suction filtration to obtain modified boron nitride.

[0175] 2) Prepare a modified boron nitride solution:

[0176] Mix the obtained 0.08 g of modified boron nitride and 100 g of distilled water, and magnetically stir at room temperature for 20 min to obtain a modified boron nitride solution.

[0177] 3) Compound modified boron nitride and graphene oxide:

[0178] 3.1) Mix 32 g of a graphene oxide dispersion with a solid content of 0.7 wt.% and 100 g of distilled water, and ultrasonically disperse at high frequency for 10 min to obtain a graphene oxide solution.

[0179] 3.2) The obtained graphene oxide solution and the obtained modified boron nitride solution are mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0180] 3.3) Add 70 mol of hydroiodic acid to every 1 g of graphene oxide, and stir the obtained first mixed solution and hydroiodic acid with a glass rod for 3 min at room temperature to mix them evenly, to obtain a second mixed solution.

[0181] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in a 70° C. oven for 6 h to reduce the graphene oxide to reduced graphene oxide, and the solvent was removed. The obtained three-dimensional gel filler was washed with distilled water and then freeze-dried to obtain a three-dimensional composite filler.

[0182] (ii) Dispersed three-dimensional composite fillers:

[0183] 0.037 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred for 10 min at room temperature, and ultrasonically dispersed for 10 min under high-frequency ultrasound to obtain a filler dispersion.

[0184] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0185] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0186] Step 3: Prepare the film-forming solution:

[0187] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0188] Step 4: Solution pouring:

[0189] The film-forming liquid was poured into a culture dish and sealed with plastic wrap, then placed in a fume hood at 30°C for 5 hours, and then transferred to a 40°C oven for drying for 8 hours to obtain an insulating and highly thermally conductive EVA encapsulation film.

[0190] Example 7

[0191] This embodiment provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps:

[0192] Step 1: Prepare filler dispersion:

[0193] (I) Preparation of three-dimensional composite fillers:

[0194] 1) Preparation of modified boron nitride:

[0195] 1 g of hBN was added to 200 mL of an alcohol-water mixed solution with an alcohol-water volume ratio of 8:2.5 and stirred for 8 h. Subsequently, 34 mol of dopamine was added and magnetic stirring was performed at room temperature for 36 h. The solution was then filtered to obtain modified boron nitride.

[0196] 2) Preparation of modified boron nitride solution:

[0197] 0.08 g of the obtained modified boron nitride and 100 g of distilled water were mixed and magnetically stirred at room temperature for 20 min to obtain a modified boron nitride solution.

[0198] 3) Composite modified boron nitride and graphene oxide:

[0199] 3.1) 32 g of a graphene oxide dispersion having a solid content of 10 wt.% and 100 g of distilled water were mixed by high-frequency ultrasound for 10 min to obtain a graphene oxide solution.

[0200] 3.2) The obtained graphene oxide solution and the obtained modified boron nitride solution are mixed, magnetically stirred at room temperature for 20 minutes, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a uniformly dispersed first mixed solution.

[0201] 3.3) According to the ratio of adding 245 mol of ascorbic acid per 1 g of graphene oxide, the obtained first mixed solution and ascorbic acid were stirred with a glass rod at room temperature for 3 min to mix them evenly, thereby obtaining a second mixed solution.

[0202] 3.4) The obtained second mixed solution was placed in three small beakers respectively, and heated in an oven at 85° C. for 2 h to reduce the graphene oxide to reduced graphene oxide, and the solvent was removed. The obtained three-dimensional gel filler was washed with distilled water, and then freeze-dried to obtain a three-dimensional composite filler.

[0203] (ii) Dispersed three-dimensional composite fillers:

[0204] 0.37 g of the obtained three-dimensional composite filler was dispersed in 30 g of ethyl acetate solvent, magnetically stirred at room temperature for 10 min, and ultrasonically dispersed under high-frequency ultrasound for 10 min to obtain a filler dispersion.

[0205] Step 2, preparing ethylene-vinyl acetate copolymer solution:

[0206] 3.7 g of ethylene-vinyl acetate copolymer was dispersed in 50 g of ethyl acetate solvent and stirred at 80° C. for 30 minutes under magnetic stirring to obtain an ethylene-vinyl acetate copolymer solution.

[0207] Step 3: Prepare the film-forming solution:

[0208] The obtained ethylene-vinyl acetate copolymer solution and the obtained filler dispersion were mixed, magnetically stirred at room temperature for 20 minutes to mix evenly, ultrasonically dispersed under high-frequency ultrasound for 10 minutes, and then magnetically stirred at room temperature for 12 hours to obtain a film-forming solution.

[0209] Step 4: Solution pouring:

[0210] The film-forming liquid was poured into a culture dish and sealed with plastic wrap, then placed in a fume hood at 40°C for 2 hours, and then transferred to a 60°C oven for drying for 4 hours to obtain an insulating and highly thermally conductive EVA packaging film.

[0211] Comparative Example 1

[0212] This comparative example provides an insulating and highly thermally conductive EVA encapsulation film for a photovoltaic module, which is prepared by the following steps:

[0213] 3.7 g of ethylene-vinyl acetate copolymer and 50 g of ethyl acetate solvent were stirred under magnetic force at 80°C for 30 min to obtain an EVA solution. The EVA solution was poured into a petri dish and sealed with plastic wrap, then placed in a fume hood at room temperature for 4 h, and then transferred to a 50°C oven for drying for 6 h to obtain a pure EVA film with a filler content of 0.

[0214] That is, the difference between this comparative example and Example 1 is only that:

[0215] In this comparative example, no three-dimensional composite filler is added, and the insulating and highly thermally conductive EVA packaging film obtained in this comparative example is recorded as 0filler.

[0216] Experimental Section

[0217] (I) Morphology test

[0218] Since the three-dimensional composite fillers prepared in Examples 1 to 5 of the present invention have similar structures, in order to avoid redundant description, the present invention uses the three-dimensional composite filler -NH prepared in Example 1 as an example. 2 As an example, a SEM test was performed on it, and the test results are as follows Figure 3 As shown, it can be seen that the three-dimensional composite filler-NH 2 It presents a three-dimensional interconnected network structure, indicating that a three-dimensional composite filler has been successfully prepared.

[0219] The present invention takes the insulating high thermal conductivity EVA packaging film of Examples 1 to 5 and Comparative Example 1 as examples, and tests the thermal conductivity, electrical insulation performance and volume resistivity thereof, and the test results are summarized as shown in Tables 1 and Figure 4 shown.

[0220] Table 1 Thermal conductivity and electrical insulation performance test results of Examples 1 to 5 and Comparative Example 1

[0221] project <![CDATA[Thermal conductivity / W·m -1 ·K -1 > Volume resistivity / Ω·cm Example 1 0.587 <![CDATA[2.4×10 14 ]]> Example 2 0.995 <![CDATA[3.2×10 14 ]]> Example 3 1.75 <![CDATA[1.5×10 14 ]]> Example 4 2.57 <![CDATA[1.3×10 13 <!-- 11 -->]]> Example 5 3.45 <![CDATA[2.8×10 12 ]]> Comparative Example 1 0.245 <![CDATA[1.1×10 15 ]]>

[0222] Table 1 shows the test results of thermal conductivity and electrical insulation performance of Examples 1 to 5 and Comparative Example 1. Figure 4 The volume resistivity test results of Examples 1 to 5 and Comparative Example 1 are shown.

[0223] From Table 1 and Figure 4 The test results show that the insulating high thermal conductivity EVA encapsulation film prepared by the present invention has good electrical insulation performance, and its volume resistivity is >109Ω·cm. Moreover, when the content of the three-dimensional composite filler is 9wt%, the thermal conductivity of the composite film reaches a maximum value of 3.45W·m -1 ·K -1 , compared with pure EVA film 0.245W·m -1 ·K -1 The thermal conductivity of the EVA film has been increased by 1308%, which greatly improves the thermal conductivity of the EVA film, helps to promote the heat dissipation of photovoltaic modules, extend the service life of photovoltaic modules, and improve the efficiency of photovoltaic power generation.

[0224] Obviously, the above embodiments are only some embodiments 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 creative work are within the scope of protection of the present invention.

Claims

1. An insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules, comprising a film matrix and a filler uniformly distributed in the matrix, characterized in that: The film matrix is ​​ethylene-vinyl acetate copolymer; The filler is a three-dimensional composite filler, and the three-dimensional composite filler accounts for 1wt.% to 10wt.% of the total mass of the insulating high thermal conductive EVA packaging film, and the rest is ethylene-vinyl acetate copolymer; The three-dimensional composite filler is prepared by compounding and gelling modified boron nitride and reduced graphene oxide; The modified boron nitride is hexagonal boron nitride or spherical boron nitride having active groups on the surface; wherein the active groups are amino groups or carboxyl groups.

2. The insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to claim 1, characterized in that: The three-dimensional composite filler is prepared by the following steps: The boron nitride raw material is dispersed in a solvent, and then a surface modifier is added, and the mixture is stirred at room temperature to introduce active groups on the surface of the boron nitride raw material through the surface modifier to obtain modified boron nitride; wherein the boron nitride raw material is hexagonal boron nitride or spherical boron nitride; dispersing the modified boron nitride in water to obtain a modified boron nitride solution; The graphene oxide dispersion is dispersed in the modified boron nitride solution, and then a reducing agent is added and mixed, and a heating treatment is performed so that during the gelation of the graphene oxide and the modified boron nitride, the reducing agent reduces the graphene oxide to reduced graphene oxide in situ, and the reduced graphene oxide / modified boron nitride aerogel is obtained after washing and freeze-drying to obtain a reduced graphene oxide / modified boron nitride aerogel with a three-dimensional structure, and the reduced graphene oxide / modified boron nitride aerogel is used as a three-dimensional composite filler.

3. The insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules as claimed in claim 2, characterized in that: The mass concentration of the graphene oxide dispersion is 0.7wt.% to 1.6wt.%; The mass ratio of the graphene oxide in the graphene oxide dispersion to the modified boron nitride in the modified boron nitride solution is 3.5-4.5:

1.

4. The insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules as claimed in claim 2, characterized in that: The reducing agent is one or more of hydroiodic acid, hydrazine hydrate and ascorbic acid; And for every 1g of graphene oxide, 70mol to 245mol of the reducing agent is added.

5. The insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules as claimed in claim 2, characterized in that: The surface modifier is one or more of tannic acid, dopamine and silane coupling agent; For every 1 g of boron nitride raw material, 3 mol to 34 mol of surface modifier is added.

6. The method for preparing the insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to claim 2, characterized in that: The solvent is a mixed solvent of ethanol and water in a volume ratio of 8:1.5 to 2.

5.

7. The method for preparing the insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to claim 2, characterized in that: The stirring treatment time is 12h to 36h.

8. The method for preparing the insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to claim 1, characterized in that: The ethylene-vinyl acetate copolymer is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 25 wt.% and a melt index of 19 g / 10 min; When hexagonal boron nitride is used as the boron nitride raw material, the flake diameter of the hexagonal boron nitride is 1 μm to 2 μm, and the flake thickness is 1 nm to 2 nm.

9. A method for preparing the insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to any one of claims 1 to 8, comprising the following steps: dispersing the three-dimensional composite filler in an organic solvent to obtain a filler dispersion; dispersing ethylene-vinyl acetate copolymer in an organic solvent to obtain an ethylene-vinyl acetate copolymer solution; mixing the ethylene-vinyl acetate copolymer solution and the filler dispersion to obtain a film-forming solution; The film-forming liquid is made into a composite film by a solution casting method, and the obtained composite film is used as an insulating and highly thermally conductive EVA packaging film; Wherein, the organic solvent is any one of ethyl acetate, tetrahydrofuran and xylene.

10. The method for preparing the insulating and highly thermally conductive EVA encapsulation film for photovoltaic modules according to claim 9, characterized in that: The mass ratio of the three-dimensional composite filler in the filler dispersion to the ethylene-vinyl acetate copolymer in the ethylene-vinyl acetate copolymer solution is 0.01 to 0.1:1.

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