Encapsulation adhesive film, method of making and use thereof
By forming a dynamic covalent cross-linked network in the encapsulation film, the problem of easy delamination of the encapsulation material under dynamic mechanical stress is solved, improving the curl resistance and interface stability, delaying the increase of water vapor permeability, and enhancing the resistance to complex environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CANNNOVATION LOW CARBON NEW ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2026-06-10
- Publication Date
- 2026-07-24
AI Technical Summary
Existing encapsulation materials are prone to delamination at the interface between the encapsulant film and the battery cell/backsheet under dynamic mechanical stress, resulting in increased water vapor permeability, insufficient resistance to microcrack propagation, and poor interface stability in complex environments.
An encapsulating film with a dynamic covalent crosslinking network structure is formed by using a copolymer matrix resin containing soft segments in the main chain and reactive functional groups in the side or end groups, and a dynamic crosslinking agent. Energy is dissipated by the reversible breakage of dynamic covalent bonds under heat or stress, thus avoiding permanent damage to the polymer main chain.
It improves the curl resistance, interface stability and material modulus stability of the encapsulating film, slows down the increase of water vapor permeability, enhances the resistance to complex environments, and prevents permanent microcracks and interface delamination.
Smart Images
Figure CN122445296A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic equipment technology, and more specifically, to an encapsulating film, its preparation method, and its application. Background Technology
[0002] With the rapid development of renewable energy technologies, the market demand for photovoltaic (PV) modules continues to grow in building-integrated photovoltaics (BIPV), portable power supplies, and special applications. Flexible PV modules, with their lightweight, bendable, and adaptability to complex curved surfaces, have become an important technological approach in distributed energy systems. Traditional encapsulation technologies primarily use thermoplastic polyolefins (such as POE and EVA) or silicone materials, achieving cell protection and electrical insulation through lamination processes. These materials exhibit good light transmittance, electrical insulation, and initial bond strength in static applications.
[0003] In dynamic mechanical stress scenarios, flexible components must withstand complex loads such as wind-induced vibration after installation and winding-unwinding cycles during transportation and storage. Existing encapsulation material systems are prone to delamination at the interface between the encapsulation film and the battery cell / backsheet due to the orientation relaxation of polymer molecular chains and the accumulation of interfacial stress during repeated bending deformation. Simultaneously, the design orientation of low modulus and high elasticity often limits the molecular crosslinking density and crystallinity of the materials, resulting in insufficient resistance to microcrack propagation. The inventors' research found that after more than 1000 bending cycles, the water vapor transmission rate (WVTR) of conventional encapsulation films increases by 30%-50%, corresponding to a 2-3 times higher power decay rate compared to static applications. Furthermore, the reduced material modulus to maintain flexibility weakens the encapsulation system's resistance to sudden loads such as hail impacts and mechanical scratches, and affects long-term interfacial stability under harsh environments such as humidity, heat, and ultraviolet radiation.
[0004] Therefore, designing and manufacturing an encapsulating film that is resistant to curling, has excellent interface stability, and stable material modulus is particularly important in the fabrication of photovoltaic devices. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide an encapsulating film, its preparation method, and its applications. This invention, through component design of the encapsulating film, uses a copolymer matrix resin containing soft segments in the main chain and side or end groups containing first reactive functional groups, and a dynamic crosslinking agent monomer containing second reactive functional groups as the main reactants. This results in an encapsulating film with a dynamic covalent crosslinked network structure, exhibiting characteristics such as resistance to curling, high interfacial stability, and stable material modulus, making it suitable for preparing various photovoltaic modules.
[0006] The embodiments of the present invention can be implemented as follows: In a first aspect, the present invention provides an encapsulating film comprising: An encapsulating film, by weight percentage, comprises the following raw materials: 60% ~ 90% matrix resin, 5% ~ 20% dynamic crosslinking agent, 0.5% ~ 10% nano-reinforcing filler, 0.5% ~ 5% weather-resistant functional additives, 0.5% ~ 3% composite initiator, 0.1% ~ 3% silane coupling agent; The matrix resin has soft segments in its main chain and the side groups or end groups contain first reactive functional groups; the dynamic crosslinking agent is a monomer and contains second reactive functional groups. The first reactive functional group and the second reactive functional group can react with each other to form a dynamic covalent crosslinking network by reacting the matrix resin with the dynamic crosslinking agent; the soft segment chain is a polyether type soft segment chain, a polycarbonate type soft segment chain, or a polyester type soft segment chain.
[0007] Optionally, the first reactive functional group is one of a furan group and a maleimide group, and the second reactive functional group is the other of a furan group and a maleimide group.
[0008] Optionally, the first reactive functional group is one of maleic anhydride group, acrylic acid group or epoxy group, and the second reactive functional group is mercapto group.
[0009] Optionally, the first reactive functional group is selected from any two of maleic anhydride groups, acrylic acid groups, or epoxy groups, and the second reactive functional group is a thiol group.
[0010] Optionally, the nano-reinforcing filler is selected from any one or a combination of at least two of surface-modified silica, surface-modified titanium dioxide, and nanofibers.
[0011] Optionally, the aspect ratio of the nanofibers is above 50.
[0012] Optionally, the weather-resistant functional additives are selected from any one or a combination of at least two of the following: ultraviolet absorbers, light stabilizers, antioxidants, and rare earth light-converting agents.
[0013] Optionally, the thickness of the encapsulating film ranges from 0.3 to 0.8 mm.
[0014] Secondly, the present invention provides a method for preparing an encapsulating film, used to prepare the encapsulating film in any of the above optional embodiments, the method comprising: S1, add the matrix resin, nano-reinforcing filler, weather-resistant functional additive, silane coupling agent and processing aid to the mixer according to the formula amount, and control the reaction temperature at 35~60℃; S2, the reaction temperature is lowered to below 10℃, and a dynamic crosslinking agent and a composite initiator are added; S3 is melt-extruded and cast into a film using an extruder; S4 is formed to a preset thickness by calendering rolls.
[0015] Thirdly, the present invention provides an application of an encapsulating film, wherein the encapsulating film in any of the above optional embodiments is used in a photovoltaic module, the photovoltaic module comprising a protective layer, a first encapsulating film layer, a cell layer, a second encapsulating film layer and a backsheet layer arranged sequentially.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the interaction between the first reactive functional group of the matrix resin in the raw material and the second reactive functional group of the dynamic crosslinking agent to form a dynamic covalent crosslinking network. Because the encapsulating film possesses this dynamic covalent crosslinking network, when subjected to curling, heat, or external stress, the dynamic covalent bonds in the covalent crosslinking network preferentially dissipate energy and release localized stress through reversible self-breakage, avoiding permanent damage to the polymer backbone and ultimately improving the overall performance of the encapsulating film. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.
[0018] Figure 1 This is a flowchart of the preparation method of the encapsulating film in an embodiment of the present invention. Detailed Implementation
[0019] The technical solution of the present invention is further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are merely illustrative of the present invention and should not be construed as limiting the invention.
[0020] The sources of some components in the examples and comparative examples are as follows: Polyurethane acrylate (containing furan side groups): Changshu Hengyao New Materials Co., Ltd., JF-3392; Polyolefin elastomers (POE): Dow Chemical Company, 7367; Modified polyolefin elastomers: ExxonMobil, 6102; Bismaleimide: Wuhan Yuancheng Chemical Co., Ltd.; 1,2-Ethylene glycol bis(3-mercaptopropionate): Guangzhou Shanghe Chemical Technology Co., Ltd.; Fumed silica: Evonik Industries; Nano-calcium carbonate: Guangxi Huana New Materials Co., Ltd.; 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole: BASF AG; Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate: BASF AG; Lauroyl peroxide: Jiangsu Gaoqi New Materials Co., Ltd.; Dicumyl peroxide: Jiangsu Gaoqi New Materials Co., Ltd.; γ-aminopropyltriethoxysilane: Hangzhou Jessica Chemical Co., Ltd.; tert-butyl peroxide-2-ethylhexanoate: Jiangsu Gaoqi New Materials Co., Ltd.; tert-butyl peroxide: Jiangsu Gaoqi New Materials Co., Ltd.; Vinyltrimethoxysilane: Dow Chemical Company; (Z)-13-Dicosenoamide: Nantong Haimen Zhongteng New Material Technology Co., Ltd.; Hydroxyl-terminated polyurethane acrylate prepolymer: Wanhua Chemical Co., Ltd., 7010; Bis(2-hydroxyethyl) disulfide: Shanghai Aladdin Reagent Co., Ltd.; Bismaleimide (BMI): Hubei Xinlantian New Materials Co., Ltd.; Furfuryl acrylate (FA): Nanjing Milan Chemical Co., Ltd.; Benzoyl peroxide (BPO): Jiangsu Gaoqi New Materials Co., Ltd.; Di-tert-butyl peroxide (DTBP): Jiangsu Gaoqi New Materials Co., Ltd.; Silane coupling agent: Hangzhou Jessica Chemical Co., Ltd.; Antioxidant: BASF AG.
[0021] Example 1 This embodiment provides an encapsulating film and its preparation method, wherein the encapsulating film comprises the following raw material components by weight percentage: Polyurethane acrylate (containing furan side groups) 70% Polyolefin elastomer (POE) 13.5% 10% bismaleimide 3% fumed silica 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole 1% Lauroyl peroxide + dicumyl peroxide 1.5% γ-aminopropyltriethoxysilane 0.5% Calcium stearate 0.5% The matrix resin is composed of a dual matrix (polyurethane acrylate and polyolefin elastomer), with polyurethane acrylate containing furan side groups being dominant. 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole is a weather-resistant functional additive, specifically acting as a UV absorber. When ultraviolet light irradiates the material surface, the UV absorber molecules preferentially capture the light energy of the ultraviolet light and convert it into harmless heat energy. In the added composite initiator, lauroyl peroxide acts as a low-temperature initiator, and dicumyl peroxide acts as a high-temperature initiator, with a weight ratio of 1:1. Calcium stearate acts as a processing aid, serving as a lubricant and acid absorber in the reaction.
[0022] refer to Figure 1 The preparation method of the above-mentioned encapsulating film is as follows: Polyurethane acrylate containing furan side groups, polyolefin elastomer, fumed silica, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, γ-aminopropyltriethoxysilane, and calcium stearate were mixed at 35°C–40°C and a rotation speed of 45–55 r / min for 2 hours until homogeneous (initial mixing). The reaction temperature was then lowered to below 10°C, the rotation speed was adjusted to 32 r / min, and bismaleimide, lauroyl peroxide, and dicumyl peroxide were added and mixed until homogeneous (secondary mixing). The mixture was melt-extruded using a single-screw extruder, extruded into a film with a wide die head, and then calendered to a thickness of 0.5 mm before being wound up for later use.
[0023] Example 2 This embodiment provides an encapsulating film and its preparation method, wherein the encapsulating film comprises the following raw material components by weight percentage: Modified polyolefin elastomer 80% 1,2-Ethylene glycol bis(3-mercaptopropionate) 12% Nano calcium carbonate 5% Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate 0.8% 1.2% tert-butyl peroxide-2-ethylhexanoate + tert-butyl peroxide Vinyltrimethoxysilane 0.8% (Z)-13-Docosenoamide 0.2% In this embodiment, the matrix resin is a single matrix (modified polyolefin elastomer), and the molecular chains of the modified polyolefin elastomer have disulfide bonds at their end groups. Nano-calcium carbonate serves as a nano-reinforcing filler; due to its large specific surface area and interfacial effect, it can form strong physical interactions with the polymer molecular chains, effectively transferring and dispersing stress, thus playing a "pinning" and reinforcing role. Bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate is a weather-resistant functional additive, specifically acting as a UV absorber. When the material is exposed to ultraviolet radiation, the internal chemical bonds are broken, generating highly unstable "free radicals." The addition of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate can rapidly capture and neutralize these destructive free radicals, converting them into stable substances, thereby directly interrupting the chain reaction of material aging. In the added composite initiator, tert-butyl peroxide-2-ethylhexanoate serves as a low-temperature initiator, and tert-butyl peroxide-benzoate serves as a high-temperature initiator, with a weight percentage of 2:1. (Z)-13-dodecenoamide is a processing aid that can significantly reduce the coefficient of friction of the material surface and improve slip properties during the reaction, thereby speeding up the processing and improving the efficiency of packaging operations.
[0024] refer to Figure 1 The preparation method of the above-mentioned encapsulating film is as follows: Modified polyolefin elastomer, nano-calcium carbonate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, vinyltrimethoxysilane, and (Z)-13-dococarbeneamide were mixed at 35-45°C and a rotation speed of 45-55 r / min for 3 h until homogeneous. The reaction temperature was then lowered to 9°C, the rotation speed adjusted to 30 r / min, and 1,2-ethylene glycol bis(3-mercaptopropionate), tert-butyl peroxide-2-ethylhexanoate, and tert-butyl peroxide were added and mixed until homogeneous. The mixture was melt-extruded using a single-screw extruder, extruded into a film with a wide die head, and then calendered to a thickness of 0.5 mm before being wound up for later use.
[0025] Example 3 This embodiment provides an encapsulating film and its preparation method, wherein the encapsulating film comprises the following raw material components by weight percentage: Modified polyolefin elastomer 50% 25% hydroxyl-terminated polyurethane acrylate prepolymer 8% bis(2-hydroxyethyl) disulfide Bismaleimide (BMI) 6% 8% furfuryl acrylate (FA) (benzoyl peroxide + di-tert-butyl peroxide = 2:1) 1.5% 0.5% silane coupling agent Antioxidant 1% refer to Figure 1 The preparation method of the above-mentioned encapsulating film is as follows: 1. Premixing: Add hydroxyl-terminated polyurethane acrylate prepolymer, furfuryl acrylate, silane coupling agent, and antioxidant sequentially to a mixer. Stir at 200 r / pm for 40 minutes under conditions of 50℃~60℃ and vacuum degree -0.08 MPa until the filler is uniformly dispersed and the system is degassed.
[0026] 2. Chain extension and dynamic crosslinking introduction: Cool the premix to below 15°C. Under nitrogen protection, slowly add bis(2-hydroxyethyl) disulfide and stir at a low speed of 50 r / pm for 20 minutes to allow it to react initially with the terminal isocyanate groups (-NCO) of the prepolymer, thereby extending the chain and introducing disulfide bonds into the main chain.
[0027] 3. Initiator addition and mixing: Cool to 5°C, add bismaleimide and the complex peroxide initiator. Stir at 100 r / pm for 10 minutes to ensure uniform mixing and avoid premature decomposition of the initiator.
[0028] 4. Extrusion film formation: The uniformly mixed material is quickly transferred to a single-screw extruder for melt extrusion. The wide film head is extruded into a film, which is then rolled into a 0.5 mm thick film by calendering rollers and wound up for later use.
[0029] Example 4 An embodiment provides an encapsulating film and a method for preparing the same, wherein the encapsulating film comprises the following raw material components by weight percentage: Modified polyolefin elastomer 60% 15% hydroxyl-terminated polyurethane acrylate prepolymer 5% bis(2-hydroxyethyl) disulfide Bismaleimide (BMI) 7% 9% furfuryl acrylate (FA) (benzoyl peroxide + di-tert-butyl peroxide = 2:1) 2% 1% silane coupling agent Antioxidant 1% Preparation process: 1. Premixing: In a mixer, add hydroxyl-terminated polyurethane acrylate prepolymer, furfuryl acrylate, silane coupling agent, and antioxidant in sequence. Stir at 200 r / pm for 40 minutes under conditions of 50-60℃ and a vacuum of -0.08 MPa until the filler is uniformly dispersed and the system is degassed.
[0030] 2. Chain extension and dynamic crosslinking introduction: Cool the premix to below 15°C. Under nitrogen protection, slowly add bis(2-hydroxyethyl) disulfide and stir at a low speed of 50 r / pm for 20 minutes to allow it to react initially with the terminal isocyanate groups (-NCO) of the prepolymer, thereby extending the chain and introducing disulfide bonds into the main chain.
[0031] 3. Initiator addition and mixing: Cool to 5°C, add bismaleimide and the complex peroxide initiator. Stir at 100 r / pm for 10 minutes to ensure uniform mixing and avoid premature decomposition of the initiator.
[0032] 4. Extrusion film formation: The uniformly mixed material is quickly transferred to a single-screw extruder for melt extrusion. The wide film head is extruded into a film, which is then rolled into a 0.6 mm thick film by calendering rollers and wound up for later use.
[0033] Comparative Example 1 This comparative example uses commercially available Haiyouwei POEP507M1 encapsulant film, specifically a polyolefin (POE) encapsulant film for photovoltaic module encapsulation produced by Shanghai Haiyouwei New Material Co., Ltd.
[0034] Performance Comparison Five sets of encapsulating films with a thickness of 0.5 mm, representing Examples 1-4 and Comparative Example 1, were selected as experimental subjects and subjected to a high-pressure boiling test. The test conditions for the high-pressure boiling test (PCT-48) were set as follows: continuous boiling for 48 hours at 121℃, 100% relative humidity, and approximately 0.2 MPa of saturated steam. The adhesive strength of each set of samples was measured before and after the test. Three parallel samples were selected for each set of samples, and the average value was taken for the tests of these three parallel samples. Finally, the adhesive strength attenuation rate of each set of samples was obtained by combining the measured adhesive strength values before and after the high-pressure boiling test.
[0035] The test data is as follows: Table 1
[0036] As shown in Table 1, the present invention, through the component design of the encapsulating film, utilizes the interaction between the first reactive functional group in the matrix resin and the second reactive functional group in the dynamic crosslinking agent to form a dynamic covalent crosslinking network. This effectively slows down the aging rate of the encapsulating film and delays the degradation of its surface adhesion properties, thereby significantly improving the overall performance of the material. Specifically, the dynamic covalent bonds in the covalent crosslinking network can undergo reversible breakage and recombination under thermal or stress activation. The microscopic "flow" and rearrangement of the covalent crosslinking network significantly enhances the encapsulating film's ability to withstand cyclic loads, effectively preventing the generation of permanent microcracks and interfacial delamination. Furthermore, the high elasticity provided by the soft segments ensures the overall flexibility of the encapsulating film.
[0037] In the comparative example, the commercially available photovoltaic POE film did not form a dynamic covalent cross-linked network structure. Compared with the encapsulation film that formed a dynamic covalent cross-linked network structure, the commercially available photovoltaic POE film showed a significant decrease in adhesion after completing the PCT-48 test. This demonstrates that, thanks to the reversible breakage and recombination of the dynamic covalent cross-linked network under heat and stress, the dynamic covalent bonds preferentially dissipate energy and release stress through self-breakage, avoiding permanent damage to the polymer backbone.
[0038] In summary, this invention utilizes the interaction between the first reactive functional group of the matrix resin in the raw materials and the second reactive functional group of the dynamic crosslinking agent to form a dynamic covalent crosslinking network. Because the encapsulating film possesses this dynamic covalent crosslinking network, under conditions of curling, heat, or external stress, the dynamic covalent bonds in the network preferentially dissipate energy and release localized stress through reversible self-breakage, preventing permanent damage to the polymer backbone and ultimately improving the overall performance of the encapsulating film. Furthermore, a composite initiator is employed during the preparation process. This initiator is added at a low temperature (below 10°C) during secondary mixing to prevent premature reaction of the raw materials during mixing, ensuring process stability and controllable construction of the dynamic covalent crosslinking network, resulting in a uniform distribution of dynamic covalent bonds within the system.
[0039] The applicant declares that the present invention is illustrated by the above embodiments to describe the process flow of the present invention, but the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. An encapsulating film, characterized in that, The encapsulating film comprises the following raw materials by weight percentage: 60% ~ 90% matrix resin, 5% ~ 20% dynamic crosslinking agent, 0.5% ~ 10% nano-reinforcing filler, 0.5% ~ 5% weather-resistant functional additives, 0.5% ~ 3% composite initiator, 0.1% ~ 3% silane coupling agent; The matrix resin has a soft segment chain on its main chain, and the side groups or end groups contain a first reactive functional group; the dynamic crosslinking agent is a monomer and contains a second reactive functional group. The first reactive functional group and the second reactive functional group can react with each other to react the matrix resin with the dynamic crosslinking agent to form a dynamic covalent crosslinking network; the soft segment chain is a polyether type soft segment chain, a polycarbonate type soft segment chain, or a polyester type soft segment chain.
2. The encapsulating film according to claim 1, characterized in that, The first reactive functional group is one of a furan group and a maleimide group, and the second reactive functional group is the other of a furan group and a maleimide group.
3. The encapsulating film according to claim 1, characterized in that, The first reactive functional group is one of maleic anhydride group, acrylic acid group or epoxy group, and the second reactive functional group is mercapto group.
4. The encapsulating film according to claim 1, characterized in that, The first reactive functional group is selected from any two of maleic anhydride groups, acrylic acid groups, or epoxy groups, and the second reactive functional group is a thiol group.
5. The encapsulating film according to claim 1, characterized in that, The nano-reinforcing filler is selected from any one or a combination of at least two of surface-modified silica, surface-modified titanium dioxide, and nanofibers.
6. The encapsulating film according to claim 5, characterized in that, The aspect ratio of the nanofibers is above 50.
7. The encapsulating film according to claim 1, characterized in that, The weather-resistant functional additive is selected from any one or a combination of at least two of the following: ultraviolet absorbers, light stabilizers, antioxidants, and rare earth light-converting agents.
8. The encapsulating film according to claim 1, characterized in that, The thickness of the encapsulating film ranges from 0.3 to 0.8 mm.
9. A method for preparing an encapsulating film, used to prepare the encapsulating film according to any one of claims 1-8, characterized in that, The preparation method includes: S1, add the matrix resin, nano-reinforcing filler, weather-resistant functional additive, silane coupling agent and processing aid to the mixer according to the formula amount, control the reaction temperature at 35~60℃, and mix evenly; S2, the reaction temperature is lowered to below 10℃, and a dynamic crosslinking agent and a composite initiator are added; S3 is melt-extruded and cast into a film using an extruder; S4 is formed to a preset thickness by calendering rolls.
10. An application of an encapsulating film, characterized in that, The encapsulating film is used in photovoltaic modules, which include a protective layer, a first encapsulating film layer, a cell layer, a second encapsulating film layer, and a backsheet layer arranged sequentially.