Self-repairable EVA adhesive film and preparation method thereof

Abstract

The application provides a self-repairable EVA adhesive film and a preparation method thereof, and relates to the technical field of solar photovoltaic module packaging. The self-repairable EVA adhesive film realizes a double self-repairing mechanism of photovoltaic module packaging adhesive film through Diels-Alder reaction group grafting and silane coupling agent microencapsulation technology, and the double self-repairing mechanism includes physical rearrangement repair and chemical bonding repair. While maintaining high light transmittance (>= 90%) and bonding strength (>= 96 N / cm), the aging resistance (Delta YI <= 3) and service life of the EVA adhesive film are significantly improved, and the problems that the traditional EVA adhesive film is prone to aging and micro-damage caused by mechanical stress in extreme environments are solved. The preparation process of the application is compatible with the existing production line, and has high industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of solar photovoltaic module encapsulation technology, specifically relating to a self-healing EVA film and its preparation method. Background Technology

[0002] In the encapsulation structure of photovoltaic modules, EVA (ethylene-vinyl acetate copolymer) film plays multiple key roles: bonding the cells to the glass / backsheet, providing electrical insulation, protecting the cells from environmental corrosion, and assisting in the optimization of optical performance. However, traditional EVA films face many technical bottlenecks in practical applications, which restrict the long-term performance stability of photovoltaic modules in harsh environments.

[0003] Environmental stress-induced material aging is a challenge faced by EVA encapsulants. Photovoltaic modules are exposed to the outdoor environment for extended periods, suffering from multiple environmental factors including ultraviolet radiation, temperature cycling (-40℃ to 85℃), humidity (up to 100%RH), and acid rain. Studies have shown that traditional EVA encapsulants are prone to hydrolysis in humid and hot environments, releasing acetic acid. This increases the acidity inside the module, corroding the cells and solder ribbons, leading to power degradation. Acetic acid release also accelerates the aging process of EVA itself, creating a vicious cycle. Furthermore, ultraviolet radiation can cause EVA molecular chain breakage, leading to yellowing of the encapsulant and decreased light transmittance, directly affecting the module's power generation efficiency.

[0004] Accumulation of micro-damage caused by mechanical stress is another technical challenge. Photovoltaic modules are subjected to various mechanical stresses during transportation, installation, and operation, including wind pressure, snow load, thermal expansion and contraction stress, and localized stress concentration caused by improper installation. These stresses can cause micron- or even nanometer-scale cracks and interfacial debonding within the EVA encapsulant film. Initially, this micro-damage may not immediately affect module performance, but it gradually expands over time, eventually leading to significant power loss or even module failure. More seriously, these micro-damages become channels for moisture and oxygen penetration, accelerating cell corrosion and electrode oxidation.

[0005] The limitations of existing solutions have prompted engineers in the field to seek more advanced technological paths. Chinese invention patent CN119242200A reduces acetic acid release by adding a special deacidifying agent. Chinese invention patent CN119019940A uses polyisobutylene and mesoporous materials to improve the material's resistance to photothermal stress. However, these methods are essentially "passive defense" strategies and cannot fundamentally solve the problem of performance recovery after material damage. While Chinese invention patent CN118562412A makes some improvements in the process—the EVA photovoltaic encapsulation film includes: ethylene-vinyl acetate copolymer, anti-PID (potentially induced degradation) masterbatch, main crosslinking agent, co-crosslinking agent, and antioxidant; the anti-PID masterbatch includes: ethylene-vinyl acetate copolymer, one-dimensional organic polymer nanomaterials, two-dimensional layered nanomaterials, and silane coupling agents; the one-dimensional organic polymer nanomaterials are at least one of cellulose nanofibers with multiple hydroxyl groups, cellulose nanocrystals, and bacterial cellulose; the two-dimensional layered nanomaterials are organosodium montmorillonite; however, it still does not overcome the limitation that the material cannot repair itself.

[0006] Self-healing materials are a class of smart materials capable of autonomously sensing damage and restoring all or part of their performance through specific mechanisms. Based on different self-healing mechanisms, they can be divided into two main categories: exogenous (e.g., microcapsule-based) and intrinsic (based on dynamic chemical bonds). Chinese invention patent CN118676230A discloses a self-healing and self-cleaning photovoltaic module. The module's metal frame, from top to bottom, consists of tempered glass, a polyethylene-polyvinyl acetate copolymer film, and photovoltaic cells; a hyperbranched PDMS (polydimethylsiloxane) composite self-healing and self-cleaning superhydrophobic coating is physically deposited on the tempered glass. A hyperbranched PDMS composite self-healing and self-cleaning superhydrophobic coating is obtained as follows: 1,2,5-benzenetricarboxylic acid chloride and tetrahydrofuran are stirred to obtain a TMC / THF (1,2,5-benzenetricarboxylic acid chloride / tetrahydrofuran) solution. Then, diaminopropyl-terminated polydimethylsiloxane is dissolved in tetrahydrofuran, followed by the addition of pyridine and the TMC / THF solution. After sufficient reaction, a hyperbranched PDMS solution is obtained. Finally, the hyperbranched PDMS solution is poured onto tempered glass, and after the solution dries, a hyperbranched PDMS composite coating is formed on the tempered glass. This invention utilizes the fact that increased temperature promotes the movement of hyperbranched PDMS molecular chains, causing the hyperbranched PDMS polymer near the damaged area to tend to move towards the void region. The broken hydrogen bonds undergo non-directional recombination, thereby repairing microscopic defects, giving the hyperbranched PDMS composite self-healing and self-cleaning superhydrophobic coating self-healing capabilities. However, its self-healing ability is limited under harsh light and heat conditions.

[0007] Therefore, it is necessary to conduct in-depth research on the composition and preparation methods of EVA films in order to break through the performance limits of traditional materials, realize a virtuous cycle of "damage-self-repair" in photovoltaic modules, and significantly extend their service life. Summary of the Invention

[0008] This invention addresses the problems of existing technologies by providing a self-healing EVA film and its preparation method. It introduces a self-healing mechanism into the EVA film system for photovoltaic encapsulation. Through multi-scale material design and synergistic principles, the EVA film achieves autonomous repair under the operating environment of photovoltaic modules. When photovoltaic modules encounter mechanical damage or environmental aging, it triggers a dual repair mechanism (physical and chemical repair) to restore the material's original properties. The technical solution of this invention retains the excellent encapsulation performance of EVA film while endowing it with intelligent response capabilities not found in traditional materials, providing a new solution for the long-term reliability of photovoltaic modules.

[0009] This invention proposes a practical and self-healing EVA film solution through creative improvements to materials and processes, providing a new technological path for the sustainable development of the photovoltaic packaging industry.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] On the one hand, the present invention provides a self-healing EVA film, the components of which include: modified ethylene-vinyl acetate copolymer (modified EVA), microencapsulated repair agent, dynamic reversible crosslinking agent and other additives;

[0012] The microencapsulated repair agent uses polyurea-formaldehyde as the wall material and a coupling agent as the core material; the dynamic reversible crosslinking agent is a compound containing maleimide groups;

[0013] The other additives include light stabilizers, antioxidants, crosslinking agents, and silane coupling agent A.

[0014] Preferably, the EVA film, by weight, comprises: 81.0-89.3 parts of modified ethylene-vinyl acetate copolymer, 4.0-12.5 parts of microencapsulated repair agent, 2.4-6.7 parts of dynamic reversible crosslinking agent, 0.4-2.5 parts of light stabilizer, 0.2-1.3 parts of antioxidant, 0.4-1.7 parts of crosslinking agent, and 0.4-2.5 parts of silane coupling agent A.

[0015] More preferably, the EVA film, by weight, comprises: 84.3 parts of modified ethylene-vinyl acetate copolymer, 8.4 parts of microencapsulated repair agent, 4.2 parts of dynamic reversible crosslinking agent, 0.9 parts of light stabilizer, 0.4 parts of antioxidant, 0.9 parts of crosslinking agent, and 0.9 parts of silane coupling agent A.

[0016] Preferably, before modification, the ethylene-vinyl acetate copolymer contains 28%-33% vinyl acetate (VA) in EVA resin.

[0017] More preferably, before modification, the ethylene-vinyl acetate copolymer is an EVA resin with a melt index of 15 g / 10 min to 25 g / 10 min.

[0018] More preferably, the preparation method of the modified ethylene-vinyl acetate copolymer includes the steps of: melt blending EVA resin with a graft monomer containing furan groups, and carrying out a grafting reaction under the action of a peroxide initiator to obtain the modified ethylene-vinyl acetate copolymer.

[0019] More preferably, the graft monomer containing the furan group is furan methacrylate.

[0020] More preferably, the peroxide initiator is selected from at least one of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), tert-butyl hydroperoxide (TBHP), and benzoyl peroxide (BPO).

[0021] In some embodiments of the present invention, the peroxide initiator is dicumyl peroxide (DCP).

[0022] More preferably, the mass ratio of the EVA resin, the grafted monomer containing furan groups, and the peroxide initiator is 100:2-4:0.2-0.5.

[0023] In some embodiments of the present invention, the mass ratio of the EVA resin, the grafted monomer containing furan groups, and the peroxide initiator is 100:3:0.3.

[0024] More preferably, the melt blending conditions are: melting at 110-130℃ for 10-20 minutes.

[0025] In some embodiments of the present invention, the melt blending conditions are: melting at 120°C for 15 minutes.

[0026] Preferably, the microencapsulated repair agent is a microcapsule with polyurea-formaldehyde as the wall material and silane coupling agent B as the core material.

[0027] More preferably, the preparation method of the microencapsulated repair agent includes the following steps: silane coupling agent B is mixed with an emulsifier to form an oil phase, urea and formaldehyde aqueous solution is used as an aqueous phase, and polyurea-formaldehyde wall material is used to form microcapsules of silane coupling agent through interfacial polymerization reaction. After washing and drying, the microencapsulated repair agent is obtained.

[0028] More preferably, the silane coupling agent B is selected from one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltrimethoxysilane.

[0029] More preferably, the emulsifier is selected from at least one of Tween-60 and Tween-80.

[0030] More preferably, in the oil phase, the mass ratio of silane coupling agent B to emulsifier is 15-25:1.

[0031] In some embodiments of the present invention, the mass ratio of silane coupling agent B to emulsifier in the oil phase is 20:1.

[0032] More preferably, the pH of the aqueous phase is 8-9, and the reagent used to adjust the pH is triethanolamine.

[0033] More preferably, in the aqueous phase, the mass ratio of urea to formaldehyde aqueous solution is 1:1.5-3.

[0034] In some embodiments of the present invention, the mass ratio of urea and formaldehyde aqueous solution in the aqueous phase is 1:2.

[0035] More preferably, the formaldehyde aqueous solution has a mass concentration of 30%-40%.

[0036] In some embodiments of the present invention, the mass concentration of the formaldehyde aqueous solution is 37%.

[0037] More preferably, the conditions for the interfacial polymerization reaction are: 50-70℃ for 3-5 hours.

[0038] In some embodiments of the present invention, the conditions for the interfacial polymerization reaction are: reaction at 60°C for 4 hours.

[0039] Preferably, the average particle size of the microencapsulated repair agent is 10-50 μm.

[0040] More preferably, the average particle size of the microencapsulated repair agent is 30 μm.

[0041] Preferably, the dynamic reversible crosslinking agent is selected from at least one of bis(2-maleimide ethyl)amine (TMEA), bismaleimide (BMI), and 1,6-dimaleimide hexane (BMH).

[0042] Preferably, the light stabilizer is selected from at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-n-octyloxybenzophenone.

[0043] Preferably, the antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

[0044] Preferably, the crosslinking agent is selected from at least one of dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, triallyl isocyanurate, and divinylbenzene.

[0045] Preferably, the silane coupling agent A is selected from at least one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0046] On the other hand, the present invention provides a method for preparing the above-mentioned EVA film, comprising the steps of:

[0047] (1) Preparation of microencapsulated repair agent: Silane coupling agent B is mixed with emulsifier to form an oil phase, and urea and formaldehyde aqueous solution is used as the aqueous phase. Through interfacial polymerization reaction, polyurea-formaldehyde wall material is formed to encapsulate silane coupling agent microcapsules. After washing and drying, microencapsulated repair agent is obtained.

[0048] (2) EVA grafting modification: EVA resin is melt-blended with grafting monomers containing furan groups, and grafting reaction is carried out under the action of peroxide initiator to obtain furan group functionalized EVA, that is, modified EVA.

[0049] (3) Preparation of premix: The modified EVA, dynamic reversible crosslinking agent, microencapsulated repair agent and other additives are mixed evenly to obtain the premix;

[0050] (4) Extrusion molding: The premixed material is melted and extruded to form an EVA film.

[0051] Preferably, in step (1), the silane coupling agent B is selected from one of 3-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

[0052] Preferably, in step (1), the emulsifier is selected from at least one of Tween-60 and Tween-80.

[0053] Preferably, in step (1), the mass ratio of the silane coupling agent B to the emulsifier is 15-25:1.

[0054] More preferably, in step (1), the mass ratio of the silane coupling agent B to the emulsifier is 20:1.

[0055] Preferably, in step (1), the pH of the aqueous phase is 8-9, and the reagent used to adjust the pH is triethanolamine.

[0056] Preferably, in step (1), the mass ratio of urea to formaldehyde aqueous solution is 1:1.5-3.

[0057] More preferably, in step (1), the mass ratio of the urea and formaldehyde aqueous solution is 1:2.

[0058] More preferably, in step (1), the mass concentration of the formaldehyde aqueous solution is 30%-40%.

[0059] In some embodiments of the present invention, in step (1), the mass concentration of the formaldehyde aqueous solution is 37%.

[0060] Preferably, in step (1), the conditions for the interfacial polymerization reaction are: 50-70℃ for 3-5 hours.

[0061] More preferably, in step (1), the conditions for the interfacial polymerization reaction are: reaction at 60°C for 4 hours.

[0062] Preferably, in step (2), the graft monomer containing furan groups is furan methacrylate.

[0063] Preferably, in step (2), the mass ratio of the EVA resin, the grafted monomer containing furan groups, and the peroxide is 100:2-4:0.2-0.5.

[0064] More preferably, in step (2), the mass ratio of the EVA resin, the grafted monomer containing furan groups, and the peroxide is 100:3:0.3.

[0065] Preferably, in step (2), the melt blending conditions are: melting at 110-130℃ for 10-20 minutes.

[0066] More preferably, in step (2), the melt blending conditions are: melting at 120°C for 15 minutes.

[0067] Preferably, in step (2), the melt blending is carried out in a mixer.

[0068] Preferably, in step (4), the temperature of the melt extrusion is set as follows: Zone 1 85-95℃, Zone 2 100-115℃, Zone 3 120-130℃, Zone 4 110-115℃, and the die head temperature 100-115℃.

[0069] More preferably, in step (4), the temperature of the melt extrusion is set as follows: 90°C in zone 1, 110°C in zone 2, 120°C in zone 3, 115°C in zone 4, and 110°C in the die head.

[0070] Preferably, in step (4), the melt extrusion is performed using a single-screw extruder.

[0071] Preferably, in step (4), the molding process is carried out by casting or calendering.

[0072] Preferably, in step (4), the thickness of the EVA film is 0.3-0.8 mm.

[0073] More preferably, in step (4), the thickness of the EVA film is 0.5 mm.

[0074] Preferably, the preparation method further includes a post-treatment step after extrusion molding; the post-treatment specifically involves subjecting the EVA film to electron beam irradiation to induce the formation of a partially cross-linked structure and improve the initial strength of the EVA film.

[0075] In this invention, the ethylene-vinyl acetate copolymer provides basic encapsulation and mechanical properties; the microencapsulated repair agent and the dynamically reversible crosslinking agent are responsible for providing self-repair.

[0076] In this invention, the dynamic reversible crosslinking agent is a compound containing maleimide groups, which can form a Diels-Alder reversible crosslinking dynamic network (dual repair mechanism) between EVA molecular chains.

[0077] The EVA film of this invention has a dual self-healing mechanism:

[0078] 1. Physical self-repair: Based on the Diels-Alder reversible reaction, furan groups and maleimide groups reversibly form a cross-linked network at 60-80℃. When the film is damaged, appropriate heating can dissociate the broken cross-linked bonds, allowing the molecular chains to move and fill the cracked area. Subsequently, cooling can reform the cross-linking, achieving physical repair.

[0079] 2. Chemical self-healing: When the EVA film cracks and the microcapsules rupture, the core material silane coupling agent B is released. Under the influence of ambient humidity, it hydrolyzes to generate silanol, which forms new chemical bonds with the polar groups on the EVA molecular chain and the substrate surface, thus achieving chemical repair of the crack.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] 1. This invention possesses a self-healing capability not found in traditional EVA films. By constructing a self-healing system that synergistically combines a dynamic reversible covalent crosslinking network with a microencapsulated repair agent, the EVA film material can trigger the following repair mechanisms when subjected to mechanical damage or microcracks: (1) Dynamic reversible Diels-Alder bonds undergo reversible breakage and recombination under external stimuli such as heat and light, achieving dynamic reconstruction of molecular chains; (2) Microcapsules rupture to release repair monomers, which undergo in-situ polymerization under the action of a catalyst to fill the damaged area. This dual repair mechanism combines dynamic bonding at the molecular level with macroscopic material replenishment, realizing the multi-level self-healing function of the material. Experimental results show that while possessing self-healing properties, this invention can maintain other properties similar to or even better than traditional EVA films; the self-healing EVA film of this invention has excellent light transmittance (≥90%) and bonding strength (peel strength from glass ≥96N / cm).

[0082] 2. The self-healing EVA film of the present invention also has process compatibility and environmental adaptability. It is compatible with existing EVA film production lines during the preparation process and can be industrialized without large-scale equipment modification. The self-healing EVA film of the present invention is suitable for extreme environments with large temperature differences and strong radiation, solving the problem of easy aging and failure of traditional EVA films under harsh climates. Attached Figure Description

[0083] Figure 1 This is a schematic diagram of the conventional EVA film structure of the present invention.

[0084] Figure 2 This is a schematic diagram of the structure of the self-healing EVA film of the present invention.

[0085] Figure 3 This is a schematic diagram illustrating the working principle of the self-healing EVA film of the present invention. Detailed Implementation

[0086] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0087] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0088] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means. The bismaleimide was purchased from Aladdin Biochemical Technology Co., Ltd., catalog number D111448; the light stabilizer Tinuvin 770 was purchased from Shanghai McLean Biochemical Technology Co., Ltd., catalog number T817619; the antioxidant 1010 was purchased from Saen Chemical Technology (Shanghai) Co., Ltd., catalog number A100307; the triallyl isocyanurate was purchased from Tianjin Xiens Biochemical Technology Co., Ltd., catalog number T849015; the silane coupling agent KH570 was purchased from Momentive High-Tech Materials (Jiangxi) Co., Ltd., catalog number Silquest A-174M; the silane coupling agent KH550 was purchased from Momentive High-Tech Materials (Jiangxi) Co., Ltd., catalog number Silquest A-1100M; the vinyltrimethoxysilane was purchased from Momentive High-Tech Materials (Jiangxi) Co., Ltd., catalog number Silquest A-171MSilane; products from different manufacturers did not have a significant impact on the effect.

[0089] Example 1

[0090] A self-healing EVA film, the raw materials by weight are: 84.3 parts modified EVA, 4.2 parts bismaleimide (4,4'-bismaleimide diphenylmethane, its molecular formula is C... 21 H 14 N2O4 (BMI), 8.4 parts microencapsulated repair agent, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0091] A method for preparing a self-healing EVA film is as follows:

[0092] (1) Preparation of microencapsulated repair agent: 20g of 3-aminopropyltriethoxysilane (KH550) and 1g of Span-80 were mixed as the oil phase; 15g of urea and 30g of formaldehyde aqueous solution (37wt%) were dissolved in 100g of water, and the pH was adjusted to 8-9 with triethanolamine as the aqueous phase; the oil phase was added to the aqueous phase and emulsified by high-speed shearing to form an O / W emulsion; the temperature was raised to 60℃ and the reaction was carried out for 4h. After filtration, washing and drying, the microencapsulated repair agent with an average particle size of about 30μm was obtained.

[0093] (2) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0094] (3) Preparation of premix: 84.3 parts by weight of modified EVA, 4.2 parts by weight of bismaleimide (BMI), 8.4 parts by weight of microencapsulated repair agent, 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (tracelyl isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0095] (4) Extrusion molding: The premixed material is melt-extruded through a single screw extruder. The barrel temperature is set as follows: Zone 1 90℃, Zone 2 110℃, Zone 3 120℃, Zone 4 115℃, and the die temperature is 110℃. After cooling and shaping by the casting roller, an EVA film with a thickness of 0.5mm is obtained.

[0096] Example 2

[0097] A self-healing EVA film, the raw materials by weight are: 84.3 parts modified EVA, 4.2 parts bismaleimide (BMI), 8.4 parts microencapsulated repair agent, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (tracene propyl isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0098] A method for preparing a self-healing EVA film is as follows:

[0099] (1) Preparation of microencapsulated repair agent: 20g of γ-methacryloxypropyltrimethoxysilane (KH570) and 1g of Span-80 were mixed as the oil phase; 15g of urea and 30g of formaldehyde aqueous solution (37wt%) were dissolved in 100g of water, and the pH was adjusted to 8-9 with triethanolamine as the aqueous phase; the oil phase was added to the aqueous phase and emulsified by high-speed shearing to form an O / W emulsion; the temperature was raised to 60℃ and reacted for 4h. After filtration, washing and drying, the microencapsulated repair agent with an average particle size of about 30μm was obtained.

[0100] (2) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0101] (3) Preparation of premix: 84.3 parts by weight of modified EVA, 4.2 parts by weight of bismaleimide (BMI), 8.4 parts by weight of microencapsulated repair agent, 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (tracelyl isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0102] (4) Extrusion molding: The premixed material is melt-extruded through a single screw extruder. The barrel temperature is set as follows: Zone 1 90℃, Zone 2 110℃, Zone 3 120℃, Zone 4 115℃, and the die temperature is 110℃. After cooling and shaping by the casting roller, an EVA film with a thickness of 0.5mm is obtained.

[0103] Example 3

[0104] A self-healing EVA film, the raw materials by weight are: 84.3 parts modified EVA, 4.2 parts bismaleimide (BMI), 8.4 parts microencapsulated repair agent, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (tracene propyl isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0105] A method for preparing a self-healing EVA film is as follows:

[0106] (1) Preparation of microencapsulated repair agent: 20g of vinyltrimethoxysilane (A171) and 1g of Span-80 were mixed as the oil phase; 15g of urea and 30g of formaldehyde aqueous solution (37wt%) were dissolved in 100g of water, and the pH was adjusted to 8-9 with triethanolamine as the aqueous phase; the oil phase was added to the aqueous phase and emulsified by high-speed shearing to form an O / W emulsion; the temperature was raised to 60℃ and the reaction was carried out for 4h. After filtration, washing and drying, the microencapsulated repair agent with an average particle size of about 30μm was obtained.

[0107] (2) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0108] (3) Preparation of premix: 84.3 parts by weight of modified EVA, 4.2 parts by weight of bismaleimide (BMI), 8.4 parts by weight of microencapsulated repair agent, 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (tracelyl isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0109] (4) Extrusion molding: The premixed material is melt-extruded through a single screw extruder. The barrel temperature is set as follows: Zone 1 90℃, Zone 2 110℃, Zone 3 120℃, Zone 4 115℃, and the die temperature is 110℃. After cooling and shaping by the casting roller, an EVA film with a thickness of 0.5mm is obtained.

[0110] Example 4

[0111] Unlike Example 2, the self-healing EVA film contains different weight proportions of each raw material, specifically:

[0112] 81 parts modified EVA, 2.4 parts bismaleimide (BMI), 12.5 parts microencapsulated repair agent, 0.4 parts light stabilizer (Tinuvin 770), 1.3 parts antioxidant (1010), 0.4 parts crosslinking agent (tracelyl isocyanurate, TAIC), and 2.5 parts silane coupling agent (KH570).

[0113] The preparation method of the self-healing EVA film is the same as in Example 2.

[0114] Example 5

[0115] Unlike Example 2, the self-healing EVA film contains different weight proportions of each raw material, specifically:

[0116] 89.3 parts modified EVA, 6.7 parts bismaleimide (BMI), 4.0 parts microencapsulated repair agent, 2.5 parts light stabilizer (Tinuvin 770), 0.2 parts antioxidant (1010), 1.7 parts crosslinking agent (tracelyl isocyanurate, TAIC), and 0.4 parts silane coupling agent (KH570).

[0117] The preparation method of the self-healing EVA film is the same as in Example 2.

[0118] Comparative Example 1

[0119] Unlike Example 2, no dynamic reversible crosslinking agent and microencapsulation repair agent were added to the EVA film.

[0120] An EVA film, the raw materials by weight are: 84.3 parts modified EVA, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0121] The preparation method of EVA film is as follows:

[0122] (1) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0123] (2) Preparation of premix: 84.3 parts by weight of modified EVA, 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0124] (3) Extrusion molding: Same as in Example 2.

[0125] After artificially created cracks, the product showed no self-healing function after being treated at 70℃ for 2 hours, and its performance declined significantly after damp heat aging.

[0126] Comparative Example 2

[0127] Unlike Example 2, no microencapsulated repair agent was added to the EVA film.

[0128] An EVA film, the raw materials by weight are: 84.3 parts modified EVA, 4.2 parts bismaleimide (BMI), 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0129] The preparation method of EVA film is as follows:

[0130] (1) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0131] (2) Preparation of premix: 84.3 parts by weight of modified EVA, 4.2 parts by weight of bismaleimide (BMI), 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0132] (3) Extrusion molding: Same as in Example 2.

[0133] Comparative Example 3

[0134] Unlike Example 2, no dynamic reversible crosslinking agent was added to the EVA film.

[0135] The EVA film contains the following raw materials by weight: 84.3 parts modified EVA, 8.4 parts microencapsulated repair agent, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 0.9 parts crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts silane coupling agent (KH570).

[0136] The preparation method of EVA film is as follows:

[0137] (1) EVA grafting modification: 100 kg of EVA (VA content 28%, melt index 25 g / 10 min) resin, 3 kg of furan methacrylate and 0.3 kg of dicumyl peroxide (DCP) were added to a mixer; the mixture was melt-mixed at 120 °C for 15 min to obtain furan group functionalized EVA (modified EVA).

[0138] (2) Preparation of premix: 84.3 parts by weight of modified EVA, 8.4 parts by weight of microencapsulated repair agent, 0.9 parts by weight of light stabilizer (Tinuvin 770), 0.4 parts by weight of antioxidant (1010), 0.9 parts by weight of crosslinking agent (trimethylene isocyanurate, TAIC), and 0.9 parts by weight of silane coupling agent (KH570) are mixed evenly.

[0139] (3) Extrusion molding: Same as in Example 2.

[0140] Comparative Example 4

[0141] Unlike Example 2, the weight proportions of each component in the EVA film are different, specifically:

[0142] The raw materials, by weight, are: 84.3 parts modified EVA, 8.4 parts bismaleimide (BMI), 4.2 parts microencapsulated repair agent, 0.9 parts light stabilizer (Tinuvin 770), 0.4 parts antioxidant (1010), 1.6 parts crosslinking agent (tracene propyl isocyanurate, TAIC), and 0.2 parts silane coupling agent (KH570).

[0143] The preparation method of the EVA film is the same as in Example 2.

[0144] Comparative Example 5

[0145] Unlike Example 2, the dynamic reversible crosslinking agent bismaleimide (BMI) in the EVA film was replaced with tert-butyl peroxycarbonate-2-ethylhexyl ester (TBEC).

[0146] The preparation method of the EVA film is the same as in Example 2.

[0147] Experiment 1: Comparison of Initial Properties of EVA Films

[0148] Test method:

[0149] 1. Light transmittance: Refer to GB / T 2410-2008 (380-1100nm).

[0150] 2. Peel strength: Refer to GB / T 2790-1998 (peel strength with glass).

[0151] 3. Repair Efficiency: Using a utility knife, constant pressure is applied to the surface of the adhesive film to cut out a square "nine-square grid" pattern with a side length of 3.0cm. After artificially creating cracks, the cracks are treated at 70℃ for 2 hours, and the self-healing function is evaluated by tensile strength repair efficiency.

[0152] 4. ΔYI (yellowing index) after aging: Refer to IEC 61215-2021 (after 1000h of damp heat aging at 85℃ / 85%RH).

[0153] The comparison results of the initial properties of the EVA films in each embodiment and comparative example are shown in Table 1.

[0154] Table 1

[0155]

[0156] Experiment 2 Self-healing performance comparison

[0157] Table 2 shows the performance comparison results of each embodiment and the comparative example after treatment under DH 2000h and PCT 48h conditions.

[0158] DH 2000h refers to the EVA film being kept in a constant temperature and humidity environment of 85±2℃ and 85±5% relative humidity for 2000 hours to evaluate its aging resistance under high temperature and high humidity conditions.

[0159] PCT 48h refers to a key accelerated life test that assesses the resistance of EVA film to high temperature and high humidity aging by subjecting it to continuous treatment at 121°C and 100%RH saturated vapor pressure for 48 hours.

[0160] 1. Light transmittance: Refer to GB / T 2410-2008 (380-1100nm).

[0161] 2. Peel strength: Refer to GB / T 2790-1998 (peel strength with glass).

[0162] 3. Repair Efficiency: Using a utility knife, a square "nine-square grid" pattern with a side length of 3.0cm was cut out on the surface of the adhesive film under constant pressure. After artificially creating cracks, the cracks were treated at 70℃ for 2 hours, and the self-healing function was evaluated by tensile strength recovery rate.

[0163] 4. ΔYI (yellowing index) after aging: Refer to IEC 61215-2021 (after 1000h of damp heat aging at 85℃ / 85%RH).

[0164] Table 2

[0165]

[0166] This invention applies self-healing technology to the field of solar photovoltaics, and successfully prepares a self-healing EVA film to solve the problem of traditional photovoltaic modules bearing various mechanical stresses during transportation, installation and operation, including wind pressure, snow load, thermal expansion and contraction stress, as well as local stress concentration caused by improper installation.

[0167] The material prepared in this invention achieves a comprehensive performance improvement through the following technical solutions: First, in terms of molecular structure design, a dynamic reversible cross-linked network is constructed using Diels-Alder reactive group grafting technology, endowing the material with chemical bonding repair capabilities; second, repair factors are implanted through silane coupling agent microencapsulation technology, forming a physical rearrangement repair system. These two repair mechanisms work synergistically, enabling the film to achieve self-repair at the molecular level when damaged.

[0168] As can be seen from the technical effects in Tables 1 and 2, the self-healing EVA film of this invention maintains excellent optical performance, with a light transmittance exceeding 90%, ensuring high light energy conversion efficiency for photovoltaic modules. Its aging resistance is significantly improved; after accelerated aging testing, the color difference change ΔYI ≤ 3, far superior to traditional EVA films. The production process of the self-healing EVA film material of this invention is fully compatible with existing photovoltaic module production lines, enabling large-scale production without additional equipment investment. This invention provides a solution to the long-term reliability degradation problem of photovoltaic modules under harsh environments such as humidity, heat, and ultraviolet radiation.

[0169] Figure 1 This is a schematic diagram of the traditional EVA film structure of the present invention. Specifically, the traditional EVA film reacts at the cross-linking points of the EVA molecular chains to form an irreversible three-dimensional network structure. This structure has the characteristics of being static and permanent, thus making it impossible for the material to self-repair after being damaged.

[0170] Figure 2This is a schematic diagram of the structure of the self-healing EVA film of the present invention. Specifically, a dynamic reversible crosslinking agent induces the formation of a reversible crosslinked dynamic network structure between EVA molecular chains, constructing a reversible system with a three-dimensional network. At the same time, the microcapsules are uniformly dispersed and stably distributed inside the EVA film through a stirring process.

[0171] Figure 3 This diagram illustrates the working principle of the self-healing EVA film of the present invention. Specifically, when the EVA film material is damaged due to mechanical damage or microcracks, its internal dynamic network structure can undergo reversible pyrolysis and recombination (dynamic bond breaking and recombination) and silane bonding under external stimuli such as heat and light, thereby effectively repairing the cracked area. Simultaneously, the microcapsules embedded in the material rupture upon damage, releasing a repair agent (microcapsule release of repair agent). This repair agent, under the action of a catalyst, triggers an in-situ polymerization reaction, further filling and bridging the crack, thus healing it. These two mechanisms work synergistically to achieve multi-level self-repair of the damaged area of ​​the material.

[0172] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A self-healing EVA film, characterized in that, By weight, the components include: 81.0-89.3 parts of modified ethylene-vinyl acetate copolymer, 4.0-12.5 parts of microencapsulated repair agent, 2.4-6.7 parts of dynamic reversible crosslinking agent, 0.4-2.5 parts of light stabilizer, 0.2-1.3 parts of antioxidant, 0.4-1.7 parts of crosslinking agent, and 0.4-2.5 parts of silane coupling agent A; The modified ethylene-vinyl acetate copolymer is prepared by: melt blending EVA resin with a graft monomer containing furan groups, and carrying out a grafting reaction under the action of a peroxide initiator to obtain the modified ethylene-vinyl acetate copolymer. The microencapsulated repair agent uses polyurea-formaldehyde as the wall material and a coupling agent as the core material; the dynamic reversible crosslinking agent is a compound containing maleimide groups.

2. The EVA film according to claim 1, characterized in that, By weight, the components include: 84.3 parts of modified ethylene-vinyl acetate copolymer, 8.4 parts of microencapsulated repair agent, 4.2 parts of dynamic reversible crosslinking agent, 0.9 parts of light stabilizer, 0.4 parts of antioxidant, 0.9 parts of crosslinking agent and 0.9 parts of silane coupling agent A.

3. The EVA film according to any one of claims 1-2, characterized in that, The ethylene-vinyl acetate copolymer contains 28%-33% vinyl acetate and has a melt index of 15g / 10min-25g / 10min.

4. The EVA film according to any one of claims 1-2, characterized in that, The microencapsulated repair agent is a microcapsule with polyurea-formaldehyde as the wall material and silane coupling agent B as the core material, and the average particle size of the microencapsulated repair agent is 10-50 μm.

5. The EVA film according to any one of claims 1-2, characterized in that, The dynamic reversible crosslinking agent is selected from at least one of bis(2-maleimide ethyl)amine, bismaleimide, and 1,6-dimaleimide hexane.

6. The EVA film according to any one of claims 1-2, characterized in that, The light stabilizer is selected from at least one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-n-octyloxybenzophenone; The antioxidant is selected from at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; The crosslinking agent is selected from at least one of dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, triallyl isocyanurate, and divinylbenzene; The silane coupling agent A is selected from at least one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane.

7. The method for preparing the EVA film according to any one of claims 1-6, characterized in that, Including the following steps: (1) Preparation of microencapsulated repair agent: Silane coupling agent B is mixed with emulsifier to form an oil phase, and urea and formaldehyde aqueous solution is used as the aqueous phase. Through interfacial polymerization reaction, polyurea-formaldehyde wall material is formed to encapsulate silane coupling agent microcapsules. After washing and drying, microencapsulated repair agent is obtained. (2) EVA grafting modification: Ethylene-vinyl acetate copolymer resin is melt-blended with grafting monomers containing furan groups, and grafting reaction is carried out under the action of peroxide initiator to obtain furan group functionalized ethylene-vinyl acetate copolymer, that is, modified EVA. (3) Preparation of premix: The modified EVA, dynamic reversible crosslinking agent, microencapsulated repair agent and other additives are mixed evenly to obtain the premix; (4) Extrusion molding: The premixed material is melted and extruded to form an EVA film.

8. The preparation method according to claim 7, characterized in that, In step (1), the silane coupling agent B is selected from one of 3-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and vinyltrimethoxysilane; the emulsifier is selected from at least one of Tween-60 and Tween-80. In step (1), the mass ratio of silane coupling agent B to emulsifier is 15-25:1; in step (1), the pH of the aqueous phase is 8-9, and the reagent used to adjust the pH is triethanolamine; in step (1), the mass ratio of urea to formaldehyde aqueous solution is 1:1.5-3; in step (1), the mass concentration of formaldehyde aqueous solution is 30%-40%; in step (1), the conditions for the interfacial polymerization reaction are: 50-70℃ for 3-5 hours.

9. The preparation method according to claim 7, characterized in that, In step (2), the grafted monomer containing furan groups is furan methacrylate; in step (2), the mass ratio of the ethylene-vinyl acetate copolymer resin, the grafted monomer containing furan groups and the peroxide initiator is 100:2-4:0.2-0.5; in step (2), the melt blending conditions are: melting at 110-130℃ for 10-20 min.

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