Method for testing and evaluating corrosion resistance of encapsulant film for photovoltaic module

Abstract

The application provides a kind of photovoltaic module encapsulation adhesive film corrosion resistance testing evaluation method.The method comprises the following steps: sample preparation stage: the laminated piece with encapsulation adhesive film is subjected to aging treatment, to peel off the encapsulation adhesive film in the sample after aging treatment as the measured adhesive film;Test stage: the measured adhesive film is placed in solvent for leaching treatment to obtain the content of acid in the measured adhesive film, which is denoted as C;After peeling off the measured adhesive film in the sample after aging treatment, the measured adhesive film needs to be leached within 30 min;Use C to represent the corrosion resistance of encapsulation adhesive film, wherein the larger C represents the worse corrosion resistance of encapsulation adhesive film.Based on this, the application can more reliably and effectively test and evaluate the corrosion resistance of adhesive film in practical application in a short time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic cells, in particular to a method for testing and evaluating the corrosion resistance of encapsulation adhesive film for photovoltaic modules. BACKGROUND

[0002] The encapsulation adhesive film plays a crucial role in ensuring the service life of the module. In the prior art, EVA / EP encapsulation adhesive film is one of the more mature solar cell encapsulation materials at home and abroad, and its price is lower than that of POE encapsulation adhesive film, which is more conducive to the realization of the goal of parity of photovoltaic industry. After long-term aging and water vapor intrusion, the EVA / EP adhesive film (adhesive film containing EVA raw material) is prone to cause degradation of the molecular chain of the EVA adhesive film, releasing acetic acid. At the same time, some organic additives added in the encapsulation adhesive film may also decompose into acidic substances after aging, causing corrosion to the paste and solder strip on the surface of the cell, and thus affecting the power generation of the module. However, in the prior art, the corrosion resistance of the encapsulation adhesive film is evaluated by testing the EL (electroluminescence) of the aged photovoltaic module and combining the power attenuation of the module to evaluate the corrosion resistance of the adhesive film. However, this method involves the influence of the performance of many raw material components, such as the difference in corrosion resistance of the cell itself, the difference in process parameters during the preparation of the photovoltaic module, and cannot evaluate the performance of the encapsulation adhesive film itself. On the other hand, this evaluation process usually takes a long time to age and test. Therefore, it is necessary to provide a new method for testing and evaluating the corrosion resistance, which can effectively and reliably evaluate the corrosion resistance of the encapsulation adhesive film for photovoltaic modules in a short time. SUMMARY

[0003] The main purpose of the present application is to provide a method for testing and evaluating the corrosion resistance of encapsulation adhesive film for photovoltaic modules, to solve the problem that the corrosion resistance of encapsulation adhesive film for photovoltaic modules cannot be effectively and reliably evaluated in a short time in the prior art.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for testing and evaluating the corrosion resistance of encapsulation adhesive film for photovoltaic modules is provided, the method comprising the following steps: sample preparation stage: the laminated piece with encapsulation adhesive film is subjected to aging treatment to strip the encapsulation adhesive film in the sample after aging treatment as the adhesive film to be tested; test stage: the adhesive film to be tested is immersed in a solvent for leaching treatment to obtain the content of acid in the adhesive film to be tested, which is denoted as C; after stripping the adhesive film to be tested from the sample after aging treatment, the adhesive film to be tested is subjected to leaching treatment within 30 minutes to obtain a leaching solution; C is used to represent the corrosion resistance of the encapsulation adhesive film, wherein the larger C is, the worse the corrosion resistance of the encapsulation adhesive film is.

[0005] Further, the encapsulation adhesive film is an adhesive film containing ethylene-vinyl acetate copolymer in the raw material.

[0006] Further, the content of the acid in the to-be-tested adhesive film is obtained by ion chromatography; preferably, at least part of the leaching solution is taken as the sample solution, the sample solution is tested by ion chromatography, and the C value is obtained by calculation according to the formula C=a1×V1 / m1, wherein a1 represents the measured value of the acid content in the sample solution, V1 represents the volume of the solvent, and m1 represents the weight of the to-be-tested adhesive film.

[0007] Further, the content of the acid in the to-be-tested adhesive film is obtained by titration; preferably, the titration includes: taking at least part of the leaching solution as the to-be-tested solution, titrating the to-be-tested solution with a base, and calculating the C value according to the formula C=M×(V2-V3)×C M ×1000 / m2, wherein M represents the molar mass of the base, V2 represents the volume of the solution of the base consumed by the to-be-tested solution, V3 represents the volume of the solution of the base consumed by the blank comparison sample, C M represents the molar concentration of the solution of the base, and m2 represents the weight of the to-be-tested adhesive film; further preferably, the base is potassium hydroxide, and the solution of the base is an ethanol solution of potassium hydroxide.

[0008] Further, the encapsulation adhesive film includes a first adhesive film and a second adhesive film, and the laminated component is obtained by laminating the glass, the first adhesive film, the battery piece, the second adhesive film and the cover plate in sequence; the size of the encapsulation adhesive film is greater than or equal to the size of the glass.

[0009] Further, the processing temperature of the lamination is 120-160°C, and the processing time is 10-30 min.

[0010] Further, the temperature during the aging treatment is -40-150°C, and the humidity is 80-100% RH.

[0011] Further, when the content of acetic acid in the to-be-tested adhesive film is obtained by ion chromatography, the leaching treatment includes: placing the to-be-tested adhesive film in a closed container, adding a solvent to the closed container, and pressing the to-be-tested adhesive film below the liquid level of the closed container with a polypropylene filter screen, and then performing water bath heating on the closed container; preferably, the solvent is one or more of deionized water, distilled water or ultrapure water.

[0012] Further, the temperature of the water bath heating is 25-99°C, and the time is 0.5-4 h; preferably, the liquid level of the water bath heating is not less than 4 / 5 of the liquid level in the closed container.

[0013] Further, the weight ratio of the to-be-tested adhesive film to the solvent during the leaching treatment is 1:(5-50).

[0014] Further, in the titration method for obtaining the content of acetic acid in the tested adhesive film, the leaching treatment comprises: placing the tested adhesive film into a container, adding a solvent into the container, and then performing ultrasonic treatment on the solvent, wherein the solvent is one or more of toluene, xylene or tetrahydrofuran mixed with alcohol.

[0015] Further, the ultrasonic frequency of the ultrasonic treatment is 20-40 kHz, and the ultrasonic time is 5-60 min; preferably, the ultrasonic frequency is 30-40 kHz, and the ultrasonic time is 15-30 min.

[0016] Further, in the titration method for obtaining the content of acetic acid in the tested adhesive film, the leaching treatment comprises: placing the tested adhesive film into a container, adding a solvent into the container, and then performing ultrasonic treatment on the solvent, wherein the solvent is one or more of toluene, xylene or tetrahydrofuran mixed with alcohol.

[0017] Further, in the titration method for obtaining the content of acetic acid in the tested adhesive film, the leaching treatment comprises: placing the tested adhesive film into a container, adding a solvent into the container, and then performing ultrasonic treatment on the solvent, wherein the solvent is one or more of toluene, xylene or tetrahydrofuran mixed with alcohol.

[0018] Generally, after long-term aging and water vapor intrusion, the encapsulating adhesive film is prone to cause degradation of the molecular chain of the adhesive film itself, and release a part of acid. At the same time, a part of organic additives added in the encapsulating adhesive film may also decompose a part of acidic substances after aging. These acidic substances (including one or more of acetic acid, phenol, carbonic acid or silanol decomposed from the adhesive film itself and / or some additives) can cause corrosion to the paste on the surface of the battery piece and the solder strip, and further affect the power generation of the module. Based on the above-mentioned steps, the application simulates the assembly and aging state of the encapsulating adhesive film for actual photovoltaic modules, so as to effectively and reliably obtain the content (i.e. C) of the acid generated by the encapsulating adhesive film in actual application (after long-term aging and water vapor intrusion). And for the first time, it is innovatively proposed that the corrosion resistance of the encapsulating adhesive film can be characterized by the content of this part of acid, that is, the larger the C value is, the worse the corrosion resistance of the encapsulating adhesive film is. Based on this, the application can more reliably and effectively test and evaluate the corrosion resistance of the adhesive film in actual application in a short time, so as to more truly reflect the degradation resistance of the adhesive film in actual application, further improve the accuracy of the test results, and reduce the human error. At the same time, based on this test and evaluation method, the test efficiency is higher, the operation is simpler, and the evaluation reliability is higher. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0020] Figure 1 The battery sheet corrosion EL test graph after aging for 96h at 125℃, 95% RH using encapsulant film W with poor corrosion resistance is shown;

[0021] Figure 2 The battery sheet corrosion EL test graph after aging for 96h at 125℃, 95% RH using encapsulant film M with medium corrosion resistance is shown;

[0022] Figure 3 The battery sheet corrosion EL test graph after aging for 96h at 125℃, 95% RH using encapsulant film B with better corrosion resistance is shown;

[0023] Figure 4 The battery sheet corrosion EL test graph after aging for 192h at 125℃, 95% RH using encapsulant film W with poor corrosion resistance is shown;

[0024] Figure 5 The battery sheet corrosion EL test graph after aging for 192h at 125℃, 95% RH using encapsulant film M with medium corrosion resistance is shown;

[0025] Figure 6 The battery sheet corrosion EL test graph after aging for 192h at 125℃, 95% RH using encapsulant film B with better corrosion resistance is shown. DETAILED DESCRIPTION

[0026] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0027] As described in the background section, there is a problem in the prior art that the corrosion resistance of encapsulant film for photovoltaic modules cannot be effectively and reliably evaluated in a short time. In order to solve this problem, the present application provides a test and evaluation method for the corrosion resistance of encapsulant film for photovoltaic modules, which comprises the following steps: sample preparation stage: the laminated piece with encapsulant film is subjected to aging treatment to strip the encapsulant film in the sample after aging treatment as the test film; test stage: the test film is placed in a solvent for leaching treatment to obtain the content of acid in the test film, which is denoted as C; the test film is stripped from the sample after aging treatment, and the leaching treatment of the test film needs to be completed within 30 minutes; C is used to represent the corrosion resistance of the encapsulant film, wherein the larger C is, the poorer the corrosion resistance of the encapsulant film is.

[0028] Generally, the encapsulation adhesive film is prone to cause degradation of the molecular chain of the adhesive film itself after long-term aging and water vapor intrusion, and release a part of acid. At the same time, part of the organic additives added in the encapsulation adhesive film may also decompose a part of acidic substances after aging. These acidic substances (including the acid decomposed from the adhesive film itself and / or the acid produced by the decomposition of some additives, such as one or more of acetic acid, phenol, carbonic acid or silanol) will cause corrosion to the paste on the surface of the battery piece and the solder strip, etc., and then affect the power generation of the module. Based on the above steps, the present application simulates the assembly and aging state of the actual encapsulation adhesive film for photovoltaic module to effectively and reliably obtain the content (i.e. C value) of the acid produced by the encapsulation adhesive film in actual application (after long-term aging and water vapor intrusion). And for the first time, it is innovatively proposed that the corrosion resistance of the encapsulation adhesive film can be characterized by the content of this part of acid, that is, the larger the C value, the worse the corrosion resistance of the encapsulation adhesive film. Based on this, the present application can more reliably and effectively test and evaluate the corrosion resistance of the adhesive film in actual application in a short time, so as to more truly reflect the degradation resistance of the adhesive film in actual application, further improve the accuracy of the test results, and the human error is smaller. At the same time, based on this test and evaluation method, the test efficiency is higher, the operation is simpler, and the evaluation reliability is higher.

[0029] Specifically, in subsequent actual application, the technicians in the field can selectively extract some batch adhesive films produced in the factory as samples to pre-evaluate the corrosion resistance of the encapsulation adhesive film by the above test and evaluation method, and then can feedback and adjust the production parameters to improve the product quality.

[0030] In an optional embodiment of the present application, the encapsulation adhesive film is a film containing ethylene-vinyl acetate copolymer in the raw material, such as EVA film, multi-layer co-extrusion film containing EVA.

[0031] For the encapsulation adhesive film containing EVA raw material, the test of the content of acetic acid produced by the degradation of the adhesive film after aging is an important index for evaluating the corrosion resistance of the adhesive film. In a preferred embodiment of the present application, the present application simulates the assembly and aging state of the actual encapsulation adhesive film based on the above steps, and quantitatively obtains the content of acetic acid in the actual encapsulation adhesive film by ion chromatography analysis of the encapsulation adhesive film after aging. Among them, the typical ion exchange mode is that the ion to be tested replaces OH - groups on the anion exchange resin and is temporarily and selectively retained on the stationary phase. At the same time, the retained anions are replaced by OH - groups in the eluent and are eluted from the column. The resin has a stronger affinity for OH -Weak anions pass through the column faster than anions with a strong affinity for the anion exchange sites, and this process determines the separation between the anions in the sample. Finally, the eluate passes through a suppressor and a conductivity cell for conductivity detection. During ion chromatography testing, to reduce the background conductivity value, the suppressor will convert the cations eluted from the column into H + Therefore, the corrosion resistance obtained by ion chromatography testing is the sum of the acetic acid and acetate in the test liquid. Based on this, the present application can more reliably and effectively evaluate the corrosion resistance of the packaging adhesive film containing EVA raw materials in actual application (including acetic acid and acetate converted from acetic acid). At the same time, based on this test method, the test efficiency is higher and the operation is simpler. It should be additionally pointed out that, since only EVA raw materials in the adhesive film materials used in the current solar cell photovoltaic module can produce acetic acid, the content of acetic acid in the test adhesive film is the corrosion resistance released by the degradation of the adhesive film. The content of acetic acid obtained by ion chromatography can be more accurately obtained to evaluate the reliability of the corrosion resistance of the adhesive film.

[0032] In a preferred embodiment, when the content of acetic acid in the test adhesive film is obtained by ion chromatography, the leaching treatment includes: cutting the test adhesive film into pieces with a size of (2-5) mm x (2-5) mm and placing them in a closed container, adding a solvent to the closed container, and pressing the test adhesive film below the liquid level of the closed container with a polypropylene filter screen; and then water-bath heating the closed container. Based on this, the test adhesive film can be better soaked in the solvent, the leaching treatment effect is better, more acetate ions in the test adhesive film can enter the leaching solution, the leaching rate of the acetate ions is higher, and then the test result obtained by subsequent ion chromatography can more truly, reliably and comprehensively reflect the actual content of acetic acid in the test adhesive film.

[0033] In order to improve the leaching rate of acetate ions and thus improve the test accuracy, the temperature of water-bath heating is preferably 60-99℃, and the time is 0.5-4h; the liquid level of water-bath heating is not less than 4 / 5 of the liquid level in the closed container.

[0034] In order to further improve the leaching rate of acetate ions and thus improve the test accuracy, the weight ratio of the test adhesive film to the solvent during the leaching treatment is preferably 1:(5-50).

[0035] In order to further improve the detection accuracy of ion chromatography, a gradient elution mode is preferably used in the ion chromatography test process: the elution time is 15min, the concentration of the elution mobile phase is controlled to be 2mMol within 0-7min, and the concentration of the elution mobile phase is controlled to be 40mMol within 8-15min; more preferably, the elution mobile phase is potassium hydroxide, and the test instrument is ICS-600. In actual operation, those skilled in the art can adjust the elution time and concentration to improve the detection accuracy, which will not be described here.

[0036] In another alternative embodiment of the present application, the acid content in the tested adhesive film can also be obtained by titration. A portion of the leaching solution is taken as the tested solution, and the tested solution is titrated with a base. The C value can be obtained by the formula C = M x (V2-V3) x C M x 1000 / m2, wherein M represents the molar mass of the base, V2 represents the volume of the base solution consumed by the tested solution, V3 represents the volume of the base solution consumed by the blank control sample, C M represents the molar concentration of the base solution, and m2 represents the weight of the tested adhesive film. The blank control sample can be a mixed solution of xylene and ethanol or a mixed solution of toluene and ethanol, which can be determined according to the actual test mixed solution. Further preferably, the base is potassium hydroxide, and the base solution is an ethanol solution of potassium hydroxide. The titration method is mainly used to test the H + content in the solution, which includes not only acetic acid decomposed from EVA but also acids produced by aging decomposition of some additives such as peroxide, silane coupling agent or ester crosslinking agent. The titration method can be an indicator colorimetric titration method or a potentiometric titration method.

[0037] In a preferred embodiment, the reagents required in the titration test are as follows: anhydrous ethanol (analytical pure AR, moisture ≤0.2%), xylene (analytical pure AR, moisture ≤0.03%), KOH reagent (analytical pure AR, purity ≥90%), potassium hydrogen phthalate (analytical pure AR, purity ≥99.8%), and bromothymol blue reagent (acid-base indicator) as the titration test reagents. The mixed solvent is a mixed solution of xylene and anhydrous ethanol, and the volume ratio of xylene to anhydrous ethanol is 2:1. The base standard titration solution is a KOH solution with a certain concentration, and a concentration of 0.001 mol / L to 0.01 mol / L is recommended. The water is of a purity specified in GB / T6682, at least third-grade water. The indicator is a 0.05 g / 100 mL concentration of bromothymol blue ethanol solution, wherein the volume ratio of ethanol to water is 1:4. The standard uses bromothymol blue solution as the titration indicator. The instruments required are as follows: a burette (meeting the requirements of GB / T 12805, with a capacity of 50 mL and an accuracy of 0.1 mL), an Erlenmeyer flask (a 250 mL Erlenmeyer flask with a ground glass stopper), a beaker (a 250 mL beaker), a graduated cylinder (a 100 mL graduated cylinder with an accuracy of 1 mL), an ultrasonic instrument with an ultrasonic frequency of more than 40 kHz, and an analytical balance with an accuracy of 0.1 mg.

[0038] In actual operation, the photovoltaic packaging adhesive film taken out from the sample after lamination, curing and aging is ultrasonically swollen by the organic mixed solvent, so that the free acid in the packaging adhesive film is dissolved in the mixed solvent. The dissolved free acid is titrated by the acid-base titration principle to evaluate the corrosion resistance of the adhesive film. The specific steps are as follows:

[0039] 1. Preparation of KOH ethanol solution: Weigh a certain mass of KOH solid and dissolve it in a certain volume of anhydrous ethanol. After dissolving and constant volume, stand for 4-6 days. The recommended concentration of KOH ethanol solution is 0.001 mol / L-0.01 mol / L. The specific concentration used is determined according to the estimated acid content, and the volume of KOH ethanol solution titrated at a time is less than 25 mL.

[0040] 2. Preparation of potassium hydrogen phthalate aqueous solution: Before use, first take out the potassium hydrogen phthalate reagent and place it in a clean container, and dry it in an oven at 105-110°C until the weight is constant. Take about 0.075g of potassium hydrogen phthalate reagent and dissolve it in 50g of water (concentration is about 0.0073mol / L). Record the actual mass of potassium hydrogen phthalate taken (m1), calculate the actual concentration of potassium hydrogen phthalate solution (c1), and the result is retained to 0.0001mol / L. Note: The above concentration of potassium hydrogen phthalate aqueous solution corresponds to a KOH ethanol solution concentration of 0.01mol / L. For different KOH ethanol solutions, prepare an appropriate concentration of potassium hydrogen phthalate aqueous solution.

[0041] 3. Sample preparation: Laminated parts preparation and treatment, prepare one piece of super white embossed tempered glass not less than 200mmx200mm, two pieces of encapsulation adhesive film samples to be tested and one piece of back plate. Stack the above materials according to the structure of super white embossed tempered glass / samples to be tested / samples to be tested / back plate, then laminate according to the requirements, and the crosslinking degree of the encapsulation adhesive film after lamination should reach more than 80%. After trimming the edges of the laminated parts, seal the edges with aluminum foil tape. According to GB / T 29848-2018 standard, place the laminated parts in a certain condition of accelerated aging environment test chamber for aging treatment.

[0042] 4. Preparation of titration sample, within 12 hours after aging is completed, take out the laminated parts from the test chamber, and take samples at a distance of at least 50mm from the edge of the laminated parts. Peel off the encapsulation adhesive film from the glass surface and remove the back plate. If the back plate is brittle and cannot be removed completely, at least the PET layer of the back plate should be removed; cut the peeled encapsulation adhesive film into small pieces of about 5mmx5mm, weigh about 1g of sample (record the actual mass M1) and add it to a conical flask containing mixed solution (40ml of xylene + 20ml of ethanol), seal with a glass plug, and ultrasonic for 15min. The ultrasonic power is recommended to be set at 40kHZ, so that the organic acid in the adhesive film is fully dissolved in the mixed solution after the adhesive film is swelled. The water temperature should be controlled during ultrasonic, and the recommended temperature is below 40°C. After ultrasonic, immerse the conical flask in cold water for cooling. Note: Sampling should be carried out at room temperature, and the laminated parts cannot be heated; the adhesive film should be added to the mixed solution and sealed for ultrasonic within 10min after being peeled off from the glass surface.

[0043] 5. Calibration and testing, blank comparison sample: take 50 mL water in a conical flask, and drop about 0.3 g of bromothymol blue indicator, titrate with KOH ethanol solution after standing, until the end point color (light green), and keep 1 min unchanged color. Record the actual consumption of KOH ethanol solution volume (V1). Potassium hydrogen phthalate aqueous solution: take 50 mL potassium hydrogen phthalate aqueous solution in a conical flask, and drop about 0.3 g of bromothymol blue indicator, titrate with KOH ethanol solution after standing, until the end point color (light green) is consistent with the blank comparison sample, and keep 30 s unchanged color. Record the actual consumption of KOH ethanol solution volume (V2).

[0044] 6. KOH solution concentration calculation, calculate the concentration of KOH ethanol solution according to formula (1), and the result is kept to 3 significant figures.

[0045]

[0046] In the formula:

[0047] m - potassium hydrogen phthalate mass, unit is gram (g);

[0048] V1 - potassium hydrogen phthalate aqueous solution consumption of KOH ethanol solution volume, unit is milliliter (mL);

[0049] V2 - blank sample consumption of KOH ethanol solution volume, unit is milliliter (mL);

[0050] 204.22 - molar mass of potassium hydrogen phthalate, unit is gram per mole (g / mol).

[0051] 7. Titration of acid value of sample to be tested, blank comparison sample: take 40 mL of xylene and 20 mL of ethanol mixed in a conical flask, and drop about 0.3 g of bromothymol blue indicator, titrate with KOH ethanol solution of the same day calibration concentration, until the end point color (light green), and keep 30 s unchanged color. Record the actual consumption of KOH ethanol solution volume (V3). Titration test sample: drop about 0.3 g of bromothymol blue indicator in the conical flask containing the mixed solution of the sample to be tested after ultrasonic treatment, titrate with KOH ethanol solution of the same day calibration concentration, until the end point color (light green) is consistent with the blank comparison sample, and keep at least 30 s unchanged color. Record the actual consumption of KOH ethanol solution volume (V4).

[0052] 8. Calculation of test acid value, calculate the acid value of the sample according to formula (2), expressed by micrograms of potassium hydroxide consumed per gram of sample, and the result is an integer.

[0053]

[0054] In the formula:

[0055] C - Acid value of the sample, in micrograms per gram (ug / g);

[0056] V3 - Volume of KOH ethanol solution consumed by the sample to be tested, in milliliters (mL);

[0057] V4 - Volume of KOH ethanol solution consumed by the blank comparative sample (xylene + ethanol mixed solvent), in milliliters (mL);

[0058] C (KOH) - Actual concentration of KOH ethanol solution, in moles per liter (mol / L);

[0059] 56.1 - Constant, molar mass of potassium hydroxide, in grams per mole (g / mol);

[0060] M1 - Mass of the sample, in grams (g).

[0061] 9. Representation of the results, two samples are tested from the same piece of laminate, the arithmetic average of the two results is taken as the acid value of the sample to be tested, and the result is kept as an integer. If the difference between the two results and the average value exceeds 15%, then the sample is taken again according to the above sampling procedure, and the titration is carried out according to the above titration procedure until the two results meet the requirements.

[0062] In order to further improve the accuracy of the titration method and thus improve the evaluation reliability, in a preferred embodiment, when the content of acetic acid in the sample to be tested is obtained by titration, the leaching treatment includes: placing the sample to be tested in a container, adding a solvent to the container, and then performing ultrasonic treatment on the solvent, and the solvent is a mixed solvent of one or more of toluene, xylene or tetrahydrofuran and an alcohol. Alternatively, in another preferred embodiment, when the content of acetic acid in the sample to be tested is obtained by titration, the leaching treatment includes: placing the sample to be tested in a container, adding a solvent to the container, and then performing ultrasonic treatment on the solvent, and the solvent is a mixed solvent of one or more of cyclohexane, carbon tetrachloride, ethylene glycol monobutyl ether, 2,2-dichloropropane, 1,2-dichloropropane, acetone, benzene, methyl ethyl ketone, chloroform, tetrahydronaphthalene or 1,2-dichloroethane and an alcohol. More preferably, the ultrasonic frequency of the ultrasonic treatment is 20-40 kHz, and the ultrasonic time is 5-60 min; preferably the ultrasonic frequency is 30-40 kHz, and the ultrasonic time is 15-30 min. During the leaching treatment, the volume of the solvent used is 30-120 mL per gram of the weight of the sample to be tested.

[0063] In order to further simulate the structure of the actual encapsulation film more accurately, thereby improving the test accuracy, in an alternative embodiment, the laminated piece is obtained by laminating the glass, the encapsulation film and the back plate in sequence; the size of the encapsulation film is greater than or equal to the size of the glass; preferably, the size of the glass is (20-35) cm x (20-35) cm. In another alternative embodiment, the encapsulation film comprises a first film and a second film, and the laminated piece is obtained by laminating the glass, the first film, the battery piece, the second film and the back plate in sequence; preferably, a non-stick film is further provided between the glass and the first film, between the first film and the battery piece, between the battery piece and the second film, and between the second film and the back plate, respectively and independently; preferably, the non-stick film is an ETFE film; further preferably, the size of the ETFE film is (2-5) cm x (2-5) cm.

[0064] The processing temperature of the lamination is 120-160°C, and the processing time is 10-30 min. The size of the film is (20-35) cm x (20-35) cm; the back plate is selected from the back plates commonly used in photovoltaic modules, such as BEC303, a Dow co-extrusion back plate, a transparent CPC back plate or a transparent TPC back plate. The lamination process can use conventional lamination techniques and conventional consumables in the art, and there is no special requirement here. Those skilled in the art can choose according to their own product needs, and no further description is given here.

[0065] In a preferred embodiment, the laminated piece is trimmed to remove the excess film around the edges, and an aluminum tape is used to seal the edges of the laminated piece to prevent moisture from entering the edges and causing delamination of the sample after aging. The encapsulation film sealed by the aluminum tape is placed in an aging oven, and a gap is left between the samples, which cannot be stacked or piled together. In this way, each laminated piece can be in a consistent temperature and humidity aging environment.

[0066] In order to further simulate the actual aging state more accurately, thereby improving the test accuracy and reliability, the temperature during the aging process is -40-150°C, and the humidity is 80-100% RH. For example, it can be HAST, DH, HF, TC or DHUV (GB / T29848-2018). Those skilled in the art can set the aging conditions according to their own needs when using the test method of the present application, and no further description is given here. In order to further improve the timeliness of the test, the further preferred aging condition is HAST (note: 125°C, 95% RH), and the aging time can be 95-97 h.

[0067] In a preferred embodiment, within 8 hours after the completion of the aging, the sample after aging treatment that meets the test conditions (no delamination, no bubbles, etc. of the interface between the adhesive film and the glass, the adhesive film and the back plate, the adhesive film and the battery sheet) is taken out, about 0.3-1 g of the adhesive film is peeled off at a position within 50 mm from the boundary of the sample, and the back plate debris on the surface of the adhesive film is scraped off.

[0068] In order to further improve the accuracy of the ion chromatography test method, after the leaching liquid after the leaching treatment is taken out, the leaching liquid needs to be tested by ion chromatography within 4 hours. After the test adhesive film in the sample after the aging treatment is peeled off, the test adhesive film needs to be treated by leaching within 30 minutes. Preferably, the laminated sample after the packaging treatment needs to be aged within 12 hours in the aging treatment stage. If the ion chromatography test of the leaching liquid cannot be completed within 4 hours, the leaching liquid sample needs to be stored in a refrigerator at <5°C for 24 hours, and then taken out for testing when it can be tested. The test also needs to be completed within 4 hours after the leaching liquid is taken out.

[0069] The application will be further described in detail below in combination with specific examples, which cannot be understood as limiting the scope of the application claimed.

[0070] Example 1

[0071] According to the structure of 23 cm x 23 cm glass / first packaging adhesive film (EVA adhesive film W with poor corrosion resistance) / second packaging adhesive film (EVA adhesive film W with poor corrosion resistance) / back plate (BEC303), the laminated and laminated, the laminating temperature is 145°C, and the laminating time is 16 minutes.

[0072] After the laminated laminated part is cooled to room temperature, the laminated part is trimmed to remove the excess adhesive film around the periphery, and the laminated part is sealed around the periphery with an aluminum adhesive tape to prevent water vapor from entering the edge and causing delamination of the sample after aging.

[0073] The laminated part sealed with the aluminum adhesive tape is placed in an aging oven, and a gap is left between the samples, which cannot be stacked or stacked together. The sample after aging needs to ensure no delamination, bubbles and other defects. The aging condition is HAST (125C-95%), and the time is 96 hours.

[0074] Within 8 hours after the completion of the aging, the laminated part that meets the test conditions (no delamination, no bubbles, etc.) is taken out, about 0.5 g of the first packaging adhesive film / second packaging adhesive film is peeled off at a position within 50 mm from the edge, and the back plate debris on the surface of the adhesive film is scraped off.

[0075] The peeled adhesive film is cut into pieces of about 3 mm x 3 mm, and 0.5000 g of the sample (accurate to 0.0001 g) is weighed.

[0076] The cut pieces were put into 20ml glass bottles, 10ml of ultrapure water was added, and the film was pressed below the water surface with a polypropylene filter (which can maintain its own stability in water at room temperature - 90°C), and the bottle was sealed with a cap, and heated in a water bath, with the water surface of the water bath not less than 4 / 5 of the water surface in the bottle. The sample preparation should be completed within 30 minutes after the film was peeled off from the glass.

[0077] After 3h in the water bath, the glass bottle containing the sample was removed and cooled at room temperature (23±2°C) for 30min, then the supernatant was sucked out with a clean syringe and filtered with a filter head smaller than 0.22um and sealed in an ion chromatography test tube for testing.

[0078] Ion chromatography test method: instrument: ion chromatography (ICS-600 is currently used); gradient elution method, 0.01-7min, KOH concentration is 2mMol, 8-15min, KOH concentration is 40mMol.

[0079] C was calculated by the formula C=a x V1 / m1 to be 358.

[0080] Example 2

[0081] The difference from Example 1 is only that the film is EVA packaging film M with medium corrosion resistance.

[0082] C was calculated by the formula C=a x V1 / m1 to be 245.

[0083] Example 3

[0084] The difference from Example 1 is only that the film is EVA packaging film B with better corrosion resistance.

[0085] C was calculated by the formula C=a x V1 / m1 to be 155.

[0086] Example 4

[0087] The difference from Example 1 is only that the laminates were stacked and laminated according to the structure of 23cm x 23cm glass / first packaging film / battery piece / second packaging film backboard (BEC303), and the sampling position was the second packaging film alone, the lamination temperature was 145°C, and the lamination time was 16min.

[0088] C was calculated by the formula C=a x V1 / m1 to be 388.

[0089] Example 5

[0090] The difference from Example 1 is only that the laminates are stacked and laminated according to the structure of 23 cm x 23 cm glass / first encapsulant film / cell sheet / second encapsulant film backsheet (BEC303), the sampling position is the first encapsulant film / second encapsulant film at the edge of the assembly without cell sheet, the lamination temperature is 145°C, and the lamination time is 16 min.

[0091] C is calculated by formula C=a x V1 / m1 to be 345.

[0092] Example 6

[0093] 1. Preparation of KOH ethanol solution: a certain mass of KOH solid is dissolved in a certain volume of anhydrous ethanol. After dissolution and constant volume, it is left to stand for 4-6 days. The recommended concentration of KOH ethanol solution is 0.001 mol / L-0.01 mol / L. The specific concentration to be used is determined according to the estimated acid content, and the volume of KOH ethanol solution titrated at one time is ensured to be <25 mL.

[0094] 2. Preparation of potassium hydrogen phthalate aqueous solution: before use, first take out the potassium hydrogen phthalate reagent and place it in a clean container, and dry it to constant weight in a 105°C-110°C oven. About 0.075 g of potassium hydrogen phthalate reagent is dissolved in 50 g of water (concentration is about 0.0073 mol / L). Record the actual mass of potassium hydrogen phthalate taken (m1), calculate the actual concentration of potassium hydrogen phthalate solution (c1), and the result is rounded to 0.0001 mol / L. Note: the above concentration of potassium hydrogen phthalate aqueous solution corresponds to a KOH ethanol solution concentration of 0.01 mol / L. For different KOH ethanol solutions, prepare a potassium hydrogen phthalate aqueous solution with an appropriate concentration.

[0095] 3. Sample preparation: laminate preparation and processing, prepare one piece of super white embossed tempered glass not less than 200 mm x 200 mm, two pieces of encapsulant film samples to be tested and one piece of backsheet. After stacking the above materials according to the structure of super white embossed tempered glass / less corrosion resistant EVA film W / less corrosion resistant EVA film W / backsheet, laminate according to requirements, and the crosslinking degree of the encapsulant film after lamination should reach more than 80%. After trimming the edges of the laminates, the four edges are sealed with aluminum foil tape. According to GB / T29848-2018 standard, place the laminates in an accelerated aging environment test chamber under certain conditions for aging treatment.

[0096] 4. Sample preparation, within 12 hours after the end of aging, take out the laminated material in the test chamber, and take samples at a distance of at least 50 mm from the edge of the laminated material. Peel the encapsulation film from the glass surface, and remove the back plate. If the back plate is brittle and cannot be removed completely, at least the PET layer of the back plate should be removed; cut the peeled encapsulation film into small pieces of about 5 mm x 5 mm in size, weigh about 1 g of sample (record the actual mass M1), and add it into a conical flask containing a mixed solution (40 ml of xylene + 20 ml of ethanol), seal it with a glass plug, and ultrasonic for 15 min. It is recommended to set the ultrasonic power to 40 kHz, so that the organic acid in the film is fully dissolved into the mixed solution after the film is swelled. Control the water temperature during ultrasonic, and it is recommended to be lower than 40°C. After ultrasonic, immerse the conical flask in cold water for cooling. Note: sampling should be carried out at room temperature, and the laminated material cannot be heated; the film should be added into the mixed solution within 10 min after being peeled from the glass surface.

[0097] 5. Calibration and testing, blank comparison sample: take 50 mL of water in a conical flask, and add about 0.3 g of bromothymol blue solution indicator, titrate with KOH ethanol solution after standing, until the end point color (light green) and keep it for 1 min without color change. Record the actual consumption volume of KOH ethanol solution (V1). Potassium hydrogen phthalate aqueous solution: take 50 mL of potassium hydrogen phthalate aqueous solution in a conical flask, and add about 0.3 g of bromothymol blue indicator, titrate with KOH ethanol solution after standing, until the end point color (light green) is consistent with the blank comparison sample, and keep it for 30 s without color change. Record the actual consumption volume of KOH ethanol solution (V2).

[0098] 6. Calculation of KOH solution concentration, calculate the concentration of KOH ethanol solution according to formula (1), and the result is kept to 3 significant figures.

[0099]

[0100] In the formula:

[0101] m— mass of potassium hydrogen phthalate, unit: gram (g);

[0102] V1— volume of KOH ethanol solution consumed by potassium hydrogen phthalate aqueous solution, unit: milliliter (mL);

[0103] V2— volume of KOH ethanol solution consumed by blank sample, unit: milliliter (mL);

[0104] 204.22— molar mass of potassium hydrogen phthalate, unit: gram per mole (g / mol).

[0105] 7. Titrating the acid value of the sample to be tested, blank comparison sample: take 40 mL of xylene and 20 mL of ethanol and mix in a conical flask, and drop about 0.3 g of bromothymol blue indicator, use the KOH ethanol solution of the same day to titrate, until the end color (light green), and keep for 30 s without changing color. Record the actual volume of KOH ethanol solution consumed (V3). Titrating the test sample: after ultrasonic treatment, drop about 0.3 g of bromothymol blue indicator in the conical flask containing the mixed solution of the sample to be tested, use the KOH ethanol solution of the same day to titrate, until the end color (light green) and consistent with the blank comparison sample, and keep for at least 30 s without changing color. Record the actual volume of KOH ethanol solution consumed (V4).

[0106] 8. Calculating the test acid value, calculate the acid value of the sample according to formula (2), expressed in micrograms of potassium hydroxide consumed per gram of sample, and the result is rounded to the nearest integer.

[0107]

[0108] In the formula:

[0109] C - the acid value of the sample, in micrograms per gram (ug / g);

[0110] V3 - the volume of KOH ethanol solution consumed by the sample to be tested, in milliliters (mL);

[0111] V4 - the volume of KOH ethanol solution consumed by the blank comparison sample (xylene + ethanol mixed solvent), in milliliters (mL);

[0112] C (KOH) - the actual concentration of KOH ethanol solution, in moles per liter (mol / L);

[0113] 56.1 - constant, molar mass of potassium hydroxide, in grams per mole (g / mol);

[0114] M1 - the mass of the sample, in grams (g).

[0115] 9. Representation of the results, take 2 samples for testing from the same piece of laminate, take the arithmetic mean of the two results as the acid value of the sample to be tested, and the result is rounded to the nearest integer. If the difference between the two results and the average value exceeds 15%, then take a sample according to the previous sampling procedure on the laminate, and titrate according to the previous titration process until the two results meet the requirements.

[0116] C is 682.

[0117] Example 7

[0118] The difference between Example 6 and this example is that the adhesive film to be tested is EVA packaging adhesive film M with medium corrosion resistance, and the C value is 478.

[0119] Example 8

[0120] The difference between Example 6 and this example is that the adhesive film to be tested is EVA packaging adhesive film B with better corrosion resistance, and the C value is 183.

[0121] Example 9

[0122] The difference between Example 6 and this example is that the solvent consisting of 40 mL of xylene and 20 mL of ethanol is replaced with an equal amount of 40 mL of cyclohexane and 20 mL of ethanol, and the C value is 668.

[0123] Example 10

[0124] The difference between Example 6 and this example is that the solvent consisting of 40 mL of xylene and 20 mL of ethanol is replaced with an equal amount of 40 mL of carbon tetrachloride and 20 mL of ethanol, and the C value is 671.

[0125] Example 11

[0126] The difference between Example 6 and this example is that the solvent consisting of 40 mL of xylene and 20 mL of ethanol is replaced with an equal amount of 40 mL of ethylene glycol monobutyl ether and 20 mL of ethanol, and the C value is 685.

[0127] Example 12

[0128] The difference between Example 6 and this example is that the solvent consisting of 40 mL of xylene and 20 mL of ethanol is replaced with an equal amount of 40 mL of 1,2-dichloroethane and 20 mL of ethanol, and the C value is 694.

[0129] Example 13

[0130] The difference between Example 6 and this example is that the solvent consisting of 40 mL of xylene and 20 mL of ethanol is replaced with an equal amount of 40 mL of acetone and 20 mL of ethanol, and the C value is 693.

[0131] Performance characterization:

[0132] The EVA adhesive film W with poor corrosion resistance in Example 1, the packaging adhesive film M with medium corrosion resistance in Example 2, and the packaging adhesive film B with better corrosion resistance in Example 3 are respectively taken, and the laminated parts are stacked and laminated according to the structure of 23 cm x 23 cm of glass / adhesive film / battery piece / adhesive film / backboard (BEC303), the lamination temperature is 145°C, and the lamination time is 16 min. After packaging, EL (solar module EL defect tester) and power (solar photovoltaic module power tester) tests are performed, and the power attenuation results are shown in Table 1.

[0133] Table 1

[0134]

[0135] Note: A negative sign in the power attenuation result indicates attenuation.

[0136] Figure 1 The corrosion EL results of the battery cell after aging at 125℃-95%RH for 96 hours with an encapsulation film W that has poor corrosion resistance are shown. Figure 2 The corrosion EL results of the battery cell after aging at 125°C and 95% RH for 96 hours with a moderately corrosion-resistant encapsulating film M are shown. Figure 3 The corrosion EL results of the battery cell after aging at 125℃-95%RH for 96 hours with encapsulation film B, which has superior corrosion resistance, are shown.

[0137] Figure 4 The corrosion EL results of the battery cell after aging at 125℃-95%RH for 192 hours with an encapsulating film W that has poor corrosion resistance are shown. Figure 5 The corrosion EL results of the battery cell after aging at 125°C and 95% RH for 192 hours with a moderately corrosion-resistant encapsulating film M are shown. Figure 6 The corrosion EL results of the battery cell after aging at 125℃-95%RH for 192 hours with encapsulating film B, which has superior corrosion resistance, are shown.

[0138] As can be seen from Examples 1, 2, and 3, the corrosion resistance of the encapsulating film in Example 1 is less than that in Example 2, which is less than that in Example 3. Figures 1 to 6 The EL diagram and power attenuation results in Table 1 confirm this. Accordingly, the C value in Example 1 is greater than the C value in Example 2, which is greater than the C value in Example 3. As can be seen from Examples 6, 7, and 8, the corrosion resistance of the encapsulating film in Example 6 is less than that in Example 7, which is less than that in Example 8. Accordingly, the C value in Example 6 is greater than that in Example 7, which is greater than that in Example 8. Therefore, the evaluation method of the present invention is reliable and effective.

[0139] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing and evaluating the corrosion resistance of an encapsulant film for a photovoltaic module, characterized by, The method comprises the following steps: A sample preparation stage: the laminated piece with encapsulation adhesive film is aged to peel off the encapsulation adhesive film in the sample after aging as a to-be-tested adhesive film; A test stage: the to-be-tested adhesive film is immersed in a solvent to obtain the acid content in the to-be-tested adhesive film, which is denoted as C; the to-be-tested adhesive film is peeled off from the sample after aging, and the immersion treatment is performed on the to-be-tested adhesive film within 30 minutes; The C is used to represent the corrosion resistance of the encapsulation adhesive film, wherein the larger the C is, the worse the corrosion resistance of the encapsulation adhesive film is; The encapsulation adhesive film is an adhesive film containing ethylene-vinyl acetate copolymer in raw materials; The temperature in the aging process is -40-150 DEG C, and the humidity is 80-100% RH.

2. The method for evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 1, characterized by, The acid content in the to-be-tested adhesive film is obtained by ion chromatography.

3. The method according to claim 2, wherein the method is characterized by, At least part of the leaching solution after the immersion treatment is taken as a sample injection liquid, the sample injection liquid is tested by ion chromatography, and the C value is obtained by calculation through the formula C=a1*V1 / m1; wherein a1 represents the measured value of the acid content in the sample injection liquid, V1 represents the volume of the solvent, and m1 represents the weight of the to-be-tested adhesive film.

4. The method for testing and evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 1, characterized by, The acid content in the to-be-tested adhesive film is obtained by titration.

5. The method for testing and evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 4, characterized by, The titration method comprises: taking at least part of the leaching solution after the leaching treatment as a to-be-tested solution, titrating the to-be-tested solution with an alkali, and calculating the C value through the formula C=M×(V2-V3)×C M ×1000 / m2, wherein M represents the molar mass of the alkali, V2 represents the volume of the solution of the alkali consumed by the to-be-tested solution, V3 represents the volume of the solution of the alkali consumed by a blank comparison sample, C M represents the molar concentration of the solution of the alkali, and m2 represents the weight of the to-be-tested gel film.

6. The method for testing and evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 5, characterized in that, The base is potassium hydroxide, and the solution of the base is an ethanol solution of potassium hydroxide.

7. The method for evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to any one of claims 1 to 6, characterized in that, The encapsulation adhesive film comprises a first adhesive film and a second adhesive film, and the laminated piece is obtained by laminating glass, the first adhesive film, a battery piece, the second adhesive film and a cover plate in sequence; the size of the encapsulation adhesive film is greater than or equal to the size of the glass.

8. The method according to claim 7, wherein the method is characterized by, The lamination treatment temperature is 120-160 DEG C, and the treatment time is 10-30 min.

9. The method for evaluating the corrosion resistance of the encapsulant film for photovoltaic modules according to claim 2, characterized by, When the content of acetic acid in the to-be-tested adhesive film is obtained by ion chromatography, the immersion treatment comprises: placing the to-be-tested adhesive film in a closed container, adding the solvent to the closed container, and pressing the to-be-tested adhesive film below the liquid level of the closed container with a polypropylene filter screen, and then water-bath heating the closed container.

10. The method for evaluating the corrosion resistance of the encapsulant film for photovoltaic modules according to claim 9, characterized by, The solvent is one or more of deionized water, distilled water or ultrapure water.

11. The method for evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 9, characterized by, The temperature of the water-bath heating is 25-99 DEG C, and the time is 0.5-4 h.

12. The method for evaluating the corrosion resistance of the encapsulant film for photovoltaic modules according to claim 9, characterized by, The liquid level of the water-bath heating is not less than 4 / 5 of the liquid level in the closed container.

13. The method for evaluating the corrosion resistance of an encapsulant film for a photovoltaic module according to claim 9, characterized by, The weight ratio of the to-be-tested adhesive film to the solvent in the immersion treatment process is 1: (5-50).

14. The method according to claim 4, wherein the method is characterized by, When the content of acetic acid in the to-be-tested adhesive film is obtained by titration, the immersion treatment comprises: placing the to-be-tested adhesive film in a container, adding the solvent to the container, and then ultrasonic treating the solvent, wherein the solvent is a mixed solvent of one or more of toluene, xylene or tetrahydrofuran and alcohol.

15. The method for testing and evaluating the corrosion resistance of the encapsulating film for photovoltaic modules according to claim 14, characterized in that, The ultrasonic frequency of the ultrasonic treatment is 20-40 kHz, and the ultrasonic time is 5-60 min.

16. The method for evaluating the corrosion resistance of the encapsulant film for photovoltaic modules according to claim 15, characterized by, The ultrasonic frequency is 30-40 kHz, and the ultrasonic time is 15-30 min.

17. The method according to claim 14, wherein the method is characterized by, In the immersion treatment process, the volume of the solvent is 30-120 mL per gram of the to-be-tested adhesive film.

18. The method according to claim 4, wherein the method is characterized by, When the titration method is used to obtain the content of acetic acid in the rubber film to be tested, the leaching treatment comprises: placing the rubber film to be tested in a container, adding the solvent into the container, and then performing ultrasonic treatment on the solvent, wherein the solvent is a mixed solvent of one or more of cyclohexane, carbon tetrachloride, ethylene glycol monobutyl ether, 2,2-dichloropropane, 1,2-dichloropropane, acetone, benzene, methyl ethyl ketone, chloroform, tetrahydronaphthalene or 1,2-dichloroethane and an alcohol.

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