Method for detecting batch-to-batch stability of a coating of a photovoltaic backsheet

Abstract

This invention relates to the technical field of photovoltaic backsheet coating testing, and discloses a method for testing the batch-to-batch stability of photovoltaic backsheet coatings. The method includes: cutting square samples from photovoltaic backsheets of different batches but with the same formulation; scraping a quantitative coating sample from the square sample, allowing some backsheet substrate to remain in the coating sample; weighing the quantitative coating sample as the test sample for DSC testing; measuring the DSC exothermic curve of the test sample using a DSC instrument in a heating-isothermal-rapid cooling-isothermal-reheating manner; obtaining the first derivative curve of the second heating curve of the test sample based on the second heating curve of the DSC exothermic curve; taking the peak temperature of the first derivative curve as the Tg of the test sample; and obtaining the stability of the coating of different batches of photovoltaic backsheets based on the changes in Tg of each test sample. This testing method is reliable, highly operable, reproducible, accurate, simple to prepare, and fast to test.

Description

Technical Field

[0001] This invention relates to the technical field of photovoltaic backsheet coating testing, and specifically to a method for testing the batch-to-batch stability of photovoltaic backsheet coatings. Background Technology

[0002] Photovoltaic backsheets provide excellent protection and support for solar cell modules (PV modules), and are crucial materials for ensuring the normal operation of PV modules in harsh outdoor environments for extended periods. The coating on the backsheet substrate is also indispensable for protecting the backsheet material. In practical applications, the coatings used for PV backsheets are all thermosetting resin systems. For thermosetting resins, differences in curing temperature and even slight variations in the proportions of components in the coating can lead to significant differences in the performance of the final product. Therefore, testing the stability of the coatings on different batches of PV backsheets is essential.

[0003] In actual production, to verify whether each batch of finished product meets the target requirements for a photovoltaic backsheet coating, a common method is to wipe it with methyl ethyl ketone (MEK). This is also a way to check the degree of coating curing, as the degree of curing is a crucial indicator in thermosetting resin systems, directly affecting the surface properties, mechanical properties, aging resistance, and corrosion resistance of the final cured product. However, due to differences in individual wiping habits and variations in the force applied during wiping, it is not possible to accurately compare the actual condition of coatings from different batches of photovoltaic backsheets, especially for coatings that exhibit excellent resistance to MEK.

[0004] In addition, existing methods for determining the degree of coating curing include using DSC to measure the residual exothermic heat of the sample and using Fourier transform infrared spectroscopy (FTIR) to measure the peak area of ​​unreacted functional groups. However, in actual DSC testing, because the coating on the photovoltaic backsheet is too thin (usually at the micrometer level) and adheres very tightly to the backsheet substrate (this is to provide good protection for the backsheet substrate and prevent the photovoltaic backsheet from delaminating due to long-term outdoor use), the backsheet substrate is easily scraped off during the coating removal process, making it difficult to measure the heat of reaction. While soaking the coating in solvent to soften it before removing it avoids the introduction of the backsheet substrate, the solvent soaking dissolves the uncrosslinked components inside the coating and damages some of the already crosslinked structures. Therefore, the final heat of reaction measurement results in the DSC test will have a large dispersion and cannot reflect the true stability of the coating in each batch of photovoltaic backsheets.

[0005] In infrared spectroscopy, the sample often requires at least one independent, non-reactive functional group peak as a reference absorption peak, and the absorption peak of the reactive functional group in the sample cannot be enclosed within the absorption peaks of other functional groups. This method has significant limitations and is difficult to implement. For photovoltaic backsheet coating samples, the two existing methods for testing the degree of coating curing suffer from problems such as difficult sample preparation, high implementation difficulty, inaccurate results, and poor repeatability. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for testing the batch-to-batch stability of coatings for photovoltaic backsheets.

[0007] Based on this, the present invention discloses a method for detecting the batch-to-batch stability of coatings on photovoltaic backsheets, comprising the following steps:

[0008] S1, cut square samples from corresponding positions of coated photovoltaic backsheets from different batches with the same formula;

[0009] S2, scrape off a fixed amount of coating sample from each of the cut square samples;

[0010] S3, Weigh a fixed amount of each coating sample to be used as the test sample for DSC testing, and then use a DSC instrument to heat and cool each test sample to obtain the DSC exothermic curve of each test sample; wherein, the heating and cooling process is as follows: for each test sample, perform a first heating, a first isothermal, a first cooling, a second isothermal, and a second heating in sequence.

[0011] S4. Based on the second heating curve of the DSC exothermic curve of each test sample, obtain the first derivative curve of the second heating curve of each test sample. Take the peak temperature of the first derivative curve as the glass transition temperature of the corresponding test sample. Then, based on the change of the glass transition temperature of each test sample, obtain the stability of the coating of different batches of photovoltaic backsheets.

[0012] Preferably, in step S1, a square sample is cut from the left, middle, or right side of the photovoltaic backsheet with coating; the length and width of the square sample are both controlled within the range of 3mm-300mm.

[0013] Preferably, in step S2, the weight of the coating sample scraped off each of the square samples is 3-100 mg.

[0014] Preferably, the photovoltaic backsheet includes a backsheet substrate and the coating adhered to the surface of the backsheet substrate;

[0015] In step S2, the scraped-off coating sample may contain a portion of the backing substrate.

[0016] Preferably, in step S3, at least three test samples for DSC testing are prepared for each batch of coating samples, corresponding to three DSC exothermic curves.

[0017] Preferably, in step S3, 2-10 mg of each of the coating samples is weighed into a DSC crucible to prepare a test sample for DSC testing.

[0018] Preferably, in step S3, at the highest temperature of the first heating process of the DSC test, the coating of the sample to be tested does not undergo a second crosslinking reaction.

[0019] More preferably, in step S3, the first heating process of the sample to be tested is: heating at a heating rate of 1-30℃ per minute until the maximum temperature reaches 80-120℃.

[0020] Preferably, in step S3, the first cooling process of the sample to be tested is: cooling down to -10 to -30°C at a cooling rate of 20-40°C per minute;

[0021] The first and second isothermal treatments for the sample to be tested each lasted 1-10 minutes.

[0022] Preferably, in step S3, the second heating process of the sample to be tested is: heating at a heating rate of 5-20℃ per minute until the maximum temperature reaches 80-120℃.

[0023] Preferably, in step S4, the horizontal axis of the first derivative curve of the second heating curve is temperature or time.

[0024] Although the coating thickness of photovoltaic backsheets is very small, typically only on the micrometer scale, it is crucial for protecting the backsheet substrate, such as PET film. Therefore, controlling the performance of this coating is extremely important. Since the coating systems of photovoltaic backsheets are all thermosetting resin systems, the degree of curing and cross-linking is a decisive factor in their performance. Generally, for polymer materials, the glass transition temperature is mainly affected by the structure of the molecular chains and the density of curing and cross-linking. Generally speaking, the greater the rigidity of the molecular chains or the higher the density of curing and cross-linking, the higher the glass transition temperature of the material.

[0025] In this invention, under the same formulation, the molecular chain structure of the cured coating is similar, thus the glass transition temperature of the cured coating is positively correlated with the degree of curing; that is, the higher the curing crosslinking density, the higher the glass transition temperature of the photovoltaic backsheet coating. Therefore, by obtaining the distribution of glass transition temperatures of photovoltaic backsheet coatings from different batches, this invention can effectively detect the curing crosslinking density of photovoltaic backsheet coatings from different batches, and thus detect the stability of the coatings from different batches.

[0026] Furthermore, since the glass transition temperature is a physical property of the material itself, it will not change significantly due to differences in the appearance of the photovoltaic backsheet coating sample or differences in the sample preparation process. Moreover, the inclusion of the backsheet substrate during sample preparation and the complexity of the infrared absorption peak of the backsheet substrate will not affect the glass transition temperature of the photovoltaic backsheet coating. Therefore, compared with existing methods such as wiping with methyl ethyl ketone (MEK), the measurement results of this invention have excellent reproducibility and reliability. In addition, this invention also has the advantages of simple sample preparation, low implementation difficulty, and fast detection speed.

[0027] Meanwhile, since coating materials often have a thermal history during the manufacturing process, to improve the accuracy of test results, a heating and cooling process is required first when using DSC to determine the glass transition temperature to eliminate the influence of the thermal history. Then, a second heating process is used to determine the glass transition temperature of the photovoltaic backsheet coating. By observing the changes in the glass transition temperature determined during the second heating process for each photovoltaic backsheet coating, the stability of the coatings in different batches can be accurately obtained. Furthermore, since the coating system of the photovoltaic backsheet is a thermosetting resin system, the finished coating often contains incompletely cured components. Therefore, in the first heating and cooling process of DSC measurement to eliminate the thermal history, this invention ensures that the highest temperature of the photovoltaic backsheet coating system does not exceed the temperature at which the residual exothermic peak of the resin begins, further improving the accuracy and reliability of the detection method.

[0028] Therefore, the detection method provided by this invention is reliable, highly operable, reproducible, accurate, simple in sample preparation, easy to implement, and fast in detection. It effectively solves the problems of sample preparation difficulties, implementation challenges, poor data reproducibility, low accuracy, and inability to find infrared reference absorption peaks in the process of comparing the stability of photovoltaic backsheet coatings between batches using existing DSC methods for measuring residual exothermics and existing FTIR methods for comparing peak changes. Furthermore, this method has no special requirements on the state of the photovoltaic backsheet coating; it can effectively identify coatings on single-sided, double-sided, or even double-sided photovoltaic backsheets with different colors. This provides a good detection method for ensuring the stability of coatings in different batches of photovoltaic backsheets in actual production.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] This invention can effectively detect the curing crosslinking density of the coating of photovoltaic backsheets from different batches by obtaining the distribution of glass transition temperature of the coating. This allows for a direct display of the stability of the coating of photovoltaic backsheets from different batches. The detection results of this invention are objective, reliable, and have good repeatability. The sampling process is very simple and convenient, with no special requirements for coating thickness, color, etc., and the detection speed is fast.

[0031] Furthermore, in photovoltaic backsheet structures, to provide good protection, the coating is bonded very tightly to the backsheet substrate. Since the coating itself is very thin, it is very easy to remove the backsheet substrate during the coating sample preparation process. However, because the backsheet substrate of photovoltaic backsheets is often a film material such as polyethylene terephthalate (PET), which has a significantly different glass transition temperature from the coating, the detection method of this invention does not affect the accuracy of the test results even if some backsheet substrate is removed during coating sample preparation. This invention's method is highly inclusive and has a wide range of applications. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the cross-sectional structure of a photovoltaic backsheet.

[0033] Figure 2 This is a flowchart illustrating the steps of a method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to the present invention.

[0034] Figure 3 The curve of the transparent coating of the photovoltaic backsheet roll product of batch 1 in Example 1 is obtained by DSC test in test number 1.

[0035] Reference numerals: 1. Backing substrate; 2. Coating. Detailed Implementation

[0036] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The manufacturer of the DSC testing equipment used in Examples 1-3 is TA Instruments, Inc., USA, and the model is DSC 25.

[0037] Example 1

[0038] In this embodiment, the photovoltaic backsheet rolls produced with the same formula but from different production batches and bearing a transparent coating 2 are tested. The backsheet substrate 1 is made of polyethylene terephthalate (PET). The structure of the finished photovoltaic backsheet roll is as follows: Figure 1 As shown, it includes a back plate substrate 1 and a transparent coating 2 coated on the surface of the back plate substrate 1.

[0039] This embodiment describes a method for testing the batch-to-batch stability of a photovoltaic backsheet coating. See [link to relevant documentation]. Figure 2 The testing process includes the following steps:

[0040] S1. Cut a square sample with a side length of 6cm from the right side of all different batches of finished photovoltaic backsheet rolls with transparent coating 2, within a range of 2-8cm from the edge.

[0041] S2, after wiping the knife clean with alcohol, scrape off 20mg of coating sample from each of the cut square samples (unless otherwise specified, the coating samples in the following embodiments all contain a certain amount of backing substrate 1); and after scraping off a batch of square samples, the knife must be wiped clean with alcohol again before scraping off the next batch of square samples.

[0042] S3, Weigh 5mg of coating sample into the DSC crucible to prepare the test sample for DSC testing; three test samples are prepared for each batch of coating samples, and three DSC exothermic curves are obtained accordingly. The heating and cooling process of the DSC test is set as follows: heat from 20℃ to 120℃ at a rate of 10℃ per minute (unless otherwise specified, this process is the first heating process in the following embodiments), hold at the temperature for 3 minutes; then cool down to -20℃ at a rate of 20℃ per minute (unless otherwise specified, this process is the first cooling process in the following embodiments), hold at the temperature for 2 minutes; then heat up to 100℃ at a rate of 10℃ per minute (unless otherwise specified, this process is the second heating process in the following embodiments, and the exothermic curve obtained in this process is called the second heating curve of the DSC exothermic curve).

[0043] S4. The second heating curve of each DSC exothermic curve obtained in step S3 is processed using a DSC testing device (unless otherwise specified, this processing is automatically performed by the DSC testing device in the following embodiments, so it will not be described in detail) to obtain the first derivative curve of the second heating curve. The peak temperature of the first derivative curve is taken as the glass transition temperature (Tg) of the sample to be tested. Then, by observing the change in the glass transition temperature of each sample to be tested, the stability of the transparent coating 2 on different batches of photovoltaic backsheet roll products is obtained.

[0044] In this embodiment, the reason why the highest temperature of the first heating process can be set at 120°C during the DSC test is that the curing temperature in the production workshop of the photovoltaic backsheet roll material is already far higher than 120°C. In step S3, the principle for setting the highest temperature of the first heating process of the DSC test is to ensure that the coating 2 of the sample to be tested will not undergo significant exothermic phenomena (i.e., re-crosslinking reaction of coating 2) at the highest temperature set in the first heating process.

[0045] In this embodiment, during the DSC test, the minimum temperature set during the subsequent cooling process is -20°C. This is mainly to ensure that the glass transition temperature of the coating 2 of the tested sample is covered within the temperature range of the cooling process. Simultaneously, three test samples are prepared for each batch of coating samples, and three DSC exothermic curves are obtained accordingly. This is primarily to ensure the accuracy of the test results.

[0046] The detection results of this embodiment are as follows: Figure 3 As shown in Table 1:

[0047] Table 1. Tg (°C) data of transparent coating for different batches of photovoltaic backsheet roll products.

[0048] Batch 1 20.05 19.89 19.98 19.97 Batch 2 20.12 20.26 19.92 20.10 Batch 3 19.51 19.44 19.54 19.50 Batch 4 20.09 20.13 19.99 20.07 Batch 5 20.29 20.22 20.13 20.21

[0049] As can be seen from Table 1:

[0050] In the transparent coating 2 of each individual batch of photovoltaic backsheet roll finished product, the results of the three Tg measurements were very close, indicating that the test results were very stable.

[0051] In addition, the average Tg values ​​of the five batches show that the Tg values ​​of batches 1, 2, 4 and 5 are relatively close, indicating that the curing degree of the transparent coating 2 of the photovoltaic backsheet roll products of these four batches is also relatively close, which means that the stability of the transparent coating 2 of the photovoltaic backsheet roll products of these four batches is good.

[0052] Compared to other batches, the Tg value of batch 3 was significantly lower, indicating that the curing degree of the transparent coating 2 of the photovoltaic backsheet roll material in batch 3 was insufficient. Insufficient curing degree can lead to differences in other properties of the transparent coating 2 of the photovoltaic backsheet roll material in batch 3, such as surface properties, mechanical properties, aging resistance, and corrosion resistance. Therefore, the quality of the transparent coating 2 of the photovoltaic backsheet roll material in batch 3 is likely to be insufficient, and special attention should be paid to whether it meets the standard requirements of photovoltaic modules.

[0053] Example 2

[0054] In this embodiment, the photovoltaic backsheet rolls produced with the same formula but from different production batches and bearing a white coating 2 are tested. The backsheet substrate 1 is made of polyethylene terephthalate (PET). The structure of the finished photovoltaic backsheet roll is as follows: Figure 1 As shown, it includes a back panel substrate 1 and a white coating 2 applied to the surface of the back panel substrate 1.

[0055] This embodiment describes a method for testing the batch-to-batch stability of a photovoltaic backsheet coating. See [link to relevant documentation]. Figure 2 The testing process includes the following steps:

[0056] S1. Cut square samples with a side length of 8cm from the right side of all different batches of finished photovoltaic backsheet rolls with white coating 2, within a range of 0-8cm from the edge.

[0057] S2. After wiping the blade clean with alcohol, scrape off 30mg of coating sample from each of the cut square samples. After scraping off one batch of square samples, the blade must be wiped clean with alcohol again before starting the next batch of square samples.

[0058] S3, weigh 5 mg of coating sample into the DSC crucible to prepare the test sample for DSC testing; three test samples are prepared for each batch of coating samples, and three DSC exothermic curves are obtained accordingly. The heating and cooling process of the DSC test is set as follows: heat from 20℃ to 110℃ at a rate of 10℃ per minute, hold at the temperature for 3 minutes; then cool down to -10℃ at a rate of 20℃ per minute, hold at the temperature for 2 minutes; then heat up to 110℃ at a rate of 10℃ per minute.

[0059] S4. The second heating curve of each DSC exothermic curve obtained in step S3 is processed using DSC testing equipment to obtain the first derivative curve of the second heating curve. The peak temperature of the first derivative curve is taken as the glass transition temperature of the sample to be tested. Then, by observing the change in the glass transition temperature of each sample to be tested, the stability of the white coating 2 on different batches of photovoltaic backsheet roll products is obtained.

[0060] In this embodiment, the highest temperature of the first heating process was set at 110°C during the DSC test because the curing temperature in the production workshop of the photovoltaic backsheet roll material was already lower than that of Example 1. Therefore, a relatively lower temperature was set to ensure that the coating 2 of the test sample in this embodiment would not undergo a re-crosslinking reaction. Similarly, three test samples were prepared for each batch of coating samples, and three DSC exothermic curves were obtained accordingly. This was mainly to ensure the accuracy of the test results.

[0061] The detection results of this embodiment are shown in Table 2 below:

[0062] Table 2: Tg (°C) data of white coating of different batches of photovoltaic backsheet roll products

[0063] Batch 1 41.10 41.34 41.30 41.25 Batch 2 41.50 41.28 41.41 41.40 Batch 3 41.31 41.25 41.36 41.31 Batch 4 41.45 41.20 41.19 41.28 Batch 5 42.05 41.97 41.85 41.96

[0064] As can be seen from Table 2:

[0065] Except for batch 5, which had a higher average Tg, the average Tg values ​​of the other four batches were basically similar. This indicates that the white coating 2 of the photovoltaic backsheet roll material in batch 5 had a higher degree of curing, while the white coating 2 in the other four batches had a relatively lower degree of curing. Theoretically, the white coating 2 with a higher degree of curing has better performance; however, in practical applications, further testing should be conducted on other properties of the white coating 2 of the photovoltaic backsheet roll material in batch 5 (such as surface properties, mechanical properties, aging resistance, and corrosion resistance) to ensure that it truly meets the standard requirements for photovoltaic modules.

[0066] Example 3

[0067] The photovoltaic backsheet roll material with white coating 2 from batch 1 of Example 2 was tested in this embodiment (its structure is shown in [reference]). Figure 1 ).

[0068] This embodiment describes a method for testing the batch-to-batch stability of a photovoltaic backsheet coating. See [link to relevant documentation]. Figure 2 The testing process includes the following steps:

[0069] S1, a square sample with a side length of 15cm is cut from the right side of the finished photovoltaic backsheet roll material of batch 1 in Example 2, within a range of 0-15cm from the edge.

[0070] S2. After wiping the knife clean with alcohol, scrape off 100mg of coating sample from the cut square sample.

[0071] S3, Weigh 3 mg of the coating sample from step S2 into the DSC crucible to prepare sample 1 for DSC testing. Perform DSC testing on sample 1 to obtain its DSC exothermic curve. The heating and cooling process for the DSC test is as follows: heat from 20°C to 100°C at a rate of 10°C per minute and hold for 3 minutes; then cool to -10°C at a rate of 20°C per minute and hold for 2 minutes; then heat to 100°C at a rate of 10°C per minute.

[0072] S4. The second heating curve of the DSC exothermic curve of sample 1 is processed by the DSC test equipment to obtain the first derivative curve of the second heating curve. The peak temperature of the first derivative curve is taken as the glass transition temperature of sample 1.

[0073] S5, weigh 5 mg of the coating sample from step S2 into the DSC crucible to prepare sample 2 for DSC testing, and then refer to steps S3-S4 of this embodiment to obtain the glass transition temperature of sample 2.

[0074] S6, weigh 5 mg of the coating sample from step S2 into the DSC crucible to prepare sample 3 for DSC testing. Then, refer to steps S3-S4 of this embodiment (wherein, compared with sample 1 in step S3, the heating and cooling process for DSC testing of sample 3 is set as follows: heating from 20°C to 90°C at a rate of 10°C per minute, holding at that temperature for 3 minutes; then cooling to -10°C at a rate of 20°C per minute, holding at that temperature for 2 minutes; then heating back to 90°C at a rate of 10°C per minute) to obtain the glass transition temperature of sample 3.

[0075] S7, weigh 5 mg of the coating sample from step S2 into the DSC crucible to prepare sample 4 for DSC testing. Then, refer to steps S3-S4 of this embodiment (wherein, compared with sample 1 in step S3, the heating and cooling process for DSC testing of sample 4 is set as follows: heating from 20°C to 110°C at a rate of 10°C per minute, holding at that temperature for 3 minutes; then cooling to -10°C at a rate of 30°C per minute, holding at that temperature for 2 minutes; then heating back to 110°C at a rate of 10°C per minute) to obtain the glass transition temperature of sample 3.

[0076] The test results of samples 1-4 in this embodiment are shown in Table 3:

[0077] Table 3: Tg (°C) data of photovoltaic backsheet roll products of batch 1 in Example 2 under different test parameters

[0078] Batch 1 of Example 2 41.22 41.31 41.39 41.33

[0079] As can be seen from Table 3:

[0080] While keeping the heating rate constant during the second heating process of the DSC test, the weight of the samples was appropriately changed (see Sample 1 and Sample 2), the maximum temperature reached during the heating process was appropriately reduced (see Sample 2 and Sample 3), and the cooling rate during the cooling process was appropriately adjusted (see Sample 2 and Sample 4). These changes did not significantly affect the test results of the actual glass transition temperature of each sample, and therefore had little impact on the comparison of the curing degree and stability of coating 2 of each batch of photovoltaic backsheet roll products. This also shows that this method has good inclusiveness and strong operability.

[0081] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0082] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for testing the batch-to-batch stability of a photovoltaic backsheet coating, characterized in that, Includes the following steps: S1, square samples are cut from corresponding positions of photovoltaic backsheets with coatings from different batches and with the same formula; the photovoltaic backsheet includes a backsheet substrate and the coating bonded to the surface of the backsheet substrate. S2, scrape off a fixed amount of coating sample from each of the cut square samples; in step S2, the scraped coating sample may contain a portion of the backing substrate; S3, Weigh a fixed amount of each coating sample to be used as the test sample for DSC testing, and then use a DSC instrument to heat and cool each test sample to obtain the DSC exothermic curve of each test sample; wherein, the heating and cooling process is as follows: for each test sample, perform a first heating, a first isothermal, a first cooling, a second isothermal, and a second heating in sequence. S4. Based on the second heating curve of the DSC exothermic curve of each test sample, obtain the first derivative curve of the second heating curve of each test sample. Take the peak temperature of the first derivative curve as the glass transition temperature of the corresponding test sample. Then, based on the change of the glass transition temperature of each test sample, obtain the stability of the coating of different batches of photovoltaic backsheets.

2. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S1, a square sample is cut from the left, middle or right side of the photovoltaic backsheet with coating; the length and width of the square sample are controlled within the range of 3mm-300mm.

3. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S2, the weight of the coating sample scraped off each of the square samples is 3-100 mg.

4. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S3, at least three test samples for DSC testing are prepared for each batch of coating samples, corresponding to three DSC exothermic curves.

5. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S3, 2-10 mg of each of the coating samples is weighed into the DSC crucible to prepare the test sample for DSC testing.

6. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S3, at the highest temperature of the first heating process of the DSC test, the coating of the sample to be tested does not undergo a second crosslinking reaction.

7. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 6, characterized in that, In step S3, the first heating process of the sample to be tested is as follows: the temperature is raised to the maximum temperature of 80-120℃ at a heating rate of 1-30℃ per minute.

8. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S3, the first cooling process of the sample to be tested is as follows: cooling down to -10 to -30°C at a cooling rate of 20-40°C per minute. The first and second isothermal treatments for the sample to be tested each lasted 1-10 minutes.

9. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S3, the second heating process of the sample to be tested is as follows: the temperature is raised to the maximum temperature of 80-120℃ at a heating rate of 5-20℃ per minute.

10. The method for detecting batch-to-batch stability of a photovoltaic backsheet coating according to claim 1, characterized in that, In step S4, the horizontal axis of the first derivative curve of the second heating curve is temperature or time.

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