Method for testing thermal diffusion coefficient of polymer film material based on laser flash method

Abstract

The invention belongs to the technical field of material thermal performance testing, and discloses a method for testing a thermal diffusion coefficient of a polymer film material based on a laser flash method. According to the method, a one-step spraying method is adopted, graphite is sprayed in combination with direct-current sputtering, a very thin graphite coating with the nanoscale thickness is directly sprayed on the surface of the polymer film material, nano-graphite particles are high in adhesive force and can be tightly attached to the surface of the polymer film material with the oleophobic surface, and the graphite coating is more uniform; moreover, the graphite layer is easy to oxidize and fall off at high temperature, so that the test signal is influenced, and the nano graphite particles have high-temperature stability, so that the high-temperature test signal can be maintained, and the accuracy of the test result is improved. Meanwhile, the sample treatment method disclosed by the invention is simple and easy to operate, short in sample preparation time, low in cost and high in accuracy, and is particularly suitable for characterizing the thermal diffusion coefficient of a high-molecular polymer film material with relatively poor surface adhesion by using a laser flash method and testing the high-temperature thermal diffusion coefficient of the material.

Description

Technical Field

[0001] This invention belongs to the field of material thermal performance testing technology, specifically relating to a method for testing the thermal diffusivity of polymer film materials based on laser flash method. Background Technology

[0002] Thermal diffusivity is an important parameter for evaluating the thermal properties of materials. Traditional methods for testing thermal diffusivity typically require samples to have a certain thickness and optical opacity. However, due to their light transmission characteristics, transparent or semi-transparent materials are difficult to test directly using laser flash methods. In existing technologies, surface treatment or coating of transparent materials is usually required to enhance their light absorption capacity.

[0003] Traditional graphite sputtering methods suffer from problems such as uneven film layer and poor adhesion for some oleophobic and smooth polymer film materials. Therefore, it is difficult to directly attach a graphite carbon layer to the surface of these materials, which directly affects the accuracy of the test results. In addition, for some thin films, traditional sputtering methods have difficulty controlling the thickness of the coating, resulting in an excessively thick coating layer, which increases experimental error and reduces the reliability of the test results. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for testing the thermal diffusivity of polymer film materials based on laser flash method. This testing method is simple and quick to operate, highly reliable, and can not only effectively save sample preparation time and cost, but also obtain high accuracy of thermal diffusivity test at high temperature.

[0005] The inventive concept of this invention is as follows: This invention primarily targets polymer film material samples with oleophobic surfaces, where the thermal conductivity cannot be directly tested using laser flash spectrometry after processing with traditional solution-based graphite can spraying methods. Furthermore, existing methods that first spray a nano-metal coating followed by graphite can spraying incur additional testing costs. Therefore, this invention employs DC sputtering to directly spray a nanometer-thick graphite coating onto the surface of the sample to be tested. This surface treatment method not only solves the problem of graphite layer adhesion via graphite can spraying due to the oleophobic nature of polymer materials but also significantly reduces the impact of coating thickness on test results. In other words, this surface treatment method, through a one-step graphite spraying process, not only solves the influence of interfacial contact layers caused by multi-layer coatings on the results but also addresses the adhesion problem of traditional solution-based graphite on the sample surface, greatly enhancing surface adhesion while also providing a light-shielding effect. Therefore, compared with traditional sample preparation techniques for testing thermal diffusivity, this invention provides a rapid, simple and effective pretreatment method for polymer film materials with oleophobic surfaces and micron-level thickness. In addition, the graphite layer sputtered by sputtering is thin, uniform and dense, which not only provides light shielding but also adheres tightly to the film surface. The contact surface is more stable during high-temperature testing, less prone to falling off, and the test results are more reliable.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a method for testing the thermal diffusivity of a polymer film material, comprising the following steps: (1) A graphite coating is sprayed onto the surface of the sample to be tested using a DC sputtering method. The sample to be tested is a polymer film material. (2) The sample to be tested after step (1) is tested by laser flash method, and the thermal diffusivity of the sample to be tested is measured.

[0007] Specifically, this invention employs a one-step DC sputtering method to deposit a graphite layer, which enhances the adhesion of graphite to the surface of the oleophobic and smooth polymer film material sample. The coating is denser and thinner, making the graphite layer less prone to falling off during high-temperature testing. This avoids affecting the test results due to uneven or loose coating. Thus, it effectively improves the reliability of the thermal diffusivity test results of film materials using the laser flash method.

[0008] In some embodiments of the present invention, the polymer membrane material is a proton exchange membrane material. For example, perfluorosulfonic acid polymer membrane materials, polyimide (PI) film materials, etc.

[0009] In some embodiments of the present invention, the polymer film material is a transparent or translucent material. The test method of the present invention does not have special requirements regarding the light transmittance of the polymer film material; both transparent and translucent materials are applicable.

[0010] In some embodiments of the present invention, the thickness of the sample to be tested is 20 μm to 1 mm. Preferably, the thickness of the sample to be tested is 40 μm to 0.4 mm.

[0011] In some embodiments of the present invention, in step (1), the current of the spraying is 20-40mA and the spraying time is 30-60s.

[0012] In some embodiments of the present invention, in step (1), the DC sputtering method is performed in a sputtering apparatus, and the target material used in the sputtering apparatus is graphite.

[0013] In some embodiments of the present invention, in step (1), the graphite coating is sprayed onto the upper and lower surfaces of the sample to be tested.

[0014] In some embodiments of the present invention, the thickness of the graphite coating on both the upper and lower surfaces is 20-50 nm, that is, a 20-50 nm graphite coating is sprayed onto both the upper and lower surfaces of the sample to be tested.

[0015] In some embodiments of the present invention, in step (2), the laser flash method is performed in a laser thermal conductivity meter, and the test atmosphere is an inert atmosphere. Preferably, the inert atmosphere is a nitrogen atmosphere.

[0016] In some embodiments of the present invention, in step (2), the temperature range of the test is from room temperature to 600°C. The specific temperature range of the test is determined by the physical properties of the sample to be tested.

[0017] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The present invention adopts a one-step sputtering method, combined with DC sputtering to sputter graphite, to directly spray a very thin graphite coating with a nanometer-level thickness on the surface of the polymer film material. The nano-graphite particles have strong adhesion and can adhere tightly to the surface of the oleophobic polymer film material, making the graphite coating more uniform. Moreover, since the graphite layer is easily oxidized and falls off at high temperatures, thus affecting the test signal, while the nano-graphite particles have high temperature stability, which is beneficial to maintaining the high temperature test signal, thereby improving the accuracy of the test results.

[0018] (2) The sample processing method of the present invention is simple and easy to operate, with short sample preparation time, low cost, and high accuracy. It is especially suitable for testing the thermal diffusivity and high-temperature thermal diffusivity of polymer film materials with a thickness of less than 1 mm and poor surface adhesion by using the laser flash method. It has high practical application value. Attached Figure Description

[0019] Figure 1 Graph of temperature rise signal of thermal diffusivity measured in Example 1; Figure 2 Graph of temperature rise signal of thermal diffusivity measured in Example 2; Figure 3 Graph of temperature rise signal of thermal diffusivity measured in Example 3; Figure 4 Graph of temperature rise signal of thermal diffusivity measured in Example 4; Figure 5 Comparative Example 1: Temperature rise signal of thermal diffusivity measured in Example 1; Figure 6 Comparative Example 2: Temperature rise signal of thermal diffusivity measured; Figure 7 Comparative Example 3: Temperature rise signal of thermal diffusivity measured. Detailed Implementation

[0020] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0021] Example 1 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) A commercial perfluorosulfonic acid polymer membrane material (DuPont, Nafion 117 membrane) was selected as the sample to be tested. The sample thickness was 0.179 mm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) Place the cut sample into the sputtering instrument. The target material is graphite. Set the sputtering current to 30mA and the time to 40s. Use DC sputtering to spray graphite coating on the upper and lower surfaces of the sample. The coating thickness on the upper and lower surfaces is 25nm. (3) Place the sample to be tested, processed in step (2), on the sample holder and into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample three times at 30℃, 60℃, 80℃ and 100℃ respectively. The results are shown in Table 1, and the corresponding test temperature rise signal graph is shown in Table 1. Figure 1 As shown.

[0022] Table 1:

[0023] As shown in Table 1, the standard deviation of the three thermal diffusivity tests was 0, indicating good repeatability. The thermal diffusivity of the perfluorosulfonic acid polymer film is approximately 0.07-0.12 mm² / s, and the results obtained using the method of this invention (0.095-0.099 mm² / s) fall within this range, demonstrating the high reliability of the test results provided by this invention and thus proving the effectiveness of the test method provided by this invention. Furthermore, from... Figure 1 It can be seen that the response signal curve and the fitted curve highly overlap, further verifying the reliability of the test method of the present invention.

[0024] Example 2 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) Commercial PI film material (DuPont, Kapton film) was selected as the sample to be tested. The sample thickness was 0.183 mm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) Place the cut sample into the sputtering instrument. The target material is graphite. Set the sputtering current to 20mA and the time to 50s. Use DC sputtering to spray graphite coating on the upper and lower surfaces of the sample. The coating thickness on the upper and lower surfaces is 20nm. (3) Place the sample to be tested, processed in step (2), on the sample holder and into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample three times at 30℃, 60℃, 80℃ and 100℃ respectively. The results are shown in Table 2, and the corresponding test temperature rise signal graph is shown in Table 2. Figure 2 As shown.

[0025] Table 2:

[0026] As shown in Table 2, the standard deviation of the three thermal diffusivity tests was 0, indicating good repeatability. The thermal diffusivity of the PI film is approximately 0.1-0.2 mm² / s, and the results obtained using the method of this invention (0.167-0.185 mm² / s) fall within this range, demonstrating the high reliability of the test results provided by this invention and thus proving the effectiveness of the test method provided by this invention. Furthermore, from... Figure 2 It can be seen that the response signal curve and the fitted curve highly overlap, further verifying the reliability of the test method of the present invention.

[0027] Example 3 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) Commercial PI film material (DuPont, Kapton film) was selected as the sample to be tested. The sample thickness was 50 μm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) Place the cut sample into the sputtering instrument. The target material is graphite. Set the sputtering current to 40mA and the time to 35s. Use DC sputtering to spray graphite coating on the upper and lower surfaces of the sample. The coating thickness on the upper and lower surfaces is 30nm. (3) Place the sample to be tested, processed in step (2), on the sample holder and put it into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample to be tested three times at 50℃ and 350℃ respectively. The results are shown in Table 3, and the corresponding test temperature rise signal graph is shown in Table 3. Figure 3 As shown.

[0028] Table 3:

[0029] Table 3 shows that, based on the results of the three thermal diffusivity tests, the standard deviation of the three tests was 0, indicating good repeatability. The thermal diffusivity of the PI film is approximately 0.1-0.2 mm² / s, and the results tested using the method of this invention (0.117-0.159 mm² / s) fall within this range, indicating that the test results provided by this invention are highly reliable and have low sensitivity to test temperature. Furthermore, from... Figure 3 It can be seen that the response signal curve and the fitted curve highly overlap, further verifying the reliability of the test method of the present invention.

[0030] Example 4 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) Commercial PDMS film material (Dow Company, DC184 film) was selected as the sample to be tested. The sample thickness was 0.362 mm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) Place the cut sample into the sputtering instrument. The target material is graphite. Set the sputtering current to 30mA and the time to 40s. Use DC sputtering to spray graphite coating on the upper and lower surfaces of the sample. The coating thickness on the upper and lower surfaces is 25nm. (3) Place the sample to be tested, processed in step (2), on the sample holder and put it into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample to be tested three times at 30℃, 60℃, 80℃ and 100℃ respectively. The results are shown in Table 4, and the corresponding test temperature rise signal graph is shown in Table 4. Figure 4 As shown.

[0031] Table 4:

[0032] Table 4 shows that, based on the results of the three thermal diffusivity tests, the standard deviation of the three tests was 0, indicating good repeatability. The thermal diffusivity of the self-made thin film is approximately 0.1-0.15 mm² / s, and the results tested using the method of this invention (0.099-0.111 mm² / s) fall within this range, indicating high reliability of the test results provided by this invention, thus proving the effectiveness of the test method provided by this invention. Meanwhile, from... Figure 4 It can be seen that the response signal curve and the fitted curve highly overlap, further verifying the reliability of the test method of the present invention.

[0033] Comparative Example 1 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) The same commercial perfluorosulfonic acid polymer membrane material as in Example 1 was selected as the sample to be tested. The sample thickness was 0.179 mm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) The cut sample to be tested was sprayed with graphite on the upper and lower surfaces of the sample using the traditional graphite spraying method. After standing and letting the graphite dry naturally, it was found that the graphite could not be completely adhered to the film sample. (3) Place the sample to be tested, processed in step (2), on the sample holder and into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample at 30℃, 60℃, 80℃ and 100℃ respectively. As a result, the instrument reported an error, the test could not be carried out normally, and no normal test results were obtained; and the sample to be tested was transparent, and the corresponding test temperature rise signal graph is as follows. Figure 5 As shown.

[0034] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses the traditional graphite spray can method to spray graphite.

[0035] Comparative Example 2 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) The polymer film prepared by the same preparation method as in Example 4 was selected as the sample to be tested. The sample thickness was 0.362 mm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) The cut sample to be tested was sprayed with graphite on the upper and lower surfaces of the sample using the traditional graphite spraying method. After standing and letting the graphite dry naturally, it was found that the graphite could not be completely adhered to the film sample. (3) Place the sample to be tested, processed in step (2), on the sample holder and into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample at 30℃, 60℃, 80℃ and 100℃ respectively. As a result, the instrument reported an error, the test could not be carried out normally, and no normal test results were obtained; and the sample to be tested was transparent, and the corresponding test temperature rise signal graph is as follows. Figure 6 As shown.

[0036] The difference between Comparative Example 2 and Example 4 is that Comparative Example 2 uses the traditional graphite spray can method to spray graphite.

[0037] Comparative Example 3 A method for testing the thermal diffusivity of a polymer film material includes the following steps: (1) The same commercial PI film material as in Example 3 was selected as the sample to be tested. The sample thickness was 50 μm, and it was cut into pieces with a side length of 8 mm × 8 mm. (2) Place the cut sample into the sputtering instrument. The target material is platinum. Set the sputtering current to 40mA and the time to 25s. Use DC sputtering to spray platinum coating on the upper and lower surfaces of the sample. The thickness of the platinum coating on the upper and lower surfaces is 20nm. (3) The sample to be tested, after being processed in step (2), is coated with graphite on the upper and lower surfaces using the traditional graphite spraying method. The thickness of the graphite coating on the upper and lower surfaces is 20 μm. Let it stand and allow the graphite to dry naturally. (4) Place the sample to be tested, processed in step (3), on the sample holder and into the laser thermal conductivity meter. Turn on the nitrogen protective gas, input the sample thickness and test temperature, and use the laser flash method to test the thermal diffusivity of the sample three times at 50℃ and 350℃ respectively. The results are shown in Table 5, and the corresponding test temperature rise signal graph is shown in Table 5. Figure 7 As shown.

[0038] The difference between Comparative Example 3 and Example 3 is that Comparative Example 3 uses a method of first spraying a platinum metal coating and then spraying graphite using a traditional graphite spray can.

[0039] Table 5:

[0040] from Figure 7 It can be seen that there is a partial deviation between the response signal curve and the fitted curve, indicating that the reliability of the test method in Comparative Example 3 is not as good as that in Example 3.

[0041] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method of testing the thermal diffusivity of a polymeric film material, characterized by, The method comprises the following steps: (1) a graphite coating is sprayed on the surface of a sample to be tested by a direct current sputtering method, wherein the sample to be tested is a polymer film material; (2) the sample to be tested treated in step (1) is tested by a laser flash method, and the thermal diffusivity of the sample to be tested is measured.

2. The method of testing a polymer film material thermal diffusivity coefficient according to claim 1, wherein, The polymer film material is a proton exchange membrane material.

3. The method of testing a polymer film material thermal diffusivity coefficient according to claim 1 or 2, characterized in that, The polymer film material is a transparent material or a semi-transparent material.

4. The method of testing a polymer film material thermal diffusivity coefficient according to claim 1, wherein, The thickness of the sample to be tested is 20-1,000 micrometers.

5. The method of testing a polymer film material thermal diffusivity coefficient according to claim 1, wherein, In step (1), the current for spraying is 20-40 mA, and the spraying time is 30-60 seconds.

6. The method of testing a polymer film material thermal diffusivity coefficient of claim 1, wherein, In step (1), the direct current sputtering method is performed in a spraying instrument, and the target material used in the spraying instrument is graphite.

7. The method of testing a polymer film material thermal diffusivity coefficient according to claim 1, wherein, In step (1), the graphite coating is sprayed on the upper surface and the lower surface of the sample to be tested.

8. The method of testing a polymer film material thermal diffusivity coefficient according to claim 7, wherein, The thickness of the graphite coating on the upper surface and the lower surface is 20-50 nanometers.

9. The method of testing a polymer film material thermal diffusivity coefficient of claim 1, wherein, In step (2), the laser flash method is performed in a laser heat conduction instrument, and the testing atmosphere is an inert atmosphere.

10. The method of testing a polymer film material thermal diffusivity coefficient of claim 1, wherein, In step (2), the testing temperature range is room temperature to 600 DEG C.

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