Method for detecting content of perfluoroether monomer in fluoropolymer

Abstract

The application provides a detection method of perfluoroether monomer content in fluoropolymers. The detection method comprises the following steps: heating and softening the fluoropolymer, and pressing into a sample piece; using an infrared spectrometer to test the infrared spectrum of the sample piece in a transmission mode; and calculating the content of the ether monomer in the fluoropolymer according to a corrected calculation formula. The detection method provided by the application can clearly detect the bending vibration absorption peak of the non-main chain C-F bond directly connected with the O atom in the perfluoroether monomer and the deformation vibration absorption peak of the main chain C-F bond in the fluoropolymer, and combined with the corrected calculation formula, a more accurate detection result of the ether monomer content can be obtained, so that the purpose of accurate quantitative detection is achieved.

Description

Technical Field

[0001] This invention belongs to the field of chemical analysis technology, and specifically relates to a method for detecting the content of perfluoroether monomers in fluoropolymers. Background Technology

[0002] Fluoropolymers such as polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE) are chemically stable and possess excellent properties such as high-temperature resistance, acid and alkali resistance, anti-blocking, and impermeability. They are commonly used to manufacture rods, sheets, and films, and are widely applied in the chemical, semiconductor, and electronics industries. However, fluoropolymers are prone to creep under load and suffer from drawbacks such as easy cold flow and difficulty in molding, which limits their applications. Adding trace amounts of perfluoroether modified monomers (such as perfluoropropyl vinyl ether, PPVE) during the polymerization process of fluoropolymers can significantly improve their creep properties, while also giving them superior impermeability, insulation, and surface smoothness.

[0003] During the polymerization reaction, the amount of perfluoroether modified monomers added (i.e., the actual amount participating in the polymerization reaction) largely determines the processing and application performance of fluoropolymer products. However, the amount of perfluoroether modified monomers added during the polymerization reaction often does not equal the actual reaction amount. Moreover, fluoropolymers are insoluble, making it impossible to detect the content of perfluoroether modified monomers in samples using chromatography or NMR. Existing infrared detection methods also fail to detect the content of perfluoroether modified monomers in fluoropolymers because the absorption wavelengths of CF bond stretching vibrations are very close to those of CO bond stretching vibrations, and the CF bond content in fluoropolymers is much higher than that of CO bonds. The absorption peak of CO ether bonds is often overwhelmed by the absorption peak of CF bonds.

[0004] Therefore, there is a need in this field to study a method that can accurately detect trace amounts of perfluoroether modified monomers in fluoropolymers. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for detecting the content of perfluoroether monomers in fluoropolymers.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for detecting the content of perfluoroether monomers in fluoropolymers, the method comprising the following steps:

[0008] The fluoropolymer is heated and softened, then molded into a sample.

[0009] The infrared spectrum of the sample was measured using an infrared spectrometer in transmission mode.

[0010] The content of perfluoroether monomers in the fluoropolymer is calculated using the following formula:

[0011]

[0012] Wherein, n% is the molar content of perfluoroether monomers in the fluoropolymer, k1 is the absorption peak area of ​​the bending vibration of the non-main chain CF bond directly connected to the O atom in the perfluoroether monomer, k2 is the absorption peak area of ​​the deformation vibration of the main chain CF bond in the fluoropolymer, x is the number of non-main chain CF bonds directly connected to the O atom in the perfluoroether monomer, N is the number of main chain CF bonds in each main structural unit of the fluoropolymer, and δ is the thickness of the sample.

[0013] It should be noted that the molar content of perfluoroether monomers in this invention refers to the molar ratio of the structural units of perfluoroether monomers to all structural units in the fluoropolymer. The main chain CF bond refers to the CF bond formed between a C atom and its directly bonded F atom in the main chain of the fluoropolymer; non-main chain CF bonds refer to CF bonds other than those in the main chain. The main structural unit refers to the structural unit that constitutes the majority of the fluoropolymer. Since perfluoroether monomers are usually used as modifying monomers and are present in very small amounts in fluoropolymers, the main structural unit in this invention refers to structural units other than those of the perfluoroether monomers.

[0014] In conventional infrared detection methods, because the absorption wavelengths of CF bonds and CO bonds are quite close, and because fluoropolymers have a high CF content and strong signal intensity, the CO bond absorption peak is often overwhelmed by the CF bond absorption peak in TR (transmission) mode, and the CO bond absorption peak cannot be detected in ATR (attenuated total reflection) mode. Therefore, quantitative analysis of perfluoroether monomers is not possible. Moreover, the absorption intensity of CO bonds is not entirely linearly related to the content of perfluoroether monomers, so even if the CO bond signal is detected, it is difficult to accurately quantify the content of perfluoroether monomers.

[0015] In this invention, heating and softening the fluoropolymer facilitates its compression molding and improves the transmittance of the sample to infrared light. By preparing the sample using the above method and combining it with infrared spectroscopy in transmission mode, the bending vibration absorption peak of the non-main chain CF bond directly connected to the O atom in perfluoroether monomers and the deformation vibration absorption peak of the main chain CF bond in the fluoropolymer (typically with a wavenumber of 936 cm⁻¹) can be clearly detected. -1 (Approximately), and by using the above calculation formula, a more accurate detection result can be obtained.

[0016] In some embodiments of the present invention, the fluoropolymer is a copolymer of a perfluoroether monomer and a fluoroolefin, preferably a copolymer of a perfluoroether monomer and a fluoroolefin.

[0017] Preferably, the fluoroolefin is tetrafluoroethylene or trifluorochloroethylene.

[0018] In some embodiments of the present invention, the fluoropolymer is polytetrafluoroethylene modified with perfluoroether monomers or polychlorotrifluoroethylene modified with perfluoroether monomers.

[0019] In some embodiments of the present invention, the perfluoroether monomer is perfluoromethyl vinyl ether, perfluoron-propyl vinyl ether, or perfluoromethoxyethoxy vinyl ether.

[0020] In some embodiments of the present invention, the temperature of the heating and softening is ≥T. S -10℃, for a time of 45 minutes or more (e.g., 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 120 minutes, or 150 minutes, etc.);

[0021] Among them, T S This is the softening point of the fluoropolymer.

[0022] In this invention, maintaining the heating temperature and time within the aforementioned range helps ensure that the fluoropolymer is fully softened. If the temperature is too low, the fluoropolymer will not soften sufficiently, making it impossible to hot-press it into a completely transparent sample. If the holding time is too short, some polymer may not soften, resulting in an uneven hot-pressed film.

[0023] In some embodiments of the present invention, the pressure of the plastic compression is 0.2-0.8 MPa; for example, it can be 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa or 0.8 MPa, etc.

[0024] In some embodiments of the present invention, the compression time is 0.5-2 min; for example, it can be 0.5 min, 0.6 min, 0.8 min, 1 min, 1.2 min, 1.5 min, 1.8 min or 2 min, etc.

[0025] In some embodiments of the present invention, the thickness of the sample is 0.4-0.6 mm; for example, it can be 0.4 mm, 0.42 mm, 0.45 mm, 0.48 mm, 0.5 mm, 0.52 mm, 0.55 mm, 0.58 mm or 0.6 mm, etc.

[0026] If the sample thickness is too large, the infrared optical path will change, which can easily lead to poor reproducibility of the integrated data and may also cause absorption peak signal overflow, resulting in a flat-top infrared peak, thus reducing the accuracy of the detection results. If the sample thickness is too small, the absorption peak intensity will be low, the signal-to-noise ratio will be low, which can easily lead to inaccurate integrated data and poor accuracy of the detection results.

[0027] In some embodiments of the present invention, the testing conditions for the infrared spectrum are: a scanning range of 400-4000 cm⁻¹. -1 More than 16 scans, 1cm resolution -1 .

[0028] In some embodiments of the present invention, the detection method includes the following steps:

[0029] Add the fluoropolymer into the mold and keep it at 80-100℃ for at least 45 minutes.

[0030] The fluoropolymer is pressed under a pressure of 0.2-0.8 MPa for 0.5-2 minutes to form a sample with a thickness of 0.4-0.6 mm. After the sample is cooled to room temperature, it is demolded and the thickness is measured.

[0031] The infrared spectrum of the sample was measured using an infrared spectrometer in transmission mode.

[0032] The content of perfluoroether monomers in the fluoropolymer is calculated using the following formula:

[0033]

[0034] Wherein, n% is the molar content of perfluoroether monomers in the fluoropolymer, k1 is the absorption peak area of ​​the bending vibration of the non-main chain CF bond directly connected to the O atom in the perfluoroether monomer, k2 is the absorption peak area of ​​the deformation vibration of the main chain CF bond in the fluoropolymer, x is the number of non-main chain CF bonds directly connected to the O atom in the perfluoroether monomer, N is the number of main chain CF bonds in each main structural unit of the fluoropolymer, and δ is the thickness of the sample.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The detection method provided by this invention can clearly detect the bending vibration absorption peak of the non-main chain CF bond directly connected to the O atom in perfluoroether monomers, and the deformation vibration absorption peak of the main chain CF bond in fluoropolymers. Combined with the corrected calculation formula, a more accurate detection result of the perfluoroether monomer content can be obtained, achieving the purpose of accurate quantitative detection. Attached Figure Description

[0037] Figure 1 The infrared spectrum obtained in Example 1 of the present invention;

[0038] Figure 2 is Figure 1 a partial enlarged view of;

[0039] Figure 3 The infrared spectrum obtained in Example 6 of the present invention;

[0040] Figure 4 The infrared spectrum obtained in Comparative Example 1 of the present invention;

[0041] Figure 5 The infrared spectrum obtained in Comparative Example 2 of the present invention. Detailed implementation manners

[0042] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation manners. Those skilled in the art should understand that the specific implementation manners are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0043] Determination of calculation formula:

[0044] Standard sample experiment: Accurately weigh PPVE-modified polytetrafluoroethylene resin powder standard samples (PPVE contents are 0.53 wt%, 0.64 wt%, 0.78 wt% respectively) with a mass of m = 145.0 mg, put them into a stainless steel columnar mold with a diameter of 12.95 mm, keep them static at 85 °C in an oven for 1 h, take out the mold, immediately use a tablet press for plastic pressing, and demold after the mold naturally cools to room temperature. A sample sheet with a thickness of 0.50 mm is qualified. If the thickness error exceeds ±0.005 mm, reweigh and make the sample sheet. Put the sample sheet into an infrared spectrometer and scan in the TR mode. The scanning range is 400 - 4000 cm -1 , the number of scans is 16 times, and the resolution is 1 cm -1 . Analyze the obtained infrared spectrum, measure the integrated area k1 of the absorption peak at a wavenumber of 996 cm -1 , and the integrated area k2 of the absorption peak at a wavenumber of 936 cm -1 . The test results are shown in Table 1 below.

[0045] Table 1

[0046]

[0047]

[0048] According to the data in Table 1, the relational formula between k1 and n1 is obtained by fitting as k1 = a1 × x × n1 + b1, the correlation coefficient a1 = 4.1, the intercept b1 = 0.2459, R 2=0.9996;

[0049] The relationship between k2 and n1, n2 is k2=a2×(n1N1+n2N2), with a correlation coefficient a2=0.016 and R. 2 =0.9992;

[0050] Where x = 2, N1 = 3, and N2 = 4.

[0051] Since the value of b1 is relatively small, k1 is approximately equal to 4.1x × n1;

[0052] Therefore, n1 = k1 / (4.1x), n2 = k2 / (0.016N2) - (N1 / N2) × n1;

[0053]

[0054] One issue is that the thickness δ of the molded sample cannot be precisely measured to 0.5 mm, resulting in a slight error. This thickness variation will cause changes in the optical path length of the sample in the infrared spectrometer, leading to quantitative errors. Additionally, in the standard sample experiment, the fitting formulas for the integrals k1 and k2 contain intercept values, which, although small, may still introduce slight errors to the test results. All of these errors are corrected using a correction formula: Φ = a3 × (δ / 0.5 cm) × (k1 / x) / (k2 / N²). Fitting multiple sets of experimental data, the correlation coefficient a3 = 0.0012 was calculated, i.e., Φ = 0.0012 × (δ / 0.5 mm) × (k1 / x) / (k2 / N) = 0.0024 × (δ·mm²). -1 )×(N / x)×(k1 / k2).

[0055] Therefore, the molar content of perfluoroether monomers in fluoropolymers is:

[0056]

[0057] Example 1

[0058] This embodiment provides a method for detecting the PPVE content in PPVE-modified polytetrafluoroethylene resin, and the specific steps are as follows:

[0059] (1) Accurately weigh the PPVE-modified polytetrafluoroethylene resin powder standard (PPVE content is 0.53wt%) and record the mass m = 145.3mg;

[0060] (2) Place the accurately weighed PPVE modified polytetrafluoroethylene resin into a stainless steel column mold with a diameter of 12.95 mm, and let it stand at a constant temperature of 85°C in an oven for 1 hour.

[0061] (3) Remove the mold and immediately use a tablet press to press the PPVE modified polytetrafluoroethylene resin, maintaining a pressure of 0.5MPa for 1 minute;

[0062] (4) After the mold has cooled to room temperature, demold it and use a vernier caliper to measure the thickness of the pressed sample δ = 0.52 mm.

[0063] (5) Place the sample in the infrared spectrometer and acquire spectral data in TR mode, scanning range 400-4000 cm⁻¹. -1 16 scans, 1cm resolution -1 The infrared spectrum is obtained, such as Figure 1 As shown; will Figure 1 The dotted line portion is magnified locally, such as... Figure 2 As shown;

[0064] (6) The obtained infrared spectrum was analyzed, and the bending vibration absorption peak of the non-main chain CF bond directly connected to the O atom in PPVE (993 cm⁻¹) was measured. -1 The integral area k1 = 3.501, and the absorption peak of the deformation vibration of the CF bond in the main chain of PPVE modified polytetrafluoroethylene resin (936 cm⁻¹) is also observed. -1 The integral area of ​​) is k2 = 6.331;

[0065] (7) The molar content n% and mass content w of PPVE in PPVE-modified polytetrafluoroethylene resin are quantitatively calculated using the following formulas:

[0066]

[0067] w = (n% × M) PPVE ) / [n%×M PPVE +(1-n%)×M TFE ];

[0068] In this embodiment, x = 2, N1 = 3, N2 = 4, δ = 0.52 mm, M PPVE M is the molar mass of PPVE. TFE denoted as , where is the molar mass of tetrafluoroethylene.

[0069] Example 2

[0070] This embodiment provides a method for detecting the PPVE content in PPVE-modified polytetrafluoroethylene resin. The only difference from Example 1 is that in step (2), the sample is kept at a constant temperature of 90°C for 1.5 hours in an oven, and in step (3), the pressure is maintained at 0.2 MPa for 2 minutes. After cooling, the sample thickness δ = 0.41 mm.

[0071] Example 3

[0072] This embodiment provides a method for detecting the PPVE content in PPVE-modified polytetrafluoroethylene resin. The only difference from Example 1 is that in step (2), the sample is kept at a constant temperature of 100°C for 45 minutes in an oven, and in step (3), the pressure is maintained at 0.8 MPa for 0.5 minutes. After cooling, the sample thickness δ = 0.58 mm.

[0073] The PPVE content detection results of Examples 1-3 above are shown in Table 2 below:

[0074] Table 2

[0075] Test Project Example 1 Example 2 Example 3 n％ 0.304％ 0.301％ 0.292％ w 0.538wt% 0.534wt% 0.523wt% error 1.5％ 0.7％ 1.3％

[0076] As can be seen from the experimental results in Table 2, the PPVE mass content measured in Examples 1-3 is close to the calibrated content of 0.53 wt%, with an error of <5%, indicating that the detection method provided by the present invention has high accuracy.

[0077] Example 4

[0078] A method for detecting the PPVE content in PPVE-modified polytetrafluoroethylene resin is provided, which differs from Example 1 only in that the amount of PPVE-modified polytetrafluoroethylene resin is adjusted so that the thickness of the sample is 1 mm.

[0079] In this embodiment, the mass content of PPVE was measured to be 0.36 wt%, with an error of 32.1%, and the data deviation of multiple consecutive tests was large, exceeding ±0.07 wt%.

[0080] Example 5

[0081] A method for detecting the PPVE content in PPVE-modified polytetrafluoroethylene resin is provided. The only difference from Example 1 is that the amount of PPVE-modified polytetrafluoroethylene resin is adjusted so that the thickness of the sample is 0.2 mm.

[0082] In this embodiment, the measured PPVE content was 0.61 wt%, with an error of 15.1%, and the data deviations in multiple consecutive tests were large, exceeding ±0.15 wt%.

[0083] Compared with Example 1, Example 4 has a larger sample thickness, which changes the optical path and poses a risk of signal overflow, resulting in larger test data errors and poor repeatability; Example 5 has a smaller sample thickness, which results in lower signal, lower signal-to-noise ratio, and increased error.

[0084] Example 6

[0085] This embodiment provides a method for detecting the PPVE content in PPVE-modified polychlorotrifluoroethylene (PCTFE) resin. The specific steps are as follows:

[0086] (1) Accurately weigh the PPVE-modified PCTFE resin powder (the amount of PPVE added during the polymerization reaction is 0.65wt%), and record the mass m = 152.8mg;

[0087] (2) Place the accurately weighed PPVE modified PCTFE resin into a stainless steel column mold with a diameter of 12.95 mm, and let it stand at a constant temperature of 85°C in an oven for 1 hour.

[0088] (3) Remove the mold and immediately use a tablet press to press the PPVE modified PCTFE resin, maintaining a pressure of 0.5MPa for 1 minute;

[0089] (4) After the mold has cooled to room temperature, demold the sample and measure the thickness of the pressed sample with vernier calipers to obtain δ = 0.53 mm;

[0090] (5) Place the sample in the infrared spectrometer and acquire spectral data in TR mode, scanning range 400-4000 cm⁻¹. -1 16 scans, 1cm resolution -1 The infrared spectrum is obtained, such as Figure 3 As shown;

[0091] (6) The obtained infrared spectrum was analyzed, and the bending vibration absorption peak (960 cm⁻¹) of the non-main chain CF bond directly connected to the O atom in PPVE was measured. -1 The integral area k1 = 2.06, and the absorption peak of the deformation vibration of the CF bond in the main chain of PPVE modified PCTFE resin (936 cm⁻¹) is also observed. -1 The integral area of ​​) is k2 = 4.76;

[0092] (7) The molar content n% and mass content w of PPVE in PPVE-modified PCTFE resin are quantitatively calculated using the following formulas:

[0093]

[0094] w = (n% × M) PPVE ) / [n%×M PPVE +(1-n%)×M CTFE ];

[0095] In this embodiment, x = 2, N1 = N2 = 3, δ = 0.53 mm, M PPVE M is the molar mass of PPVE. CTFE This represents the molar mass of trifluorochloroethylene;

[0096] The calculations yielded n% = 0.170% and w = 0.319wt%, indicating that PPVE did not fully participate in the reaction, and its actual aggregated input was less than the added amount.

[0097] Example 7

[0098] This embodiment provides a method for detecting the content of perfluoromethyl vinyl ether (PMVE) in PMVE-modified polytetrafluoroethylene resin. The specific steps are as follows:

[0099] (1) Accurately weigh PMVE-modified polytetrafluoroethylene resin powder (PMVE addition amount during polymerization reaction is 0.5wt%), and record the mass m = 150.3mg;

[0100] (2) Place the accurately weighed PMVE modified polytetrafluoroethylene resin into a stainless steel column mold with a diameter of 12.95 mm, and let it stand at a constant temperature of 85°C for 1 hour in an oven.

[0101] (3) Remove the mold and immediately use a tablet press to press the PMVE modified polytetrafluoroethylene resin, maintaining a pressure of 0.5MPa for 1 minute;

[0102] (4) After the mold has cooled to room temperature, demold it and use a vernier caliper to measure the thickness of the pressed sample δ = 0.48 mm.

[0103] (5) Place the sample in the infrared spectrometer and acquire spectral data in TR mode, scanning range 400-4000 cm⁻¹. -1 16 scans, 1cm resolution -1 The infrared spectrum was obtained;

[0104] (6) The obtained infrared spectrum was analyzed, and the bending vibration absorption peak of the non-main chain CF bond directly connected to the O atom in PMVE (994 cm⁻¹) was measured. -1 The integral area k1 = 1.46, and the absorption peak of the deformation vibration of the CF bond in the main chain of PMVE modified polytetrafluoroethylene resin (936 cm⁻¹) is also observed. -1 The integral area of ​​) is k2 = 6.35;

[0105] (7) The molar content n% and mass content w of PMVE in PMVE-modified polytetrafluoroethylene resin are quantitatively calculated using the following formulas:

[0106]

[0107] w = (n% × M) PMVE ) / [n%×M PMVE +(1-n%)×M TFE ];

[0108] In this embodiment, x = 3, N1 = 3, N2 = 4, δ = 0.48 mm, M PMVE M is the molar mass of PMVE. TFE is the molar mass of tetrafluoroethylene;

[0109] The calculations yielded n% = 0.084% and w = 0.132wt%, indicating that PMVE did not fully participate in the reaction, and its actual aggregation input was less than the amount added.

[0110] Example 8

[0111] Following the method in Example 1, the PPVE content in PPVE-modified polytetrafluoroethylene resins with different PPVE addition amounts was detected to verify the accuracy of the detection method provided by this invention. The detection results for PPVE addition amount and PPVE content are shown in Table 3 below:

[0112] Table 3

[0113]

[0114] As can be seen from the test results in Table 3, when the amount of PPVE added is below 2wt%, the amount of PPVE added increases at a similar rate as the amount of PPVE added increases; when the amount of PPVE added increases to more than 2wt%, the rate of increase of PPVE added slows down due to the limitation of monomer reactivity, which is consistent with the reaction mechanism.

[0115] Example 9

[0116] Following the method of Example 6, the PPVE content in PPVE-modified polychlorotrifluoroethylene resins with different PPVE addition amounts was detected to verify the accuracy of the detection method provided by this invention. The detection results for PPVE addition amount and PPVE content are shown in Table 4 below:

[0117] Table 4

[0118]

[0119]

[0120] As can be seen from the test results in Table 4, when the amount of PPVE added is below 4 wt%, the amount of PPVE accessed calculated by the method provided by this invention increases at a similar rate as the amount of PPVE added increases; when the amount of PPVE added increases to above 4 wt%, the rate of increase in the amount of PPVE access slows down due to the limitation of monomer reactivity, which is consistent with the reaction mechanism.

[0121] Example 10

[0122] Following the method of Example 7, the PMVE content in PMVE-modified polytetrafluoroethylene resins with different PMVE addition amounts was detected to verify the accuracy of the detection method provided by this invention. The detection results for PMVE addition amount and PMVE content are shown in Table 5 below:

[0123] Table 5

[0124]

[0125] As can be seen from the test results in Table 5, when the amount of PMVE added is below 2wt%, the amount of PMVE accessed by the method provided by this invention increases at a similar rate as the amount of PMVE added increases. When the amount of PMVE added increases to more than 2wt%, the rate of increase of PMVE access slows down due to the limitation of monomer reactivity, which is consistent with the reaction mechanism.

[0126] Comparative Example 1

[0127] A method for detecting the PPVE content in polytetrafluoroethylene resin is provided, which differs from Example 1 only in that:

[0128] Polytetrafluoroethylene resin was directly molded at room temperature and kept at 5 MPa pressure for 0.5 min to make a sample.

[0129] The infrared spectrum obtained in Comparative Example 1 is as follows: Figure 4 As shown. From Figure 4 It can be seen that this method cannot collect the target absorption peak and cannot calculate the PPVE content.

[0130] Comparative Example 2

[0131] A method for detecting the PPVE content in polytetrafluoroethylene resin is provided, which differs from Example 1 only in that:

[0132] Polytetrafluoroethylene resin was directly molded at room temperature and kept at 5 MPa pressure for 0.5 min to make a sample; infrared spectra were tested using ATR mode.

[0133] The infrared spectrum obtained in Comparative Example 2 is as follows Figure 5 As shown. From Figure 5 It can be seen that this method cannot collect the target absorption peak and cannot calculate the PPVE content.

[0134] Comparative Example 3

[0135] A method for detecting PPVE content in polytetrafluoroethylene resin is provided, the only difference from Example 1 is that the infrared spectrum is tested using the ATR mode.

[0136] The method in Comparative Example 3 could not collect the target absorption peak, and the PPVE content could not be calculated.

[0137] Comparative Example 4

[0138] A method for detecting the PPVE content in polytetrafluoroethylene resin is provided, the only difference from Example 1 is that the isothermal standing temperature of the polytetrafluoroethylene resin is 60°C.

[0139] The sample prepared by the method in Comparative Example 4 was not transparent, the target absorption peak could not be collected, and the PPVE content could not be calculated.

[0140] Comparative Example 5

[0141] A method for detecting the PPVE content in polytetrafluoroethylene resin is provided, which differs from Example 1 only in that the isothermal standing time of the polytetrafluoroethylene resin is 0.5h.

[0142] The method used in Comparative Example 5 yielded a PPVE content of 0.13 wt%, with an error of 75.5%.

[0143] As can be seen from the detection results of the above embodiments and comparative examples, the method provided by the present invention can accurately detect the content of perfluoroether monomers in fluoropolymers.

[0144] Compared with Example 1, Comparative Examples 1-3, which were performed at room temperature and / or used ATR mode for infrared detection, could not clearly collect the target absorption peak and therefore could not calculate the PPVE content.

[0145] Compared with Example 1, Comparative Example 4 had an excessively low heat preservation temperature, and Comparative Example 5 had an excessively short heat preservation time. Both of these resulted in the sample powder failing to be pressed into a completely transparent film, leaving large irregular opaque areas. Consequently, signals could not be stably acquired in TR mode, or the test error was relatively large.

[0146] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for detecting the PPVE content in PPVE-modified tetrafluoroethylene resin, wherein, PPVE refers to perfluoropropyl vinyl ether, characterized in that the detection method includes the following steps: PPVE-modified tetrafluoroethylene resin is heated and softened, and then molded into a sample while hot. The infrared spectrum of the sample was measured using an infrared spectrometer in transmission mode. The content of PPVE monomer in the PPVE-modified tetrafluoroethylene resin is calculated using the following formula: Wherein, n% is the molar content of PPVE in the PPVE-modified tetrafluoroethylene resin, k1 is the absorption peak area of ​​the bending vibration of the non-main chain CF bond directly connected to the O atom in the PPVE, k2 is the absorption peak area of ​​the deformation vibration of the main chain CF bond in the PPVE-modified tetrafluoroethylene resin, x is the number of non-main chain CF bonds directly connected to the O atom in the PPVE, N1 is the number of main chain CF bonds in each PPVE, N2 is the number of main chain CF bonds in each main structural unit of the PPVE-modified tetrafluoroethylene resin, and δ is the thickness of the sample.

2. The detection method according to claim 1, characterized in that, The temperature of the heating softening is ≥T S -10℃, for more than 45 minutes; Among them, T S The softening point of the PPVE-modified tetrafluoroethylene resin is given.

3. The detection method according to claim 1, characterized in that, The pressure of the plastic compression is 0.2-0.8 MPa.

4. The detection method according to claim 1, characterized in that, The compression time is 0.5-2 minutes.

5. The detection method according to claim 1, characterized in that, The thickness of the sample is 0.4-0.6 mm.

6. The detection method according to any one of claims 1-5, characterized in that, The infrared spectroscopy test conditions are: scanning range 400-4000 cm⁻¹ -1 More than 16 scans, 1cm resolution -1 .

7. The detection method according to any one of claims 1-5, characterized in that, The detection method includes the following steps: PPVE-modified tetrafluoroethylene resin is added to the mold, and the temperature is ≥T. S Incubate at -10℃ for at least 45 minutes. S The softening point of the PPVE-modified tetrafluoroethylene resin; While still hot, the PPVE-modified tetrafluoroethylene resin is pressed under a pressure of 0.2-0.8 MPa for 0.5-2 minutes to form a sample with a thickness of 0.4-0.6 mm. After the sample cools to room temperature, it is demolded and the thickness is measured. The infrared spectrum of the sample was measured using an infrared spectrometer in transmission mode. The PPVE content in the PPVE-modified tetrafluoroethylene resin is calculated using the following formula: Wherein, n% is the molar content of PPVE in the PPVE-modified tetrafluoroethylene resin, k1 is the absorption peak area of ​​the bending vibration of the non-main chain CF bond directly connected to the O atom in the PPVE, k2 is the absorption peak area of ​​the deformation vibration of the main chain CF bond in the PPVE-modified tetrafluoroethylene resin, x is the number of non-main chain CF bonds directly connected to the O atom in the PPVE, N is the number of main chain CF bonds in each main structural unit of the PPVE-modified tetrafluoroethylene resin, and δ is the thickness of the sample.

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