Reflection infrared spectrum quantitative method for trace acetate in polylactic acid fiber

Abstract

The invention discloses a reflection infrared spectrum quantitative method for trace acetate in polylactic acid fiber. The method comprises the following steps: preparing a polylactic acid film standard substance; testing the infrared spectrum of the standard substance by using an attenuated total reflection mode; the method comprises the following steps: selecting an acetate characteristic absorption peak at 1571 cm <-1 > and a polylactic acid characteristic absorption peak at 1753 cm <-1 > from an infrared spectrum of a standard substance, calculating a peak intensity ratio of the two characteristic peaks as infrared characteristic intensity, and deducing a quantitative functional expression; testing the infrared spectrum of the polylactic acid film sample by using an attenuated total reflection mode to obtain infrared characteristic intensity; and substituting the infrared characteristic intensity into a quantitative functional expression, and calculating to obtain the acetate content. According to the reflection infrared spectrum quantitative method, the limitation that the traditional infrared technology is weak in response to trace components and is easily interfered by a matrix is effectively overcome, the detection accuracy and repeatability are remarkably improved, and a reliable analysis means is provided for quality monitoring of a material surface modification process.

Description

A quantitative method for trace acetate in polylactic acid fibers using reflectance infrared spectroscopy Technical Field

[0001] This invention relates to the fields of oily wastewater separation research and trace testing, and in particular to a quantitative method for trace acetate in polylactic acid fibers using reflectance infrared spectroscopy. Background Technology

[0002] Polylactic acid (PLA), a biodegradable polyester derived from renewable resources, shows promising application prospects in the green treatment of oily wastewater when produced through electrospinning and surface modification. Specifically, coating the surface of PLA fibers with a trace amount of 1-ethyl-3-methylimidazolium acetate ionic liquid can effectively improve its surface hydrophilicity, thereby enhancing oil-water separation efficiency. Precise control, uniformity, and stability of this surface coating amount are key factors determining the performance of the separation membrane.

[0003] Currently, the analysis of modified components in polylactic acid (PLA) films largely relies on infrared spectroscopy, but existing research primarily focuses on qualitative characterization. For example, some literature reports have confirmed the successful loading of metal-organic frameworks or antioxidants onto PLA surfaces using infrared spectroscopy, observing a trend of increasing characteristic peak intensity with increasing content. However, these methods can only demonstrate the presence of modified components and their general variation patterns; a systematic and precise quantitative analysis procedure has not yet been established. Especially for trace components with a content below 5%, existing techniques suffer from insufficient sensitivity, susceptibility to matrix interference, and inability to provide accurate concentration data.

[0004] Therefore, the further development of polylactic acid surface modification technology urgently requires an analytical method that can accurately quantify trace coating components to overcome the limitations of existing technologies that can only perform qualitative analysis and cannot accurately quantify, and to meet the stringent quality control requirements in material research and development and actual production processes. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned quantitative methods of reflectance infrared spectroscopy, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a quantitative method for the reflection infrared spectroscopy of trace acetate in polylactic acid fibers. The aim is to establish an infrared spectroscopy detection method that can accurately quantify trace acetate (especially 1-ethyl-3-methylimidazolium acetate ionic liquid) in polylactic acid films.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: the quantitative method of reflectance infrared spectroscopy includes the following steps: preparing a series of polylactic acid film standards with known acetate content.

[0008] The infrared spectrum of the standard was tested using attenuated total reflectance mode.

[0009] After preprocessing the infrared spectrum of the standard, a value located at 1571 cm⁻¹ was selected. -1 The characteristic absorption peak of acetate is located at 1753 cm⁻¹. -1 The characteristic absorption peak of polylactic acid was determined, and the ratio of the peak intensities of the two characteristic peaks was calculated as the infrared characteristic intensity. Based on this intensity and the acetate concentration, a quantitative function was derived.

[0010] The infrared spectra of polylactic acid film samples with unknown acetate content were tested using attenuated total reflectance mode to obtain their infrared characteristic intensities.

[0011] The acetate content of the unknown sample is calculated by substituting its infrared characteristic intensity into the quantitative function.

[0012] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the standard is prepared by impregnation and evaporation method, the acetate content ranges from 0% to 2%, and includes 5 to 6 standards with different contents.

[0013] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the acetate is 1-ethyl-3-methylimidazolium acetate.

[0014] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the standard and the unknown sample are both subjected to tableting under the same mass and pressure conditions before testing.

[0015] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the infrared spectrum is preprocessed, including converting the attenuated total reflectance mode intensity-wavenumber curve into an absorbance-wavenumber curve and performing baseline correction.

[0016] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the baseline correction is selected at 2000 cm⁻¹. -1 The area with no infrared absorption signal nearby is used as a baseline reference.

[0017] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, wherein: the 1571 cm⁻¹ -1 The integral range of the characteristic peak is centered on its peak position and should cover the entire absorption peak region as much as possible; the 1753 cm⁻¹ -1 The integral range of the characteristic peak is centered on its peak position.

[0018] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the quantitative function is a linear function that conforms to the Lambert-Beer law.

[0019] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, the infrared spectra of each of the standards and each of the unknown samples are collected at multiple test points, and the average value of the ratio of the characteristic intensities of each test point is taken as the final infrared characteristic intensity.

[0020] As a preferred embodiment of the quantitative method for reflectance infrared spectroscopy described in this invention, in the tableting process, the sample mass is 0.2 g, the pressure is 20 MPa, and the tableting time is 3 minutes.

[0021] The beneficial effects of this invention: This invention employs attenuated total reflectance (ATR) infrared spectroscopy, combined with the characteristic absorption region of acetate (1571 cm⁻¹). -1 ) and the internal standard peak region of polylactic acid (1753 cm⁻¹) -1 This method precisely selects and processes ratios, and systematically standardizes the entire process of standard preparation, tableting conditions, spectral preprocessing, and quantitative function establishment, achieving rapid, stable, and highly sensitive quantitative analysis of trace acetate in polylactic acid films. This method effectively overcomes the limitations of traditional infrared technology, such as weak response to trace components and susceptibility to matrix interference, significantly improving the accuracy and repeatability of detection, and providing a reliable analytical tool for quality monitoring of material surface modification processes. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 shows a schematic diagram of infrared spectroscopy testing in total reflectance mode according to an embodiment of the present invention; Figure 2 shows the infrared absorption spectrum curves of the 0-2% series of standards according to an embodiment of the present invention; Figure 3 shows the infrared spectra of acetate ionic liquid and pure polylactic acid according to an embodiment of the present invention; Figure 4 shows the 1571 cm⁻¹ infrared spectrum of acetate ionic liquid according to an embodiment of the present invention. -1 Schematic diagram of baseline and integration range selection during characteristic peak integration; Figure 5 shows the polylactic acid 1753 cm⁻¹ in an embodiment of the present invention. -1 A schematic diagram of baseline and integration range selection during characteristic peak integration; Figure 6 shows a schematic diagram of acetate concentration-infrared characteristic intensity curves according to an embodiment of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0025] The terminology used in this invention is that which is currently widely used in the art in consideration of the function of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new technology in the art. Furthermore, specific terms may be chosen by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terms used in this specification should not be construed as simple names, but rather based on their meanings and the overall description of the invention.

[0026] Example 1, referring to Figures 1-6, this example provides an infrared spectral quantitative method for trace amounts of 1-butyl-3-methylimidazolium chloride in polylactic acid fibers, including the following steps: Step 100-Step 500.

[0027] Step 100: Prepare a series of polylactic acid (PLA) film standards with known acetate content. A certain amount of PLA fibers are immersed in methanol, ethanol, or an aqueous solution containing a certain mass of acetate. The immersion container is then placed in a hot ultrasonic cleaner. As the solvent evaporates to dryness, the acetate adheres evenly to the fiber surface. The fibers are then dried in a 105°C oven for 0.5 hours, removed, and cooled in a desiccator to obtain the PLA film standards.

[0028] Step 200: Test the infrared spectrum of the standard sample using ATR mode. Place a certain mass of the standard sample in a mold, press it into a pellet, and dry it. Test in attenuated total reflectance mode, testing at least three test points for each sample in parallel to obtain infrared spectrum curves for multiple test points.

[0029] Step 300: After preprocessing the infrared spectrum of the standard, select the region located at 1571 cm⁻¹. -1 The characteristic absorption peak of acetate is located at 1753 cm⁻¹. -1 The characteristic absorption peak of polylactic acid is obtained, and the ratio of the peak intensities of the two characteristic peaks is calculated as the infrared characteristic intensity. The quantitative function is derived based on the intensity and acetate concentration. The process includes the following steps: (1) Preprocessing of the spectrum curve: ATR mode correction is performed, and the original ATR intensity-wavenumber curve is converted into an absorbance-wavenumber curve and the baseline is automatically corrected.

[0030] (2) Determining the quantitative characteristic absorption peak of acetate ionic liquid: In the infrared spectrum of acetate ionic liquid, 1571 cm⁻¹ -1 The strongest peak is characteristic of acetate (CH3COO-) and does not overlap with the strong infrared peaks characteristic of polylactic acid, so it can be used as a quantitative characteristic absorption peak.

[0031] (3) Determination of the characteristic absorption peak of polylactic acid: 1753 cm⁻¹ -1 The strong peak is a characteristic of the carbonyl group in polylactic acid and does not intersect with the ionic liquid curve, so it is regarded as the characteristic absorption peak of polylactic acid.

[0032] (4) Determination of quantitative parameters: Based on the principle that the fingerprint characteristics of the spectral curve remain unchanged, for the same substance, regardless of the changes in the spectral signal caused by the micromorphology of the test, the ratio of its independent acetate characteristic absorption peak to its independent polylactic acid characteristic absorption peak is positively correlated with the acetate content. At the same time, the average value of data from multiple test points is taken to improve the quantitative accuracy. The ratio of the area of ​​the acetate characteristic peak at 1571 cm⁻¹ to the area of ​​the polylactic acid internal standard peak at 1753 cm⁻¹ is taken as the infrared characteristic intensity, and this ratio is multiplied by 100 and used as the modeling variable.

[0033] (6) Take the average value of the data from each test point of the standard sample, and obtain the quantitative function with Y = infrared intensity and X = concentration. This function should be a linear function.

[0034] Step 400: Use ATR mode to test the infrared spectrum of the polylactic acid film sample with unknown acetate content to obtain its characteristic infrared intensity. The polylactic acid film sample with unknown content is subjected to the same procedure parameters as the standard for tableting, drying, testing, and spectral data analysis to obtain the characteristic infrared intensity value of the sample with unknown content.

[0035] Step 500: Substitute the infrared characteristic intensity of the unknown sample into the quantitative function to calculate its acetate content. Substitute the infrared intensity value of the sample with unknown content as the X value into the mathematical model to obtain the content Y.

[0036] In one specific embodiment, the standard is prepared by impregnation and evaporation method, with an acetate content ranging from 0% to 2%, and includes 5 to 6 standard samples with different contents.

[0037] The standard series is prepared by impregnation and evaporation. Specifically, a certain amount of polylactic acid fiber is immersed in a volatile solvent (such as methanol, ethanol, or water) containing different masses of acetate. Through heating, ultrasonic assistance, and natural or slow evaporation of the solvent, the acetate is uniformly loaded onto the polylactic acid matrix, thereby obtaining a standard series with five or more gradient concentrations covering the expected detection range (e.g., 0% to 2%).

[0038] In one specific embodiment, the acetate is 1-ethyl-3-methylimidazolium acetate.

[0039] In one specific implementation, both the standard and the unknown sample are compressed into tablets under the same mass and pressure conditions before testing.

[0040] Before conducting attenuated total reflectance mode infrared (ATR) testing, both the standard and the unknown samples must undergo a pelletizing process to form flat, dense sheets. This process requires ensuring that all samples use molds of the same specifications and are pressed under a uniform and precisely controllable pressure level to guarantee consistent contact between the sample and the ATR crystal, thereby reducing spectral fluctuations.

[0041] In one specific embodiment, the infrared spectrum is preprocessed, including converting the attenuated total reflection mode intensity-wavenumber curve into an absorbance-wavenumber curve and performing baseline correction.

[0042] Before deriving the quantitative function from the standard sample spectrum, the acquired raw attenuated total reflectance mode spectral data needs to be preprocessed. Preprocessing includes at least: correcting the reflectance intensity-wavenumber curve directly output by the instrument according to the characteristics of the attenuated total reflectance mode, converting it into an absorbance-wavenumber curve suitable for quantitative analysis; and performing baseline correction on the converted spectrum to eliminate baseline drift caused by factors such as light scattering and instrument background.

[0043] In one specific implementation, baseline correction is selected at 2000 cm. -1 The area with no infrared absorption signal nearby is used as a baseline reference.

[0044] In the baseline correction operation, a flat region (e.g., 2000 cm⁻¹) with no characteristic absorption signal in all sample spectra should be selected. -1 Using nearby bands as a baseline reference point, the baseline of the entire spectrum is adjusted to the level of that point through software algorithms or manual operation.

[0045] In one specific embodiment, 1571 cm -1 The integral range of the characteristic peak is centered on its peak position and should cover the entire absorption peak region as much as possible; 1753 cm⁻¹ -1 The integral range of the characteristic peak is centered on its peak position.

[0046] When calculating the intensity of characteristic peaks, it is necessary to clearly define the integration region for each peak. For the acetate characteristic peak (approximately 1570 cm⁻¹), this is crucial. -1 The integration range should be centered at the peak apex, extending to both sides to the position where the absorption signal returns to the baseline, covering as much of the characteristic peak area as possible, while avoiding including adjacent polylactic acid absorption signals. For the polylactic acid internal standard peak (approximately 1750 cm⁻¹), the integration range should be... -1 Its integration range is also defined with its peak as the center.

[0047] In one specific implementation, the quantitative function is a linear function that conforms to the Lambert-Beer law.

[0048] The derived quantitative function is linear, meaning that there is a linear relationship between the infrared characteristic intensity (characteristic peak intensity ratio) of acetate and its concentration, which conforms to the basic principle of Lambert-Beer Law.

[0049] In one specific implementation, infrared spectra are collected at multiple test points for each standard and each unknown sample, and the average value of the characteristic intensity ratio of each test point is used as the final infrared characteristic intensity.

[0050] To improve the precision and representativeness of the method, attenuated total reflectance mode infrared spectroscopy should be performed multiple times (no less than three times) at different locations for each compressed standard or unknown sample. The final infrared characteristic intensity value used for calculation or modeling is the average of the results from all valid test points for the same sample.

[0051] In one specific embodiment, during the tableting process, the sample mass is 0.2 g, the pressure is 20 MPa, and the tableting time is 3 minutes.

[0052] The specific process parameters for tableting are as follows: weigh a predetermined mass of sample powder, place it in a tableting mold of a specific diameter, maintain it under a preset constant pressure for a set time, and then remove it to obtain a test tablet.

[0053] Example 2: Based on Example 1 above, this example provides a more detailed description of the technical solution of this application in conjunction with actual production.

[0054] The present invention provides an analysis of the 1-ethyl-3-methylimidazolium acetate content in polylactic acid nanofibers, comprising the following steps: Step 100: Weigh 10g of polylactic acid fiber matrix and immerse it in 100mL of methanol solution, wherein the methanol solution contains precisely weighed 1-ethyl-3-methylimidazolium acetate with masses of 0g, 0.02g, 0.05g, 0.08g, 0.10g, and 0.20g, respectively. The weighing is performed using an analytical balance with an accuracy of 0.0001g. A watch glass is used to cover the immersion system, ensuring that the liquid level just covers the fiber. Subsequently, the immersion container is placed in an ultrasonic cleaner at 50°C to promote the evaporation of methanol to dryness, thereby ensuring that the 1-ethyl-3-methylimidazolium acetate is evenly distributed inside the fiber. Finally, the loaded fibers were dried in an oven at 105°C for 0.5 hours, then removed and cooled in a desiccator to obtain a series of standard products with mass fractions of 0%, 0.2%, 0.5%, 0.8%, 1.0% and 2.0%.

[0055] Step 200: Accurately weigh 0.2g of sample from each standard and place it in a 10mm diameter tableting mold. Press under 20MPa pressure for 3 minutes to form a test tablet. Prepare two tablets in parallel for each standard. Using an infrared spectrometer equipped with an attenuated total reflectance accessory, collect infrared spectra at three different test points for each tablet in ATR mode to obtain the infrared spectral curves of each standard.

[0056] Step 300: Preprocess the obtained infrared spectrum: First, perform ATR correction to convert the original ATR intensity-wavenumber curve into an absorbance-wavenumber curve, then perform automatic baseline correction; determine the quantitative characteristic peak of acetate, which is 1571 cm⁻¹ in the infrared spectrum of 1-ethyl-3-methylimidazolium acetate. -1 The strongest absorption peak at that point belongs to COO. - The bond vibration characteristics, and the fact that they do not overlap with the bulk infrared absorption of polylactic acid, led to its selection as a quantitative characteristic peak; the characteristic peak of the polylactic acid internal standard was determined to be 1753 cm⁻¹. -1 The strong absorption peak at [value] is due to the characteristic vibration of the carbonyl group in polylactic acid, and it does not overlap with the absorption of ionic liquids; therefore, it is used as the characteristic peak of the internal standard; its baseline correction interval is set at 2700 cm⁻¹. -1 Up to 2000cm -1 The integration range is set to 1783cm. -1 Up to 1723cm -1 ; Determine quantitative parameters based on the principle of invariance of spectral fingerprint characteristics, using 1571 cm⁻¹ as an example. -1 The characteristic peak area of ​​acetate is 1753 cm⁻¹ -1 The ratio of the area of ​​the polylactic acid internal standard peak at point A (A (1571)i / A (1753)i The ratio of infrared characteristic intensity to infrared characteristic intensity was multiplied by 100 and used as a modeling variable. The average value of multiple test points for each standard was taken to obtain the standard test data shown in the table below: Table 1 Standard Test Data Table

[0057] Using infrared characteristic intensity (multiplied by 100) as the independent variable X and acetate content as the dependent variable Y, a linear regression analysis was performed to obtain the following quantitative mathematical function and related parameters: Table 2 Quantitative mathematical function parameters (X: infrared characteristic intensity × 100, Y: content %, m / m)

[0058] Step 400: The polylactic acid film sample with unknown content to be tested is pressed into tablets, dried, and subjected to infrared spectroscopy testing according to the same procedure described in Step 2. The spectral data is then processed according to the method described in Step 3 to obtain its infrared characteristic intensity value. For example, the average infrared characteristic intensity obtained from testing a batch of samples is 0.62 (i.e., Y×100=0.62).

[0059] Step 500: Substitute the infrared characteristic intensity value of the unknown sample (Y×100=0.62) into the quantitative mathematical function established in Step 3 to calculate its mass percentage content:

[0060] The calculation results show that the content of 1-ethyl-3-methylimidazolium acetate in this batch of samples is 0.50% ± 0.03% (m / m).

[0061] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values ​​(e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims. Furthermore, for the purpose of providing a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features not relevant to the currently considered best mode for carrying out the invention, or those features not relevant to implementing the invention) may be omitted.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A quantitative method for trace amounts of acetate in polylactic acid fibers using reflectance infrared spectroscopy, characterized in that, The quantitative method for reflectance infrared spectroscopy includes the following steps: preparing a series of polylactic acid film standards with known acetate content; testing the infrared spectra of the standards using attenuated total reflectance mode; and, after preprocessing the infrared spectra of the standards, selecting a wavelength at 1571 cm⁻¹. -1 The characteristic absorption peak of acetate is located at 1753 cm⁻¹. -1 The characteristic absorption peaks of polylactic acid are identified, and the ratio of the peak intensities of the two characteristic peaks is calculated as the infrared characteristic intensity. Based on this intensity and the acetate concentration, a quantitative function is derived. The infrared spectrum of a polylactic acid film sample with unknown acetate content is tested using the attenuated total reflectance mode to obtain its infrared characteristic intensity. The infrared characteristic intensity of the unknown sample is substituted into the quantitative function to calculate its acetate content.

2. The quantitative method for reflectance infrared spectroscopy according to claim 1, characterized in that, The standard was prepared by impregnation and evaporation method, with an acetate content ranging from 0% to 2%, and included 5 to 6 standard samples with different contents.

3. The quantitative method for reflectance infrared spectroscopy according to claim 2, characterized in that, The acetate is 1-ethyl-3-methylimidazolium acetate.

4. The quantitative method for reflectance infrared spectroscopy according to claim 1, characterized in that, Both the standard and the unknown sample were compressed into tablets under the same mass and pressure conditions before testing.

5. The quantitative method for reflectance infrared spectroscopy according to any one of claims 1, characterized in that, The infrared spectrum is preprocessed, including converting the attenuated total reflection mode intensity-wavenumber curve into an absorbance-wavenumber curve and performing baseline correction.

6. The quantitative method for reflectance infrared spectroscopy according to claim 5, characterized in that, The baseline correction was selected at 2000 cm. -1 The area with no infrared absorption signal nearby is used as a baseline reference.

7. The quantitative method for reflectance infrared spectroscopy according to claim 1, characterized in that, The 1571 cm -1 The integral range of the characteristic peak is centered on its peak position and should cover the entire absorption peak region as much as possible; the 1753 cm⁻¹ -1 The integral range of the characteristic peak is centered on its peak position.

8. The quantitative method for reflectance infrared spectroscopy according to claim 1, characterized in that, The quantitative function is a linear function that conforms to the Lambert-Beer law.

9. The quantitative method for reflectance infrared spectroscopy according to claim 4, characterized in that, Infrared spectra were collected at multiple test points for each of the aforementioned standards and each of the aforementioned unknown samples, and the average value of the characteristic intensity ratios at each test point was taken as the final infrared characteristic intensity.

10. The quantitative method for reflectance infrared spectroscopy according to claim 4, characterized in that, In the tableting process, the sample mass is 0.2 g, the pressure is 20 MPa, and the tableting time is 3 minutes.

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