Quantitative analysis method for components of natural rubber and ethylene propylene diene monomer

Abstract

The invention discloses a quantitative analysis method for components of natural rubber and ethylene propylene diene monomer, which comprises the following steps: pretreating a blend rubber sample, and extracting the blend rubber for three times by using a solvent; preparing a sample from the extracted blend glue sample, detecting by using a Fourier transform infrared spectrometer, and preliminarily calculating the contents of the two components; putting a proper amount of extracted rubber sample into a thermogravimetric analyzer, drawing a thermogravimetric analysis curve, and calculating the content ratio of the natural rubber to the ethylene propylene diene monomer by fitting a weightlessness curve; the method is verified to be effective if an error is within an allowable range compared with an actual value. According to the quantitative analysis method for the components of the natural rubber and the ethylene propylene diene monomer, a comprehensive thermal analyzer is combined with a Fourier infrared analysis method, a method for conveniently, rapidly and accurately detecting the content of the NR and the content of the EPDM in the blended rubber sample is found, and the problem of the ratio of virtual-scale high-price rubber types in the NR / EPDM blended rubber is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of quantitative analysis, and particularly to a method for quantitatively analyzing the components of natural rubber and ethylene propylene diene monomer rubber. Background Art

[0002] Blended rubbers are widely used in various industries and have broad market prospects, but there are still some problems restricting their development. In particular, the compatibility problem between the components of blended rubber composites. Only when the components of the composite are highly compatible can the synergistic effect between the components be fully exerted to prepare high-performance rubber composites.

[0003] Natural rubber (NR) and ethylene propylene diene monomer rubber (EPDM) are very similar in structure. NR is mainly composed of cis-1,4-polyisoprene, and EPDM is formed by the directional polymerization of ethylene molecules and propylene molecules in a certain proportion. Analyzing from the structural formula, NR only has one more carbon-carbon double bond than EPDM, with a highly similar structure and very good compatibility, making it suitable for use in blended rubbers.

[0004] NR and EPDM are complementary in performance and are often used in the form of NR / EPDM blends in rubber products in production. Appropriately blending a certain amount of EPDM in NR can, to a certain extent, improve its heat and oxygen aging resistance; while appropriately blending a certain amount of NR in EPDM mainly aims to improve its production process performance.

[0005] The ratio of the two components of NR and EPDM has a great influence on the properties of the blended rubber, such as Mooney viscosity, vulcanization characteristics, and physical and mechanical properties. The market price of EPDM is relatively high. In order to reduce product costs and seek benefits, a few unqualified manufacturers falsely mark up the dosage of EPDM in the blended rubber products, and the product performance will also decline accordingly.

[0006] NR and EPDM have a high degree of similarity in structure and good compatibility between the two components. It is difficult to identify the proportion of the dosages of the two components from the appearance of the blended rubber product. Even using some conventional detection methods, it is difficult to identify the dosages of each component of NR and EPDM in the blended rubber. Although nuclear magnetic resonance (NMR) technology can theoretically distinguish between the two, due to the complicated sample preparation technology and extremely expensive testing costs, it is not suitable for popularization and application as a conventional detection method.

[0007] At present, there is no universal method for detecting the content of the two components in the NR / EPDM blend rubber at home and abroad, let alone industry standards or national standards. Thermal analysis technology is widely used in the rubber industry. Thermal analysis technology is mostly applied to the study of rubber properties, and there is little research on the quantitative analysis of the content of the two components in blend rubber. There is no report on the quantitative analysis of NR / EPDM blend rubber. Fourier transform infrared spectroscopy is also one of the common analytical and testing methods in the rubber industry, and is often used to analyze and identify the molecular chain structures of different rubbers.

[0008] In the present invention, a comprehensive thermal analyzer is used to study the structure and component ratio of NR and EPDM, combined with Fourier transform infrared analysis method, in order to explore a quantitative analysis method for the two components in NR / EPDM blend rubber. Summary of the Invention

[0009] The purpose of the present invention is to provide a quantitative analysis method for natural rubber and ethylene propylene diene monomer rubber components. By using a comprehensive thermal analyzer combined with Fourier transform infrared analysis method, a method for conveniently, quickly and accurately detecting the respective contents of NR and EPDM in the blend rubber sample is found, effectively solving the problem of falsely high proportion of high-price rubber species in NR / EPDM blend rubber, and eliminating the possible problem of counterfeiting in the market of NR / EPDM blend rubber.

[0010] To achieve the above object, the present invention provides a quantitative analysis method for natural rubber and ethylene propylene diene monomer rubber components, including the following steps: Step 1, pretreat the blend rubber sample, and then select different solvents to extract the blend rubber three times. Each extraction uses a different solvent; Step 2, prepare the sample of the extracted blend rubber, detect it with a Fourier transform infrared spectrometer, compare with the standard spectra of pure natural rubber and pure ethylene propylene diene monomer rubber, analyze the changes in characteristic absorption peaks, and initially calculate the content of the two components based on the changes in peak intensity and peak area in combination with Lambert-Beer's law; Step 3, take an appropriate amount of the extracted rubber sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat it from room temperature to a high temperature, record the weight loss data in different temperature ranges, draw a thermogravimetric analysis curve, and calculate the content ratio of natural rubber and ethylene propylene diene monomer rubber by fitting the weight loss curve; Step 4, compare infrared spectroscopy and thermogravimetric analysis, select standard samples of natural rubber / ethylene propylene diene monomer rubber blend rubber with known different ratios, detect them with the optimized method, compare with the actual values, and verify the effectiveness of the method when the error is within ±3%.

[0011] Preferably, in Step 1, the sample pretreatment includes the following steps: Crush and grind the measured sample through a 100-200 mesh sieve, collect the sieved sample powder, and dry it in a drying oven.

[0012] Preferably, in step one, the solvent for the first extraction is anhydrous ethanol, the solvent for the second extraction is one of N,N-dimethylformamide, ethyl acetate, dimethyl sulfoxide, and acetone, and the solvent for the third extraction is one or more of chloroform, cyclohexane, toluene, and dichloromethane.

[0013] Preferably, when the solvent for the second extraction is N,N-dimethylformamide, ethyl acetate, or dimethyl sulfoxide, the solvent for the third extraction is chloroform, cyclohexane, or toluene; when the solvent for the second extraction is acetone, the solvent for the third extraction is dichloromethane.

[0014] Preferably, the volume ratio of chloroform, cyclohexane, and toluene is (0.5 - 1.2):(1.2 - 2.3):(0.8 - 1.9).

[0015] Preferably, in step one, the mass ratio of the sample to the solvent volume for each extraction is 1:10 - 1:35.

[0016] The advantages and beneficial effects of the quantitative analysis method of the above natural rubber and ethylene propylene diene monomer rubber components in the present invention are as follows: 1. For the structural identification and content analysis of the two components of NR and EPDM in the NR / EPDM blend rubber, by using technical means such as infrared spectroscopy analysis and thermogravimetric analysis, and by analyzing NR and EPDM with different blending ratios, a method for conveniently, quickly, and accurately detecting the respective contents of NR and EPDM in the blend rubber sample is found. It effectively solves the problem of falsely marking the ratio of high-priced rubber species in the NR / EPDM blend rubber and prevents the possible problem of counterfeiting in the market for NR / EPDM blend rubber.

[0017] 2. In the present invention, by pretreating the sample, grinding and sieving the sample into finer powder, increasing the surface area of the particles, making the solvent and the sample fully mixed and contacted, and improving the extraction efficiency.

[0018] 3. In the present invention, by performing three extractions on the sample, removing the impurities in the sample to avoid affecting the infrared spectroscopy analysis and thermogravimetric analysis, and improving the accuracy of the analysis.

[0019] Next, through the drawings and examples, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0020] Figure 1 is the FTIR spectrum of natural rubber; Figure 2 is the FTIR spectrum of ethylene propylene diene monomer rubber sample 6537; Figure 3 is the FTIR spectrum of ethylene propylene diene monomer rubber sample 5890; Figure 4It is the FTIR spectrum of the ethylene-propylene rubber K980 sample; Figure 5 It is the TGA curve of pure natural rubber NB under a nitrogen protection atmosphere; Figure 6 It is the TGA curve of pure ethylene-propylene-diene monomer (EPDM) under a nitrogen protection atmosphere. Specific implementation manners

[0021] The technical solution of the present invention will be further described below through the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0023] Unless otherwise defined, the reagents and equipment used in the present invention are all obtained from regular commercial sources.

[0024] A quantitative analysis method for natural rubber and ethylene-propylene-diene monomer components includes the following steps: Step 1, pretreat the blended rubber sample. Crush and grind the measured sample through a 100-200 mesh sieve, collect the sieved sample powder, and dry it in an oven. Then extract the blended rubber three times with a solvent. The mass ratio of the sample to the solvent volume for each extraction is 1:10 - 1:35. Different solvents are used for each extraction; the solvent for the first extraction is absolute ethanol, the solvent for the second extraction is one of N,N-dimethylformamide, ethyl acetate, dimethyl sulfoxide, and acetone, and the solvent for the third extraction is one or more of chloroform, cyclohexane, toluene, and dichloromethane. When the solvent for the second extraction is N,N-dimethylformamide, ethyl acetate, or dimethyl sulfoxide, the solvent for the third extraction is chloroform, cyclohexane, or toluene; the volume ratio of chloroform, cyclohexane, and toluene is (0.5 - 1.2):(1.2 - 2.3):(0.8 - 1.9). When the solvent for the second extraction is acetone, the solvent for the third extraction is dichloromethane.

[0025] Step 2, prepare a sample of the extracted blended rubber, detect it using a Fourier transform infrared spectrometer, compare it with the standard spectra of pure natural rubber and pure ethylene-propylene-diene monomer, analyze the changes in characteristic absorption peaks, and initially estimate the contents of the two components based on the changes in peak intensity and peak area in combination with the Lambert-Beer law.

[0026] Infrared spectroscopy analysis can reveal the chemical structure characteristics of natural rubber and ethylene-propylene-diene monomer in the blended rubber. Both natural rubber and ethylene-propylene-diene monomer have their own specific functional groups, and these functional groups have characteristic absorption peaks in the infrared spectrum. Natural rubber has a stretching vibration peak of carbon-carbon double bonds (C=C), indicating the presence of an unsaturated double bond structure in the natural rubber molecular chain; ethylene-propylene-diene monomer has -CH2 - The rocking vibration peak reflects the structural characteristics of its molecular chain. By identifying these characteristic absorption peaks, qualitative judgment can be made on the natural rubber and ethylene propylene diene monomer (EPDM) rubber in the blended rubber to determine whether they exist in the sample. At the same time, by using the peak area integration method and comparing the intensities of these characteristic peaks with those of a standard sample with a known ratio, the relative contents of the two rubbers in the blended rubber can be preliminarily estimated.

[0027] If the peak area of the characteristic peak of natural rubber accounts for a relatively large proportion in the spectrum, it indicates that the relative content of natural rubber in the blended rubber is high.

[0028] Step 3: Take an appropriate amount of the extracted rubber sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat it from room temperature to a high temperature, record the weight loss data in different temperature ranges, plot the thermogravimetric analysis curve, and calculate the content ratio of natural rubber and EPDM rubber by fitting the weight loss curve.

[0029] Thermogravimetric analysis (TGA) can provide the thermal stability of natural rubber and EPDM rubber at different temperatures. Since the thermal decomposition temperatures and decomposition rates of natural rubber and EPDM rubber are different, by observing the thermogravimetric (TG) curve and derivative thermogravimetric (DTG) curve, the temperature at which they start to decompose, the decomposition rate, and the weight loss in different temperature ranges can be determined. Natural rubber starts to decompose at a relatively low temperature, while EPDM rubber has better thermal stability and a relatively high decomposition temperature.

[0030] Based on the weight loss in a specific temperature range and combined with a mathematical model, calculate the content ratio of each component of natural rubber and EPDM rubber in the blended rubber. In a certain temperature range, the mass loss is mainly caused by the decomposition of natural rubber. By analyzing the degree of mass loss in this stage, the proportion of natural rubber in the blended rubber can be deduced.

[0031] Step 4: Compare the infrared spectroscopy and thermogravimetric analysis. Select standard samples of blended rubber of natural rubber / EPDM rubber with known different ratios, detect them by the optimized method, and compare with the actual values. If the error is within ±3%, the method is verified to be effective.

[0032] Example 1 A quantitative analysis method for natural rubber and EPDM rubber components includes the following steps: Step 1: Pretreat the NR / EPDM blend sample. Crush and grind the sample to be measured through a 100-mesh sieve, collect the sieved sample powder, and dry it in an oven. Then, select different solvents to extract the NR / EPDM blend three times, with different solvents used each time. The mass ratio of the sample to the solvent volume for each extraction is 1:10. The solvent for the first extraction is absolute ethanol, the solvent for the second extraction is N,N-dimethylformamide, and the solvent for the third extraction is a mixture of chloroform, cyclohexane, and toluene with a volume ratio of 0.5:1.5:1. The NR / EPDM blend is a product with multiple components mixed together. Besides the NR and EPDM rubber species, there are also various additives such as vulcanization additives, protective additives, processing additives, adhesion additives, and additives with special functions. Therefore, before analysis and testing, the NR / EPDM blend needs to be extracted and washed. Through three extractions, impurities such as additives in the blend are removed to avoid affecting infrared spectroscopy and thermogravimetric analysis and improve the accuracy rate.

[0033] Step 2: Prepare the sample of the extracted NR / EPDM blend and detect it using a Fourier transform infrared spectrometer. Compare with the standard spectra of natural rubber and pure ethylene propylene diene monomer rubber, analyze the changes in characteristic absorption peaks, and preliminarily estimate the content of the two components based on the changes in peak intensity and peak area combined with Lambert-Beer's law.

[0034] Step 3: Take an appropriate amount of the extracted rubber sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat it from room temperature to a high temperature, record the weight loss data in different temperature ranges, plot the thermogravimetric analysis curve, and calculate the content ratio of natural rubber and ethylene propylene diene monomer rubber by fitting the weight loss curve.

[0035] Step 4: Compare the infrared spectroscopy and thermogravimetric analysis. Select standard samples of natural rubber / ethylene propylene diene monomer rubber blends with known different ratios, detect them using the optimized method, and compare with the actual values. If the error is within ±3%, the method is verified to be effective.

[0036] It can be seen from Figure 1-4 that the FTIR spectra of the three ethylene propylene diene monomer rubber samples 6537, 5890, and K980 are almost the same, indicating that their structures are similar. There are methyl groups -CH 3 on the side chains of the three rubbers, and characteristic absorption peaks of methyl groups appear in the spectra. For example, 2925 cm -1 is the symmetric stretching vibration peak of methyl -CH 3 , 2850 cm -1 is the asymmetric stretching vibration peak of methyl -CH 3 , 1456 cm -1 is the asymmetric deformation vibration peak of methyl -CH 3 , and 1375 cm -1 is the symmetric deformation vibration peak of methyl -CH 3 .

[0037] In addition to the above infrared absorption peaks, natural rubber also has double bonds in the main chain, and there is an olefinic hydrogen =C-H group on the double bond. Therefore, at 3076 cm -1 appears the stretching vibration peak ν(=C-H) of olefinic hydrogen, and at 1646 cm -1 appears the stretching vibration peak ν(C=C) of the olefinic group C=C. NR is prone to oxidation during storage, and the olefinic group C=C can be oxidized to C=O, and at 1715 cm -1 also appears the stretching vibration peak ν(C=O) of the oxygen-containing group carbonyl C=O. Therefore, natural rubber and EPDM ethylene-propylene rubber can be easily distinguished from the infrared spectrum.

[0038] From Figure 5 it can be seen that the initial thermal degradation temperature of NR is 353.23 °C, the termination thermal degradation temperature is 421.82 °C, and the thermal weight loss rate is 97.26%.

[0039] From Figure 6 it can be seen that the initial thermal degradation temperature of EPDM is 457.14 °C, the termination thermal degradation temperature is 500.89 °C, and the thermal weight loss rate is 99.67%.

[0040] The thermal decomposition curves of NR and pure EPDM are different. Obviously, the thermal stability of EPDM is better than that of NR. Analyzing the reasons, the chemical formula of the repeating unit structure of the main chain of NR is cis-1,4-polyisoprene with good flexibility and low thermal stability. At the same time, the content of cis-1,4-polyisoprene in NR is generally 92-95%, and the rest are some low-molecular-weight substances such as fats, waxes, sterols, and sterol esters, which also further reduce the thermal degradation temperature of NR. Therefore, its thermal degradation temperature range is 353.23-421.82 °C; while EPDM is a synthetic rubber with high purity and saturated carbon bonds on the main chain, so its thermal degradation temperature is higher, at 457.14-500.89 °C.

[0041] Example 2 A quantitative analysis method for the components of natural rubber and ethylene-propylene-diene monomer rubber, comprising the following steps: Step 1, pretreat the blended rubber sample. Crush and grind the measured sample through a 150-mesh sieve, collect the sieved sample powder, and dry it in a drying oven. Then select different solvents to extract the blended rubber three times, and the solvents used for each extraction are different. The mass ratio of the sample to the solvent volume for each extraction is 1:15. The solvent corresponding to the first extraction is anhydrous ethanol, the solvent corresponding to the second extraction is ethyl acetate, and the solvents corresponding to the third extraction are chloroform, cyclohexane, and toluene. The volume ratio of chloroform, cyclohexane, and toluene is 0.8:1.2:1.2.

[0042] Step 2: Prepare a sample using the extracted gum, and detect it using a Fourier transform infrared spectrometer. Compare with the standard spectra of pure natural rubber and pure ethylene propylene diene monomer (EPDM) rubber, analyze the changes in characteristic absorption peaks, and initially estimate the contents of the two components based on the changes in peak intensity and peak area in combination with the Lambert-Beer law.

[0043] Step 3: Take an appropriate amount of the extracted gum sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat from room temperature to a high temperature, record the weight loss data in different temperature ranges, plot the thermogravimetric analysis curve, and calculate the content ratio of natural rubber and EPDM rubber by fitting the weight loss curve.

[0044] Step 4: Compare the infrared spectrum and thermogravimetric analysis. Select standard samples of natural rubber / EPDM rubber blends with known different ratios, detect them using the optimized method, compare with the actual values, and verify the effectiveness of the method if the error is within the allowable range.

[0045] Example 3 A quantitative analysis method for natural rubber and EPDM rubber components includes the following steps: Step 1: Pretreat the blend sample. Crush and grind the measured sample through a 180-mesh sieve, collect the sieved sample powder, and dry it in an oven. Then select different solvents to extract the blend three times, with different solvents used for each extraction. The mass ratio of the sample to the solvent volume for each extraction is 1:20. The solvent for the first extraction is anhydrous ethanol, the solvent for the second extraction is dimethyl sulfoxide, and the solvents for the third extraction are chloroform, cyclohexane, and toluene. The volume ratio of chloroform, cyclohexane, and toluene is 1:1.5:1.9.

[0046] Step 2: Prepare a sample using the extracted gum, and detect it using a Fourier transform infrared spectrometer. Compare with the standard spectra of pure natural rubber and pure EPDM rubber, analyze the changes in characteristic absorption peaks, and initially estimate the contents of the two components based on the changes in peak intensity and peak area in combination with the Lambert-Beer law.

[0047] Step 3: Take an appropriate amount of the extracted gum sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat from room temperature to a high temperature, record the weight loss data in different temperature ranges, plot the thermogravimetric analysis curve, and calculate the content ratio of natural rubber and EPDM rubber by fitting the weight loss curve.

[0048] Step 4: Compare the infrared spectrum and thermogravimetric analysis. Select standard samples of natural rubber / EPDM rubber blends with known different ratios, detect them using the optimized method, compare with the actual values, and verify the effectiveness of the method if the error is within the allowable range.

[0049] Example 4 A quantitative analysis method for natural rubber and EPDM rubber components includes the following steps: Step 1: Pretreat the blended rubber sample. Crush and grind the measured sample through a 200-mesh sieve, collect the sieved sample powder, and dry it in an oven. Then, select different solvents to extract the blended rubber three times, with different solvents used for each extraction. The mass-to-volume ratio of the sample to the solvent for each extraction is 1:30. The solvent for the first extraction is absolute ethanol, the solvent for the second extraction is acetone, and the solvent for the third extraction is dichloromethane.

[0050] Step 2: Prepare the sample of the extracted blended rubber, detect it using a Fourier transform infrared spectrometer, compare it with the standard spectra of natural rubber and pure ethylene propylene diene monomer (EPDM) rubber, analyze the changes in characteristic absorption peaks, and preliminarily calculate the contents of the two components based on the changes in peak intensity and peak area in combination with the Lambert-Beer law.

[0051] Step 3: Take an appropriate amount of the extracted rubber sample and place it in a thermogravimetric analyzer. Under a nitrogen atmosphere, heat it from room temperature to a high temperature, record the weight loss data in different temperature ranges, plot the thermogravimetric analysis curve, and calculate the content ratio of natural rubber and EPDM rubber by fitting the weight loss curve.

[0052] Step 4: Compare the infrared spectroscopy and thermogravimetric analysis. Select standard samples of natural rubber / EPDM rubber blended rubber with known different ratios, detect them using the optimized method, compare with the actual values, and verify the effectiveness of the method if the error is within the allowable range.

[0053] Select an industrial common blended rubber with a known ratio of natural rubber to EPDM rubber of 7:3, analyze the content ratio of natural rubber and EPDM rubber respectively using the analysis methods of Examples 1-4, and compare the results of thermogravimetric analysis and infrared spectroscopy analysis. The specific analysis results are shown in Tables 1-2.

[0054] Table 1 Analysis Results

[0055] Table 2 Optimization Results of Analysis Methods

[0056] Select an industrial common NR / EPDM 80 / 20 blended rubber with a known ratio of natural rubber to EPDM rubber, analyze the content ratio of natural rubber and EPDM rubber respectively using the analysis methods described in Examples 1-4, and compare the results of thermogravimetric analysis and infrared spectroscopy analysis. The specific analysis results are shown in Tables 3-4.

[0057] Table 3 Analysis Results

[0058] Table 4 Optimization Results of Analysis Methods

[0059] Select the commonly used industrial NR / EPDM 20 / 80 blend rubber with a known proportion of natural rubber and ethylene propylene diene monomer rubber, and use the analysis methods described in Examples 1-4 to analyze the content ratio of natural rubber and ethylene propylene diene monomer rubber respectively. Compare the results of thermogravimetric analysis and infrared spectroscopy analysis. The specific analysis results are shown in Tables 5-6.

[0060] Table 5 Analysis Results

[0061] Table 6 Preferred Results of Analysis Methods

[0062] Therefore, the present invention adopts the above quantitative analysis method for the components of natural rubber and ethylene propylene diene monomer rubber. By using a comprehensive thermal analyzer in combination with Fourier transform infrared analysis method, a method for conveniently, quickly and accurately detecting the respective contents of NR and EPDM in the blend rubber sample is found, effectively solving the problem of falsely marking the proportion of high-price rubber species in the NR / EPDM blend rubber and eliminating the problem of possible counterfeiting of NR / EPDM blend rubber in the market.

[0063] Finally, 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 them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A quantitative analysis method for natural rubber and EPDM rubber components, characterized in that: The steps include: Step 1, pre-treating the combined rubber sample, and then extracting the combined rubber three times with a solvent, each extraction corresponding to a different solvent; Step 2: Prepare a sample of the extracted rubber sample, detect it by Fourier transform infrared spectrometer, compare the standard spectra of pure natural rubber and pure EPDM rubber, analyze the changes of characteristic absorption peaks, and preliminarily estimate the contents of the two components based on the changes of peak intensity and peak area combined with Lambert-Beer law; Step 3, taking an appropriate amount of the extracted rubber sample and placing it in a thermogravimetric analyzer, heating it from room temperature to high temperature under a nitrogen atmosphere, recording the weight loss data at different temperature sections, drawing a thermogravimetric analysis curve, and calculating the content ratio of natural rubber and EPDM rubber by fitting the weight loss curve; Step 4: Compare infrared spectrum and thermogravimetric analysis, select standard samples of natural rubber / EPDM rubber with different known ratios, detect them using the optimization method, compare them with the actual values, and verify the effectiveness of the method if the error is within ±3%.

2. The quantitative analysis method of natural rubber and EPDM rubber components according to claim 1, characterized in that: In step 1, sample pretreatment includes the following steps: The sample to be tested was crushed and ground to pass through a 100-200 mesh sieve, and the sieved sample powder was collected and dried in a drying oven.

3. The quantitative analysis method of natural rubber and EPDM rubber components according to claim 1, characterized in that: In step 1, the solvent corresponding to the first extraction is anhydrous ethanol, the solvent corresponding to the second extraction is one of N,N dimethylformamide, ethyl acetate, dimethyl sulfoxide, and acetone, and the solvent corresponding to the third extraction is one or more of chloroform, cyclohexane, toluene, and dichloromethane.

4. The quantitative analysis method of natural rubber and EPDM rubber components according to claim 3, characterized in that: When the corresponding solvent for the second extraction is N,N-dimethylformamide, ethyl acetate, and dimethyl sulfoxide, the corresponding solvent for the third extraction is chloroform, cyclohexane, and toluene; when the corresponding solvent for the second extraction is acetone, the corresponding solvent for the third extraction is dichloromethane.

5. The quantitative analysis method of natural rubber and EPDM rubber components according to claim 3, characterized in that: The volume ratio of chloroform, cyclohexane and toluene is (0.5-1.2):(1.2-2.3):(0.8-1.9).

6. The quantitative analysis method of natural rubber and EPDM rubber components according to claim 1, characterized in that: In step 1, the ratio of the mass of the extracted sample to the volume of the solvent is 1:10-1:35 each time.

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