A detection method for identifying ethylene propylene diene monomer rubber products

Abstract

The present invention discloses a detection method for identifying ethylene propylene diene monomer (EPDM) rubber products, comprising the following steps: 1) extracting a test sample m with first and second organic solvents, filtering out the insoluble matter and drying it to a constant weight to obtain a rubber compound m1; 2) removing the inorganic substances in the rubber compound m1 to obtain an insoluble matter m2; 3) heating the insoluble matter m2 to 330-350 °C and then keeping it at a constant weight to obtain an undecomposed substance m3: taking the undecomposed substance m3 for ATR testing, reading the characteristic peaks of the structural characteristic functional groups, and determining the type of the rubber resin main body; 5) quantitative analysis; 6) performing LF-NMR testing on the undecomposed substance m3 to identify the crosslinked structure after vulcanization, and comprehensively determining the material type of the test. The present invention can not only qualitatively and quantitatively identify the main resin in the EPDM raw rubber, but also qualitatively and quantitatively identify whether the test sample is a qualified vulcanized rubber at the same time, and can directly exclude whether other rubbers containing unsaturated bonds are doped in the product, which is accurate and efficient.

Description

Technical Field

[0001] The invention relates to a detection method for identifying vulcanized ethylene-propylene rubber products, belonging to the technical field of detection of vulcanized ethylene-propylene rubber products. Background Art

[0002] According to the different types of copolymers, EPDM rubber is mainly divided into EPDM and EPDM. EPDM is made by the polymerization of ethylene and propylene, and the whole molecule does not contain unsaturated bonds or polar substituents; EPDM is based on EPDM, through the copolymerization of a small amount of non-conjugated dienes (usually about 1%-2% by mass), ethylene, and propylene. There are very few unsaturated groups in the molecule, but they are all on the side chain. Therefore, the properties of EPDM and EPDM are basically similar, and they are collectively referred to as EPDM. The molecular structure of EPDM is saturated and the molecular chain is soft. After vulcanization, it has high tensile elongation, tear strength, excellent aging resistance and waterproof properties. When EPDM raw rubber is mixed with additives and vulcanized to make rubber products, it has good elasticity, aging resistance and organic solvent resistance. It is currently widely used in primary and secondary school plastic tracks, track and field venues and other fields, and the price is relatively expensive.

[0003] Natural rubber (NR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), and polybutadiene rubber (BR) cannot achieve the same performance as EPDM in important properties such as elasticity and aging resistance, but they are cheap and similar in appearance to EPDM, and are often used to impersonate EPDM rubber products.

[0004] Due to the formation of a complex and stable cross-linked structure during the vulcanization of ethylene-propylene rubber raw rubber, it can only swell in solvents and cannot be dissolved in organic solvents. However, the ethylene-propylene rubber raw rubber has not undergone a cross-linking reaction, and its organic components are soluble in organic solvents. Therefore, in the prior art, there is no relevant report on directly identifying the type of the rubber matrix resin and determining whether vulcanization has reached the cross-linked structure by vulcanizing ethylene-propylene rubber. It is only possible to analyze the vulcanized rubber by testing the ethylene-propylene rubber raw rubber before vulcanization. And it can only analyze the main resin components in the ethylene-propylene rubber raw rubber, and it is impossible to directly exclude whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are doped in the product. For example, the prior art method for analyzing ethylene-propylene rubber is as follows: first, perform pretreatment on the ethylene-propylene rubber raw rubber, and then use infrared spectroscopy to identify the rubber matrix resin, or use the peak attribution and peak area in the solid nuclear magnetic resonance spectrum to calculate the mass percentage of the three monomers in ethylene-propylene rubber (Hao Fengling et al.). However, due to the lack of standard products for ethylene-propylene rubber, it is impossible to directly identify the nature by comparing with standard products. And the prior art method for pretreating ethylene-propylene rubber raw rubber is as follows: first, dissolve all the organic components in the ethylene-propylene rubber raw rubber, including the rubber matrix, paraffin oil (organic solvent), organic additives, etc., using n-heptane, etc., and then further separate the organic components according to the differences in solubility, boiling point, etc. of the dissolved organic substances. Finally, characterize the rubber matrix by means of infrared and other means, that is, first dissolve all the organic substances and then separate them one by one. For rubber products with unknown synthetic raw materials, it is impossible to judge which organic substances are carried out during dissolution. Therefore, there are problems such as great difficulty in further separating organic components, high cost, and low efficiency.

[0005] Therefore, there is an urgent need to develop a convenient, accurate, and efficient detection method for quickly identifying whether it is a vulcanized ethylene-propylene rubber product to ensure the quality of plastic runways, etc. and protect the health and safety of users. Summary of the Invention

[0006] The present invention provides a detection method for identifying vulcanized ethylene-propylene rubber products, which can effectively identify vulcanized ethylene-propylene rubber products. It can not only identify the main resin in the ethylene-propylene rubber raw rubber, but also simultaneously identify whether the sample is a qualified vulcanized rubber, and can directly exclude whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are doped in the product.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A detection method for identifying vulcanized ethylene-propylene rubber products includes the following steps:

[0009] 1) Extraction of organic additives: The test sample m is extracted with the first organic solvent for 5 - 8 hours to remove the surface solvent, and then extracted with the second organic solvent for 6 - 8 hours. The material insoluble in the organic solvent is filtered out and dried to a constant weight to obtain the rubber compound m1, thus removing the organic additives in the test sample;

[0010] 2) Decomposition of inorganic substances: Dilute hydrochloric acid is added dropwise to the rubber compound m1 until it is submerged and the pH value of the solution is adjusted to 3. After standing for 25 - 30 min when no bubbles are observed by the naked eye, it is filtered and dried to a constant weight to obtain the insoluble substance m2, separating the inorganic salts in the sample that react with hydrochloric acid;

[0011] 3) Decomposition of some inorganic substances and low - chain alkanes: The insoluble substance m2 is heated to 330 - 350 °C and then kept at this temperature (330 - 350 °C) until a constant weight is reached to remove the alkane oils with small molecular chains, obtaining the undecomposed substance m3, which is the main body of the rubber resin;

[0012] 4) Identification of the main resin by reflection method: The undecomposed substance m3 is subjected to ATR test, and the characteristic peaks reflecting the structural characteristic functional groups are read to determine the type of the main body of the rubber resin;

[0013] 5) Quantitative analysis: The mass of the undecomposed substance m3 is the mass of the main body of the rubber resin. The mass content a of the main body of the rubber resin in the test sample = m 3 / m X × 100%;

[0014] Or, the undecomposed substance m3 is placed at the bottom of a glass test tube and heated to 450 °C ± 20 °C with an electric furnace until the sample is pyrolyzed to a constant weight to obtain the pyrolysis product m4. The pyrolysis product m4 is subjected to 1 1H - NMR test for quantitative analysis;

[0015] 6) LF - NMR test is carried out on the undecomposed substance m3 to identify the cross - linking degree after vulcanization, and the material type of the test is comprehensively determined.

[0016] All extractions in this application are carried out at the reflux temperature.

[0017] In step 5) of this application, quantitative analysis can be achieved by subjecting the pyrolysis product m4 to 1 1H - NMR test. The intensity of the nuclear magnetic resonance signal is proportional to the number of hydrogen atoms generating the signal. By measuring the peak area or peak height of a specific hydrogen atom signal and comparing it with the signal of a standard substance with a known concentration, the content of the corresponding compound in the sample can be calculated.

[0018] Quantitative analysis can also refer to the following literature: [1] Wang Xiuping, Wang Bo, Zhang Xinrong. Quantitative Analysis of Ethylene Propylene Diene Monomer Rubber by 1H-NMR [J]. Chemical Engineering & Technology, 2013, 21(06): 45-47+51. DOI: 10.16664 / j.cnki.issn1008-0511.2013.06.013; [2] Hao Fengling, Tian Chunguang, Yin Xiangyu. Determination of Ethylene and Propylene Composition in Ethylene Propylene Rubber by Infrared Spectroscopy [J]. Elastomer, 2000, (04): 17-20. DOI: 10.16665 / j.cnki.issn1005-3174.2000.04.006.

[0019] The idea of this application is completely different from, or even opposite to, the existing raw rubber testing methods. The existing raw rubber testing methods require dissolving the rubber main body first, while this application requires retaining the rubber main body. That is to say, instead of dissolving the rubber main body, this application removes the organic solvents, organic additives, and inorganic additives in the vulcanized rubber by dissolution, leaving the rubber main body, thus omitting the steps of separating different organic substances in the main rubber according to different solubilities, boiling points, etc., simplifying the operation, improving the accuracy, and enhancing the efficiency.

[0020] To further improve the detection accuracy, in step 1), the first organic solvent is at least one of isopropanol or methanol, and more preferably a mixed solvent of isopropanol and methanol (volume ratio: 1:3). The second organic solvent is at least one of acetone, dichloromethane, or chloroform, and more preferably a mixed solvent of acetone and dichloromethane (volume ratio: 1:1), or a mixed solvent of acetone and chloroform (volume ratio: 1:2).

[0021] In the above step 2), the mass concentration of the dilute hydrochloric acid is 1-3 mol / L;

[0022] To further improve the detection accuracy, in the above step 4), the conditions for ATR testing are: diamond crystal, resolution of 4 cm -1 , 16 scanning times, and the scanning range is 500-4000 cm -1 .

[0023] To further improve the detection accuracy, in the above step 5), 1 the conditions for 1H-NMR testing are: 1 1H-NMR working frequency: 400 MHz, pulse sequence: zg30, solvent: deuterated chloroform (CDCl3), isotope purity 99.8%, internal standard: tetramethylsilane (TMS), volume fraction 0.03%; experimental temperature: 298 K.

[0024] To further improve the detection accuracy, in step 6) above, the conditions for LF-NMR testing are as follows: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C. Cut the sample to be tested into a rectangular strip of about 10 mm × 6 mm × 1 mm and place it at the bottom of a test tube with an outer diameter of 10 mm. Keep the sample in an oven at 50 °C for 10 min to make the temperature of each area of the sample the same, then move it to the heating area of the NMR instrument, set the temperature to 50 °C, keep it at a constant temperature and stable for 5 min, and scan the sample. The sample uses the CPMG pulse sequence, test temperature: 90 °C; SF (MHz): 22, 01 (Hz): 101597.5, P1 (μs): 3.12, P2 (μs): 5.68, TW (ms): 1500, TE (ms): 0.1417, NECH: 46, SW (KHz): 200, RFD (ms): 0.02, NS: 8, RG1 (dB): 10, DRG1 (dB): 3, PRG: 3.

[0025] SF (MHz): represents the sweep frequency, with the unit of megahertz (MHz). 01 (Hz): represents the starting frequency, with the unit of Hz. P1 (μs): represents the width of radio frequency pulse 1, with the unit of microsecond (μs). P2 (μs): represents the width of radio frequency pulse 2, with the unit of microsecond (μs). TW (ms): refers to the waiting time, with the unit of millisecond (ms). TE (ms): that is, the echo time, with the unit of millisecond (ms). NECH: represents the number of echoes, with the unit of times. SW (KHz): refers to the sweep width, with the unit of kilohertz (KHz). RFD (ms): refers to the radio frequency attenuation time, with the unit of millisecond (ms). NS: represents the number of scans, with the unit of times. RG1 (dB): refers to the receiver gain 1, with the unit of decibel (dB). DRG1 (dB): refers to the dynamic range gain 1, with the unit of decibel (dB). PRG: refers to the pulse repetition gain, with the unit of times.

[0026] This method separates the organic additives and inorganic fillers in the sample by means of organic solvent extraction, acidification, heating in different temperature segments, etc. It verifies the type of rubber matrix in the sample through pyrolysis molding and direct testing. Finally, low-field NMR determines whether the sample is vulcanized to form a three-dimensional cross-linked network structure, and comprehensively determines whether the sample to be tested is a vulcanized ethylene-propylene rubber product.

[0027] If directly subjecting vulcanized ethylene-propylene rubber to infrared 1For tests such as H-NMR, ATR, and LF-NMR, due to the presence of impurities such as organic solvents, organic additives, and inorganic additives, there are many interference peaks, and at the same time, it will affect the density of the rubber matrix, making it impossible to accurately judge the matrix type and crosslinking degree, and impossible to rule out whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are doped in the product.

[0028] This method can accurately identify the structure of ethylene-propylene rubber vulcanizate products.

[0029] Unless otherwise specified in this application, the temperature is carried out at room temperature, and unless otherwise specified, the pressure is carried out at normal pressure.

[0030] For technologies not mentioned in the present invention, refer to the prior art.

[0031] The detection method for identifying ethylene-propylene rubber vulcanizate products of the present invention can effectively identify ethylene-propylene rubber vulcanizate products after vulcanization. It can not only qualitatively and quantitatively identify the main resin in the ethylene-propylene rubber raw rubber, but also qualitatively and quantitatively identify whether the test sample is a qualified vulcanized rubber at the same time. It can directly rule out whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are doped in the product; the pretreatment is simple, omitting the steps of separating different organic substances in the main rubber according to different solubilities, boiling points, etc., simplifying the operation, improving the efficiency, and the accuracy reaches 100%. Brief Description of the Drawings

[0032] Figure 1 It is a flow chart of the detection method for identifying ethylene-propylene rubber vulcanizate products of the present invention;

[0033] Figure 2 It is the ATR spectrogram of m3 after pretreatment in Example 1;

[0034] Figure 3 It is the T2 relaxation spectrogram of m3 after pretreatment in Example 1;

[0035] Figure 4 It is the ATR spectrogram of m3 after pretreatment in Example 2;

[0036] Figure 5 It is the T2 relaxation spectrogram of m3 after pretreatment in Example 2;

[0037] Figure 6 It is the ATR spectrogram of m3 after pretreatment in Example 3;

[0038] Figure 7 It is the T2 relaxation spectrogram of m3 after pretreatment in Example 3; Detailed Description of the Invention

[0039] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments only.

[0040] The drying temperature in each example was 60 °C. The extraction in each example was carried out at the reflux temperature.

[0041] Example 1

[0042] A detection method for identifying ethylene propylene diene monomer (EPDM) rubber products specifically includes the following steps:

[0043] (1) The sample to be tested is a commercially available product labeled "ethylene propylene diene monomer (EPDM) prefabricated plastic runway". Accurately weigh m = 2.0018 g of the sample to be tested, cut it into pieces and wrap it with filter paper; use a mixed solution of 200 mL of isopropanol and methanol (volume ratio: 1:3) as the solution and extract it in a Soxhlet extractor for 6 h; after removing the surface solvent, then extract it with a mixed solution of 150 mL of acetone and chloroform (volume ratio: 1:2) for 8 h, filter, and dry to constant weight; after removing the organic additives in the sample to be tested, weigh it and record it as m1 = 1.8005 g;

[0044] (2) Add 3M hydrochloric acid dropwise to the sample m1 until the sample is immersed, and adjust the pH of the solution to 3; observe the bubbles released after the inorganic salts in the sample react with dilute hydrochloric acid; after no obvious bubbles are generated (no bubbles are observed with the naked eye), let it stand for 30 min, filter, and dry to constant weight, and weigh it and record it as m2 = 0.7210 g; separate the inorganic salts that react with hydrochloric acid in the sample;

[0045] (3) Heat the insoluble matter m2 to 350 °C, keep it at 350 °C, weigh it after 1 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h until constant weight, and record it as m3 = 0.3009 g (the weight at constant weight after keeping it at 350 °C for 4 h); achieve the removal of alkane oils with small molecular chains and some inorganic substances, and the remaining substance is the rubber resin main body, and its mass content in the sample to be tested is 0.3009 / 2.0018 X 100% = 15.03%.

[0046] (4) Conduct an ATR test at a flat position on m3. Test conditions: diamond crystal, resolution of 4 cm -1 , number of scans 16 times, scanning range 500 - 4000 cm -1 . The infrared spectrum of the rubber main body material is shown in Figure 2 , and it can be seen from Figure 2 that the peak wavenumbers at point (A) are 2918 cm -1 and 2849 cm -1 , which belong to the characteristic peaks of the symmetric stretching vibration of methylene in the EPDM molecular structure; 1416 cm -1 ​Characteristic peaks of the bending vibration of methylene and the antisymmetric bending vibration peak of methyl in the EPDM molecular structure; 1376 cm -1 Characteristic peak of the deformation vibration of methyl in the EPDM molecular structure; 712 cm -1 Characteristic peak of the in-plane stretching vibration of methylene in the EPDM molecular structure. There are no other obvious peaks of unsaturated C-H bonds in the spectrum, and it can be determined that the main resin is 100% ethylene propylene diene monomer (EPDM).

[0047] (5) Perform LF-NMR testing on the undecomposed substance m3. The testing conditions are: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C; cut the sample to be tested into rectangular strips of about 10 mm × 6 mm × 1 mm, and place them at the bottom of a test tube with an outer diameter of 10 mm. Keep the sample in an oven at 50 °C for 10 min to make the temperature of each area of the sample the same, then move it to the heating area of the nuclear magnetic instrument, set the temperature to 50 °C, keep it at a constant temperature and stable for 5 min, and scan the sample; the sample uses the CPMG pulse sequence, the testing temperature: 90 °C; SF (MHz): 22, 01 (Hz): 101597.5, P1 (μs): 3.12, P2 (μs): 5.68, TW (ms): 1500, TE (ms): 0.1417, NECH: 46, SW (KHz): 200, RFD (ms): 0.02, NS: 8, RG1 (dB): 10, DRG1 (dB): 3, PRG: 3. The measured crosslinking density: 6.7883×10 -4 mol / mL, belonging to medium crosslinking strength, and it can be accurately determined as vulcanized rubber.

[0048] According to the above method, the sample to be tested was measured 5 times, and the judgment accuracy of the main type of rubber resin reached 100% in all cases. The relative deviations of the mass content and crosslinking density of the main body of the rubber resin were both less than 0.0001%.

[0049] Comparative Example 1

[0050] Replace the 200 mL of isopropanol and methanol in step (1) of Example 1 with 200 mL of isopropanol. The rest are all referred to Example 1. Result: After the extraction of the organic auxiliary agent, the remaining m1 = 1.8464 g, and the extraction efficiency is 77.20% of that in Example 1. The inventor believes that the reason is that the solubility of isopropanol is less than that of the mixed solvent with a volume ratio of isopropanol to methanol of 1:3, resulting in incomplete extraction of the organic solvent.

[0051] Comparative Example 2

[0052] Replace the 200 mL of isopropanol and methanol in step (1) of Example 1 with 200 mL of methanol. The rest is the same as in Example 1. Result: After extraction with the organic auxiliary agent, the remaining m1 = 1.8273 g, and the extraction efficiency is 86.69% of that in Example 1. The reason is that the inventor believes that the solubility of methanol is less than that of the mixed solvent with a volume ratio of 1:3, and at the same time, the reflux temperature of methanol (65 °C) is lower than that of the mixed solvent with a volume ratio of 1:3 of isopropanol and methanol (80 °C), resulting in incomplete extraction of the organic solvent.

[0053] Comparative Example 3

[0054] Replace the 200 mL of isopropanol and methanol (volume ratio: 1:3) in step (1) of Example 1 with 200 mL of isopropanol and methanol (volume ratio: 1:5). The rest is the same as in Example 1. Result: After extraction with the organic solvent, the remaining m1 = 1.8199 g, and the extraction efficiency is 90.36% of that in Example 1. The reason is that the inventor believes that the solubility of methanol is less than that of the mixed solvent with a volume ratio of 1:3, and at the same time, when the proportion of methanol increases, the reflux temperature drops (the reflux temperature of the mixed solvent with a volume ratio of 1:5 of isopropanol and methanol is 72 °C), resulting in incomplete extraction of the organic solvent.

[0055] Comparative Example 4

[0056] Replace the 200 mL of isopropanol and methanol (volume ratio: 1:3) in step (1) of Example 1 with 200 mL of isopropanol and methanol (volume ratio: 1:1). The rest is the same as in Example 1. Result: After extraction with the organic solvent, the remaining m1 = 1.8146 g, and the extraction efficiency is 92.96% of that in Example 1. The reason is that the inventor believes that the solubility of the organic auxiliary agent in isopropanol is less than that of the mixed solvent with a volume ratio of 1:3 of isopropanol and methanol, resulting in incomplete extraction of the organic solvent.

[0057] Comparative Example 5

[0058] Replace the 200 mL of isopropanol and methanol in step (1) of Example 1 with 200 mL of n-heptane. The rest is the same as in Example 1. Result: After extraction with the organic solvent, the remaining m1 = 1.8725 g, and the extraction efficiency is 64.23% of that in Example 1. The reason is that the inventor believes that n-heptane is a good solvent for ethylene-propylene-diene monomer (EPDM), ethylene-propylene monomer (EPM) and other mixed raw rubbers, but due to the highly cross-linked molecular structure in vulcanized EPDM rubber, it only swells and does not dissolve in n-heptane; the solubility of n-heptane in the organic solvent is not high, resulting in incomplete extraction of the organic solvent.

[0059] Comparative Example 6

[0060] Replace the 200 mL of isopropanol and methanol in step (1) of Example 1 with 200 mL of ethanol. The rest is the same as in Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8206 g, and the extraction efficiency is 90.01% of that in Example 1. The reason is that the solubility of the organic auxiliary agent in ethanol is less than that in the mixed solvent of isopropanol and methanol with a volume ratio of 1:3, resulting in incomplete extraction of the organic solvent.

[0061] Comparative Example 7

[0062] Omit the step of "extracting with a mixed solution of 200 mL of isopropanol and methanol (volume ratio: 1:3) as the solution in a Soxhlet extractor for 6 h" in step (1) of Example 1. Directly extract the sample to be tested with a mixed solution of 150 mL of acetone and chloroform (volume ratio: 1:2) for 8 h, filter, and dry to constant weight. The rest is the same as in Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8359 g, and the extraction efficiency is 82.41% of that in Example 1. The reason is that the organic auxiliary agent with a higher boiling point is not completely extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0063] Comparative Example 8

[0064] Replace the 150 mL of acetone and chloroform in step (1) of Example 1 with 150 mL of acetone. The rest is the same as in Example 1. Result: The remaining m1 = 1.8189 g, and the extraction efficiency is 90.86% of that in Example 1. The reason is that the organic auxiliary agent with low solubility and high boiling point in the isopropanol / acetone mixed solvent is not completely extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0065] Comparative Example 9

[0066] Replace the 150 mL of acetone and chloroform in step (1) of Example 1 with 150 mL of chloroform. The rest is the same as in Example 1. Result: The remaining m1 = 1.8247 g, and the extraction efficiency is 87.98% of that in Example 1. The reason is that the solubility of the single solvent chloroform is lower than that of the acetone and chloroform mixed solvent with a volume ratio of 1:2, and the organic auxiliary agent is not completely extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0067] Comparative Example 10

[0068] Replace the 150 mL of acetone and chloroform in step (1) of Example 1 with 150 mL of dichloromethane. The rest are all referred to Example 1. Result: The remaining m1 = 1.8305 g, and the extraction efficiency is 85.09% of that in Example 1. The reason is that the solubility of the single solvent dichloromethane is lower than that of the acetone and chloroform mixed solvent with a volume ratio of 1:2, and the reflux temperature drops, resulting in incomplete extraction of the organic auxiliary agent and a decrease in the extraction efficiency of the organic solvent.

[0069] Comparative Example 11

[0070] Replace the 150 mL of acetone and chloroform (volume ratio: 1:2) in step (1) of Example 1 with 150 mL of acetone and chloroform (volume ratio: 1:4). The rest are all referred to Example 1. Result: The remaining m1 = 1.8131 g, and the extraction efficiency is 93.74% of that in Example 1. The reason is that the solubility of the mixed solvent decreases, resulting in incomplete extraction of the organic auxiliary agent and a decrease in the extraction efficiency of the organic solvent.

[0071] Comparative Example 12

[0072] Replace the 150 mL of acetone and chloroform (volume ratio: 1:2) in step (1) of Example 1 with 150 mL of acetone and chloroform (volume ratio: 1:1). The rest are all referred to Example 1. Result: The remaining m1 = 1.8194 g, and the extraction efficiency is 90.61% of that in Example 1. The reason is that the solubility of the acetone and chloroform mixed solvent with a volume ratio of 1:1 may be less than that of the acetone and chloroform mixed solvent with a volume ratio of 1:2. At the same time, the reflux temperature of the mixed solvent drops, resulting in incomplete extraction of the organic auxiliary agent and a decrease in the extraction efficiency of the organic solvent.

[0073] Comparative Example 13

[0074] Replace the 150 mL of acetone and chloroform in step (1) of Example 1 with 150 mL of tetrahydrofuran. The rest are all referred to Example 1. Result: The remaining m1 = 1.8405 g, and the extraction efficiency is 80.13% of that in Example 1. The reason is that the solubility of the single solvent tetrahydrofuran is lower than that of the acetone and chloroform mixed solvent with a volume ratio of 1:2, resulting in incomplete extraction of the organic auxiliary agent and a decrease in the extraction efficiency of the organic solvent.

[0075] Comparative Example 14

[0076] Omit the step of "extracting with a mixed solution of 150 mL of acetone and chloroform (volume ratio: 1:2) for 8 h" in step (1) of Example 1. Directly use a mixed solution of 200 mL of isopropanol and methanol (volume ratio: 1:3) as the solution to extract the test sample in a Soxhlet extractor for 6 h, and then dry to a constant weight. The rest is the same as in Example 1. Result: m1 = 1.8326 g, and the extraction efficiency is 84.05% of that in Example 1. The reason is that the organic additives with low solubility in the isopropanol / methanol mixed solvent are not fully extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0077] Example 2

[0078] A detection method for identifying ethylene-propylene-diene monomer rubber products specifically includes the following steps:

[0079] (1) The test sample is a commercially available product labeled "ethylene-propylene-diene monomer (EPDM) prefabricated plastic runway". Accurately weigh m = 5.4250 g of the test sample, cut it into pieces and wrap it with filter paper; extract with 450 mL of isopropanol and methanol (volume ratio: 1:3) in a Soxhlet extractor for 8 h; after removing the surface solvent, extract with a mixed solution of 450 mL of acetone and dichloromethane (volume ratio: 1:2) for 6 h, filter, and dry to a constant weight; after removing the organic additives in the test sample, weigh and record as m1 = 4.7198 g;

[0080] (2) Add 2 M hydrochloric acid dropwise to the test sample m1 until the sample is immersed, and adjust the pH of the solution to 3; observe the evolution of bubbles when the inorganic salts in the sample react with dilute hydrochloric acid; after no obvious bubbles are generated (no bubbles are observed with the naked eye), let it stand for 30 min, filter, dry to a constant weight, and weigh and record as m2 = 2.0615 g; separate the inorganic salts that react with hydrochloric acid in the sample;

[0081] (3) Heat the insoluble matter m2 to 345 °C, keep it at 345 °C, weigh it after 1 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h until a constant weight is reached, and record as m3 = 1.1393 g (the weight at constant weight after keeping it at 350 °C for 4 h); remove the alkane oils of small molecular chains and some inorganic substances, and the remaining is the rubber resin main body, and its mass content in the test sample is 1.1393 / 5.4250 X 100% = 21%.

[0082] (4) Perform ATR testing at a flat position on m3. Testing conditions: diamond crystal, resolution of 4 cm -1 , number of scans 16 times, scanning range of 500 - 4000 cm -1 . The infrared spectrum of the rubber main body material is shown in Figure 4 , and it can be seen from Figure 4 that the peak wave number at point (B) is 2918 cm-1 and 2849 cm -1 , which is the characteristic peak of the symmetric stretching vibration of methylene in the EPDM molecular structure; 1421 cm -1 is attributed to the characteristic peak of the bending vibration of methylene and the antisymmetric bending vibration peak of methyl in the EPDM molecular structure; 1376 cm -1 is attributed to the characteristic peak of the deformation vibration of methyl in the EPDM molecular structure; 712 cm -1 is attributed to the characteristic peak of the in-plane stretching vibration of methylene in the EPDM molecular structure. There are no other obvious peaks of unsaturated C-H bonds in the spectrum, and it can be determined that the main resin is 100% ethylene propylene diene monomer (EPDM).

[0083] (5) Perform LF-NMR test on the undecomposed substance m3. The test conditions are: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C; cut the sample to be tested into rectangular strips of about 10 mm × 6 mm × 1 mm, and place them at the bottom of a test tube with an outer diameter of 10 mm. Keep the sample in an oven at 50 °C for 10 min to make the temperature of each area of the sample the same. Then move it to the heating area of the nuclear magnetic instrument, set the temperature to 50 °C, keep it at a constant temperature and stable for 5 min, and scan the sample; the sample uses the CPMG pulse sequence, test temperature: 90 °C; SF (MHz): 22, 01 (Hz): 101597.5, P1 (μs): 3.12, P2 (μs): 5.68, TW (ms): 1500, TE (ms): 0.1417, NECH: 46, SW (KHz): 200, RFD (ms): 0.02, NS: 8, RG1 (dB): 10, DRG1 (dB): 3, PRG: 3. The measured crosslinking density is 8.2356×10 -4 mol / mL, belonging to medium crosslinking strength, and it can be accurately determined as vulcanized rubber.

[0084] According to the above method, the sample to be tested was measured 5 times, and the judgment accuracy of the main type of rubber resin reached 100%, and the relative deviations of the mass content and crosslinking density of the main body of the rubber resin were both less than 0.0001%.

[0085] Example 3

[0086] A detection method for identifying vulcanized ethylene propylene diene rubber products specifically includes the following steps:

[0087] (1) The sample to be tested is a commercially available product labeled as "Ethylene-Propylene Copolymer Prefabricated Plastic Track". Accurately weigh m = 3.6550 g of the sample to be tested, cut it into pieces and wrap it with filter paper. Use a mixed solution of 200 mL of isopropanol and methanol (volume ratio: 1:3) as the solution and extract it in a Soxhlet extractor for 7 h. After removing the surface solvent, extract it with a mixed solution of 200 mL of acetone and chloroform (volume ratio: 1:2) for 7 h, filter, and dry to constant weight. After removing the organic additives in the sample to be tested, weigh it and record it as m1 = 3.3261 g;

[0088] (2) Add 1 M hydrochloric acid dropwise to the test sample m1 until the sample is immersed, and adjust the pH of the solution to 3. Observe the bubbles released after the inorganic salts in the sample react with dilute hydrochloric acid. After no obvious bubbles are produced (no bubbles are observed with the naked eye), let it stand for 30 min, filter, and dry to constant weight, and weigh it and record it as m2 = 1.3889 g; Separate the inorganic salts that react with hydrochloric acid in the sample;

[0089] (3) Heat the insoluble matter m2 to 350 °C, keep it at 350 °C for 1 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h and then weigh it until it reaches constant weight, and record it as m3 = 0.8041 g (the weight after keeping it at 350 °C for 4 h and reaching constant weight); Remove the alkane oils with small molecular chains and part of the inorganic substances, and the remaining is the rubber resin main body, and its mass content in the sample to be tested is 0.8041 / 3.6550 X 100% = 22%.

[0090] (4) Conduct ATR test at a flat position on m3, test conditions: diamond crystal, resolution is 4 cm -1 , the number of scans is 16 times, and the scanning range is 500 - 4000 cm -1 . The infrared spectrum of the rubber main body material is shown in Figure 6 , from Figure 6 it can be seen that the peak wavenumbers at point (C) are 2918 cm -1 and 2849 cm -1 , which belong to the symmetric stretching vibration characteristic peaks of methylene in the EPDM molecular structure; 1421 cm -1 belongs to the bending vibration characteristic peak of methylene and the antisymmetric bending vibration peak of methyl in the EPDM molecular structure; 1376 cm -1 belongs to the deformation vibration characteristic peak of methyl in the EPDM molecular structure; 712 cm -1 belongs to the in-plane stretching vibration characteristic peak of methylene in the EPDM molecular structure. There are no other obvious peaks of unsaturated C-H bonds in the spectrum, and it can be determined that the main resin is 100% ethylene-propylene-diene monomer (EPDM)

[0091] (5) Perform LF-NMR testing on the undegraded substance m3. The testing conditions are as follows: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C; cut the sample to be tested into rectangular strips of about 10 mm × 6 mm × 1 mm, place them at the bottom of a test tube with an outer diameter of 10 mm, keep the sample in an oven at 50 °C for 10 min to make the temperature of each area of the sample the same, then move it to the heating area of the nuclear magnetic instrument, set the temperature to 50 °C, keep it constant and stable for 5 min, and scan the sample; the sample uses the CPMG pulse sequence, testing temperature: 90 °C; SF (MHz): 22, 01 (Hz): 101597.5, P1 (μs): 3.12, P2 (μs): 5.68, TW (ms): 1500, TE (ms): 0.1417, NECH: 46, SW (KHz): 200, RFD (ms): 0.02, NS: 8, RG1 (dB): 10, DRG1 (dB): 3, PRG: 3. The measured crosslink density is 7.4974×10 -4 mol / mL, belonging to medium crosslinking strength, and can be accurately determined as vulcanized rubber.

[0092] According to the above method, the sample to be tested was measured 5 times, and the judgment accuracy of the main type of rubber resin reached 100%, and the relative deviations of the mass content and crosslink density of the main body of the rubber resin were both less than 0.0001%.

[0093] The detection method for identifying ethylene-propylene-diene monomer (EPDM) rubber products in the above Examples 1-3 can effectively identify vulcanized EPDM rubber products. It can not only qualitatively and quantitatively identify the main resin in raw EPDM rubber, but also qualitatively and quantitatively identify whether the sample is a qualified vulcanized rubber at the same time. It can directly exclude whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are doped in the product; the pretreatment is simple, omitting the steps of separating different organic substances in the main rubber according to different solubilities, boiling points, etc., simplifying the operation, with an accuracy of 100% and improving the efficiency.

Claims

1. A detection method for identifying ethylene propylene diene monomer rubber products, characterized in that: It includes the following steps: 1) Extraction of organic auxiliaries: Extract the test sample m with the first organic solvent for 5 - 8 hours to remove the surface solvent, then extract it with the second organic solvent for 6 - 8 hours. Filter out the material insoluble in the organic solvent and dry it to constant weight to obtain the rubber compound m1; 2) Decomposition of inorganic substances: Drop dilute hydrochloric acid into the rubber compound m1 until it is submerged and adjust the pH value of the solution to 3. After no bubbles are generated, let it stand for 25 - 30 min, filter, and dry to constant weight to obtain the insoluble substance m2; 3) Decomposition of some inorganic substances and low-chain alkanes: Heat the insoluble substance m2 to 330 - 350 °C and then keep it at 330 - 350 °C until constant weight to obtain the undecomposed substance m3; 4) Identification of the main resin by the reflection method: Take the undecomposed substance m3 for ATR test, read the characteristic peaks reflecting the structural characteristic functional groups, and determine the type of the main rubber resin; 5) Quantitative analysis: The mass of the undecomposed substance m3 is the mass of the main rubber resin. The mass content a of the main rubber resin in the test sample = m3 / m × 100%; Alternatively, place the undecomposed substance m3 at the bottom of a glass test tube and heat it to 450 °C ± 20 °C using an electric furnace until the sample is pyrolyzed to a constant weight to obtain the pyrolysis product m4, and perform 1 1H-NMR testing on the pyrolysis product m4 for quantitative analysis; 6) Conduct LF-NMR test on the undecomposed substance m3 to identify the crosslinking degree after vulcanization, and comprehensively determine the material type of the test; In step 1), the first organic solvent is a mixed solvent with the volume ratio of isopropanol to methanol being 1:3; the second organic solvent is a mixed solvent with the volume ratio of acetone to dichloromethane being 1:1, or the second organic solvent is a mixed solvent with the volume ratio of acetone to chloroform being 1:

2.

2. The detection method for identifying ethylene propylene diene monomer rubber products according to claim 1, wherein: In step 2), the mass concentration of the dilute hydrochloric acid is 1 - 3 mol / L.

3. The detection method for identifying ethylene propylene diene monomer rubber products according to claim 1 or 2, characterized in that: In step 4), the conditions for ATR test are: diamond crystal, resolution of 4 cm -1 , 16 scanning times, and the scanning range is 500~4000 cm -1 .

4. The detection method for identifying ethylene propylene diene monomer rubber products according to claim 1 or 2, characterized in that: In step 5), 1 The conditions for the 1H-NMR test are as follows: 1 1H-NMR working frequency: 400 MHz, pulse sequence: zg30, solvent: chloroform-d, isotopic purity 99.8%, internal standard: tetramethylsilane, volume fraction 0.03%; experimental temperature: 298 K.

5. The detection method for identifying ethylene propylene diene monomer rubber products according to claim 1 or 2, characterized in that: In step 6), the conditions for LF-NMR test are: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C; Cut the test sample into a rectangular strip of about 10 mm × 6 mm × 1 mm, put it at the bottom of a test tube with an outer diameter of 10 mm, keep the sample in an oven at 50 °C for 10 min to make the temperature of each area of the sample the same, then move it to the heating area of the nuclear magnetic instrument, set the temperature to 50 °C, keep it at a constant temperature and stable for 5 min, and scan the sample; The sample uses the CPMG pulse sequence, test temperature: 90 °C; SF (MHz): 22, 01 (Hz): 101597.5, P1 (μs): 3.12, P2 (μs): 5.68, TW (ms): 1500, TE (ms): 0.1417, NECH: 46, SW (KHz): 200, RFD (ms): 0.02, NS: 8, RG1 (dB): 10, DRG1 (dB): 3, PRG: 3.

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