Detection method for identifying vulcanized ethylene propylene rubber product

Abstract

The invention discloses a detection method for identifying a vulcanized ethylene propylene rubber product, which comprises the following steps: 1) extracting a test sample m through a first organic solvent and a second organic solvent, filtering out insoluble substances, and drying to constant weight to obtain a rubber material m1; 2) removing inorganic matters in the sizing material m1 to obtain an insoluble substance m2; and 3) heating the insoluble substance m2 to 330-350 DEG C, then preserving heat to constant weight to obtain an undecomposed substance m3: taking the undecomposed substance m3, carrying out ATR test, reading a characteristic peak reflecting a structural characteristic functional group, and judging the rubber resin main body type. 5) quantitative analysis; and 6) carrying out LF-NMR test on the undecomposed product m3 to identify the vulcanized cross-linked structure, and comprehensively judging the material type of the test. The method not only can qualitatively and quantitatively identify the matrix resin in the ethylene propylene rubber raw rubber, but also can qualitatively and quantitatively identify whether a sample is qualified vulcanized rubber or not, can directly eliminate whether other rubber containing unsaturated bonds is doped in a product or not, and 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] Since the EPDM raw rubber generates a complex and stable cross-linked structure during vulcanization, it can only swell in a solvent and cannot be dissolved in an organic solvent. However, the EPDM raw rubber has not undergone a cross-linking reaction, and its organic components are soluble in an organic solvent. Therefore, in the prior art, there is no related report on directly identifying the type of the rubber main resin and judging whether the cross-linked structure is achieved by vulcanization of the EPDM, and the vulcanized rubber can only be analyzed by testing the EPDM raw rubber before vulcanization. Moreover, the main resin component in the EPDM raw rubber can only be analyzed, and it is impossible to directly exclude whether other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc., are mixed in the product. For example, the prior art analysis method for EPDM is: first pre-treating the EPDM raw rubber, and then using infrared spectroscopy to identify the rubber main resin, or using the peak attribution and peak area in the solid nuclear magnetic resonance spectrum to calculate the mass percentage of the three monomers in EPDM (Hao Fengling et al.), but due to the lack of standard products for EPDM, it is impossible to directly qualitatively compare with the standard products. The existing method for pre-treating EPDM raw rubber is: firstly dissolve all organic components in the EPDM raw rubber, including the rubber body, paraffin oil (organic solvent), organic additives, etc., using n-heptane or the like, and then further separate the organic components according to the solubility, boiling point, etc. of the dissolved organic matter, and finally characterize the rubber body by infrared or other means, that is, first dissolve all organic matter and then separate them one by one. However, for rubber products with unknown synthetic raw materials, it is impossible to determine which organic substances are brought out during the dissolution. Therefore, there are problems such as great difficulty, high cost, and low efficiency in further separating the organic components.

[0005] Therefore, there is an urgent need to develop a convenient, accurate and efficient detection method to quickly identify whether it is a vulcanized EPDM product, so as to ensure the quality of plastic tracks and protect the health and safety of users. Summary of the invention

[0006] The invention provides a detection method for identifying vulcanized EPDM rubber products, which can effectively identify the vulcanized EPDM rubber products, can identify the main resin in the raw EPDM rubber, and can also identify whether the sample is a qualified vulcanized rubber, and can directly exclude whether the product is mixed with other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc.

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

[0008] A detection method for identifying vulcanized EPDM products comprises the following steps:

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

[0010] 2) Decomposition of inorganic matter: Add dilute hydrochloric acid to the rubber material m1 until it is submerged and adjust the pH value of the solution to 3. After no bubbles are generated by naked eye observation, let it stand for 25 to 30 minutes, filter it, and dry it to constant weight to obtain insoluble matter m2, and separate the inorganic salts in the sample that react with hydrochloric acid;

[0011] 3) Decomposition of some inorganic substances and low-chain alkanes: Heat the insoluble matter m2 to 330-350°C, then keep it warm (330-350°C) until constant weight, remove the small molecular chain alkanes and oils, and obtain the undecomposed matter m3, which is the main body of the rubber resin;

[0012] 4) Identification of the main resin by reflection method: Take the undecomposed product m3 for ATR test, read the characteristic peaks reflecting the structural characteristic functional groups, and determine the main type of rubber resin;

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

[0014] Alternatively, place the undecomposed product m3 at the bottom of a glass test tube and heat it to 450°C ± 20°C in an electric furnace to pyrolyze the sample to constant weight to obtain the pyrolysis product m4. 1 H-NMR test for quantitative analysis;

[0015] 6) Conduct LF-NMR test on the undecomposed product m3 to identify the degree of cross-linking after vulcanization and comprehensively determine the type of material tested.

[0016] The extraction in this application is carried out at reflux temperature.

[0017] In step 5), the pyrolysis product m4 can be subjected to 1 H-NMR testing achieves quantitative analysis. The intensity of the nuclear magnetic resonance signal is proportional to the number of hydrogen atoms that produce 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 of 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. 1H-NMR quantitative analysis of EPDM rubber [J]. Chemical 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 EPDM rubber by infrared spectroscopy [J]. Elastomers, 2000, (04): 17-20. DOI: 10.16665 / j.cnki.issn1005-3174.2000.04.006.

[0019] The idea of ​​this application is completely different from that of existing raw rubber testing, and is even the opposite. The idea of ​​existing raw rubber testing is to dissolve the rubber body first, while this application requires retaining the rubber body. That is, this application does not dissolve the rubber body, but removes the organic solvents, organic additives, and inorganic additives in the vulcanized rubber by dissolving, leaving the rubber body, eliminating the step of separating different organic substances in the main rubber according to different solubilities, boiling points, etc., simplifying the operation, improving accuracy, and improving efficiency.

[0020] In order to further improve the detection accuracy, in step 1), the first organic solvent is at least one of isopropanol or methanol, and is 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 is 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 dilute hydrochloric acid is 1 to 3 mol / L;

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

[0023] In order to further improve the detection accuracy, in the above step 5), 1 The conditions of H-NMR test are: 1 H-NMR operating frequency: 400 MHz, pulse sequence: zg30, solvent: deuterated chloroform (CDCl3), isotopic purity 99.8%, internal standard: tetramethylsilane (TMS), volume fraction 0.03%; experimental temperature: 298K.

[0024] In order to further improve the detection accuracy, in the above step 6), the conditions of the LF-NMR test are: resonance frequency: 22MHz, magnet strength: 0.5T, coil diameter: 10mm, magnet temperature: 32℃. Cut the sample to be tested into rectangular strips of about 10mm×6mm×1mm and put them into the bottom of a test tube with an outer diameter of 10mm. Keep the sample in a 50℃ oven for 10min 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℃, keep the temperature stable for 5min, and scan the sample. The sample adopts CPMG pulse sequence, test temperature: 90℃; 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): Sweep Frequency, in megahertz (MHz). 01(Hz): Start frequency, in Hz. P1(μs): RF pulse 1 width, in microseconds (μs). P2(μs): RF pulse 2 width, in microseconds (μs). TW(ms): Waiting time, in milliseconds (ms). TE(ms): Echo time, in milliseconds (ms). NECH: Echo times, in times. SW(KHz): Sweep width, in kilohertz (KHz). RFD(ms): RF decay time, in milliseconds (ms). NS: Sweep times, in times. RG1(dB): Receiver gain 1, in decibels (dB). DRG1(dB): Dynamic range gain 1, in decibels (dB). PRG: Pulse repetition gain, in times.

[0026] The method separates the organic additives and inorganic fillers in the sample by means of organic solvent extraction, acidification, heating in different temperature ranges, etc., mutually verifies the type of rubber body in the sample by cracking molding and direct testing, and finally determines whether the sample is vulcanized to form a three-dimensional cross-linked network structure by low-field nuclear magnetic resonance, and comprehensively determines whether the sample to be tested is a vulcanized EPDM rubber product.

[0027] If the vulcanized EPDM rubber is directly subjected to infrared 1H-NMR, ATR, LF-NMR and other tests, due to the presence of impurities such as organic solvents, organic additives, and inorganic additives, lead to many interference peaks, which will also affect the main density of the rubber, making it impossible to accurately determine the main type and degree of cross-linking, and unable to rule out whether the product is mixed with other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc.

[0028] This method can accurately identify the structure of vulcanized EPDM rubber products.

[0029] If the temperature is not particularly specified in the present application, the reaction is carried out at room temperature; if the pressure is not particularly specified, the reaction is carried out at normal pressure.

[0030] The technologies not mentioned in the present invention are all referred to the prior art.

[0031] The detection method for identifying vulcanized EPDM rubber products of the present invention can effectively identify the vulcanized EPDM rubber products, can qualitatively and quantitatively identify the main resin in the raw EPDM rubber, and can also qualitatively and quantitatively 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 mixed in the product; the pretreatment is simple, and the step of separating different organic substances in the main rubber according to different solubilities, boiling points, etc. is omitted, the operation is simplified, the efficiency is improved, and the accuracy reaches 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a flow chart of a detection method for identifying vulcanized EPDM rubber products;

[0033] Figure 2 This is the ATR spectrum of m3 after pre-treatment in Example 1;

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

[0035] Figure 4 This is the ATR spectrum of m3 after pre-treatment in Example 2;

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

[0037] Figure 6 This is the ATR spectrum of m3 after pre-treatment in Example 3;

[0038] Figure 7 This is the T2 relaxation spectrum of m3 after pretreatment in Example 3; DETAILED DESCRIPTION

[0039] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

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

[0041] Example 1

[0042] A detection method for identifying vulcanized EPDM products, specifically comprising the following steps:

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

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

[0045] (3) The insoluble matter m2 is heated to 350°C and kept at 350°C for 1 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h, and then weighed until constant weight is obtained, which is recorded as m3 = 0.3009 g (weight at 350°C for 4 h). The small molecular chain alkane oils and some inorganic substances are removed, and the remainder is mainly rubber resin, and its mass content in the sample to be tested is 0.3009 / 2.0018 X 100%=15.03%.

[0046] (4) Select a flat position on m3 to perform ATR test. Test conditions: diamond crystal, resolution 4 cm -1 , scanning times 16 times, scanning range 500~4000cm -1 The infrared spectrum of the rubber main material is shown in Figure 2 ,from Figure 2 It can be seen that the peak wave number of point (A) is 2918cm -1 and 2849cm -1 , which is the characteristic peak of the symmetrical stretching vibration of the methylene group in the EPDM molecular structure; 1416cm -1The characteristic bending vibration peaks of the methylene group and the antisymmetric bending vibration peaks of the methyl group in the EPDM molecular structure; 1376cm -1 The characteristic peak of deformation vibration of methyl group in EPDM molecular structure; 712cm -1 The characteristic peaks of the in-plane stretching vibration of the methylene group in the EPDM molecular structure are attributed to the EPDM. There are no other obvious unsaturated CH bond peaks in the spectrum, and it can be determined that the main resin is 100% ethylene propylene diene monomer (EPDM).

[0047] (5) The undecomposed product m3 was subjected to LF-NMR test. The test conditions were: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C. The sample to be tested was cut into rectangular strips of about 10 mm × 6 mm × 1 mm and placed in the bottom of a test tube with an outer diameter of 10 mm. The sample was kept at a constant temperature in an oven at 50 °C for 10 min to make the temperature of each area of ​​the sample the same. Then, the sample was moved to the heating area of ​​the nuclear magnetic resonance instrument and the temperature was set to 50 °C. The sample was kept at a constant temperature for 5 min. Scan the sample; the sample adopts CPMG pulse sequence, the test temperature is 90℃; 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 6.7883×10 -4 mol / mL, which belongs to medium cross-linking strength and can be accurately identified as vulcanized rubber.

[0048] According to the above method, the sample to be tested was measured 5 times, and the judgment accuracy of the rubber resin main body type reached 100%, and the relative deviation of the mass content and cross-linking density of the rubber resin main body was less than 0.0001%.

[0049] Comparative Example 1

[0050] The 200 mL of isopropanol and methanol in step (1) of Example 1 were replaced with 200 mL of isopropanol. The rest was referred to Example 1. Results: After the organic auxiliary agent was extracted, the remaining m1 = 1.8464 g, and the extraction efficiency was 77.20% of that in Example 1. The inventors believed that the solubility of isopropanol was lower than that of the mixed solvent of isopropanol and methanol with a volume ratio of 1:3, resulting in incomplete extraction of the organic solvent.

[0051] Comparative Example 2

[0052] The 200 mL of isopropanol and methanol in step (1) of Example 1 were replaced with 200 mL of methanol. The rest were referred to Example 1. Result: After the organic auxiliary agent was extracted, the remaining m1 = 1.8273 g, and the extraction efficiency was 86.69% of that in Example 1. The inventors believed that the reason may be that the solubility of methanol is less than that of the mixed solvent of 1:3, and the reflux temperature of methanol (65°C) is lower than the reflux temperature (80°C) of the mixed solvent with a volume ratio of isopropanol to methanol of 1:3, resulting in incomplete extraction of the organic solvent.

[0053] Comparative Example 3

[0054] The 200 mL of isopropanol and methanol (volume ratio: 1:3) in step (1) of Example 1 were replaced with 200 mL of isopropanol and methanol (volume ratio: 1:5). The rest were all referred to Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8199 g, and the extraction efficiency was 90.36% of Example 1. The inventors believed that the solubility of methanol was less than that of the mixed solvent of 1:3, and when the proportion of methanol increased, the reflux temperature decreased (the reflux temperature of the mixed solvent with a volume ratio of isopropanol to methanol of 1:5 was 72°C), which led to incomplete organic solvent extraction.

[0055] Comparative Example 4

[0056] The 200 mL of isopropanol and methanol (volume ratio: 1:3) in step (1) of Example 1 was replaced with 200 mL of isopropanol and methanol (volume ratio: 1:1). The rest was referred to Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8146 g, and the extraction efficiency was 92.96% of that in Example 1. The inventors believed that the solubility of the organic auxiliary in isopropanol was less than that of the mixed solvent of isopropanol and methanol with a volume ratio of 1:3, resulting in incomplete organic solvent extraction.

[0057] Comparative Example 5

[0058] The 200 mL of isopropanol and methanol in step (1) of Example 1 were replaced with 200 mL of n-heptane. The rest were all referred to Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8725 g, and the extraction efficiency was 64.23% of that in Example 1. The inventors believed that n-heptane is a good solvent for mixed raw rubbers such as EPDM and EPDM, but due to the highly cross-linked molecular structure of vulcanized EPDM, it only swells but does not dissolve in n-heptane; n-heptane has low solubility in organic solvents, resulting in incomplete organic solvent extraction.

[0059] Comparative Example 6

[0060] The 200 mL of isopropanol and methanol in step (1) of Example 1 were replaced with 200 mL of ethanol. The rest were referred to Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8206 g, and the extraction efficiency was 90.01% of that in Example 1. The inventors believed that the solubility of the organic auxiliary in ethanol was less than that of the mixed solvent of isopropanol and methanol in a volume ratio of 1:3, resulting in incomplete organic solvent extraction.

[0061] Comparative Example 7

[0062] The step of "extracting in a Soxhlet extractor for 6 hours with a mixed solution of 200 mL of isopropanol and methanol (volume ratio: 1:3)" in step (1) of Example 1 was omitted, and the sample to be tested was directly extracted with a mixed solution of 150 mL of acetone and chloroform (volume ratio: 1:2) for 8 hours, filtered, and dried to constant weight. The rest was referred to Example 1. Result: After organic solvent extraction, the remaining m1 = 1.8359 g, and the extraction efficiency was 82.41% of that in Example 1. The inventors believed that the reason was that the organic auxiliary agent with a higher boiling point was not completely extracted, resulting in a decrease in the organic solvent extraction efficiency.

[0063] Comparative Example 8

[0064] The 150 mL acetone and chloroform in step (1) of Example 1 were replaced with 150 mL acetone. The rest was referred to Example 1. Result: The remaining m1 = 1.8189 g, and the extraction efficiency was 90.86% of that in Example 1. The inventors believed that the organic auxiliary agent with a low solubility and a high boiling point in the isopropanol / propanol mixed solvent was not completely extracted, resulting in a decrease in the organic solvent extraction efficiency.

[0065] Comparative Example 9

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

[0067] Comparative Example 10

[0068] The 150 mL acetone and chloroform in step (1) of Example 1 were replaced with 150 mL dichloromethane. The rest was referred to Example 1. Result: The remaining m1 = 1.8305 g, and the extraction efficiency was 85.09% of that in Example 1. The inventors believed that the solubility of the single solvent dichloromethane was lower than that of the mixed solvent of acetone and chloroform in a volume ratio of 1:2, and the reflux temperature decreased, resulting in incomplete extraction of the organic auxiliary agent, which led to a decrease in the extraction efficiency of the organic solvent.

[0069] Comparative Example 11

[0070] The 150 mL of acetone and chloroform (volume ratio: 1:2) in step (1) of Example 1 was replaced with 150 mL of acetone and chloroform (volume ratio: 1:4). The rest was referred to Example 1. Result: The remaining m1 = 1.8131 g, and the extraction efficiency was 93.74% of that in Example 1. The inventors believed that the solubility of the mixed solvent decreased, and the organic auxiliary agent was not completely extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0071] Comparative Example 12

[0072] The 150 mL of acetone and chloroform (volume ratio: 1:2) in step (1) of Example 1 were replaced with 150 mL of acetone and chloroform (volume ratio: 1:1). The rest were all referred to Example 1. Result: The remaining m1 = 1.8194 g, and the extraction efficiency was 90.61% of that in Example 1. The inventors believed that the solubility of the mixed solvent of acetone and chloroform in a volume ratio of 1:1 was lower than that of the mixed solvent of acetone and chloroform in a volume ratio of 1:2. At the same time, the reflux temperature of the mixed solvent decreased, and the organic auxiliary agent was not completely extracted, resulting in a decrease in the organic solvent extraction efficiency.

[0073] Comparative Example 13

[0074] The 150 mL acetone and chloroform in step (1) of Example 1 were replaced with 150 mL tetrahydrofuran. The rest was referred to Example 1. Result: The remaining m1 = 1.8405 g, and the extraction efficiency was 80.13% of that in Example 1. The inventors believed that the solubility of the single solvent tetrahydrofuran was lower than that of the mixed solvent of acetone and chloroform in a volume ratio of 1:2, and the organic auxiliary agent was not completely extracted, resulting in a decrease in the extraction efficiency of the organic solvent.

[0075] Comparative Example 14

[0076] The step of "extracting with 150 mL of a mixed solution of acetone and chloroform (volume ratio: 1:2) for 8 h" in step (1) of Example 1 was omitted, and the sample to be tested was directly extracted with 200 mL of a mixed solution of isopropanol and methanol (volume ratio: 1:3) as a solution in a Soxhlet extractor for 6 h, and then dried to constant weight. The rest was referred to Example 1. Result: m1 = 1.8326 g, and the extraction efficiency was 84.05% of that in Example 1. The reason was that the organic auxiliary agent with low solubility in the isopropanol / methanol mixed solvent was not fully extracted, resulting in a decrease in the organic solvent extraction efficiency.

[0077] Example 2

[0078] A detection method for identifying vulcanized EPDM products, specifically comprising the following steps:

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

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

[0081] (3) The insoluble matter m2 was heated to 345°C and kept at 345°C for 1 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h, and then weighed until constant weight was obtained, which was recorded as m3 = 1.1393 g (weight at 350°C for 4 h). The small molecular chain alkane oils and some inorganic substances were removed, and the remainder was mainly rubber resin, and its mass content in the sample to be tested was 1.1393. / 5.4250 X 100%=21%.

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

[0083] (5) The undecomposed product m3 was subjected to LF-NMR test. The test conditions were: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C. The sample to be tested was cut into rectangular strips of about 10 mm × 6 mm × 1 mm and placed in the bottom of a test tube with an outer diameter of 10 mm. The sample was kept at a constant temperature in an oven at 50 °C for 10 min to make the temperature of each area of ​​the sample the same. Then, the sample was moved to the heating area of ​​the nuclear magnetic resonance instrument and the temperature was set to 50 °C. The sample was kept at a constant temperature for 5 min. Scan the sample; the sample adopts CPMG pulse sequence, the test temperature is 90℃; 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 8.2356×10 -4 mol / mL, which belongs to medium cross-linking strength and can be accurately identified as vulcanized rubber.

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

[0085] Example 3

[0086] A detection method for identifying vulcanized EPDM products, specifically comprising the following steps:

[0087] (1) The sample to be tested is a commercial product, labeled as "EPR prefabricated plastic track". Accurately weigh the sample to be tested m = 3.6550g, cut it into pieces and wrap it with filter paper; use 200mL of a mixed solution of isopropanol and methanol (volume ratio: 1:3) as the solvent to extract it in a Soxhlet extractor for 7h; after removing the surface solvent, use 200mL of a mixed solution of acetone and chloroform (volume ratio: 1:2) to extract it for 7h, filter it, and dry it to constant weight; after removing the organic additives in the sample to be tested, weigh it and record it as m1 = 3.3261g;

[0088] (2) Add 1M hydrochloric acid to the sample m1 to be tested until the sample is immersed, and adjust the pH of the solution to 3; observe the inorganic salt in the sample reacting with the dilute hydrochloric acid to release bubbles; after no obvious bubbles are generated (no bubbles observed with the naked eye), let it stand for 30 minutes, filter, dry to constant weight, weigh and record as m2 = 1.3889 g; separate the inorganic salts in the sample that react with the hydrochloric acid;

[0089] (3) The insoluble matter m2 is heated to 350°C and kept at 350°C for 1 h, 2 h, 2.5 h, 3 h, 3.5 h, and 4 h, and then weighed until constant weight is obtained, which is recorded as m3 = 0.8041 g (weight at 350°C for 4 h). The small molecular chain alkane oils and some inorganic substances are removed, and the remainder is mainly rubber resin, and its mass content in the sample to be tested is 0.8041 / 3.6550 X 100%=22%.

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

[0091] (5) The undecomposed product m3 was subjected to LF-NMR test. The test conditions were: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 °C. The sample to be tested was cut into rectangular strips of about 10 mm × 6 mm × 1 mm and placed in the bottom of a test tube with an outer diameter of 10 mm. The sample was kept at a constant temperature in an oven at 50 °C for 10 min to make the temperature of each area of ​​the sample the same. Then, the sample was moved to the heating area of ​​the nuclear magnetic resonance instrument and the temperature was set to 50 °C. The sample was kept at a constant temperature for 5 min. Scan the sample; the sample adopts CPMG pulse sequence, the test temperature is 90℃; 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, which belongs to medium cross-linking strength and can be accurately identified as vulcanized rubber.

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

[0093] The detection method for identifying vulcanized EPDM rubber products in the above-mentioned embodiments 1-3 can effectively identify the vulcanized EPDM rubber products, and can qualitatively and quantitatively identify the main resin in the EPDM raw rubber, and can also qualitatively and quantitatively identify whether the sample is a qualified vulcanized rubber at the same time, and can directly exclude whether the product is mixed with other rubbers containing unsaturated bonds, such as NR, SBR, NBR, BR, etc.; the pretreatment is simple, and the step of separating different organic substances in the main rubber according to different solubilities, boiling points, etc. is omitted, the operation is simplified, the accuracy reaches 100%, and the efficiency is improved.

Claims

1. A method for identifying vulcanized EPDM products, characterized in that: The steps include: 1) Extraction of organic additives: extract the test sample m with the first organic solvent for 5-8 hours to remove the surface solvent, and 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 material m1; 2) Decomposition of inorganic matter: Add dilute hydrochloric acid to the rubber 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 to 30 minutes, filter it, and dry it to constant weight to obtain the insoluble matter m2; 3) Decomposition of some inorganic substances and low-chain alkanes: Heat the insoluble matter m2 to 330-350°C, and then keep it at 330-350°C until constant weight, to obtain undecomposed matter m3; 4) Identification of the main resin by reflection method: Take the undecomposed product m3 for ATR test, read the characteristic peaks reflecting the structural characteristic functional groups, and determine the main type of rubber resin; 5) Quantitative analysis: The undecomposed product m3 is the mass of the main body of the rubber resin, and the mass content of the main body of the rubber resin in the test sample a=m 3 / m X 100%; Alternatively, place the undecomposed product m3 at the bottom of a glass test tube and heat it to 450°C ± 20°C in an electric furnace to pyrolyze the sample to constant weight to obtain the pyrolysis product m4. 1 H-NMR test for quantitative analysis; 6) Conduct LF-NMR test on the undecomposed product m3 to identify the degree of cross-linking after vulcanization and comprehensively determine the type of material tested.

2. The method for identifying vulcanized EPDM products according to claim 1, characterized in that: In step 1), the first organic solvent is at least one of isopropanol or methanol.

3. The method for identifying vulcanized EPDM products according to claim 2, characterized in that: In step 1), the first organic solvent is a mixed solvent of isopropanol and methanol in a volume ratio of 1:

3.

4. The method for identifying vulcanized EPDM products according to any one of claims 1 to 3, characterized in that: In step 1), the second organic solvent is at least one of acetone, dichloromethane or chloroform.

5. The method for identifying vulcanized EPDM products according to claim 4, characterized in that: In step 1), the second organic solvent is a mixed solvent of acetone and dichloromethane in a volume ratio of 1:1, or the second organic solvent is a mixed solvent of acetone and chloroform in a volume ratio of 1:

2.

6. The method for identifying vulcanized EPDM products according to any one of claims 1 to 3, characterized in that: In step 2), the mass concentration of dilute hydrochloric acid is 1 to 3 mol / L; 7. The method for identifying vulcanized EPDM products according to any one of claims 1 to 3, characterized in that: In step 4), the ATR test conditions are: diamond crystal, resolution 4cm -1 , scanning times 16 times, scanning range 500~4000cm -1 .

8. The method for identifying vulcanized EPDM products according to any one of claims 1 to 3, characterized in that: In step 5), 1 The conditions of H-NMR test are: 1 H-NMR operating frequency: 400 MHz, pulse sequence: zg30, solvent: deuterated chloroform, isotopic purity 99.8%, internal standard: tetramethylsilane, volume fraction 0.03%; experimental temperature: 298K.

9. The method for identifying vulcanized EPDM products according to any one of claims 1 to 3, characterized in that: In step 6), the conditions of the LF-NMR test are: resonance frequency: 22 MHz, magnet strength: 0.5 T, coil diameter: 10 mm, magnet temperature: 32 ° C; the sample to be tested is cut into rectangular strips of about 10 mm × 6 mm × 1 mm, and loaded into the bottom of a test tube with an outer diameter of 10 mm. The sample is kept at a constant temperature in an oven at 50 ° C for 10 min to make the temperature of each area of ​​the sample the same, and then moved to the heating area of ​​the nuclear magnetic resonance instrument, the temperature is set to 50 ° C, the constant temperature is stabilized for 5 minutes, and the sample is scanned; The sample adopts CPMG pulse sequence, test temperature: 90℃; 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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