This standard specifies the thermogravimetric method for determining the content of total organic matter, carbon black and ash in vulcanized rubber and rubber mixes. This standard applies to the following rubber vulcanized rubber or rubber mixes used alone or in combination. This standard does not apply to those rubbers that form carbon-containing residues when cracked. This standard does not apply to various vulcanized rubbers or rubber mixes that contain compounding agents that form carbon-containing residues when cracked. This standard does not apply to vulcanized rubber or rubber mixes that contain inorganic fillers that decompose or lose crystal water within the test temperature range. GB/T 14837-1993 Determination of the content of components in rubber and rubber products by thermogravimetric analysis GB/T14837-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Rubber and rubber products-Determination of composition by thermogravimetry
Rubber and rubber products-Determination of composition by thermogravimetryGB/T 14837-93
This standard adopts the international standard ISO/DIS9924--1992 Rubber and rubber products-Determination of composition by thermogravimetry".
1 Subject content and scope of applicationwwW.bzxz.Net
This standard specifies the thermogravimetric method for determining the content of total organic matter, carbon black and ash in vulcanized rubber and rubber mixes. This standard applies to the following rubbers used alone or in combination: natural rubber (or isoprene rubber).
Butadiene rubber.
Styrene-butadiene rubber.
Butyl rubber.
Ethylene-propylene rubber.
Other vulcanizates or rubber mixes may also be analyzed if the suitability of the method has been previously verified with known vulcanizates or rubber mixes containing similar components.
This standard does not apply to rubbers that form carbonaceous residues when cracked, such as fluorine- or nitrogen-containing rubbers. This standard does not apply to various vulcanizates or rubber mixes containing compounding ingredients that form carbonaceous residues when cracked, such as vulcanizates or rubber mixes containing cobalt salts, lead salts and phenolic resins. This standard does not apply to bowl-shaped vulcanizates or rubber mixes containing inorganic fillers that decompose or lose water of crystallization within the test temperature range. If it must be used, appropriate corrections must be made to the known filler characteristics. For vulcanizates or rubber mixes with a high sulfur content, such as hard rubber, the calculation of the total polymer content needs to be corrected. 2 Reference Standards
GB/T3516 Determination of Solvent Extracts in Vulcanized Rubber 3 Method Summary
3.1 According to the predetermined procedure, the weighed sample is heated from 70℃ to 300℃ in a nitrogen flow and kept constant for 10 minutes. The weight loss approximately reflects the content of volatile non-rubber components before 300C. Usually this value is not equal to the solvent extract content. 3.2 Then, the furnace temperature is raised to 550℃ under nitrogen flow and kept constant for 15 minutes. The weight loss between 70 and 550℃ represents the total amount of organic matter. 3.3 Under nitrogen flow, the furnace temperature is reduced from 550℃ to about 300℃ (the heating furnace can be turned off), and then the nitrogen is changed to oxygen or air, and the total gas flow rate is adjusted so that the apparent mass of the sample does not change. The furnace temperature is quickly raised to 650℃ and kept constant for 15 minutes or until constant weight. The weight loss in this interval indicates the mass of carbon black contained (if graphite exists, the temperature is raised to 850℃ to completely burn the graphite). 3.4 The mass of the residue at 650℃ (850℃ if graphite exists) indicates the mass of ash. Approved by the State Administration of Technical Supervision on December 30, 1993 824
Implementation on October 1, 1994
4 Reagents and Materials
GB/T 14837-93
When performing the various operations specified in this standard, especially when using compressed gases, attention should be paid to recognized health and safety precautions.
4.1 Dry nitrogen content is more than 99.999%. 4.2 Dry air or oxygen.
4.3 Calcium carbonate (HG31066) analytical grade. 4.4 Standard reference carbon black (GB9578).
5 Instruments
5.1 Thermogravimetric analyzer: Thermoanalyzers used in this method must be inspected according to the procedures specified in Chapter 6. 5.2 DTG auxiliary element: This method recommends the use of DTG differential thermogravimetric auxiliary elements. 5.3 Analytical balance: Graduation value 0.1 mg.
6 Inspection of thermogravimetric analyzer
6.1 Measurement of purge time (t,)
6.1.1 Place a quantitative amount (usually 4~10 mg) of carbon black or carbon black-containing rubber sample in the sample pan of the thermobalance and heat it to 650℃ under nitrogen. The nitrogen flow rate shall be based on the flow rate recommended in the instrument manual (usually 25~40mL/min). 6.1.2 Introduce air or oxygen and keep the temperature constant at 650℃ until the sample is completely burned. 6.1.3 After constant weight, turn off the heating furnace and let the instrument cool to room temperature under air or oxygen atmosphere. 6.1.4 When the temperature drops back to 25 ± 5 °C, place a certain amount (usually 4 to 10 mg) of carbon black sample into the sample pan of the thermogravimetric balance with pre-set conditions, and return the heating furnace to the working position. 6.7.5 Connect pure nitrogen and record the time (tt) at the same time, and raise the furnace temperature to 650 °C as quickly as possible, and then maintain a constant temperature. 6.1.6 Observe the mass change curve of the thermogravimetric analyzer, and record the corresponding time (t2) when constant weight is reached. Note: Check that there should be residual carbon black in the sample pan, because if all the carbon black is burned during heating, the balance can also indicate constant weight. 6.1.7 The purge time (t,) required to remove all oxygen from the system can be obtained by formula (1): tp = tz tj
Where: ti--time when nitrogen is connected, min; t2--time when the sample weighs constant after nitrogen is connected, min. (1)
6.2 Identification of carbon black and calcium carbonate:
Assuming that the nitrogen content used is greater than 99.999%, the purge time required is longer than that specified in 6.1, and the system is leak-proof, the furnace design and gas flow rate ensure that all carbon dioxide is driven out of the sample chamber. The instrument will be able to distinguish between carbon black and calcium carbonate. In order to check the operation of the thermogravimetric analyzer, the following instrument function tests are required. 6.2.1 Grind equal amounts of calcium carbonate and carbon black (the mass ratio between the two should be between 0.99 and 1.01). 6.2.2
Purge the instrument with nitrogen for a time not less than the purge time (t.). 6.2.3 Turn on the thermogravimetric analyzer and adjust the furnace temperature to 25 ± 5°C. 6.2.4 Place the carbon black-calcium carbonate mixture (see 6.2.1, usually 4 to 10 mg) in the balance pan of the thermogravimetric analyzer. 6.2.5 Return the heating furnace to its working position and purge the system with nitrogen at a constant rate (usually 25-40 mL/min) for a period of time of not less than t (see 6.1).
Raise the furnace temperature to 800°C at a rate of 10°C/min. 6.2.6
6.2.7 Maintain the furnace temperature at 800°C until constant weight is reached. 6.2.8 Reduce the furnace temperature to about 300°C at a rate of 20°C/min (or turn off the heating furnace and allow the temperature to cool naturally). 825
GB/T 14837-93
6.2.9 Close or partially close the nitrogen valve and introduce air or oxygen (4.2). In order to correct the buoyancy changes of the balance pan and the sample in gases of different densities, adjust the total gas flow through the instrument so that the apparent mass of the sample does not change. 6.2.10 Raise the furnace temperature to 800°C at a rate of 20°C/min. 6.2.11 Keep the furnace temperature at 800℃ for 15 minutes or until constant weight is reached. 6.2.12 Turn off the heating furnace and replace the airflow with pure nitrogen. Turn off the recorder and pour out the ash in the sample tray. Prepare for the next test.
6.2.13 Use formula (2) to determine the ratio (R): R = Am,/Am2
Where: Am1-the weight loss of the sample in a nitrogen atmosphere (or the number of grids in the weight loss curve); Am2
-the weight loss of the sample in an air or oxygen atmosphere (or the number of grids in the weight loss curve). 6.2.14 The ratio (R) should be 0.44 ± (0.022). If this condition is met, it is considered that the instrument meets the requirements. 7 Analysis steps
7.1 Turn on the thermogravimetric analyzer and stabilize the baseline. 7.2 Weigh a certain amount (usually 4 to 10 mg, accurately weighed to 0.1 mg) of the cut rubber sample and place it in the sample pan of the thermobalance. (2)
7.3 Return the heating furnace to its working position and purge the system with nitrogen at a constant flow rate (usually 25 to 40 mL/min). The time should not be shorter than the purge time (t,) (see 6.1).
Note: ① In some types of thermogravimetric analyzers, the recorder can be adjusted to 100% after the sample is placed. In this case, the m. value in 8.1 is equivalent to 100. and it is not necessary to weigh the sample accurately in advance.
② When heating in a nitrogen atmosphere, the presence of trace amounts of air or oxygen in the instrument will lead to erroneous results, and it is impossible to obtain a constant mass during the heating of the carbon black rubber sample at 550°C. In order to shorten the purge time, it is recommended to keep the nitrogen flow flowing even when the instrument is not in use. 7.4 Raise the furnace temperature to 300°C at a rate of 10°C/min. 7.5 Keep the furnace temperature at 300℃ for 10 minutes.
7.6 Raise the furnace temperature to 550℃ at a rate of 20℃/min. 7.7 Keep the furnace temperature at 550℃ for 15 minutes.
7.8 Reduce the furnace temperature to about 300℃ at a rate of 20℃/min (or turn off the heating furnace and let it cool naturally). 7.9 Close or partially close the nitrogen valve, and let in air or oxygen (4.2). Adjust the total gas flow through the instrument so that the apparent mass of the sample does not change.
7.10 Raise the furnace temperature to 650℃ (if graphite is present, raise the temperature to 850℃) at a rate of 20℃/min. 7.11 Keep the furnace temperature at 650℃ (if graphite is present, 850℃) for 15 minutes or until constant weight is reached. 7.12 Turn off the heating furnace and replace the gas flow with pure nitrogen flow. Turn off the recorder and pour out the residual ash from the sample tray. The instrument is now ready for the next test.
Note: Extract the sample with solvents as specified in GB3516 and determine the solvent extract. For EPDM, it is recommended to use the same solvent extraction sample as for natural rubber. 8 Representation of analysis results
8.1 Instruments that express mass readings in milligrams. 8.1.1 The mass percentage of the volatile components before 300°C is given by formula (3): Volatile components before 300°C (%) = m2 = m2l × 100 mo
Where: mo——mass of the sample, mg; m1——mass of the sample at the end of constant temperature at 300°C (see 7.5), mg. 826
· (3)
GB/T 14837-93
8.1.2 The mass percentage of the total organic component is given by formula (4): mo - m2 × 100
Total organic matter (%) -
Where: m2——mass of the sample at the end of constant temperature at 550°C (see 7.7), mg. 8.1.3 The mass percentage of carbon black or graphite component is given by formula (5): mz m3 × 100
Carbon black or graphite (%) =
Where: ma
·(4)
·(5)
The mass of the sample at the end of isothermal treatment at 650°C (graphite at 850°C, see 7.11) in air or oxygen, or in a mixture of nitrogen and oxygen or nitrogen and air, mg. 8.1.4 The mass percentage of ash is given by formula (6): m2 × 100
Ash (%) =
8.2 Instruments that can normalize the sample mass to 100%. 8.2.1 The mass percentage of the volatile component at 300°C is the percentage change in mass until the end of isothermal treatment at 300°C. 8.2.2 The mass percentage of the total organic matter is the percentage of mass change at the end of isothermal treatment at 550°C. (6)
8.2.3 The mass percentage of carbon black or graphite is the percentage of mass change at the end of isothermal treatment at 650°C (for carbon black) or 850°C (for graphite) in air or oxygen or in a mixture of nitrogen and air or oxygen. 8.2.4 The mass percentage of ash is the mass percentage of the residue at the end of isothermal treatment at 650°C (for graphite at 850°C) in air or oxygen or in a mixture of nitrogen and air or oxygen. It can be read directly from the mass-temperature or mass-time curve. 8.3 The approximate percentage of the total polymer content is given by formula (7): Total polymer content % = Total organic content % - Solvent extract % Where: Total organic content % - the percentage of the total organic content in the sample; Solvent extract % - the mass percentage of the solvent extract in the sample determined according to GB3516. 9 Test report This test report shall include the following: Indication of the use of this standard; Test results; Model of the instrument used; Final temperature reached; Abnormal phenomena occurring during the test; Any operation that is not included in this national standard but may affect the test results. Additional remarks: This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Beijing Rubber Industry Research and Design Institute of the Ministry of Chemical Industry. This standard was drafted by the Shenyang Rubber Industry Products Research Institute of the Ministry of Chemical Industry. The main drafter of this standard is He Xiaodong.
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