NB/SH/T 0859-2013 Determination of thermal stability of chemical substances by thermal analysis

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: NB/SH/T 0859—2013
• Chinese title: Determination of thermal stability of chemical substances by thermal analysis
• English title: Standard test method for the thermal stability of chemicals by thermal analysis
• Replacement relationship: not provided in the available source (the foreword only states that it was modified and adopted using the redrafting method from ASTM E537-07, and does not mention the old standard number replaced)
• Adoption relationship: modified and adopted using the redrafting method from ASTM E537-07 "Standard Test Method for Thermal Stability of Chemical Substances by Differential Scanning Calorimetry"
• Publication/implementation: published by 2013-06-08, implemented by 2013-10-01; issued by the National Energy Administration
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC1)
• Drafting organization: Sinopec Research Institute of Petroleum Processing; participating drafting organizations: Sinopec Catalyst Changling Branch, National Institute of Metrology, National Chemical Building Materials Testing Center
• Main drafters: Zhou Li, Zou Kang

2. Scope of application and non-applicability

• 1.1 specifies the method for determining the approximate temperature and enthalpy change at which a micro sample undergoes an enthalpy change using differential scanning calorimetry (DSC), and the method for determining the approximate temperature at which a micro sample undergoes an enthalpy change using differential thermal analysis (DTA).
• 1.2 is applicable to samples existing in solid, liquid, or slurry form.
• 1.3 is applicable to tests conducted in inert gas or active gas, with a temperature range of 27 ℃~1200 ℃.
• 1.4 uses International System of Units [SI] units.
• Application of 1.5 may involve certain hazardous materials, operations, and equipment, but it does not address all safety issues associated with them; users are responsible for establishing appropriate safety and protective measures before use and for determining the applicability of relevant regulatory restrictions. For special safety precautions, see Chapter 8.
• Non-applicability: no explicit "non-applicability" clause is provided in the available source; the foreword states that this standard deletes the tests with pressure and related definitions, methods, etc. (China already has current petrochemical industry standards regulating tests with pressure).

3. Method principle

• 4.1 In the DSC or DTA test... (the original text here source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction))
• 4.2 Place the test sample and the reference material separately in two identical sample containers.
• 4.3 At a heating rate of 2 ℃/min (the original text here source-text extraction is suspected to be "2C/min", requires confirmation against the source standard (source-text extraction)), in a balanced atmosphere, heat the sample and the reference material synchronously. Record the analysis curve with heat flow (Δq) or temperature difference (ΔT) as the ordinate and temperature (T) or time (t) as the abscissa.
• 4.4 When the sample undergoes an enthalpy change, the baseline shifts and an endothermic peak or exothermic peak appears.
• 4.5 The DSC test determines and reports the extrapolated onset temperature (T₀), peak temperature (Tₚ), and enthalpy change (ΔH); the DTA test determines and reports the peak temperature (Tₚ).

4. Reagents and materials (purity / preparation)

• 10.3 Within the test range, the reference material must not undergo any thermal reaction. Typical reference materials include high-temperature calcined alumina, glass beads, silicone oil, or an empty container.
• 7.2.1.4 Note 1: When oxygen in the air affects the test results, nitrogen, helium (the gas identity is unclear in the source transcription; its interpretation as helium remains unverified), or argon with a purity above 99% should be used. Unless the effect of humidity needs to be studied, dry gas is recommended, especially when experiments are conducted at low temperatures.
• Test gas: inert (such as argon, helium, nitrogen) or active (such as air) gas.
• Preparation of other reagents: not provided in the available source.

5. Instruments and equipment

• 7.1 The instruments used in this standard are a differential scanning calorimeter (DSC) and a differential thermal analyzer (DTA).
• 7.2 The differential scanning calorimeter (DSC) and differential thermal analyzer (DTA) consist of the following parts:
  • 7.2.1 The sample chamber shall include:
    • 7.2.1.1 Furnace: capable of heating the sample and reference material synchronously to a constant temperature or controlling the temperature within the required range at a constant heating rate.
    • 7.2.1.2 Temperature sensor: capable of indicating the temperature of the sample and accurate to between ±0.5 ℃.
    • 7.2.1.3 Difference sensor: detects the temperature difference or heat flow difference between the sample and reference material, with a sensitivity of 0.1 ℃ or 0.2 mW.
    • 7.2.1.4 A device capable of maintaining an inert (such as argon, helium, nitrogen) or active (such as air) atmosphere in the sample chamber at a rate of 50 mL/min±5 mL/min.
    • 7.2.1.5 Temperature controller: by controlling the heating furnace, controls the temperature change process within a selected temperature range (27 ℃–1200 ℃) at a rate of 2 ℃/min–20 ℃/min (stable at 0.1 ℃/min). Note: If a suitable cooling system is used, the test temperature range can be lowered to -153 ℃, and if the equipment permits, the temperature range can be raised to 1400 ℃ or higher.
    • 7.2.1.6 Recorder: digital or analog, capable of completely recording and displaying a curve with heat flow difference or temperature difference as the ordinate and temperature as the abscissa, including signal noise.
  • 7.2.2 If low-temperature testing is performed, a cooling system capable of rapidly cooling the sample chamber and maintaining a constant low temperature is required.
• 7.3 Sample containers (sample pans, crucibles, small containers, etc.): do not react with the sample and reference material, have a suitable and complete structure and shape, and can hold the sample and reference material as required by the test.
• 7.4 Balance: capable of weighing no less than 100 mg of sample or container or both, with a sensitivity of at least 10 μg.

6. Recommended operating conditions

• 11.1 Sample amount: in the DSC test, the sample amount is generally 5 mg; if the signal is greater than 8 mW, the sample amount should be appropriately reduced; in the DTA test, the sample amount is generally 50 mg; if the signal is greater than 20° (the original unit is missing, requires confirmation against the source standard (source-text extraction)), the sample amount should be appropriately reduced. Note: To ensure safety, for unknown samples, the sample amount for the initial test is recommended to be 1 mg or less; if it is confirmed that the exothermic reaction is not violent, the sample amount can be gradually increased.
• 11.2 Heating rate: generally 10 ℃/min–20 ℃/min. If an exothermic reaction immediately follows an endothermic reaction (see 3.3 Note and Figure 3), a lower heating rate is recommended, such as 2 ℃/min–6 ℃/min. Note: The extrapolated onset temperature and peak temperature are both affected by the heating rate; only results obtained using the same heating rate are comparable.
• 11.3 Temperature range: generally 27 ℃~1200 ℃.
• 7.2.1.4 Gas supply rate: 50 mL/min±5 mL/min; Note 2: Other gas supply rates may be used, but should be noted in the report.

7. Sampling and sample preparation

• 10.1 The sample amount depends on factors such as the properties of the material, the required dilution, the sensitivity of the instrument, the magnitude of the enthalpy change, and the heating rate. In addition, for unknown samples, the possibility of sudden release of a large amount of energy must be considered. Therefore, this standard should sample as little as possible, with a sampling amount between 1 mg~50 mg.
• 10.2 The sample should be representative, such as in terms of particle size and purity.
• 12.1 Weigh and record the mass of the empty sample container, and weigh and record the sample mass m in units of mg, accurate to ±10 μg.
• 8.2 When grinding is required to reduce the sample particles, the operator should assume that the sample is sensitive to stimuli such as friction and static electricity, so appropriate tests should be conducted before grinding to test its sensitivity. When preparing samples with unknown hazards, the operator must use appropriate protective equipment. If a current material safety data sheet is available, it should be adopted and studied before handling unknown materials.

8. Analysis procedure

• 12.1 Weigh and record the mass of the empty sample container, and weigh and record the sample mass m in units of mg, accurate to ±10 μg.
• 12.2 As needed, pass the required gas into the measuring cell at an appropriate flow rate.
• 12.3 As needed, heat the measuring cell at a rate of 2 ℃/min~20 ℃/min until the required temperature, or until the sample is completely destroyed/volatilized, while recording the DSC or DTA signal. For most organic substances, the commonly used temperature range is 20 ℃~500 ℃. Note 1: Other heating rates may also be used, but must be stated in the report. Note 2: Increasing the heating rate may enhance the signal, and the temperature of the measured thermal reaction will also increase.
• 12.4 For any observed thermal reaction (see Figure 1), record the extrapolated onset temperature (T₀) and peak temperature (Tₚ).
• 12.5 After the test is completed, return the measuring cell to room temperature. Note: When encountering complex enthalpy changes, it is recommended to conduct the test at a slower heating rate (2 ℃/min~10 ℃/min) (see Figure 3 and Note 3.3).
• 12.6 Calculate the enthalpy change of the thermal reaction according to the procedure in Chapter 13.
• 9 Calibration: calibrate according to the method recommended by the instrument manufacturer in the user manual or according to the method in GB/T 13464.

9. Qualitative and quantitative and calculation formulas

• 13.1 Draw a straight line connecting a point on the baseline before the exothermic reaction to a point on the baseline after the reaction is completed (see Figure 4).
• 13.2 Integrate the area under the reaction enthalpy change curve as a function of temperature.
• 13.3 Calculate the reaction enthalpy change according to formula (1), retaining the significant decimal places.
  • ΔH = A/m ……（1）
  • Where:
    • ΔH—— reaction enthalpy change, J/g;
    • m—— mass of the test sample, mg;
    • A—— area of the exothermic curve, mJ.
• Qualitative indicators: DSC test determination and report the extrapolated onset temperature (T₀), peak temperature (Tₚ), and enthalpy change (ΔH); DTA test determination and report the peak temperature (Tₚ) (see 4.5).

10. Precision

• 15.1 From 2007 to 2009, in three laboratories, using 2 instruments and 19 test samples, the precision of the reaction enthalpy change and extrapolated onset temperature of ASTM E537-07 was verified. In four laboratories, using 5 different models of instruments and 21 test samples, referring to the method of GB/T 6379.2, the precision of the peak temperature in the temperature range of 27 ℃~1200 ℃ was calculated; the calculation results are shown in Appendix A.
• 15.2 Repeatability (95% confidence level): The variation of results within a laboratory can be evaluated by the repeatability value (r) obtained by multiplying the repeatability standard deviation by 2.8 and applying appropriate corrections. The difference between two results obtained by the same operator in the same laboratory using the same instrument on the same sample for repeated tests shall not exceed the repeatability value (r).
  • 15.2.1 The relative standard deviation of repeatability of the reaction enthalpy change is 3.5%.
  • 15.2.2 The repeatability standard deviation of the extrapolated onset temperature is 0.2 ℃ (the extrapolated-onset-temperature value is garbled in the source transcription and remains unverified).
• 15.3 Reproducibility (95% confidence level): The variation of results between laboratories can be evaluated by the reproducibility value (R) obtained by multiplying the reproducibility standard deviation by 2.8 and applying appropriate corrections. The difference between two single, independent results obtained by different operators in different laboratories using different instruments on the same sample shall not exceed the reproducibility value (R).
  • 15.3.1 The relative standard deviation of reproducibility of the reaction enthalpy change is 4.7%.
  • 15.3.2 The reproducibility standard deviation of the extrapolated onset temperature is 3.4 ℃.
• 15.4 Bias: Bias is the difference between the test result and the standard value. This standard compares the average values of the enthalpy change and extrapolated onset temperature of indium and zinc measured within and between three laboratories in their respective laboratories with the standard values; the results are shown in Table 1.
• Table 1 Test results and bias of the enthalpy change and extrapolated onset temperature of indium and zinc (source-text extraction table is incomplete, some data require confirmation against the source standard (source-text extraction)):
  • Indium: standard value of extrapolated onset temperature 156.6 ℃; laboratory I 157 ℃; laboratory II 156.6 ℃; laboratory III 156.6 ℃; bias 0.5 ℃ (correspondence requires confirmation against the source standard (source-text extraction)).
  • Zinc: standard value of extrapolated onset temperature 420.6 ℃ (the original text source-text extraction is "422.8/419.", requires confirmation against the source standard (source-text extraction)); bias 1.0 ℃ (correspondence requires confirmation against the source standard (source-text extraction)).
  • Enthalpy change (J/g): within-laboratory average values 28.8, 28.9, 28.9, 28.6, 29.1; between-laboratory average values 109.1, 112.6, 109.3, 110.3, 107.5; standard values 28.9 (indium), 107.5 (zinc) (correspondence requires confirmation against the source standard (source-text extraction)); bias 0.3, 2.8 (correspondence requires confirmation against the source standard (source-text extraction)).
• Appendix A (informative appendix) Calculation results of peak temperature precision:
  • A.1 Overview: From 2007 to 2009, in four laboratories, using 5 different models of instruments, using a total of 21 test samples including polymers, kaolin, molecular sieves, indium, and zinc, referring to the method of GB/T 6379.2, the precision of the peak temperature in the temperature range of 27 ℃~1200 ℃ was calculated.
  • A.2 Repeatability (95% confidence level): The repeatability standard deviation is 0.4 ℃ in the temperature range of 27 ℃~527 ℃ (the original text source-text extraction is "0.44C", requires confirmation against the source standard (source-text extraction)), and is 0.87 ℃ in the temperature range of 527 ℃~1200 ℃; the repeatability value is 1.30 ℃ in the temperature range of 27 ℃~527 ℃, and is 3.00 ℃ in the temperature range of 527 ℃~1200 ℃.
  • A.3 Reproducibility (95% confidence level): The reproducibility standard deviation is 1.00 ℃ in the temperature range of 27 ℃~527 ℃, and is 7.98 ℃ in the temperature range of 527 ℃~1200 ℃; the reproducibility value is 2.80 ℃ in the temperature range of 27 ℃~527 ℃, and is 23.00 ℃ in the temperature range of 527 ℃~1200 ℃.

11. Report

• 14.1 Composition, compound, chemical formula, all information on sample preparation and/or pretreatment.
• 14.2 Instrument and sample container.
• 14.3 Composition and flow rate of the test gas.
• 14.4 Heating rate and temperature range.
• 14.5 Record the extrapolated onset temperature and peak temperature determined from the DSC curve. Record the peak temperature determined from the DTA curve. Record changes that may affect the test results (such as melting).
• 14.6 Record the enthalpy change determined from the DSC curve.

12. Normative references

• GB/T 6379.2 Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method (GB/T 6379.2—2004, ISO 5725.2:1994, IDT)
• GB/T 13464 Thermal analysis test method for thermal stability of substances (the original text source-text extraction is "CB/T 13464", requires confirmation against the source standard (source-text extraction))
• ASTM E537-07 "Standard Test Method for Thermal Stability of Chemicals by Differential Scanning Calorimetry" (modified adoption)

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Reference for Questions and Answers