NB/SH/T 0901-2015 Determination of glass transition temperature of mineral oils — Differential scanning calorimetry

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Card type: Test method

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

• Standard number: NB/SH/T 0901—2015
• Chinese full title: Determination of glass transition temperature of mineral oils — Differential scanning calorimetry
• English title: Standard test method for determining the glass transition temperatures of mineral oil—Differential scanning calorimetry
• Replacement relationship: This standard is issued for the first time (original text: This standard is issued for the first time)
• Drafting rules: Drafted in accordance with GB/T 1.1—2009
• Reference relationship: Prepared using the redrafting method with reference to ASTM E1356-08 "Test method for determination of glass transition temperature by differential scanning calorimeter", and the degree of consistency with ASTM E1356-08 is non-equivalent
• Publication/implementation: Published on 2015-10-27, implemented on 2016-03-01; 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/TC.280/SC1)
• Drafting organization: Lanzhou Lubricating Oil Research and Development Center of PetroChina Company Limited
• Main drafters: Hu Yuhua, Liu Yan, Wang Peng, Wang Yi, Tu Wei, Zhang Yu

2. Scope of application and non-applicability

• This standard specifies a method for determining the glass transition temperature of mineral oils using a differential scanning calorimeter.
• It is applicable to the determination of the glass transition temperature of mineral oils, especially rubber filling oils.
• The glass transition temperature of the samples used in the precision statistical test is between -103.0 ℃ and -37.4 ℃ (original text is "-103.0C~-37.4°", unit symbol requires confirmation against the source standard (source-text extraction)).
• This standard may also be applicable when the glass transition temperature is not within this range, but if the glass transition temperature of the test sample exceeds the temperature range of the samples used in the precision verification test, the precision of the method may not be applicable.
• Non-applicable items: no explicit "non-applicable" clause is listed in the available source.

3. Method principle

The mineral oil is heated or cooled at a controlled rate, the heat flow difference or temperature difference between the reference standard sample and the mineral oil test sample is scanned, and the glass transition temperature is calculated by analyzing the differential thermal curve in the glass transition region. (Original text Chapter 4 Method summary)

4. Reagents and materials (purity / preparation)

• 8.1 Reference standard sample: The inert reference standard sample should have approximately the same heat capacity as the test sample; the inert reference standard sample may be an empty crucible.
• 8.2 Standard sample: A material with one or more sufficiently homogeneous and determined thermal properties. This material can be used for calibration of differential scanning calorimeters, evaluation of measurement methods, and evaluation of materials. For temperature calibration, it is recommended to use high-purity cyclohexane and metallic mercury below 0 ℃, and above 0 ℃, high-purity diphenyl ether, metallic indium, metallic bismuth, metallic lead, metallic zinc, etc. recommended in ASTM E967 may be used.
• 8.3 Nitrogen and helium: used for gas purging, high purity, purity ≥99.9%.

5. Instruments and equipment

• 7.1 Differential scanning calorimeter
  • 7.1.1 Differential scanning calorimeter (DSC calorimeter): The main unit consists of a test cell, a temperature sensor, a heat flow sensor, an inert gas purge system for the test cell, and a temperature controller.
  • 7.1.2 Test cell: Consists of a heating furnace capable of uniformly heating (or cooling) the test sample and the reference standard sample, so that the test sample and the reference standard sample can be held at a constant temperature to a certain temperature point, or heated (or cooled) at a fixed rate, with a temperature range of -100 ℃ to 500 ℃ (original text is "-100°~500C", unit symbol requires confirmation against the source standard (source-text extraction)).
  • 7.1.3 Temperature sensor: Capable of providing a display of the test sample temperature, with an accuracy of at least ±0.1 ℃.
  • 7.1.4 Heat flow sensor: Capable of measuring the small heat flow difference between the test sample and the reference standard sample, with a sensitivity of at least ±MW (original text is "±MW", suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
  • 7.1.5 Inert gas purge system for the test cell: Capable of maintaining an inert gas environment in the test cell, with a gas flow rate adjustable from 10 mL/min to 100 mL/min, accuracy 4 mL/min (original text is "accuracy 4mL/min", suspected missing "±", requires confirmation against the source standard (source-text extraction)); dual inert gas protection is used, and helium is required inside the furnace and nitrogen outside the furnace.
  • 7.1.6 Temperature controller: Controls the temperature program by operating the heating furnace, executing the heating rate required by the instrument manufacturer's design within -160 ℃ to 500 ℃, with a temperature control accuracy of at least: 0.5%/min (original text is "0.5%/min", suspected to be source-text extraction noise, requires confirmation against the source standard (source-text extraction)).
  • 7.1.7 The differential scanning calorimeter also needs to be equipped with a liquid nitrogen refrigeration system and a sample sealing press.
• 7.2 Data acquisition system: Acquires, stores, and displays measured and/or calculated signals. The signals output by this system should at least include heat flow, temperature, and time.
• 7.3 Aluminum crucible: Does not undergo chemical reaction with the test sample and reference standard sample, has a suitable shape, and can completely contain the test sample and reference standard sample.
• 7.4 Analytical balance: Maximum capacity exceeds 100 mg, readability 0.01 mg.

6. Recommended operating conditions

• 6.1 The heating (cooling) rate will affect the measurement results, so it should be stated in the test report.
• 6.2 The test should be carried out under inert gas protection. The glass transition temperature of mineral oils is generally below -30 ℃. During low-temperature testing, helium should be used inside the furnace.
• 6.3 The sample amount is on the milligram scale. Correct sampling techniques should be used to ensure the sample is homogeneous and representative.
• 11.2 Inert gas protection is carried out both inside and outside the furnace. Nitrogen is used outside the furnace and helium inside the furnace. The nitrogen gas flow rate is 50 mL/min, and the helium gas flow rate is 25 mL/min. Raise the sample to 60 ℃ at a rate of 10 ℃/min to eliminate the influence of thermal history on the sample. Note: Other rates may also be used, but should be stated in the report.
• 11.3 Use an isothermal program of 5 min to maintain temperature equilibrium.
• 11.4 Cool the sample to below the glass transition temperature by 50 ℃ at a rate of 5 ℃/min. Note 1: The linear cooling rate capability may differ among different differential scanning calorimeters. As long as linear cooling to below the glass transition temperature by 50 ℃ can be achieved, other cooling rates may also be used, but should be stated in the report. Note 2: When operating at low temperature, helium should be used inside the furnace. In addition to providing an inert gas atmosphere, helium has a higher thermal conductivity than nitrogen, improving the resolution of the instrument; the inert gas outside the furnace mainly provides a dry environment, especially in environments with high humidity. Other inert gases may also be used outside the furnace, and other gas flow rates may also be used, but should be stated in the report.
• 11.5 Use an isothermal program of 5 min to maintain temperature equilibrium.
• 11.6 Raise the sample to at least 20 ℃ above the glass transition temperature at a heating rate of 10 ℃/min, and record the differential thermal curve until the desired glass transition is completed. Other heating rates are also acceptable, but should be stated in the report.
• 10.2 The temperature calibration parameter settings are the same as those during the test. Use dual-path protective gases of nitrogen and helium. The nitrogen gas flow rate is 50 mL/min, and the helium gas flow rate is 25 mL/min. Heat at a rate of 10 ℃/min.

7. Sampling and sample preparation

• 9 Sampling: Unless otherwise specified, sampling should be carried out in accordance with the provisions of GB/T 4756.
• 11.1 Accurately weigh 5 mg to 20 mg of test sample and place it into an aluminum crucible and seal it well. A reference standard sample may be used, but the heat capacity of the reference standard sample should be as close as possible to the heat capacity of the test sample; an empty crucible may also be used as the reference standard sample.

8. Analysis procedure

• 11.1 Accurately weigh 5 mg to 20 mg of test sample and place it into an aluminum crucible and seal it well.
• 11.2 Inert gas protection is carried out both inside and outside the furnace of the differential scanning calorimeter. Nitrogen is used outside the furnace and helium inside the furnace. The nitrogen gas flow rate is 50 mL/min, and the helium gas flow rate is 25 mL/min. Raise the sample to 60 ℃ at a rate of 10 ℃/min to eliminate the influence of thermal history on the sample.
• 11.3 Use an isothermal program of 5 min to maintain temperature equilibrium.
• 11.4 Cool the sample to below the glass transition temperature by 50 ℃ at a rate of 5 ℃/min.
• 11.5 Use an isothermal program of 5 min to maintain temperature equilibrium.
• 11.6 Raise the sample to at least 20 ℃ above the glass transition temperature at a heating rate of 10 ℃/min, and record the differential thermal curve until the desired glass transition is completed.
• 11.6 If the glass transition region of the differential thermal curve is covered by a cold crystallization peak (see Figure 2), this phenomenon may be caused by an excessively fast linear cooling rate. In this case, the cold crystallization peak should be eliminated, and it is not necessary to reweigh the sample. Proceed with the test as follows:
  • 11.6.1 Determine the peak top temperature of the cold crystallization peak using the analysis software.
  • 11.6.2 Cool to the above peak top temperature at a rate of 5 ℃/min. Note: Other rates may also be used, but should be stated in the report.
  • 11.6.3 Hold at the peak top temperature for 10 min to allow the sample to crystallize as completely as possible.
  • 11.6.4 Cool to below the glass transition temperature by 50 ℃ at a rate of 5 ℃/min, and maintain constant temperature for 5 min. Note: Other rates may also be used, but should be stated in the report.
  • 11.6.5 Raise the sample to at least 20 ℃ above the glass transition temperature at a rate of 10 ℃/min, and record the differential thermal curve; at this time, an obvious glass transition region will appear (see Figure 3). If the phenomenon of the glass transition region being covered by a cold crystallization peak does not occur, the above test is not necessary. Note: Other rates may also be used, but should be stated in the report.
• 11.7 Use dedicated software to analyze and calculate the glass transition temperature, using the midpoint temperature to represent the glass transition temperature, with the result retained to one decimal place.
• 11.8 After analyzing and calculating the glass transition temperature of the test sample, re-test the mass of the test sample to ensure that no mass loss and no decomposition occurred during the determination. Note: The initial boiling point of most mineral oil products is higher than 60 ℃, and most will not undergo mass loss.

9. Qualitative and Quantitative and Calculation Formulas

• 3.5 The transition points related to the glass transition region are shown in Figure 1. The relevant transition points are defined as follows:
  • 3.5.1 Extrapolated end temperature (Te): the temperature corresponding to the intersection of the tangent at the maximum slope of the glass transition curve and the extrapolated baseline after the glass transition.
  • 3.5.2 Extrapolated onset temperature (Ti): the temperature corresponding to the intersection of the tangent at the maximum slope of the glass transition curve and the extrapolated baseline before the glass transition. (The original symbol is “T:”, requires confirmation against the source standard (source-text extraction))
  • 3.5.3 Inflection point temperature (Ti): the temperature corresponding to the intersection of the tangent drawn at the point of maximum slope (relative to time) of the glass transition curve and the differential thermal curve. (The original symbol is “T:”, requires confirmation against the source standard (source-text extraction))
  • 3.5.4 Midpoint temperature (Tm): the temperature corresponding to the intersection of the heat flow rate and the differential thermal curve at 1/2 between the extrapolated onset temperature and the extrapolated end temperature along the heat flow axis direction.
  • 3.5.5 First deviation temperature (To): the temperature corresponding to the intersection of the tangent where the differential thermal curve first deviates from the baseline on the low-temperature side of the glass transition region and the differential thermal curve. (The original symbol is “T.”, requires confirmation against the source standard (source-text extraction))
  • 3.5.6 Return-to-baseline temperature (Tr): the temperature corresponding to the intersection of the tangent where the differential thermal curve last deviates from the baseline on the high-temperature side of the glass transition region and the differential thermal curve. (The original symbol is “T,”, requires confirmation against the source standard (source-text extraction))
• 11.7 The midpoint temperature is used to represent the glass transition temperature, and the result is retained to one decimal place.
• Calculation formula: not provided in the available source.

10. Precision

• 13.1 Precision: This precision statistical test was completed in 5 laboratories using 10 mineral oil samples (including 7 rubber filling oil samples), in accordance with the relevant provisions of GB/T 6683. The reliability of test results is judged according to the following provisions (95% confidence level).
  • 13.1.1 Repeatability r: The difference between two test results obtained by the same operator in the same laboratory, using the same instrument under the same operating conditions, on the same test sample in continuous determinations shall not exceed 0.5 ℃ (the original text is “0.5Y”, the unit symbol requires confirmation against the source standard (source-text extraction)).
  • 13.1.2 Reproducibility R: The difference between two single, independent test results obtained by different operators in different laboratories, using different instruments under the same operating conditions, on the same test sample shall not exceed 1.5 ℃ (the original text is “1.5C”, the unit symbol requires confirmation against the source standard (source-text extraction)).
• 13.2 Bias: Since there are no reference literature data for the glass transition temperature of mineral oils, this standard does not specify bias.

11. Report

12 The result report shall include:

• 12.1 Description of the mineral oil product.
• 12.2 Parameters of the differential scanning calorimeter equipment.
• 12.3 Description of the size, geometry, and material of the aluminum crucible.
• 12.4 Heating/cooling rate.
• 12.5 Description of the temperature and heat flow calibration procedures.
• 12.6 Information such as the choice of inert gas, gas flow rate, and purity.
• 12.7 The midpoint temperature is used to represent the glass transition temperature.
• 12.8 Whether treatment to eliminate the cold crystallization peak was performed.

12. Referenced Documents

• GB/T 4756 Petroleum liquids—Manual sampling
• GB/T 6683 Petroleum products—Determination of precision data in relation to methods of test
• ASTM E967 Standard test method for temperature calibration of differential scanning calorimeters and differential thermal analyzers (Standard Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers)
• Reference: ASTM E1356-08 “Test Method for Determination of Glass Transition Temperature by Differential Scanning Calorimeter” (non-equivalent reference)
• Drafting rules: GB/T 1.1—2009

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 Q&A