SH/T 0589-1994 Determination of Transition Temperature of Petroleum Waxes (Differential Scanning Calorimetry)

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Card type: Test method

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

• Standard number: SH/T 0589-94
• Chinese name: Determination of Transition Temperature of Petroleum Waxes (Differential Scanning Calorimetry)
• English name: not provided in the available source
• Replacement relationship: not provided in the available source (the additional notes state "equivalent adoption of the American Society for Testing and Materials standard ASTM D4419-94 'Determination of Paraffin Transition Temperature by Differential Scanning Calorimetry'")
• Proposing and technical custodianship: proposed and technically custodied by Fushun Research Institute of Petroleum and Petrochemicals; drafting unit: Fushun Research Institute of Petroleum and Petrochemicals; main drafter: Zhang Qiaoge
• Approval/implementation: approved by China Petrochemical Corporation 1994-03-10, implemented on 1994-10-01

2. Scope of application and non-applicability

• Applicable to paraffin wax and microcrystalline wax.
• Not applicable: not provided in the available source.

3. Method principle

Differential scanning calorimetry is a technique for measuring the relationship between the power difference supplied to a specimen and a reference material and temperature under program-controlled temperature. For the temperature at which solid-solid crystal form changes and solid-liquid state changes of petroleum wax occur, the temperature corresponding to the apex of the endothermic peak on the scanning curve obtained by this method is the transition temperature. Place the specimen and reference material in a differential scanning calorimeter, heat at a certain rate in a nitrogen stream; because the specimen undergoes an endothermic reaction, a temperature difference is generated between it and the reference material; through a microvolt amplifier and a heat compensator, the temperature difference is made equal to zero, and its electrical power is recorded to obtain the heat change of the specimen; the transition temperature is determined from the endothermic peak on the scanning curve.

4. Reagents and materials (purity / preparation)

• 4.1 Reagents: as standard substances for temperature calibration, purity should be greater than 99%. Commonly used standard substances are as follows:

• 4.2 Nitrogen.
• 4.3 Aluminum oxide: powder form, particle size less than 200 mesh (the source source-text extraction is "20() mesh", requires confirmation against the source standard (source-text extraction)).
• 4.4 Silica gel with moisture indicator.
• 4.5 Aluminum foil.

5. Instruments and equipment

• 5.1 Differential scanning calorimeter: either power-compensation type or heat-flux type. It is required to be able to heat and cool at a rate of 10℃/min±1℃/min, with a heating temperature of 15～150℃, a temperature reading accuracy of ±0.5℃, and to automatically record the power signal as a function of temperature. (The source source-text extraction is "1090/min[unreadable sign]19C /mi n" "15 - 1509 C", requires confirmation against the source standard (source-text extraction))
• 5.2 Specimen cup: made of aluminum or other metal with high thermal conductivity; copper and its alloys must not be used.
• 5.3 Recorder: records the change in heat with temperature.
• 5.4 Analytical balance: sensitivity 0.1 mg (the source source-text extraction is ".1 mgo", requires confirmation against the source standard (source-text extraction)).
• 5.5 Oven: temperature can reach 150℃±1℃.
• 5.6 Drying tower.
• 5.7 Beaker: 50 mL, several pieces.
• 5.8 Dropper: front-end inner diameter less than 1 mm (the source source-text extraction is "]nmo", requires confirmation against the source standard (source-text extraction)).
• 5.9 Flowmeter.
• 5.10 Stainless steel blade.

6. Recommended operating conditions

• Heating/cooling rate: 10℃/min±1℃/min.
• Heating temperature range: 15～150℃.
• Nitrogen flow rate: 10～50 mL/min (the source source-text extraction is "10 - 50n&/mino", requires confirmation against the source standard (source-text extraction)).
• Temperature reading accuracy: ±0.5℃.
• Specimen amount: 10 mg±1 mg (the source source-text extraction is "1oi[unreadable characters]1[unreadable character]", requires confirmation against the source standard (source-text extraction)).
• After cooling to 15℃±5℃, hold for 30 s.
• Heat again to 20℃±5℃ above the specimen melting point or drop melting point.

7. Sampling and specimen preparation

• 6.2 Specimen preparation: take about 1 g wax sample (the source source-text extraction is "about 1 flying wax sample", requires confirmation against the source standard (source-text extraction)) and place it in a 50 mL beaker; place the beaker in an oven and heat to about 10℃ above the wax sample melting point or drop melting point; use a dropper heated under the same conditions to take the melted wax sample and drop it onto a clean metal aluminum foil sheet so that it forms a thin wax sheet. Separate the wax sheet from the aluminum foil, then use a stainless steel blade to cut it into small pieces.
• 6.3 Sampling: separately weigh 10 mg±1 mg of specimen wax sheet and aluminum oxide powder in specimen cups and place them on the sample holder and reference holder, then cover the cup lids.

8. Analytical procedure

• 6.1 Temperature calibration: select a standard substance with purity greater than 99% whose melting point is close to the specimen melting point, and calibrate the instrument temperature according to the method provided by the instrument manufacturer.
• 6.2 Specimen preparation: see Section 7.
• 6.3 Sampling: see Section 7.
• 6.4 Open the nitrogen valve; the nitrogen must be dried through silica gel. Adjust the nitrogen flow rate to 10～50 mL/min.
• 6.5 Turn on the power, set the heating rate to the 10℃/min setting, and heat the specimen to 20℃±5℃ above the specimen melting point or drop melting point. Set the cooling rate to the 10℃/min setting, cool the specimen to 15℃±5℃, and hold for 30 s.
• 6.6 Set the heating rate to the 10℃/min setting, heat the specimen again, and record the scanning curve of all endothermic peaks from 15℃ to 20℃±5℃ above the specimen melting point or drop melting point.

9. Qualitative and quantitative determination and calculation formula

• On the scanning curve, extend the tangent lines of the slopes of each endothermic peak; the temperature corresponding to the intersection of the two slope tangent lines is the transition temperature. According to the order of peak appearance, denote them as T1A, T2A.
• The temperature corresponding to the intersection of the extrapolated slope tangent line and the baseline is the initial temperature of the endothermic peak T1O, T2O (the source source-text extraction is "Tlo", requires confirmation against the source standard (source-text extraction)), and the final temperature T1E, T2E.
• The difference between the final temperature and the initial temperature is the peak width of the endothermic peak.
• Use "℃" to report the first thermal transition temperature and final temperature of the endothermic peak of one scanning curve, namely T1A, T1E, and the second thermal transition temperature and final temperature T2A, T2E (the source source-text extraction is "T2F", requires confirmation against the source standard (source-text extraction)), with an accuracy of ±0.5℃, and values taken to one decimal place.

10. Precision

Use the following provisions to judge the reliability of test results (95% confidence level).

• 8.1 Repeatability: the allowable difference between two test results by the same operator is shown in the table below.
• 8.2 Reproducibility: the allowable difference between test results by different operators in two different laboratories is shown in the table below.

11. Report

Use "℃" to report the first thermal transition temperature and final temperature of the endothermic peak of one scanning curve, namely T1A, T1E, and the second thermal transition temperature and final temperature T2A, T2E, with an accuracy of ±0.5℃, and values taken to one decimal place.

12. Referenced documents

• GB/T 2539 Determination of Paraffin Wax Melting Point (Cooling Curve)
• GB/T 8026 Determination of Drop Melting Point of Petroleum Wax and Petrolatum

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 Q&A reference