GB/T 22232.2-2026Test method for the thermal stability of chemicals - Part 2: Adiabatic calorimetry (English PDF)

5.1 Adiabatic calorimeter

5.1.1 The adiabatic calorimeter shall be able to measure, display, and record changes in temperature and pressure over time and/or temperature, and shall meet the following requirements.

a) The exothermic detection sensitivity is no greater than 0.02 °C/min;

b) The maximum test temperature shall not be less than 450 °C;

c) The temperature display resolution is not less than 0.01 °C;

d) The maximum test pressure shall not be less than 15 MPa;

e) The pressure display resolution is not less than 1 kPa.

5.1.2 The adiabatic calorimeter consists of a testing unit, a control unit, and an auxiliary and safety system. Its main components include the following parts.

a) The test unit consists of components such as the furnace cover, furnace body, furnace heater, radiant heater, and instrument housing. (Structure diagram follows.) See Figure

2.Heaters are embedded in the furnace cover and furnace body, and radiant heaters are installed at the bottom of the furnace cavity to provide uniform heating. Controlled heating. The furnace cavity temperature sensor accuracy should reach ±0.1 °C, and the sample temperature sensor accuracy should reach ±0.1 °C. The pressure sensor accuracy should reach ±1 kPa.

5.2 Calorimeter Pool

5.2.1 The material can be stainless steel, titanium, Hastelloy, or other metals or glass. The shape should be spherical and the volume should not be less than 7 mL.

5.2.2 Based on the installation location of the sample temperature sensor, calorimeters can be divided into those with the sample temperature sensor inserted internally and those with the sample temperature sensor externally connected. There are three types of calorimeters. the sample temperature sensor sleeve embedded, the sample temperature sensor sleeve embedded, and the structural schematic diagram of the calorimeter is shown in Appendix A.

5.2.3 If the calorimeter and its connecting pipes are reused, the calorimeter and any pipes that the sample may come into contact with should be cleaned with solvent after the test. Remove any remaining samples or residue from other parts and keep them clean and dry to prevent cross-contamination and corrosion.

5.3 Balance The balance should have a weighing range of no less than 100 g and an accuracy of ±0.0001 g.

6.1 Calibration

6.1.1 The adiabatic calorimeter should be calibrated before initial use and when there are significant changes to the testing equipment system, such as replacing the temperature sensor or pressure sensor. Force sensors, heaters, furnaces, etc.; should be calibrated regularly according to the testing frequency during use.

6.1.2 If the entire instrument cannot be calibrated, then the calorimeter's calorimeter temperature sensor, furnace temperature sensor, and pressure sensor should be checked. The sensor readings are calibrated to meet the following calibration requirements.

a) The temperature indication error of the calorimeter pool is within the calibration range of 0 °C~350 °C, and the difference between the temperature indication and the actual value shall not exceed ±2 °C;

b) The temperature indication error of the heating furnace, with a calibration range of 0 °C ~ 350 °C, shall not differ from the temperature indication of the sample temperature sensor by more than [amount not specified]. ±3 °C;

c) Temperature rise rate indication error, the calibration range is the temperature rise rate within 20 minutes starting from the moment the calorimeter pool temperature reaches 100 °C, compared with the set value. The difference between the set values shall not exceed ±3%;

d) Pressure indication error, calibration range 0 kPa~15 MPa, the difference between the pressure indication and the actual value of the sealed pipeline connected to the calorimeter. Not exceeding ±10%.

6.2 Verification

6.2.1 After calibration, the adiabatic calorimeter should be verified using a reference material. During use, it should be verified periodically according to the testing frequency. For verification methods, please refer to Appendix B.

6.2.2 The commonly used reference material is a 20% (mass fraction) di-tert-butyl peroxide (DTBP) toluene solution.

7.1 Requirements

7.1.1 The sample volume should not exceed 2/3 of the calorimeter filling volume.

7.1.2 For highly reactive samples with unknown hazards, preliminary screening should be conducted using differential scanning calorimetry or an equivalent rapid screening calorimetry method. test.

7.1.3 For samples that are prone to chemical reactions with oxygen or water, such as alkyl aluminum, the samples should not come into contact with oxygen or water during the test operation.

7.1.4 For liquid samples with obvious backflow during the exothermic process, a flow-stopping device should be installed at the inlet of the calorimeter to prevent backflow.

7.2 Sample Pretreatment

7.2.1 Heterogeneous liquid samples, such as suspensions, should be homogenized beforehand; viscous liquid samples should be preheated.

7.2.2 Solid samples with a particle size larger than the diameter of the calorimeter inlet tube should be pre-sieved or crushed/ground. Before crushing or grinding the sample... It should be confirmed first that the crushing and grinding operations will not change the physicochemical properties of the sample.

7.2.3 For highly reactive solid samples, their thermal stability and impact/friction sensitivity should be assessed before crushing and grinding. Crushing and grinding should be carried out in accordance with... Adhere to the safe operating procedures for hazardous chemicals, and take effective protective and control measures in light of factors such as sample characteristics, operating environment, and equipment conditions. Measures include, but are not limited to, wearing protective gear, controlling the force and speed of operation, and using specialized protective equipment.

8.1 Safety Measures

8.1.1 Some chemicals involved in this test may release toxic, corrosive, or flammable gases. All test procedures should be conducted in an environment with effective ventilation. When operating in windy conditions, personnel should wear personal protective equipment appropriate for the hazards.

8.1.2 Samples with high reactivity should undergo preliminary screening tests. Based on the results of these tests, an appropriate sample quantity should be selected to prevent adverse reactions due to improper testing. Excessive sample volume caused the calorimeter to rupture.

8.1.3 The pipeline connecting the calorimeter and the pressure sensor should be checked regularly for blockages, and cleaned or replaced in a timely manner.

8.1.4 Before opening the pressure relief valve to reduce pressure and disassembling the calorimeter after the test, the potential hazards of pressure release and remaining samples in the calorimeter should be analyzed. Potential hazards to test operators (e.g., isocyanate generates hydrogen cyanide at high temperatures, acrylonitrile generates hydrogen cyanide at high temperatures, alkyl aluminum thermal testing) (The vehicle may still spontaneously combust after testing), and necessary safety measures should be taken, including but not limited to wearing a gas mask, protective gloves, and goggles, in well-ventilated areas. Operate in well-ventilated areas, equipped with fire extinguishers, etc., to avoid injury to test personnel.

8.2 Test Environment

8.2.1 The test shall be conducted in an environment with a temperature of 15 °C to 35 °C and a relative humidity of no more than 85%.

8.2.2 The adiabatic calorimeter should be installed in a well-ventilated environment, or the outlet of the pressure relief valve should be connected to a suitable well-ventilated environment; The area is free from strong vibrations and corrosive gases, and other cold and heat sources should be avoided.

8.3 Parameter Settings

8.3.1 Select appropriate parameter settings based on the actual situation. The experimental parameter settings are as follows:

a) The test start temperature should be at least 10 °C lower than the initial exothermic temperature of the sample;

b) The end temperature of the test should not exceed the highest test temperature of the adiabatic calorimeter;

c) The temperature rise interval should be set within the range of 3°C to 10°C, and preferably set to 5°C;

d) Waiting time, set within the range of 15 min ~ 30 min, preferably set to 15 min;

e) Search time, set within the range of 5 min ~ 10 min, preferably set to 5 min;

f) The exothermic detection sensitivity should not exceed 0.02 °C/min.

8.3.2 Select the headspace atmosphere of the calorimeter pool according to the test requirements.

8.4 Test Procedure

8.4.1 Select the amount of material that will not chemically react with the sample based on the physicochemical properties of the sample and the maximum pressure range during the test. The hot pool, weigh and record the mass of the hot pool (mb), excluding the mass of the nut and sealing gasket.

8.4.2 Check the airtightness of the system by conducting a pressure test using inert gas to ensure that the calorimeter, piping, and connections can withstand the pressure during the test. It maintains an effective seal and prevents leakage.

8.4.3 Place the weighed calorimeter on the balance, zero the balance after weighing, add an appropriate amount of sample, weigh and record the mass of the added sample. ms, install the calorimeter containing the sample into the adiabatic heating furnace in preparation for testing.

8.4.4 Set up and run the test program until the test is completed.

8.4.5 Record the temperature and pressure data during the test, and observe the initial heat release temperature (T0), the maximum heat release temperature (Tmax), and the termination temperature. Parameters such as thermal temperature (Tf) and time to reach the measured maximum reaction rate (TMR).

8.4.6 After the test is completed and the temperature of the exothermic reaction system of the sample returns to room temperature, record the temperature and pressure of the calorimeter bath after it has cooled to room temperature.