GB/T 21617-2023Dangerous goods—Test methods for oxidizing solids (English PDF)

3.1 Cellulose

Dry white chemical fiber with a length of less than 100 µm, an average diameter of about 25 µm, an apparent density of about 170 kg/m³, and a pH value of 5 ~ 7.

5.1.2.1 Preparation of calcium peroxide standard substance

e) particle size: the proportion of particles with a particle size less than 75 µm is greater than or equal to 99 %, of which the proportion of particles with a particle size less than 20 µm is greater than or equal to 50 %. […]

5.1.2.2 Preparation of cellulose

Make the cellulose into a layer with a thickness of not more than 25 mm, dry it at 105 °C to constant mass (for at least 4 h), and then place it in a desiccator (with desiccant) until it cools down and is ready for use. The moisture content shall be less than 0.5 % on a dry weight basis. If necessary, the drying time shall be extended to ensure that the moisture content is less than 0.5 %.

5.1.2.3 Sample inspection

Inspect the substance to be used for transportation. If the powder with a diameter of less than 500 µm accounts for more than 10 % of the total mass, or it is fragile, all test samples shall be ground into powder before test to avoid particle size reduction during loading and unloading and transportation. Since particle size has a great influence on the results, the particle size of the tested solid shall be stated in the test report.

5.1.2.4 Preparation of test mixtures

30.0 g ± 0.1 g of the substance to be tested (of which the particle size meets the requirements of 5.1.2.3) and cellulose are prepared into test mixture I and test mixture II respectively. Each test mixture shall be stirred for at least 1 min to mix as completely as possible, avoiding excessive stirring. Each test mixture shall be prepared separately and used as soon as possible. It shall be extracted from different batches of mixtures.

5.1.2.5 Preparation of standard mixtures

30.0 g ± 0.1 g of calcium peroxide standard substance and cellulose are prepared into standard mixtures I, II and III respectively. Each standard mixture shall be stirred for at least 1 min to mix as completely as possible, avoiding excessive stirring. Each standard mixture shall be prepared separately and used as soon as possible. It shall be extracted from different batches of mixtures.

5.1.3 Instruments and equipment

5.1.3.1 Balance and accessories

5.1.3.1.1 The balance shall have a measurement range and accuracy that meet the test requirements, and have data transmission function and data acquisition interface. It can record the required data (time, mass), and check the time frequency of the data acquisition software through a stopwatch, with a frequency of more than 5 Hz.

5.1.3.1.2 Use a base plate made of solid material, a positioning plate made of flame-retardant material, and several guide rods to construct a support structure for the burning test on the balance.

5.1.3.1.3 Use a windshield to ensure that the balance is not affected by ventilation or ambient airflow.

5.1.3.1.4 The burning cone stack shall always be placed in the center of the balance to protect the balance from contact with heat sources and burning particles during the test.

5.1.3.1.5 The balance and accessories should be constructed as follows (the letters in brackets correspond to the key in Figure 1).

a) Use a sufficiently strong base plate (H) (such as a 4 mm steel plate or a 16 mm polyamide plate) to keep the metal guide rods (G) in a stable position at all times, and the base plate is larger than the balance; fix the bottom of the plate on some buffer material to reduce environmental vibration; fix 2 to 4 metal guide rods (G) on the base plate to ensure that the positioning plate (F) and the test plate (C) protect the balance during the test and are always in the same position on the balance; the balance shall always be in the center of the base plate.

b) The positioning plate (F) is made of flame-retardant, low thermal conductivity material with the same characteristics as the test plate (see 5.1.3.3); the diameter of the drilled holes on the positioning plate for fixing the guide rods shall be about 8 mm longer than the diameter of the guide rods.

c) The guide rods must always be located in the center of the drilled holes to prevent the positioning plate (F) from contacting the guide rods and affecting the operation of the balance; some kind of check mark shall be fixed on the positioning plate (F) so that the test plate (C) is in the center of the balance.

d) the connection between the power source and the ignition wire shall be flexible enough to prevent vibration or displacement from interfering with the free movement of the balance pan; flexible wiring shall be used and supports shall be used near the test plate, and the wiring between the support and the test plate shall be in a circle to increase flexibility.

e) The windshield (D) is enclosed in a closed circle and is about 10 cm higher than the equipment; it can be installed on the bottom plate or set around the entire test equipment.

5.1.3.3 Test plate

least 6 mm thick, and has a thermal conductivity (at 0 °C) less than or equal to 0.23 W/(m · K). […]

5.1.3.4 Ventilation area

A certain degree of ventilation is required, and a fume hood or other ventilation area with an airflow velocity less than or equal to 0.5 m/s is required. The smoke exhaust system shall be able to absorb harmful smoke.

5.1.4 Operation steps

5.1.4.1 Sample placement

Use a conical funnel container to make the mixture into a truncated cone with a bottom diameter of 70 mm, covering the annular ignition wire placed flat on the low thermal conductivity test plate. The test shall be carried out under normal pressure, with an ambient temperature of 20 °C ± 5 °C and a relative humidity of less than 60 % to reduce the absorption of moisture by cellulose during use.

5.1.4.2 Test

5.1.4.2.1 The balance is placed in a ventilated area and zeroed. The ignition wire is connected to the power source and remains powered during the test; if the mixture does not ignite or burn, it is kept powered for 3 min.

5.1.4.2.2 Data collection shall start before the power is turned on and continue until the reaction ends or until the mass loss rate is less than 1 g per min. If the ignition wire breaks, the test shall be repeated to ensure that the test results are not affected by the wire break. 5 valid tests shall be conducted on the standard mixtures and the test mixtures.

5.1.4.2.3 Check the status of each burning test by plotting the mass loss spectrum as a function of time. The correlation coefficient (R2) of the mass curve of each burning test shall be at least 0.90 between 20 % and 80 % of the total mass loss, otherwise repeat the test. The standard deviation of 5 tests shall not exceed 20 %.

5.2 Test of oxidizing solids (test method 2)

5.2.1 Principle of the method

The substance to be tested is made into test mixtures for test, and the burning characteristics of the mixtures are compared with those of the standard mixtures to determine its oxidizing capacity.

5.2.2 Test preparation

5.2.2.1 Preparation of potassium bromate standard substance

The standard substance is industrial pure potassium bromate with a nominal particle size of 0.15 mm ~ 0.30 mm after sieving. The standard substance shall not be ground.

The standard substance is dried at 65 °C to constant mass (for at least 12 h), and then placed in a desiccator (with desiccant) until cooled down for use.

5.2.2.2 Preparation of cellulose

Same as 5.1.2.2.

5.2.2.3 Sample inspection

Same as 5.1.2.3.

5.2.2.4 Preparation of test mixtures

30.0 g ± 0.1 g of the substance to be tested (of which the particle size meets the requirements of 5.2.2.3) and cellulose are prepared into test mixture I and test mixture II respectively. It should mix as completely as possible, avoiding excessive stirring. Each test mixture shall be prepared separately and used as soon as possible. It shall be extracted from different batches of mixtures.

5.2.2.5 Preparation of standard mixtures

30.0 g ± 0.1 g of potassium bromate standard substance and cellulose are prepared into standard mixtures IV, V and VI respectively. It should mix as thoroughly as possible, avoiding excessive stirring. Each standard mixture shall be prepared separately and used as soon as possible. It shall be extracted from different batches of mixtures.

5.2.3 Instruments and equipment

The configurations of ignition source, test plate and ventilation area are the same as 5.1.3.2 ~ 5.1.3.4.

5.2.4 Operation steps

5.2.4.1 Sample placement

Same as 5.1.4.1.

5.2.4.2 Test

5.2.4.2.1 The ignition wire is connected to the power source and remains powered during the test; if the mixture does not ignite or burn, it is kept powered for 3 min. If the mixture burns, record the burning time from when the power source is turned on to the end of the main reaction (such as flame, scorching or flameless burning).

5.2.4.2.2 Intermittent reactions after the main reaction, such as sparks or crackling, are not recorded in the burning time of the main reaction. If the ignition wire breaks during the test, the test shall be repeated unless the ignition wire break clearly does not affect the result.

5.2.4.2.3 When assigning the packing category or determining whether the substance belongs to "5.1 Oxidizing substances" classified in accordance with GB 6944-2012, each standard mixture and test mixture shall be tested 5 times, and the result shall be the average of the 5 tests.

NOTE: Oxidizing substances are substances that may not burn themselves, but usually cause or promote the burning of other substances by releasing oxygen.

6.1 Oxidizing solid mass test

6.1.1 Evaluation of results

The evaluation of results shall be based on:

a) comparison of the median burning rate (BR) of the test mixture with the median burning rate of the standard mixture;

b) whether the test mixture ignites and burns.

If there is any doubt about the test results, the results of the tests conducted when the substance was mixed with an inert material and/or in an inert atmosphere shall also be considered when evaluating the results.

6.1.2 Burning periods of the cone stack

The burning of the cone stack can be divided into three periods:

a) initial period: total mass loss from 0 % to 20 %;

b) main burning period: total mass loss from 20 % to 80 %;

c) end of reaction: total mass loss from 80 % to the end of reaction.

During the main burning period, the mass loss per unit time is quite constant. Therefore, linear regression (based on the least squares method) is used to check the mass of the collected data. If the shape of the mass loss curve indicates that the test is invalid, it shall check the mixing procedure or the test configuration that affects the free movement of the balance pan.

6.1.3 Calculation of median burning rate

The median burning rate in this test is defined as the quotient of 60 % of the total cellulose contained in the cone stack and the main burning time t20-80. Time t20-80 is the […]