GB/T 5208-1985 Flash point determination of coatings - Rapid equilibrium method
Some standard content:
National Standard of the People's Republic of China
Coatings-Flash point test
Rapid equilibrium method
UDC 667.613.7
GB 5208-85
This standard is applicable to the determination of flash point of paints and varnishes, and the flash point range is below 110℃. The results obtained from mixed solvents containing halogenated hydrocarbons are abnormal.
This standard refers to and adopts international standards ISO1523-1983 "Paints, varnishes, petroleum and related products-Determination of flash point-Closed cup method" and ISO3679-1983 "Paints, varnishes, petroleum and related products-1 Definitions-Determination of flash point-Rapid equilibrium method".
Flash point (closed cup): Under the conditions specified in this standard, when the sample in the closed cup is heated, the lowest temperature at which the escaping vapor can flash instantly in the presence of a flame.
Note: The flash point of this standard should be calibrated according to the standard atmospheric pressure of 101.3 kPa (1013 mbar or 760 mmHg). 2 Instruments
2.1 Flash point tester
2.1.1 Test cup
The test cup is made of brass or other suitable metal blocks with good thermal conductivity and corrosion resistance. There is a sample groove with a cover on the upper part of the metal block with a diameter of about 50 mm and a depth of about 10 mm. The thermometer is inserted into the thermometer hole of the metal block. Figure 1 is its plan view, and the main dimensions are shown in Figures 2 to 5.
Figure 1 Plan view of flash point tester
1—test cup cover; 2—slide plate, 3—ignition nozzle; 4 feeding hole Issued by the National Bureau of Standards on July 16, 1985
Implementation on March 1, 1986
GB5208--85
Figure 2 Section view of tester through nozzle
1—ignition nozzle, 20-type seal (see Note 1), 3—module 14—thermometer (see Note 2)
Note: ①O-type seal ring plays a sealing role when the cover is closed and is made of material that can withstand 150℃. ②The thermometer is first coated with a layer of thermoplastic material with good thermal conductivity and then inserted into the thermometer hole. ro
12.4 te.8
48.4±0.02
Figure 3 Test cup cover
Note: The test cup cover is made of brass or other suitable metal with a thickness of about 2mm. .92
GB 5208-85
Figure 4 Slide plate
Note: The slide plate is made of stainless steel or other suitable metal with a thickness of about 1.2mm. 44 *0.5
e49.7-8.9
** 1. 8 *.*
Figure 5 Section of the measuring device cut through the feeding hole 2.1.2 Test cup cover
The test cup cover is equipped with a slide plate that can be opened and closed (generally an electric device is used, and a manual device is also installed), and an ignition device that can extend the test flame (diameter is 3.5±0.5mm) into the sample groove when the slide plate is opened. When the flame is extended, the nozzle of the test flame should be 0.1mm away from the bottom of the test cup cover. There is also a small hole on the cover that extends into the sample groove to facilitate loading the sample. In order to ensure the tight combination of the cover and the test cup, an appropriate fixture can be used to make the center line of the three holes on the cover coincide with the diameter of the sample groove. When the slide on the cover is in the open position, the two holes on the slide must completely coincide with the corresponding two holes on the cover. 2.1.3 Heating device
The heating device adopts electric heating and is equipped with a temperature controller so that the temperature of the metal block can be controlled within the range of ±0.2℃ of the required temperature.
2.1.4 Cooling device
It adopts semiconductor cooling elements for cooling.
2.1.5 Timing device
It adopts digital tube timing.
2.2 Thermometer
GB 5208—85
A nitrogen-filled mercury glass thermometer placed horizontally and with a suitable range, with a minimum graduation of 0.5℃, suitable for insertion into the thermometer hole on the metal block. The maximum error in measuring the temperature of the test cup should not exceed 0.5℃. The thermometer should be calibrated regularly by the metrology department. 2.3 Syringe
The capacity is 2ml and the accuracy is ±0.1ml. A spoon can be used for high-viscosity products. 2.4 The fuel of the ignition device
Usually butane, coal gas or natural gas can also be used. 3 Sampling and sample processing
3.1 According to the provisions of GB3186-82 "Sampling of coating products", a representative sample is taken from the product to be tested. Before the test, the sample should be placed in a closed container, and the free volume in the container should not exceed 10% of the total container capacity. The sample should not be stored in a plastic bottle (such as polyethylene, polypropylene, etc.). 3.2 Since volatile components are easy to lose, the sample should be cooled to at least 10℃ below the expected flash point before opening the sample container to take out the sample. When using method 2 (see 5.2.1), the sample only needs to be cooled to 3~5℃ below the expected flash point. During the test, the sample should be mixed evenly. After taking out the sample, the sample container should be covered immediately to ensure that the loss of volatile combustible components in the container is minimized. Otherwise, the sample cannot be used for testing. 4 Preparation of the instrument
4.1 The instrument should be placed in a place away from wind and soft light, and check whether the slide switch is flexible. Select the temperature according to the expected flash point of the sample to be tested. 4.2 When using method 2 for testing, cooling water should be passed first. 5 Test steps
5.1 Method 1: Applicable to the expected flash point of room temperature to 110℃ (if the expected flash point is close to room temperature, method 2 is recommended). Note: In case of dispute, the test should be carried out at 25±1℃ and relative humidity of 60~70%. 5.1.1 Cool the sample and the sample container to 10℃ below the expected flash point. 5.1.2 Ensure that the sample groove, cover and slide are dry and clean, cover the cover and close the slide. 5.1.3 Turn on the heating device. When the temperature reaches 3℃ below the expected flash point of the sample to be tested, slowly adjust the controller of the heating device until the sample groove reaches the expected flash point temperature and remains stable. 5.1.4 Use a dry and clean syringe to absorb 2ml of sample (see 5.1.1) and quickly inject the sample into the sample groove through the feeding hole. Be careful not to lose any sample. Pull out the syringe and start the timer immediately. Note: If the viscosity of the sample to be tested is high and it is difficult to inject through the feeding hole, you can open the cover and use a spoon to add 2~3ml of sample into the sample groove. After taking out the sample, the sample container should be covered tightly and returned to a place 10℃ below the expected flash point. 5.1.5 Open the gas control valve, ignite the test flame, and adjust the flame into a spherical shape with a diameter of 3.5±0.5mm. 5.1.6 After 660s, the test temperature can be considered to have been reached. Open the slide, extend and remove the flame nozzle, close the slide, and complete an ignition test, the time is 2.5±0.5s, and observe the flash from the opening to the closing of the slide. 5.1.7 Record whether flash occurs.
Note: ① When the mixed gas of the sample vapor during the test is close to the flash point, ignition will produce a halo. However, only when a considerable blue flame appears and spreads to the entire liquid surface can the sample be considered to have flashed. ② When the slide is opened for ignition, if a continuous bright flame is observed at the hole, it means that the flash point is lower than the temperature during the test. 5.1.8 If flash is not observed, re-test with a new sample every 5℃ within the range of temperature higher than the previous test point until flash is observed.
If flash is observed, re-test with a new sample every 5℃ within the range of temperature lower than the previous test point until flash is no longer observed.
Once the sample has been subjected to the ignition test, the test shall be terminated. Each subsequent test shall be conducted with a newly taken sample. 259
GB 5208-85
5.1.9 Between the two temperatures 5°C apart at which flash and no flash have been determined, a newly taken sample shall be used again, starting from the lower temperature, and the test shall be conducted at intervals of 1°C according to the steps described in 5.1.1 to 5.1.7 until flash is observed. When flash occurs, the thermometer reading shall be accurate to 0.5°C and the result shall be recorded. This value shall be the flash point of the sample at the atmospheric pressure during the test (see Chapter 6), and the atmospheric pressure expressed in kPa, mbar or mmHg shall be recorded at the same time.
5.1.10 Repeat the determination and calculate the arithmetic mean of the corrected flash point, accurate to 0.5°C. Note: After each ignition test, the gas control valve must be closed and the sample tank and cover shall be cleaned immediately. 5.2 Method 2: Applicable to the expected flash point below room temperature. Note: Same as note 5.1.
5.2.1 Cool the sample and sample container to 3-5℃ below the expected flash point. 5.2.2 Cool the sample groove and slowly adjust it to the expected flash point temperature and keep it stable. The sample groove should be dry and clean and the slide should be closed. 5.2.3 Use a dry and clean syringe to absorb 2 ml of sample (see 5.2.1). Quickly inject the sample into the sample groove through the feeding hole, taking care not to cause any loss of the sample, pull out the syringe and start the timer immediately. Note: 冏5.1.4 Note.
5.2.4 Open the gas control valve, ignite the test flame, and adjust the flame into a spherical shape with a diameter of 3.5±0.5mm. 5.2.5 After 60s, it can be considered that the sample has reached the test temperature. Open the slide, extend and remove the flame nozzle, close the slide, and complete an ignition test, the time is 2.5±0.5s, and observe the flash from the slide opening to the closing. Note: Same as 5.1.7 Note.
5.2.6 Close the gas control valve and clean the sample groove and cover. 5.2.7 Record whether a flash occurs.
5.2.8 If no flash is observed, retest with a new sample every 5°C above the previous test point until flash is observed.
If flash is observed, retest with a new sample every 5°C below the previous test point until flash is no longer observed.
Once the sample has been tested for ignition, the test shall be terminated. Each subsequent test shall be conducted with a new sample. 5.2.9 Between the two temperatures 5°C apart at which flash and no flash have been determined, retest with a new sample starting from the lower temperature and at 1°C intervals according to the steps described in 5.2.1 to 5.2.7 until flash is observed. When flash occurs, the thermometer reading shall be accurate to 0.5°C and the result shall be recorded. This value shall be the flash point of the sample at the atmospheric pressure at the time of the test (see Chapter 6), and the atmospheric pressure expressed in kPa, mbar or mmHg shall also be recorded.
5.2.10 Repeat the measurement and calculate the arithmetic half-mean of the corrected flash point, accurate to 0.5℃. 6 Calculation of flash point correction value and expression of results 6.1 Calculation of correction value
In order to correct the measured flash point to the flash point under the standard atmospheric pressure of 101.3 kPa (1013 mbar or 760 mmHg), the correction value can be calculated according to one of the following formulas. C = 101.3 - Po
Where: C-
correction value, ℃,
or 1013-P
P——atmospheric pressure at the time of test, kPa,
atmospheric pressure at the time of test, mbar
-atmospheric pressure at the time of test, mmHg. bzxZ.net
6.2 Expression of results
The flash point of the sample is obtained by adding the correction value to the measured flash temperature. 260
760 - P2
7 Precision
7.1 Repeatability
GB 520885
The absolute difference between two test results obtained by the same operator, in the same laboratory, using the same instrument, at a certain time interval and in accordance with the determination method of this standard on the same sample should be less than 2°C, and the confidence level is 95%. 7.2 Reproducibility
The absolute difference between two test results obtained by different operators, in different laboratories, in accordance with the determination method of this standard on the same sample should be less than 3°C, and the confidence level is 95%. Additional notes:
This standard was proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of the National Technical Committee for Standardization of Paints and Pigments. This standard was drafted by Working Group 4 (SC1/WG4) of the Sub-Technical Committee on Basic Standards of Paints and Pigments. The main drafters of this standard are Liu Shimin and Cai Weihua. 261
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.