HG 3025-1986 Determination of moisture content of ethylene terephthalate pellets
Some standard content:
Chemical Industry Standard of the People's Republic of China
Determination of water content ofpoly (ethylene terephthalate) granules
Determination of water content ofpoly (ethylene terephthalate) granulesThis standard refers to the international standard ISO6188--1980 "Plastics-Determination).
1 Scope of application
UDC678.7:543.81
IG/T3025-1986(1997)
Substitute GB7140-86
-Polyethylene terephthalate granules
Water content
This standard specifies the method for determining the water content of polyethylene terephthalate granules. This method is applicable to the determination of water content within the range of 0.002～~0.05% (m/m).
The moisture content is very important for material processing. In order to prevent degradation during material processing, the moisture content should be kept below a few parts per ten thousand. This method is not suitable for polyethylene terephthalate samples containing a large amount of volatile non-water compounds with significant vapor pressure at room temperature. The error caused by the presence of a small amount of acetaldehyde in dry polyethylene terephthalate pellets is acceptable. However, a method such as gas chromatograph should be used regularly to check whether a large amount of volatile compounds exist. This inspection is particularly important for new types or grades of materials.
2 Principle
Place the sample in a closed space under high vacuum and heat it to 200±5°C to ensure complete evaporation of water. Determine the pressure increase caused. This pressure increase is proportional to the water content. A hydrate (such as sodium molybdate dihydrate) with a known accurate water content that can only lose water under test conditions is used as a reference to make a calibration curve to calculate the water content. 3 Reagents
3.1 Sodium molybdate dihydrate (Na,MoO,-2H,O) analytical grade. Note: Other hydrates that lose crystal water under the test conditions can also be used. 4 Instruments
4.1 Moisture analyzer
As shown in the figure, the moisture analyzer is a glass instrument with vacuum-tight connections. The joints are interchangeable conical ground joints. National Bureau of Standards 1986-12-30 Issued
198721001 Release
Connecting to vacuum gauge
Connecting to vacuum system
HG/T3025-1986 (1997)
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Ratio 1:3
Moisture analyzer
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A-spherical bottle, 0.5±0.05L; B-spherical bottle ≥1L; C connecting pipe D-high vacuum gauge: E, F, G-piston; L-oil pressure gauge, inner diameter 8.0mm; M-sample tube: N-vacuum rubber tube; P-selection valve
The total volume of the left space is 590ml.
Piston F is connected backwards.
HG/T 3025-1986 (1997)
The spherical bottles A and B have a volume of 0.5+0.05L and at least 1L respectively. Both spherical bottles A and B are connected to tube C. A piston G is installed in the middle of tube C to separate the two spherical bottles. On both sides of piston G, tube C is directly connected to U-shaped oil pressure gauge L. The length of the branch pipe of this oil pressure gauge is at least 350mm. The branch pipe is filled with ultra-high vacuum diffusion pump silicone oil. The piston F connected to the vacuum pump is connected to the back of tube C with sufficient distance from the sample tube M. The right end of tube C is connected to the high vacuum gauge D by vacuum rubber hose N, and the left end is connected to piston E. There is a branch pipe on the left side of this piston E, which can also be connected to the vacuum pump. The sample tube M is connected below the piston E, and its volume is about 50ml below the piston E. The pipe mouth of the sample tube M is an inverted joint. The volume difference of each group of sample tubes should not exceed 5ml. The entire instrument should be made of heat-resistant glass GG17. 4.2 Electric furnace or oil bath
The electric furnace or oil bath can heat the sample tube to 200±5℃. For easy operation, the heating device should be easy to load and unload. 4.3 Other main equipment
Vacuum pump, preferably one with oil non-backflow; fine-tuning vacuum needle valve;
Rotary vacuum gauge;
Constant temperature control system.
5 Sampling
Quickly put the representative sample into a dry container and seal it immediately to minimize the absorption of moisture from the atmosphere. 6 Operation steps
6.1 Instrument and pipeline
The instrument is connected to the vacuum pump in two ways. One way is connected to the vacuum rubber hose from piston F, which is used to evacuate the instrument. The other way is connected to the vacuum rubber hose from the left branch of piston E, which is used to evacuate the sample tube. The two rubber hoses meet at the selection valve. Then connect the rotary vacuum gauge, fine-tune the vacuum needle gauge and the vacuum pump in turn. 6.2 Leakage test of the instrument
The leak test method of the instrument is as follows:
Install the dry empty sample tube on the instrument. This tube does not need to be heated during leak test. Rotate piston E to connect the sample tube with tube C. Rotate piston G to connect spherical bottles A and B.
Evacuate the instrument to a pressure less than 70Pa, and close pistons F and G. After 1 hour, check whether the pressure is still less than 70Pa and whether the pressure difference indicated by the U-shaped oil pressure gauge is less than 2mm oil column. If these requirements are not met, the leak test should be repeated. In order to ensure airtightness during measurement, leak test should be carried out at any time as needed. Note: When swirling new oil, it may be necessary to evacuate the instrument for several hours in order to remove the gas in the new oil. 6.3 Measurement
6.3.1 Rotate piston G. Evacuate the instrument in advance to a pressure less than 70Pa. After closing piston F, close piston G. Quickly pour the sample equivalent to 12-18g into the dry sample tube, install the sample tube on the instrument, and then screw and close piston E. Note: To reduce the error caused by absorption from the atmosphere, first estimate the sample by volume. Weigh accurately after the test is completed. First, vacuum the pipeline to make the pressure less than 70Pa, rotate piston E to vacuum the sample tube for 10s, and then rotate piston E to connect the sample tube with tube C. After 1s, screw and close piston E. Record the pressure difference indicated by the oil pressure gauge as the zero point of the measurement. Rotate piston E again to connect it with tube C.
Put an electric furnace or oil bath preheated to 200±5℃ on the outside of the sample tube, and heat the sample tube at this temperature for 50min. Note: The sample to be tested may have a large amount of water content, so the oil pressure gauge should be observed frequently within the first 10min of the test. If the pressure difference rises too high, open piston G and take a smaller sample to repeat the test.
#70Pa=0.7mbar0.5mmFgg
HG/T3025-1986（1997）
After 50min, screw and close piston E. Record the pressure difference indicated by the oil pressure gauge. Accurate to the meter. Stop heating the sample tube.
Start the vacuum pump, slowly screw open piston F, and remove the water vapor in the oil pressure gauge, then close piston F. Rotate piston E to eliminate the vacuum in the sample tube. After the sample tube cools down, weigh it, accurate to 0.01g. Note: During continuous measurement, if the residual air pressure in the instrument is not greater than 70Pa, it is not necessary to screw open piston G and continue to measure. 6.3.2 Measure each sample twice. If the result difference is greater than 0.005% (m/m), check for air leakage, repeat the measurement twice, and report all the results of the four measurements. 6.4 Calibration
Weigh at least 5 samples of sodium molybdate dihydrate with a mass ranging from 10 to 70 mg and place them in a small dry test tube. Determine each sample according to the operating steps specified in 6.3.1. The heating time can be shortened from 50 min to 15 min. Use the least square method to calculate the calibration factor f corresponding to the number of milligrams of water required to produce a 100 mm oil pressure difference. Note: ① Whenever a new batch of sodium aluminate dihydrate is used, verify its water content by drying at 190℃ for 1 hour. ② Do not use water for calibration because the required amount is too small and the weighing is inaccurate. Result expression
Water content expressed as mass percentage, calculated by the following formula: 0.001×AP×f
Where: AP
8Test report
Pressure difference indicated by the oil pressure gauge, mm oil column;
Mass of the sample, g;
-Calibration factor measured according to 6.5, mgH,O/dmoil. The test report should include the following items:
a. Indicate that it is based on this national standard;
b. Complete identification statement of the sample;
c. Single test result and the average value of two measurements, accurate to 0.001% (m/m);d. Test personnel;
e. Test date.
A.1 Moisture analyzers have the following differences:
International standards
A.1.1 It is best to use a spherical ground-mouth joint. H/T30251986 (1997)
Appendix A
Adoption Instructions
(reference)
Use a conical knob joint.
A.1.2 Both spherical bottles A and B are located below tube C. A.1.3 Piston F is located above tube C.
A.1.4 The U-shaped oil pressure gauge L is connected to tube C with a spherical ground-mouth joint. The upper part of the U-shaped oil pressure gauge L has a jet head H and a check valve KA.1.5
installation.
A.1.6 In the high vacuum gauge D, tube d has no scale. National Standard
Both spherical bottles A and B are located above tube C.
Piston F is located behind tube C.
The U-shaped oil pressure gauge L is directly and fixedly connected to tube C. There is no injection head H and check valve K device on the upper part of the U-shaped oil pressure gauge L. In the high vacuum gauge D, the tube d has a scale.
Those that are not clearly stipulated in the international standard but are clearly stipulated in the national standard: A.2
International standard
A.2.1 In addition to stipulating that piston F is connected to a vacuum pump, it is not stipulated that piston E is also connected to a vacuum.
A.2.2 The total volume of the space on the left side of the instrument is not stipulated. A.2.3 The inner diameter of the branch pipe of the oil pressure gauge L is not stipulated. A.2.4 There is no stipulation on what kind of oil to be poured into the oil pressure gauge and the high vacuum gauge. A.2.5 The use of a fine-tuning direct vacuum needle valve is not recommended. A.3 The following differences are found in the measurement operation:
National standard
In addition to stipulating that piston F is connected to a vacuum pump, it is also stipulated that piston E is also connected to a vacuum pump
The total volume of the space on the left side of the instrument is stipulated to be 590ml. The inner diameter of the branch pipe of the oil pressure gauge L is specified to be 8.0 mm. It is specified to be filled with ultra-high vacuum diffusion pump silicone oil. It is recommended to use a fine-tuning vacuum needle valve.
International standard
A.3.1 Only the instrument and the sample tube are connected together to evacuate. A.3.2 The time for evacuating the sample tube and the instrument together is not specified. A.3.3bZxz.net
After evacuating, the residual air pressure in the instrument is consistent with the residual air pressure in the sample tube.
After unscrewing piston C; then unscrewing piston G. Adjust the oil level in the branch pipe of the oil pressure gauge A.3.4
When they are at the same horizontal plane, it is used as the zero point for pressure difference measurement.
National standard
The instrument and the sample tube are evacuated separately. The instrument is evacuated first, and then the sample tube. The time for evacuating the sample tube is specified to be 10 seconds. After evacuating, the residual air pressure in the instrument is not consistent with the residual air pressure in the sample tube.
Without unscrewing piston G, rotate piston E to connect the vacuumed sample to the instrument. After 1 second, close piston E. The resulting pressure difference is used as the point for pressure difference measurement.
B.1 Leakage detection in pipelines
HIG/T3025-1986(1997)
Appendix B
Calibration of high vacuum gauge in water separation measuring instrument
(Supplement)
Close pistons F and E to evacuate the pipeline. When the pipeline pressure is less than 14Pa, seal the pipeline. The pipeline pressure increase rate shall not exceed 1.4Pa/min.
B.2 Calibration of high vacuum gauge
When conducting the calibration test, connect a rotary vacuum gauge to the pipeline, fine-tune the vacuum needle valve and vacuum pump so that it can be adjusted within the pressure range of 14 to 70Pa.
Select a pressure to be calibrated within this pressure range. When the calibration test begins, the system pressure can be adjusted to be slightly greater or less than the pressure to be calibrated. Then gradually reduce the pressure or gradually increase the pressure, gradually approaching the pressure to be calibrated from both directions. The calibration of other pressures is similar.
The least square method is used to organize it.
Additional instructions:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China and is under the jurisdiction of the Chemical Method Branch of the National Plastics Standardization Technical Committee. This standard is drafted by the Fujian Provincial Central Inspection Institute. The main drafter of this standard is Chen Chuanrong.
14Pa~0.1mmHg
1.4Pa/min0601mmHg/min.
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