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Chemical Industry Standard of the People's Republic of China
HG/T223591
Determination of melting point of polyamide
Published on December 27, 1991
Ministry of Chemical Industry of the People's Republic of China
Implementation on July 1, 1992
Chemical Industry Standard of the People's Republic of China
Determination of melting point of polyamide
—Polyamide
This standard is equivalent to the international standard ISO1218-75 "Plastics—1 Subject content and scope of application
HG/T2235-91
Determination of melting point".
This standard specifies two methods for determining the melting point of polyamine. The melting point is a measured temperature with an arbitrary degree. In fact, it has a temperature range. For a homopolymer, this range is only a few degrees. Melting point determination is useful for characterizing polyamide homopolymers, but less useful for copolymers, because the melting range of copolymers may be quite wide.
The results of either test method described in this standard are very close, and the results of the two methods are also extremely consistent. Other methods, unlike these two methods, may give very different results. 2A method Capillary heating chamber method
2.1 Principle
Insert the capillary containing the polyamide sample into the heating chamber and observe the temperature when the state of the polyamide sample changes. 2.2 Materials
Standard substances
2.2.1 Bismuth: analytically pure, melting point 271.3, 2.2.2 Tin: analytically pure, melting point 231.9℃. 2.2.3 Appropriate pure compounds with known melting points. 2.3 Apparatus
42.3.1 Melting point apparatus: It consists of the following items (see Figure 1) a.
Cylindrical metal block, the upper part of which is hollow, forming a heating chamber; a metal plug with two or more holes, so that a thermometer and one or more capillaries can be inserted into the metal block (a); the heating system of the metal block (a), for example, can be composed of a resistance element installed in the metal block: a rheostat, through which the input power is adjusted if electric heating is used; d.
There are four heat-resistant glass windows on the side wall of the heating chamber, which are arranged at right angles to each other. In front of one of them, a self-mirror for observing the capillary is installed, and the other three windows illuminate the objects in the heating chamber through lights. Approved by the Ministry of Chemical Industry of the People's Republic of China on December 27, 1991 and implemented on July 1, 1992
Metal pin
Metal heating block
HG/T2235
Thermometer
Capillary
Figure 1 Capillary melting point apparatus (Method A)
2.3.2 Heat-resistant glass capillary, one end closed. Maximum outer diameter is 2mm. 2.3.3 Precision thermometer, with a scale of 20~300℃ and an interval of 1℃. 2.4 Sample
2.4.1 Use a blade to take a thin slice of about 5mm long from the polyamide resin sample and place it in the capillary tube. For one polyamine sample, two samples are sufficient. 2.4.2
2.5 Test Procedure
2.5.1 Before using the melting point apparatus for the first time and each time the thermometer is replaced, calibrate the instrument according to 2.5.2 to 2.5.7. Do not use polyamide samples for calibration. Use one or more appropriate standards whose melting points are close to or include the melting point range of the sample being tested.
2.5.2 Insert the thermometer into the melting point apparatus.
Insert the capillary tube containing the sample into the melting point apparatus and heat it at maximum power. 2.5.3
When the temperature rises to about 10℃ lower than the expected melting point, adjust the rheostat to reduce the heating rate to 2±0.5℃ per minute. 2.5.5
Turn on the melting point instrument lighting.
2.5.6Observe the sample and record the melting temperature of the sample. The temperature at which the sharp edge of the sample disappears is the melting point. Repeat the above operation with the second sample. If the difference between the two measurements is greater than 5℃, the result is invalid and two more samples are taken for 25.71
test.
2.6 Expression of results
2.6.1 The arithmetic average of the two sample temperatures measured in 2.5.6 is taken as the melting point. 2.6.2 During calibration (using tin and bismuth or other standards with known melting points), if the difference between the measured value and the theoretical melting point of the standard exceeds 2
HG/T 2235—91
IC, the temperature measured on the polyamide sample should be corrected by the above difference. Because the melting point of polyamide is an experimental temperature, the general measurement accuracy can reach 0.5℃. If the difference between the measured values is not large, no correction is required. However, when the difference between the measured value and the theoretical value of the standard exceeds 5, the melting point instrument should be further calibrated. Note:
Test report
The test report should include the following points:
Sample identification: that is, type, source, batch number, trade name and other necessary information; indicate that it is in accordance with method A of this standard;
"Melting point\ is expressed according to 2.6;
, any observed conditions that may have affected the results: d.
Test date;
Test personnel.
Heating Block Method
3.1 Principle
Observe the temperature at which the silicone oil meniscus is displaced between the hot stage and the cover glass supported by the polyamide sample. 3.2 Materials
3.2.1 Standards
.3.2.2 Bismuth: analytically pure, melting point 271.3°C. 3.2.3 Saw: analytically pure, melting point 231.9°C. 3.2.3 Appropriately pure compounds with known melting points. 3.2.4 Silicone oil (e.g. appropriate methylphenyl silicone oil). 3.3 Apparatus
3.3.1 Melting point apparatus: It consists of the following items (see Figure 2): Collimator of illuminator
HG/T2235-91
VariegatronbzxZ.net
Thermometer
Figure 2 Heating block melting point apparatus (Method B)
Note: Other corresponding heating block melting point apparatus can be used. a.
Aluminum block with a horizontal platform and horizontal circular hole, so that the thermometer fits tightly in the horizontal circular hole until the thermometer ball is close to the heating platform. Electric heating system in the aluminum block a);
Variegatron for adjusting the input power;
Lens with a magnification of 3× to 5×:
Illuminator with collimator;
In order to reduce heat loss, a transparent glass cover can be added to some instruments. 3.3.2 Precision thermometer: scale is 20~300℃, interval is 1℃. 3.3.3
Silver wool or other metal wool.
Circular cover glass: diameter is about 18mm
Slicer or any other tool that can cut thin slices, such as a blade. 3.3.5
3.3.6 Sieve: mesh size is 800μm.
3.3.7 Sieve: mesh size is 630μm
3.3.8 Punch: can cut a round piece with a diameter of 1.6mm (see Figure 3). 339 curved surgical needle
HG/T223591
3# Sample
3 Under the test conditions, the size of the amide particles significantly affects the test results, so it is necessary to use samples of roughly the same size. 34
If the polyamide sample is in powder form, use a sieve to sieve out particles of 630-800um as the sample. If the polyamide sample is not in powder form, use a slicer to cut a thin slice with a thickness of about 0.1mm, then use a punch to punch out several discs with a diameter of about 1.6mm from this slice, and then use a blade to divide each disc into four equal parts, and use one of the small pieces as the sample
34.4 For one polyamide sample, two samples can be used. 3.5 Test steps
HG/T2235-91
3.5.1 Before using the melting point instrument for the first time, and each time the thermometer is replaced, the melting point instrument should be calibrated according to the steps 3.5.2 to 3.5.10. Do not use polyamide samples for calibration, but use one or more appropriate standards whose melting points should be close to or include the melting point range of the sample being tested. When using metal standards, be sure to place a cover glass between the metal pellet and the heating table. For polyamide samples, the melting temperatures obtained with or without this cover glass are virtually identical. Measure once for each standard.
3.5.2 Insert the thermometer: Fill all the spaces between the thermometer bulb and the aluminum block hole wall with silver wool. 3.5.3 Place three drops of silicone oil on the aluminum block heating table (3.3.1a) or on the cover glass on the heating table. 3.5.4 Place the sample in the silicone oil.
3.5.5 Place the cover glass on the sample so that it is supported by the sample and kept in a slightly tilted position (see Figure 4). The silicone oil must not be in contact with the entire surface of the cover glass. A meniscus must form slightly in front of the sample. Note: Use an additional glass cover (3.3.1f) and cover it. 3.5.6 Adjust the rheostat to heat the aluminum block and make the temperature rise rapidly. Cover glass
Figure 4: Configuration of the sample on the heating block melting point instrument (Method B) Heating block
HG/T2235-91
3.5.7 When the temperature reaches about 20°C lower than the expected melting point, adjust the rheostat to reduce the temperature rise rate to 2±1°C per minute.3.5.8 Turn on the melting point instrument lighting.
3.5.9 Because the sample can no longer support the cover glass at the melting temperature, the meniscus of the silicone oil opens Note: When approaching the melting point, a flexible method can be used, such as using a bent surgical needle (3.3.9) to gently press the coverslip at 1°C intervals, while continuously observing the temperature when the meniscus begins to move across the coverslip through a lens. Read the temperature when the meniscus begins to move, accurate to ±0.5°C. 3.5.10
Repeat the above operation with the second sample. If the difference between the two measurements is greater than 5°C, the result is invalid and two more samples are taken for the 3.5.11
test.
3.6 Expression of results
3.6.1. The arithmetic mean of the temperatures of the two samples measured in accordance with 3.5.10 shall be taken as the melting point. 3.6.2 During calibration (using tin and bismuth or other standard substances with known melting points), if the difference between the measured value and the theoretical melting point of the standard substance exceeds 1°C, the temperature measured for the polyamide sample shall be corrected by the above difference. Note: Because the melting point of polyamide is an experimental temperature, the general measurement accuracy is sufficient to reach 0.5°C. If the difference between the measured values is not large, no correction is required. However, if the difference between the measured value and the theoretical value of the standard exceeds 5°C, the melting point instrument needs to be further calibrated. Test report
The test report should include the following points:
Sample identification: type, source, batch number, trade name and other necessary information; a
Indicate that method B of this standard is used;
Melting point is expressed according to 3.6;
Any observed conditions that may have affected the results; Test date;
Test personnel.
Additional notes:
This standard was proposed by the Science and Technology Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Chemical Method Branch of the National Plastics Standardization Technical Committee. This standard was drafted by the Heilongjiang Chemical Research Institute and the main drafter of this standard was Cui Shuwen.
People's Republic of China
Chemical Industry Standard
Determination of melting point of polyamide
HG/T2235-91
Editor: Chemical Industry Standard Editorial Department
(Standardization Research Institute of Ministry of Chemical Industry)
Postal Code: 100013
Printer: Standardization Research Institute of Ministry of Chemical Industry
Copyright reserved. No reproduction allowed
Format: 880×12301/16 Sheet% Number of words: 14000First edition in November 1992
First printing in November 1992
Print run: 1-500
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