This standard is applicable to the melting point determination of partially crystalline polymers in powder, granular and flake form. This standard is not applicable to the melting point determination of crystalline polymers with additives that interfere with birefringence. GB/T 4608-1984 Test method for melting point of partially crystalline polymers Optical method GB/T4608-1984 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test for melting point of
semlcrystalline polymers
Optical method
This standard is applicable to the determination of the melting point of partially crystalline polymers in powder, granular and flake form. This standard is not applicable to the determination of the melting point of crystalline polymers with additives that interfere with birefringence. Definition
Partially crystalline polymer: a polymer in which a crystal rod is surrounded by an amorphous phase. PrinciplebZxz.net
UDC 678.7 : 678
.01 586
GB 460B--84
Put the sample on the heating stage of a polarized melting point microscope, control the rising speed to a certain extent, and observe the temperature at which the birefringence disappears completely between two orthogonal polarizers. This is the melting point of the partially crystalline polymer. 3
The components of the polarizing melting point microscope used to determine the melting point of partially crystalline polymers shall meet the following requirements: 3.1 Polarizing microscope, with a magnification of 50 to 100 times and equipped with a polarizer and an analyzer. 3.2 Microscope heating table, which is an insulated metal block mounted on the polarizing microscope table. The metal block must meet the following requirements 3.2.1 There is a small hole for light passage.
3.2.2 There is a thermometer socket near the light hole. 3.2.3 There is electric heating.
8.2.4 A small empty chamber formed by the heating table and the glass cover is used for heat preservation and inductive gas coverage. 3.3 Temperature controller, used to control the heating rate. 8.4 Thermometer, with a graduation value of not more than 1°C and several calibrated measurement ranges. Cover
The thermometer should be calibrated regularly on the instrument with reagent-grade chemicals, and the heating rate selected during the test should be used for calibration. Recommended chemicals are shown in the table:
Menthol-1
Hydroxyquinoline
Cetylbenzene
Succinic acid
National Bureau of Standards 1984-07-30
Melting point,
113-114
188~189
261~262
1985-05-01 implementation
GB 4608-84
8.5 Cooling device, a metal block or other cooling device used to quickly reduce the temperature after the melting point is determined. 3,6 Microscope slides and cover glass.
3.7 Metal sampling spoon.
Or test sample
.1 Powder sample. Place 1-2 mg of sample on a clean glass slide, cover with a cover glass, then place the assembly on a heating table, raise the temperature to 10-20°C above the melting point of the polymer, gently press on the cover glass to form a film with a thickness of less than 0.05 μm, turn off the heating power, and let the sample slowly cool until fully crystallized. 4.2 Granular or flake samples. Cut 1-2 mg of sample with a blade and place it on a glass slide, cover with a cover glass, and then prepare the sample according to 4.1.
4.3 Take two samples for each sample.
Note: ① The advantage of pre-melting the sample or measuring the melting point of a thin film is that it can destroy the birefringence caused by the orientation of the crystalline polymer molecules or the existence of internal stress, and avoid the melting point error caused by this. ② For samples that can be degraded by air, when preparing the sample, the air in the small chamber on the heating table should be removed with nitrogen first, and then the sample should be prepared under the protection of a weak nitrogen flow.
5 Test steps
5.1 Place the prepared sample assembly on the heating stage of the microscope and make sure that the sample film just covers the light hole. 5.2 Turn on the light source, adjust the light source to the appropriate light intensity, and adjust the microscope to focus it. 5. Adjust the polarizer, and observe from the national mirror! After a dark field appears, the focus of the polarizing microscope can be adjusted again until a clear bright spot appears in the dark field.
5.4 For samples that are easily oxidized and degraded, a weak nitrogen flow should be introduced from the gas inlet of the empty chamber on the heating stage to cover the sample. 6.6 Adjust the temperature controller so that the heating stage is gradually heated (at a speed not higher than 10C/min) to a temperature that is lower than the predicted melting point Q by the following values:
Q<150℃, 10℃
150℃
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