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GB/T 40271-2021 English PDF (GBT40271-2021)

GB/T 40271-2021 English PDF (GBT40271-2021)

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GB/T 40271-2021: Test method for identification of textile fibers - Differential scanningcalorimetry(DSC)

This Standard describes a test method for the identification of textile fibers through a differential scanning calorimeter. This Standard is applicable to textile fibers with an obvious melting peak temperature, which is lower than decomposition temperature.
GB/T 40271-2021
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 59.080.01
CCS W 04
Test Method for Identification of Textile Fibers -
Differential Scanning Calorimetry (DSC)
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Test Principle ... 5
5 Equipment and Materials ... 6
6 Sample ... 7
7 Test Procedures ... 7
8 Result Expression ... 8
9 Test Report ... 9
Appendix A (informative) Calibration Method ... 10
Appendix B (informative) Standard Samples ... 11
Appendix C (informative) Melting Peak Temperature and Enthalpy of Fusion of Synthetic Fibers ... 12
Bibliography ... 13
Test Method for Identification of Textile Fibers -
Differential Scanning Calorimetry (DSC)
1 Scope
This Standard describes a test method for the identification of textile fibers through a differential scanning calorimeter.
This Standard is applicable to textile fibers with an obvious melting peak temperature, which is lower than decomposition temperature.
NOTE: the differential scanning calorimetry is generally not used alone, but by determining the melting peak temperature and enthalpy of fusion of fibers to assist in the identification of the fibers.
2 Normative References
The content of the following documents constitutes indispensable clauses of this document through normative references in the text. In terms of references with a specified date, only versions with a specified date are applicable to this document. In terms of references without a specified date, the latest version (including all the modifications) is applicable to this document.
FZ/T 01057.1 Test Method for Identification of Textile Fibers - Part 1: General Introduction
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Melting
Melting refers to the transition from a solid state of a completely crystalline or partially crystalline substance to a liquid state with different viscosities.
[source: GB/T 6425-2008, 3.5.5.1]
3.2 Enthalpy of Fusion
Enthalpy of fusion refers to the quantity of heat required for material melting under a constant pressure.
NOTE: it is expressed in kJ/kg or J/g.
[source: GB/T 19466.3-2004, 3.3, modified]
3.3 Differential Scanning Calorimetry
Differential scanning calorimetry refers to a technique of determining the relationship between the heat flow rate or heating power (difference) delivered to the specimen and the reference substance, and temperature or time under program control temperature and certain atmosphere.
[source: GB/T 6425-2008, 3.2.9]
3.4 Differential Scanning Calorimetry Curve (DSC curve)
Differential scanning calorimetry curve (DSC curve) refers to a graphical representation of the relationship curve between the heat flow rate or heating power (difference) delivered to the specimen and the reference substance measured by the differential scanning calorimeter, and temperature or time.
NOTE: the y-coordinate of the curve is heat flow rate, which is also known as heat flow and expressed in mW (mJ ??? s-1); the x-coordinate is temperature or time. [source: GB/T 6425-2008, 3.2.10, modified]
3.5 Calibration
Calibration refers to a set of operations of determining the relationship between the indicated value of the measuring instrument or measuring system and the already- known value corresponding to the measured value under specified conditions. 3.6 Instrument Baseline
Instrument baseline refers to a thermal analysis curve measured with empty sample cuvettes of the same mass and material, and without the use of specimen. [source: GB/T 6425-2008, 3.5.3.1 a), modified]
4 Test Principle
Under certain conditions, adopt the differential scanning calorimetry to determine and obtain the DSC curve of the fiber, as it is shown in Figure 1. In this Figure, Tpm is the melting peak temperature of the fiber; the connection points Tim and Tfm are used to draw a baseline; the area between it and the melting peak is the enthalpy of fusion of the fiber. Different types of synthetic fibers have different melting peak temperatures, based on which, the category of fibers can be identified.
the sealed empty sample cuvettes into the sample holder. In accordance with the actual test conditions, test the instrument baseline.
7.4 Take another sample cuvette (see 5.2); use the balance (see 5.4) to weigh its mass, accurate to 0.01 mg. Put the specimen into the sample cuvette; put on the cap and tightly seal it. Then, re-weigh the sample cuvette which holds the specimen, accurate to 0.01 mg.
7.5 Put the sample cuvette which holds the specimen into the sample holder at the designated position of the instrument; put the sealed empty sample cuvette into the other position as a reference.
7.6 Set the program of the instrument; deduct the instrument baseline. Under the condition of at least 50 ??C lower than the melting peak temperature, at a rate of 10 ??C/min, start to raise the temperature, until it is at least 30 ??C higher than the extrapolated final temperature (Tefm), or 20 ??C ~ 30 ??C lower than the thermal decomposition temperature; record the DSC curve. For some new types of fibers and some fibers obtained through certain special processing, they may be heated up for the first time to eliminate the thermal history of the fiber processing process, then, heated up again for the observation of the DSC curve.
NOTE: other temperature-raising rates may also be adopted; the temperature-raising rate should not exceed 20 ??C/min.
7.7 Cool down the instrument to room temperature; take out the sample cuvette; observe whether the sample cuvette is deformed, or whether the specimen overflows. If it is found that the sample cuvette is deformed or the specimen overflows, then, the test shall be invalidated and re-conducted.
7.8 Repeat steps 7.4 ~ 7.7 to test the other two specimens.
8 Result Expression
8.1 Melting Peak Temperature
The test curve of the melting peak temperature is shown in Figure 1. From the Figure, respectively read the melting peak temperature (Tpm) of each specimen; the result shall be accurate to 0.1 ??C. Take the average value of all specimens as the melting peak temperature of the sample; the result shall be rounded off to an integer. If the second temperature-raising is performed, take the value measured after the second temperature-raising as the test result. The melting peak temperature of synthetic fibers is shown in Appendix C.
8.2 Enthalpy of Fusion
The test curve of the enthalpy of fusion is shown in Figure 1. Take the area between Appendix A
(informative)
Calibration Method
A.1 General Rules of Calibration
The differential scanning calorimeter is a sensitive thermal analysis instrument, which requires regular temperature and heat calibration. Under the circumstances of changing test temperature range, changing air source and flow rate, changing refrigeration system or being idle for a long time, before use, at least two standard samples shall be used for the calibration of temperature and heat. See Appendix B for commonly used standard samples.
NOTE: other calibration requirements of the instrument may comply with the recommendations by the manufacturer, or with the assistance of the
manufacturer in the implementation.
A.2 Temperature Calibration
A.2.1 Select at least two standard samples with the same mass as the specimen to be tested and whose extrapolated initial temperature is at or close to the temperature range to be tested.
A.2.2 Under the same test conditions as the specimen to be tested, determine the extrapolated initial temperature of the standard samples and record it. A.2.3 By comparing the standard value and the recorded value of the standard samples, determine the temperature correction coefficient for calibration. Alternatively, the computer system may automatically compare and calibrate in accordance with the standard value and the recorded value.
A.3 Heat Calibration
A.3.1 Select at least two standard samples with the same mass as the specimen to be tested and whose extrapolated initial temperature is at or close to the temperature range to be tested.
A.3.2 Under the same test conditions as the specimen to be tested, determine the enthalpy of fusion of the standard samples and record it.
A.3.3 By comparing the standard value and the recorded value of the standard samples, determine the heat correction coefficient for calibration. Alternatively, the computer system may automatically compare and calibrate in accordance with the standard value and the recorded value.

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