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GB/T 40260-2021 (GB/T40260-2021)

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GB/T 40260-2021: PDF in English (GBT 40260-2021)
GB/T 40260-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.99
CCS G 85
Test Method for Determining Gas Permeability of
Polymer Membrane Materials
ISSUED ON: MAY 21, 2021
IMPLEMENTED ON: DECEMBER 1, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s 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 Instruments and Equipment ... 6 
6 Specimen ... 8 
7 Test Procedures ... 8 
8 Test Data Processing ... 9 
9 Test Report ... 11 
Appendix A (normative) Schematic Diagram of Structure of Infiltration Cell ... 12 
Appendix B (informative) Example of Preparation of Polymer Homogeneous
Dense Membrane ... 14 
Appendix C (informative) Variation Curve of Downside Pressure of Specimen
and Test Time ... 15 
Appendix D (informative) Example of Test Report ... 16 
Test Method for Determining Gas Permeability of
Polymer Membrane Materials
1 Scope
This Standard specifies the test method for determining the gas permeability of
homogeneous dense membranes of polymer membrane materials by the constant
volume method.
This Standard is applicable to the test of the gas permeability of flat polymer
homogeneous dense membranes made of polymer membrane materials. Other forms
of polymer dense membranes may take this as a reference.
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.
GB/T 2918-2018 Plastics - Standard Atmospheres for Conditioning and Testing
GB/T 6672-2001 Plastics Film and Sheeting - Determination of Thickness by
Mechanical Scanning
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Polymer Homogeneous Dense Membrane
Polymer homogeneous dense membrane refers to a non-porous membrane, which is
made of polymer materials and has a uniform overall structure.
3.2 Gas Solubility Coefficient
Gas solubility coefficient refers to the amount of gas solubilized in the membrane
materials per unit volume under the unit pressure.
NOTE: gas solubility coefficient S reflects the solvency of gas molecules by membrane
materials. It is the volume of gas that can be solubilized in a unit volume of the
membrane under a unit pressure difference under standard conditions, i.e., the
volume at the temperature of 0 °C and the pressure of 101.325 kPa.
3.3 Gas Diffusion Coefficient
Gas diffusion coefficient refers to the volume of gas diffused through a unit membrane
area in a unit time under a unit concentration gradient.
3.4 Gas Permeability Coefficient
Gas permeability coefficient refers to the capability of gas to permeate the polymer
dense membrane, i.e., the product of the gas solubility coefficient and the gas diffusion
coefficient.
NOTE: gas permeability coefficient P is the volume of gas that permeates a unit area of a
specimen per unit time at a constant temperature and unit pressure difference
under standard conditions during stable permeation, i.e., the volume at the
temperature of 0 °C and the pressure of 101.325 kPa.
3.5 Ideal Separation Coefficient
Ideal separation coefficient represents the difference in the permeability of the
membrane to different gases, i.e., the ratio of the permeability coefficients to two pure
gases.
4 Test Principle
Use a specimen to separate the infiltration cell with a constant volume into two
independent spaces; fill one side (high-pressure side) with a certain pressure of test
gas to form a pressure difference between the cavities on both sides. The test gas
permeates through the specimen from the high-pressure side and enters the low-
pressure side and causes pressure changes on the low-pressure side. By recording
the pressure changes, the gas permeation rate of the specimen can be calculated. The
capability of the gas to permeate a polymer homogeneous dense membrane is
expressed by the gas permeability coefficient. In accordance with the solubilization -
diffusion mechanism, the gas permeability coefficient equals to the product of the gas
solubility coefficient and the gas diffusion coefficient: P = S  D (P: the gas permeability
coefficient; S: the gas solubility coefficient; D: the gas diffusion coefficient). The ideal
separation coefficient  is obtained through the ratio of the permeability coefficients of
5---safety valve;
6---pressure sensor;
7---gas storage tank;
8---vacuum pump;
9---gas cylinder.
Figure 1 -- Schematic Diagram of Gas Permeability Tester
6 Specimen
6.1 Prepare polymer membrane material into polymer homogeneous dense membrane.
See Appendix B for the preparation method.
6.2 The polymer homogeneous dense membrane shall have uniform thickness, and
without wrinkles, pinholes or stains.
6.3 In accordance with the conditions specified in Chapter 6 of GB/T 2918-2018, place
the membrane in the desiccator for more than 48 h.
6.4 Cut a circular specimen with a diameter of 20 mm ~ 35 mm on the membrane. Use
a circle cutter to cut a circular ring with an outer diameter of about 70 mm and an inner
diameter smaller than the diameter of the membrane sample on the aluminum tape.
Paste the specimen on the circular aluminum tape; the sticking surface shall be flat,
and without wrinkles, so that the specimen is concentric with the tape ring.
7 Test Procedures
The test procedures of the gas permeability coefficient are as follows:
a) Take more than 10 different positions of the specimen; use the thickness
measuring instrument to measure the thickness. The arithmetic mean value
of the measurement results is the thickness of the specimen L. Use the
Vernier caliper to measure the inner diameter of the aluminum tape; take the
arithmetic mean value of the measurement results of more than 3 different
positions as the diameter of the specimen d;
b) Internally place non-woven fabric or chemical analysis filter paper in the test
cavity of the infiltration cell; evenly paste the specimen in the infiltration cell;
c) Close the needle valves F1 ~ F8 and the gas cylinder (9); open the vacuum
pump (8); successively and slowly open valve F7 and F3;
d) Successively and slowly open valve F5, F1, F8 and F6; vacuumize and degas
the entire system for at least 24 h, so that the system vacuum indicated by
the vacuum gauge (1) is ≤ 4 Pa; close valve F7, then, close the vacuum pump
(8);
e) Stabilize it for 2 h; successively close valve F1, F5 and F8. Slowly open the
test gas cylinder (9) and valve F8, so that the gas enters the gas storage tank
(7). When the pressure sensor (6) shows that the pressure is above 0.1 MPa,
lightly open valve F2 to empty the system. When the pressure of the pressure
sensor (6) is greater than 0.1 MPa, quickly close valve F2. Repeat the opening,
emptying and closing of valve F2 for 3 times to replace the residual gas in the
gas storage tank (7).
f) Close valve F6; adjust valve F8; when the pressure value displayed by the
pressure sensor (6) reaches 1.1 times of the test pressure p0, successively
close the gas cylinder (9) and valve F8;
g) Set the test temperature T on the temperature sensor (3) and turn on the
heating; after 1 h ~ 2 h, when the gas temperature in the gas storage tank (7)
is consistent with the test temperature T, start the test;
h) Close valve F3; open valve F6; lightly open valve F2; when the pressure value
displayed by the pressure sensor (6) reaches the test pressure p0, close valve
F2;
i) Record the test gas test pressure p0, test temperature T, specimen thickness
L, specimen diameter d and test start time t. Slowly open valve F1; meanwhile,
actuate the recorder to collect the pressure on the underside of the specimen
at different times; record the variation curve of the downside pressure of the
specimen and the test time. When the curve manifests linearity, then, it
reaches stable permeation and the test is finished.
Repeat step c) ~ i) for 3 times.
8 Test Data Processing
8.1 Gas Permeability Coefficient
The gas permeability coefficient P shall be calculated in accordance with Formula (1):
Where,
......
 
(Above excerpt was released on 2021-09-03, modified on 2021-09-03, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT40260-2021