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Film and sheeting -- Determination of gas-transmission rate -- Part 1: Differential-pressure methods
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GB/T 1038-2000 | English | 199 |
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Plastics. Film and sheeting. Determination of gas transmission. Differential-pressure method
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Test method for gas permeability of plastic film
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GB/T 1038.1-2022: PDF in English (GBT 1038.1-2022) GB/T 1038.1-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.140.10
CCS G 31
Replacing GB/T 1038-2000
Plastics - Film and Sheeting - Determination of Gas-
transmission Rate - Part 1: Differential-pressure Methods
(ISO 15105-1:2007, MOD)
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: MAY 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 6
1 Scope ... 7
2 Normative References ... 7
3 Terms and Definitions ... 7
4 Principle ... 8
5 Specimen ... 8
6 Instruments, Test Procedures and Result Calculation ... 8
7 Expression of Test Results ... 9
8 Precision ... 9
9 Test Report ... 9
Appendix A (normative) Pressure Sensor Method ... 10
Appendix B (normative) Gas Chromatography ... 15
Plastics - Film and Sheeting - Determination of Gas-
transmission Rate - Part 1: Differential-pressure Methods
1 Scope
This document specifies two test methods for the gas transmission of plastic film and sheeting,
as well as sandwich material under the condition of differential pressure---pressure sensor
method and gas chromatography.
This document is applicable to the determination of gas transmission of plastic film and
sheeting. The determination of gas transmission of other materials may take this as a reference.
NOTE: the differential-pressure method is also commonly referred to as the pressure differential
method.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in this 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 6672 Plastics Film and Sheeting - Determination of Thickness by Mechanical Scanning
(GB/T 6672-2001, ISO 4593:1993, IDT)
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 Gas Transmission Rate; GTR
Gas transmission rate refers to the amount of gas permeating through a unit area of the material
per unit time under the unit pressure difference on both sides of the plastic material.
NOTE: when it is expressed by the amount of substance, the unit is [mol/(m2 s Pa)]; when it is
expressed by volume, the unit is [cm3/(m2 d Pa)].
3.2 Gas Permeability; Coefficient of Gas Permeability
Gas permeability / coefficient of gas permeability refers to the amount of gas permeated per
unit area and unit thickness of the material per unit time under the unit pressure difference on
both sides of the plastic material.
NOTE 1: when it is expressed by the amount of substance, the unit is [mol m/(m2 s Pa)]; when
it is expressed by volume, the unit is [cm3 cm/(cm2 s Pa)].
NOTE 2: although P is a physical property of the polymer, the film preparation method affects the
orientation and crystal structure of the polymer material, which in turn affects the
permeability of the material.
NOTE 3: P is only used to measure single-layer plastic film and sheeting made of a single material.
4 Principle
The specimen clamped in the permeation chamber (see Figure A.1 and Figure B.1) divides the
permeation chamber into two mutually independent parts. Vacuumize the low-pressure chamber,
then, vacuumize the high-pressure chamber. Fill the test gas into the high-pressure chamber
after vacuuming, and the test gas permeates into the low-pressure chamber through the
specimen. By monitoring the pressure increase of the low-pressure chamber or through the gas
chromatograph, obtain the gas permeability of the specimen.
5 Specimen
5.1 The specimen shall be representative, uniform in thickness, and free of defects like wrinkles,
folds and pinholes, etc. The area of the specimen shall be larger than the gas permeation area
of the permeation chamber, and shall be tightly clamped on the permeation chamber.
5.2 Unless it is otherwise specified or agreed upon by the relevant parties, three specimens shall
be tested.
5.3 Mark the surface of the specimen facing the test gas.
NOTE: in principle, it is recommended that the test shall be exactly the same as the actual use
conditions, for example, for packaging materials, the gas permeates from the inside to the
outside, or from the outside to the inside.
5.4 In accordance with GB/T 6672, measure the thickness of each specimen, expressed in (m).
On the entire test area, measure no less than 5 points; record the minimum, maximum and
average values, and the results are accurate to 1 m.
6 Instruments, Test Procedures and Result Calculation
Two test methods for gas transmission rate are described in the appendixes of this document:
---Appendix A: pressure sensor method;
Appendix A
(normative)
Pressure Sensor Method
A.1 Overview
This method can be used to determine the gas transmission rate of various types of plastic
material.
A.2 Instruments and Materials
A.2.1 Overview
See Figure A.1 for the schematic diagram of an instrument using pressure sensor for the
determination of gas transmission rate. This instrument consists of permeation chamber,
pressure sensor, gas inlet device, chamber volume control device and vacuum pump. The gas
inlet device is used to supply gas to the permeation chamber. The gas permeates through the
specimen in the permeation chamber, and the pressure sensor is used to detect the pressure
change caused by the gas permeating through the specimen.
A.2.2 Permeation chamber
The permeation chamber shall consist of an upper chamber (high-pressure chamber) and a low
chamber (low-pressure chamber), with a fixed permeation area. The high-pressure chamber
shall have a gas inlet, and the low-pressure chamber shall be connected to the sensor. The
surface of the permeation chamber in contact with the specimen shall be smooth and flat, and
there shall be no gas leakage after loading the specimen. The diameter of the gas permeation
area is between 10 mm ~ 150 mm.
A.2.3 Pressure sensor
The sensor shall be able to determine the pressure change of the low-pressure chamber, and the
sensitivity shall not be lower than 5 Pa (0.038 mmHg). A mercury-free vacuum gauge,
electronic diaphragm sensor or other suitable types of sensor shall be used.
A.2.4 Gas inlet device
Introduce the test gas into the high-pressure chamber from the gas inlet device. The gas inlet
device is a gas tank for gas storage, equipped with a pressure gauge with a sensitivity of not
less than 100 Pa (0.75 mmHg). The capacity of the gas storage tank shall be large enough, so
that the pressure of the high-pressure chamber will not drop due to gas permeation.
A.2.5 Chamber volume control device
In order to extend the test range of gas transmission rate, the volume of the low-pressure
A.3 Conditioning and Test Temperature
A.3.1 Conditioning
Place the specimen in a desiccator filled with anhydrous calcium chloride or other suitable
desiccant. Under the same condition as the test temperature, dry the specimen for at least 48 h.
For non-hydroscopic materials, drying is usually not required.
A.3.2 Test temperature
The test shall be carried out under the condition of 23 C 2 C. Upon agreement of the relevant
parties, other test conditions can be selected.
A.4 Test Procedures
A.4.1 Place a filter paper with the same permeation area on the low-pressure chamber (see 3 in
Figure A.1).
NOTE: filter paper is used to support the film specimen, and it is recommended to use filter paper
with a thickness between 0.2 mm ~ 0.3 mm that is usually used for chemical analysis.
A.4.2 Evenly apply a thin layer of vacuum grease on the flat edges of the upper and lower parts
of the permeation chamber. Install the specimen on the lower chamber, and there shall be no
wrinkling or loosening.
A.4.3 Successively place a rubber sealing ring and the upper chamber on the specimen; press
the two parts of the permeation chamber with uniform pressure, so that the specimen is
completely sealed.
A.4.4 Close the gas source valve (see 9 in Figure A.1) and the block valve (see 10 in Figure
A.1); open the vent valve (see 11 in Figure A.1). Turn on the vacuum pump to vacuumize the
low-pressure chamber, so that the specimen and the filter paper fit together. Open the block
valve (see 10 in Figure A.1); vacuumize the high-pressure chamber, until the pressure in the
low-pressure chamber reaches below 27 Pa, and continue degassing for more than 3 h, so as to
remove the gas and water vapor adsorbed by the specimen. It shall be noted that the time
required to vacuumize the permeation chamber to vacuum depends on the permeability of the
specimen.
A.4.5 After vacuuming is completed, close the vacuum pump, the block valve (see 10 in Figure
A.1) and the vent valve (see 11 in Figure A.1); maintain the vacuum degree.
A.4.6 If the pressure of the low-pressure chamber rises, repeat the operations in A.4.3 ~ A.4.5,
until the pressure in the low-pressure chamber is stable; complete the degassing.
A.4.7 Open the gas source valve (see 9 in Figure A.1); introduce the gas into the high-pressure
chamber. After the pressure reaches about 0.1 MPa (1 atm), close the gas source. Record the
pressure ph of the high-pressure chamber displayed on the pressure gauge connected to the gas
inlet device. If the pressure in the low-pressure chamber begins to rise, it indicates that the gas
Appendix B
(normative)
Gas Chromatography
B.1 Applicability
This method uses a gas chromatograph equipped with a chromatographic column compatible
with the gas or mixed gas to determine the gas transmission rate. This method is especially
suitable for the determination of the gas transmission rate of each component in mixed gas.
B.2 Instruments and Materials
B.2.1 Overview
The schematic diagram of the instrument using gas chromatograph for the determination of gas
transmission rate is shown in Figure B.1. This instrument consists of gas permeation chamber,
quantitative loop, valve, gas chromatograph, test gas controller and vacuum pump. The
quantitative loop is used to collect the gas permeating through the specimen.
B.2.2 Permeation chamber
The permeation chamber shall consist of a high-pressure chamber (see the upper half of the
chamber in Figure B.1) and a low-pressure chamber (the lower half of the chamber). The high-
pressure chamber shall have an air inlet; the low-pressure chamber shall be connected to the
gas chromatograph through the quantitative loop. The surface of the permeation chamber in
contact with the specimen shall be flat; there shall be no gas leakage. The diameter of the gas
permeation area is between 10 mm ~ 150 mm.
B.2.3 Gas chromatograph
The gas chromatograph shall be able to measure the amount of permeated gas, expressed in
terms of gas pressure, with an accuracy of not lower than 5 Pa.
B.2.4 Test gas controller
The test gas controller shall be adjustable, so as to maintain a specific pressure in the high-
pressure chamber.
B.2.5 Test gas
If a single gas is used, the volumetric purity of the gas shall be higher than 99.5%. If a mixed
gas is used, when calculating GTR, the composition of the mixed gas shall be determined before
or after the test.
B.2.6 Carrier gas
4---test gas controller; 12---Valve 2;
5---test gas source; 13---Valve 3;
6---vacuum pump; 14---Valve 4;
7---quantitative loop; 15---Valve 5;
8---carrier gas inlet; 16---carrier gas outlet.
Figure B.1 -- Schematic Diagram of an Instrument Using Gas Chromatograph for the
Determination of Gas Transmission Rate
B.4 Conditioning and Test Temperature
B.4.1 Conditioning
The specimen shall be conditioned under the test conditions. In accordance with the
characteristics of the material to be tested, adjust the conditioning time.
NOTE: place the specimen in a chamber equipped with an automatic adjustment device, so as to
satisfy these conditions.
B.4.2 Test temperature
Under the condition of 23 C 2 C, 0% RH or 23 C 2 C, 50% RH, carry out the test. Upon
agreement of the relevant parties, other test conditions can also be selected.
B.5 Test Procedures
B.5.1 Place a filter paper with the same permeation area on the low-pressure chamber (see 3 in
Figure B.1).
NOTE: filter paper is used to support the film specimen, and it is recommended to use filter paper
with a thickness between 0.2 mm ~ 0.3 mm that is usually used for chemical analysis.
B.5.2 Evenly apply a thin layer of vacuum grease on the flat edges of the upper and lower parts
of the permeation chamber. Install the specimen on the lower chamber, and there shall be no
wrinkling or loosening.
B.5.3 Successively place a rubber sealing ring and the upper chamber on the specimen; press
the two parts of the permeation chamber with uniform pressure, so that the specimen is
completely sealed.
B.5.4 Close Valve 1 (see 11 in Figure B.1), Valve 4 (14 in Figure B.1) and Valve 5 (15 in Figure
B.1); open Valve 2 (12 in Figure B.1) and Valve 3 (13 in Figure B.1). Turn on the vacuum pump
to vacuumize the low-pressure chamber, so that the specimen and the filter paper fit together.
Open Valve 5 (15 in Figure B.1); vacuumize the high-pressure chamber, until the vacuuming is
completed. It shall be noted that the time required to vacuumize the permeation chamber to
vacuum depends on the permeability of the specimen.
B.5.5 After vacuuming is completed, close Valve 5 (15 in Figure B.1); stop the vacuuming of
the high-pressure chamber. Open Valve 1 (see 11 in Figure B.1); introduce the test gas into the
high-pressure chamber through the gas controller to maintain a certain pressure in the high-
pressure chamber. The test gas permeates from the high-pressure camber through the specimen
into the low-pressure chamber, and is drawn out by the vacuum pump.
B.5.6 Close Valve 2 (see 12 in Figure B.1); collect the permeated gas in the quantitative loop
(see 7 in Figure B.1). After the preset time t, close Valve 3 (see 13 in Figure B.1); use the carrier
gas (see 8 in Figure B.1) to purge the gas in the quantitative loop (see 7 in Figure B.1) into the
gas chromatographic column (see 9 in Figure B.1). Calculate the peak area of the test gas in the
chromatogram. In accordance with the calibration graph obtained in B.3, calculate the amount
of gas Vs collected by the quantitative loop within the time t, expressed in (L).
B.5.7 Repeat B.5.6, until a stable state is reached. When the amount of gas permeating through
the specimen is basically constant within the time t, it can be deemed that the stable state is
reached.
B.5.8 A blank test shall be carried out before or after the test, so as to determine the (small)
amount of gas existing in the quantitative loop at the beginning of the time t under the stable
state. Meanwhile, close Valve 2 (12 in Figure B.1) and Valve 3 (13 in Figure B.1), so as to
obtain the gas collected in the quantitative loop under the stable state; determine the amount of
gas collected Vb.
B.6 Result Calculation
B.6.1 Gas transmission rate
When the gas transmission rate (GTR) is expressed in [mol/(m2 s Pa)], it shall be calculated
in accordance with Formula (B.1):
Where,
Vs---the amount of test gas collected by the quantitative loop, expressed in (L);
Vb---the blank value (see B.5.8), expressed in (L);
k---the conversion factor for converting the volume of the quantitative loop to the total volume
of the low-pressure chamber;
T---the test temperature, expressed in (K);
A---the permeation area of the specimen, expressed in (m2);
...... Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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