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GB/T 1038.2-2022 English PDF (GBT1038.2-2022)

GB/T 1038.2-2022 English PDF (GBT1038.2-2022)

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GB/T 1038.2-2022: Plastics -- Film and sheeting -- Determination of gas-transmission rate -- Part 2: Equal-pressure methods

This document specifies two test methods for the gas transmission of plastic film and sheeting, co-extrusion material, plastic coating material and laminated board under the condition of equal pressure---coulomb sensor method and gas chromatography.
GB/T 1038.2-2022
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 83.140.10
CCS G 31
Plastics - Film and Sheeting - Determination of Gas-
transmission Rate - Part 2: Equal-pressure Methods
(ISO 15105-2:2003, MOD)
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: MAY 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 5
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
4 Principle ... 7
5 Specimen ... 7
6 Conditioning and Test Temperature ... 7
7 Instruments and Equipment ... 8
8 Diffusion Conditions ... 9
9 Test Procedures ... 10
10 Expression of Test Results ... 10
11 Precision ... 10
12 Test Report ... 10
Appendix A (normative) Coulomb Sensor Method ... 11
Appendix B (normative) Gas Chromatography ... 16
Plastics - Film and Sheeting - Determination of Gas-
transmission Rate - Part 2: Equal-pressure Methods
1 Scope
This document specifies two test methods for the gas transmission of plastic film and sheeting, co-extrusion material, plastic coating material and laminated board under the condition of equal pressure---coulomb 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. 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 partial pressure difference on both sides of the plastic material. NOTE 1: when the test gas is oxygen, the test result is oxygen transmission rate (O2GTR). NOTE 2: 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 partial 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 (Chamber A and Chamber B). The test gas is introduced into Chamber A, while the carrier gas is introduced into Chamber B for slow purge. The total pressure in each chamber is equal (ambient atmospheric pressure). Due to the relatively high partial pressure of the test gas in Chamber A, the test gas permeates through the specimen into Chamber B, and is carried to the sensor by the carrier gas. The type of sensor used depends on the specimen material and the test gas. 5 Specimen
5.1 The specimen shall be representative, free of defects like wrinkles, folds and pinholes, and uniform in thickness. 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 Conditioning and Test Temperature
6.1 Conditioning
The specimen shall:
---be placed in a desiccator filled with anhydrous calcium chloride or other desiccant for conditioning for no less than 48 h; alternatively,
---under the test conditions required by the product standard, perform the conditioning; in accordance with the characteristics of the material to be tested, adjust the conditioning time.
6.2 Test temperature
Unless it is otherwise specified, the test shall be carried out at 23 ???C ??? 2 ???C. 7 Instruments and Equipment
7.1 Overview
See Figure A.1 and Figure B.1 for the schematic diagram of an instrument for the determination of gas transmission rate.
The instrument consists of permeation chamber, sensor, gas regulator and flow meter. In the permeation chamber, the test gas permeates through the specimen, and the sensor measures the amount of test gas permeated through the specimen. The flow meter is used to measure the flow rate of the test gas and the carrier gas.
7.2 Test Gas
The test gas is single gas or mixed gas.
Under the first circumstance, the gas pressure shall be atmospheric pressure. Under the second circumstance, the gas pressure shall be the atmospheric pressure, and the partial pressure of each component depends on its concentration in the mixed gas. 7.3 Permeation Chamber
7.3.1 The permeation chamber is divided into two mutually independent chambers - Chamber A and Chamber B by the specimen to facilitate the permeation of the test gas (see 1 in Figure A.1 and 1 in Figure B.1).
7.3.2 The test gas is introduced into Chamber A under the specified conditions, and exits Chamber A through an outlet of suitable size at the ambient atmospheric pressure. 7.3.3 The carrier gas is introduced into Chamber B under the specified conditions. The pressure difference between the two chambers shall be as small as possible, so as to avoid deformation of the specimen.
7.3.4 The permeation chamber shall be shaped so that both sides of the specimen are purged in a laminar flow.
9 Test Procedures
9.1 Remove the specimen to be tested from the state conditioning environment. 9.2 Load the specimen into the permeation chamber.
9.3 Inspect the specimen for visible defects, for example, wrinkles generated during loading. 9.4 Connect the permeation chamber to the sensor.
9.5 Adjust the two valves of the upstream of the permeation chamber to allow the carrier gas to flow into Chamber A and Chamber B. The gas flow rate is generally set between 5 mL/min ~ 100 mL/min.
9.6 Check the leakage of the instrument, then, thoroughly purge the instrument, considering that the specimen may have gas desorption. Continue to purge the instrument, until the signal received by the sensor is stable.
9.7 Once a stable signal is obtained, record this value as zero point.
9.8 Let the test gas pass through Chamber A under the specified flow rate, temperature and humidity conditions. The gas flow rate is generally set between 5 mL/min ~ 100 mL/min. 9.9 Until the sensor signal is stable, record the signal.
9.10 In accordance with the above steps, test other specimens.
10 Expression of Test Results
It depends on the method used, see A.6 or B.7.
11 Precision
Due to the lack of data from different laboratories, the precision of this test method is unknown. Once data from different laboratories become available, the statement of precision will be added to the subsequent editions.
12 Test Report
It depends on the method used, see A.7 or B.8.
Appendix A
(normative)
Coulomb Sensor Method
A.1 Overview
This method is used to determine the amount of oxygen permeating through a material. A coulomb sensor is used to determine the amount of oxygen that permeates through the material and is carried to the sensor by the carrier gas.
The current generated by the sensor is proportional to the amount of oxygen permeating through the sensor per unit time.
A.2 Instruments
Figure A.1 shows a schematic diagram of a typical instrument.
Through Valve 12, connect the sensor (see 9 in Figure A.1) to the bypass to avoid exposure of the sensor to the air when clamping the specimen (see 2 in Figure A.1). The carrier gas or test gas enters Chamber A through the valve of the upstream of the permeation chamber (see 7 in Figure A.1). The catalytic device (see 11 in Figure A.1) is used to eliminate the oxygen that may exist in the carrier gas.
NOTE: other suitable methods of eliminating oxygen from the carrier gas can also be used. A.3 Carrier Gas and Test Gas
A.3.1 The carrier gas shall be dry nitrogen containing 0.5% ~ 3% (volume fraction) hydrogen. By volume, the oxygen in the carrier gas shall not exceed 100 ???L/L.
A.3.2 The test gas shall be dry oxygen, with a volumetric purity of at least 99.5%. NOTE: for materials with a high oxygen transmission rate, a mixed gas of nitrogen and oxygen can be used, for example, air (21% oxygen). The effective permeation area of the specimen can also be reduced by the method described in 7.3.5.
A.3.3 The gas regulator (see 4 in Figure A.1) shall be placed upstream of the permeation chamber to satisfy the regulating conditions in Table 1. The device for monitoring gas humidity can be installed in the carrier gas and / or the test gas pipelines.
It is recommended that the sensor be periodically calibrated with reference materials of known transmission rate.
NOTE: the oxygen sensor used in this method is a coulomb device that generates a linear output in accordance with Faraday?€?s Law. In principle, each oxygen molecule that passes through the sensor can generate four charges. Considering that the sensor is known to have a base performance of 95% ~ 98%, it can be deemed as an inherent standard and does not need to be calibrated. Therefore, this method can be used as a reference. However, if the sensor is damaged, or there is a certain degree of loss, the absorption efficiency and the response signal are reduced, then calibration is required.
A.5 Test Procedures
A.5.1 Cut the specimen that has been conditioned in accordance with the requirements of Chapter 6 into a suitable size; put it into the permeation chamber; set the test conditions. A.5.2 Use the carrier gas at a flow rate of 5 mL/min ~ 25 mL/min to purge the permeation chamber (Chamber A and Chamber B) for 30 min. For materials with extremely low transmission rate, the purging time shall be increased. First, use the carrier gas at a flow rate of 25 mL/min ~ 50 mL/min to purge Chamber A and Chamber B for 3 min ~ 4 min, then, adjust the flow rate of the carrier gas to 5 mL/min ~ 25 mL/min and purge for 30 min. A.5.3 Check the instrument for leakage.
A.5.4 Through the voltage measuring device connected to the sensor, monitor the current generated by the sensor. When the signal of the sensor is stable, record the corresponding voltage as the zero-point voltage.
A.5.5 Immediately adjust the two valves of the upstream of the permeation chamber (see 7 in Figure A.1) to allow oxygen to pass through Chamber A, until the sensor signal becomes stable, then, record the signal value.
Films with a relatively high transmission rate may reach equilibrium after 30 min ~ 60 min; thicker or more complex materials may take several hours to obtain a stable state of oxygen transmission. Record the time waited to reach equilibrium in the report. A.5.6 In accordance with the above-mentioned steps, test the other specimens. A.6 Result Calculation
A.6.1 Oxygen transmission rate
The oxygen transmission rate (O2GTR), which is expressed in [mol/(m2 ??? s ??? Pa)], shall be calculated in accordance with Formula (A.1):
Appendix B
(normative)
Gas Chromatography
B.1 Overview
This method uses a gas chromatograph for the determination of the gas transmission rate. The gas chromatograph is equipped with a chromatographic column compatible with the test gas. B.2 Principle
The gas molecules that permeate through the specimen in the permeation chamber are carried by the carrier gas into the quantitative loop of the gas chromatograph. The quantitative loop can make all the components inside it repeatedly inject into the gas chromatograph. Compare the chromatographic peak in the test gas chromatogram with the standard spectrum. NOTE: the automatic sampling valve may generate pressure backflow, resulting in excessive pressure in the permeation chamber. Under these circumstances, it is necessary to correct this overpressure, so as to avoid deformation of the specimen.
Figure B.1 shows a schematic diagram of a typical instrument.
B.3 Gas Chromatograph
B.3.1 Overview
In accordance with the test gas used, select the suitable gas chromatographic column and detector. For special test gases, other chromatographic columns and detectors can also be used to satisfy the required sensitivity.
B.3.2 Packed column used with thermal conductivity detector (TCD)
This device is applicable to:
---oxygen, carbon dioxide, nitrogen, carbon dioxide and nitrogen mixed gas; ---mixtures of the above-mentioned gases or other gases.
NOTE: gas conditioning (see Table 1) is feasible upstream of the permeation chamber, but when using a thermal conductivity detector (TCD), it is not recommended to regulate the carrier gas.
B.3.3 Packed column used with flame ionization detector (FID)
This device is applicable to:
11---gas chromatography carrier gas inlet;
12---chromatographic column;
13---TCD or FID detector.
Figure B.1 -- Schematic Diagram of an Instrument Using Gas Chromatography for the Determination of Gas Transmission Rate
B.3.4 Capillary column used with flame ionization detector (FID)
This device is applicable to high-molecular?€?mass organic vapors, for example, odors or aromas. Under this circumstance, when vapor enters the gas chromatographic column and the detector through the permeation chamber, care shall be taken to avoid condensation of the vapor. B.4 Carrier Gas and Test Gas
B.4.1 The carrier gas shall match the detection instrument.
B.4.2 The purity of the test gas and the concentration of each gas in the mixed gas shall be known and accurate to within ??? 1%.
B.4.3 The gas shall not contain impurities that may affect the test.
B.5 Calibration Graph
B.5.1 Overview
The calibration graph of the gas chromatographic column can be obtained through the following method.
B.5.2 Method A
B.5.2.1 Order a mixed gas whose concentration of the gas to be tested is known from a professional supplier, and the concentration range can satisfy the predicted results of the tests. B.5.2.2 Successively connect each gas cylinder upstream of the quantitative loop, and record the corresponding chromatogram of each gas under the same conditions.
B.5.3 Method B
B.5.3.1 This method is applicable to the detection of non-air component gases. B.5.3.2 In glass bottles designed with partitions, dilute the sample to different concentrations, for example, use air for dilution.
B.5.3.3 Use a volumetric syringe to inject a known volume of each diluted specimen into the chromatographic column. Under the same conditions, record the chromatogram of each concentration of sample.
B.5.4 Preparation of calibration graph
The chromatograms recorded by both methods can be used to generate a curve relating the detector signal to the relevant gas concentration in the carrier gas.
B.6 Test Procedures
B.6.1 In accordance with the steps described in Chapter 9, fill the gas permeating through the specimen into the quantitative loop; in accordance with the chromatograph manufacturer?€?s instructions, inject the specimen into the chromatographic column. Monitor the detector?€?s response to the target gas, until the detector signal reaches a stable value. In the rest report, record the required time.
B.6.2 Use the integrator of the gas chromatograph to calculate the peak area of the corresponding gas in the spectrum.
B.6.3 In accordance with the calibration graph prepared in B.5, calculate the concentration of the corresponding gas in the carrier gas.
B.6.4 Meanwhile, use a calibrated flow meter (for example, a soap-bubble flow meter) to determine the flow rate of the carrier gas passing through the chromatographic column. This determination can be performed at the carrier gas outlet (see 9 in Figure B.1) after closing the quantitative loop (see 10 in Figure B.1) to remove the gas from the chromatographic column. B.7 Result Calculation
B.7.1 Gas transmission rate
The gas transmission rate (GTR), which is expressed in [mol/(m2 ??? s ??? Pa)], shall be calculated in accordance with Formula (B.1):
Where,
D---the flow rate of the carrier gas, expressed in (cm3/min);
C---the concentration of the corresponding gas in the carrier gas, expressed by volume, measured from the chromatogram;
A---the effective permeation area of the specimen, expressed in (m2);
pa---the ambient atmospheric pressure, expressed in (Pa);
p0---the partial pressure of the corresponding gas in the test gas, expressed in (Pa).

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