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GB/T 1037-2021 PDF in English


GB/T 1037-2021 (GB/T1037-2021, GBT 1037-2021, GBT1037-2021)
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GB/T 1037-2021: PDF in English (GBT 1037-2021)

GB/T 1037-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.140.10
CCS G 31
Replacing GB/T 1037-1988
Test method for water vapor transmission of plastic film and
sheet - Desiccant method and water method
ISSUED ON: NOVEMBER 26, 2021
IMPLEMENTED ON: JUNE 1, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Principle and method overview ... 6
5 Samples ... 6
6 Sample conditioning ... 7
7 Instruments and reagents ... 7
8 Test conditions ... 11
9 Test procedures ... 11
10 Test results ... 14
11 Test report ... 15
Test method for water vapor transmission of plastic film and
sheet - Desiccant method and water method
1 Scope
This document specifies two cup methods for determining the water vapor transmission
properties of plastic films and sheets – the desiccant method and the water method.
This document is applicable to the determination of water vapor transmission properties
of plastic films and sheets. This document can be used as a reference to the
determinations of the water vapor transmission properties of paper, non-woven fabrics,
artificial leather, and other materials.
2 Normative references
The following documents contain the provisions which, through normative reference in
this document, constitute the essential provisions of this document. For the dated
referenced documents, only the versions with the indicated dates are applicable to this
document; for the undated referenced documents, only the latest version (including all
the amendments) is applicable to this document.
GB/T 2918 Plastics - Standard atmospheres for conditioning and testing
GB/T 6672 Plastics film and sheeting - Determination of thickness by mechanical
scanning
GB/T 6682 Water for analytical laboratory use - Specification and test methods
ISO 2602:1980 Statistical interpretation of test results - Estimation of the mean -
Confidence interval
3 Terms and definitions
The following terms and definitions apply to this document.
3.1 water vapor transmission; WVT
Under the conditions of specified temperature and relative humidity and a certain water
vapor pressure difference between both sides of the sample, the mass of water vapor
permeating the sample per unit area within 24 hours.
3.2 water vapor permeability
Pv
In a specified temperature and relative humidity environment, under a unit of water
vapor pressure difference, the mass of water vapor permeating per unit thickness and
unit area of the sample per unit time.
4 Principle and method overview
4.1 Principle
Under the specified temperature and relative humidity conditions, and a certain water
vapor pressure difference is maintained between both sides of the sample within a
certain time range, the mass of water vapor permeating the sample is tested, and then
performance parameters such as the water vapor transmission and water vapor
permeability are calculated.
4.2 Method overview
By the changing trend of the mass of the moisture-permeable cup during the test, the
cup methods can be divided into the desiccant method (that is, the mass of the moisture-
permeable cup gradually increases) and the water method (that is, the mass of the
moisture-permeable cup gradually decreases). When the desiccant method and the
water method are used for testing the same sample, the test results obtained by the two
test methods are not exactly the same. The appropriate test method shall be selected
according to factors such as the sample itself and its actual use conditions.
According to the instruments used, it can be further subdivided into the constant
temperature and humidity chamber method and the water vapor transmission
performance tester method.
NOTE: In general, samples with high water vapor transmission are more suitable for the water method.
For hygroscopic samples such as paper, non-woven fabrics, and artificial leather, attention shall be paid
to the equilibrium time when the water method is used; if both the desiccant method and the water method
can meet the test range requirements of water vapor transmission of hygroscopic samples or other special
materials, it is necessary to additionally consider the influence of 100% relative humidity in the moisture-
permeable cup on the sample in the water method.
5 Samples
5.1 The sample shall be representative, flat, uniform, and free of pollution, without
holes, pinholes, creases, scratches, and other defects. When the sample is cut, it shall
be ensured that the sample has no burrs. The sample area shall be larger than the
permeable area of the moisture-permeable cup.
5.2 At least three samples for each group shall be taken. The test surface of the sample
shall be selected correctly according to the test requirements and actual application
conditions.
6 Sample conditioning
Unless otherwise specified, according to the provisions of GB/T 2918, the sample shall
be conditioned for at least 4 hours in the “23/50” standard environment, and the
standard environment level is level 2.
7 Instruments and reagents
7.1 Instruments
7.1.1 Constant temperature and humidity chamber
The fluctuation of temperature control is not more than 0.5 °C, the fluctuation of relative
humidity is not more than 2%, and the wind speed is 0.5 m/s~2.5 m/s. After the door is
closed, the specified temperature and relative humidity shall be reached again within
15 minutes.
7.1.2 Analytical balance
The division value is not more than 0.1 mg.
7.1.3 Moisture-permeable cup
It shall be made of lightweight, corrosion-resistant, impermeable, and air-tight materials.
The effective test area shall be at least 25 cm2, and the area of desiccant or distilled
water shall not be smaller than the area of the cup mouth. Commonly used moisture-
permeable cups include circular moisture-permeable cups with guide rings, square
moisture-permeable cups with fixed molds, and circular moisture-permeable cups
without sealants. The structures are shown in Figure 1, Figure 2, and Figure 3. Moisture-
permeable cups of other shapes and structures can also be made according to test
requirements. The circular moisture-permeable cup with a guide ring shown in Figure
1 is not suitable for testing with a water vapor transmission performance tester.
7.1.4.2 Test chamber
The temperature and humidity are controllable and ensured to be constant. A suitable
support structure shall be set in the chamber for placing the moisture-permeable cup,
and a certain air flow rate shall be maintained to ensure that the test conditions at each
position in the chamber are uniform. The temperature and relative humidity shall be
monitored and recorded at intervals of 15 minutes at least. The fluctuation of
temperature control is not more than 0.5 °C, the fluctuation of relative humidity is not
more than 2%, and the wind speed is 0.3 m/s~2.5 m/s.
7.1.4.3 Balance weighing system
It can realize automatic weighing, and the system division value is not more than 0.1
mg.
7.1.5 Desiccator
It can be used to dry moisture-permeable cups, such as glass desiccators and
polycarbonate desiccators.
7.1.6 Thickness gauge
The division value of the instrument for measuring film thickness is not greater than
0.001 mm; the division value of the instrument for measuring sheet thickness is not
greater than 0.01 mm.
7.2 Reagents
7.2.1 Desiccants
It is used for desiccant method tests. Usually, anhydrous calcium chloride with a particle
size of 0.60 mm~2.36 mm that can pass through a certain size sieve is used, and it shall
be dried in an oven at 200 °C±2 °C for 2 hours before use. If another desiccant with an
adsorption effect is needed to be used, such as silica gel and molecular sieve, it shall be
activated under corresponding conditions before use.
7.2.2 Distilled water
It is used for water method tests. It shall meet the requirements of secondary water in
GB/T 6682.
7.2.3 Sealants
It shall not be softened and deform under the environmental conditions of 38 °C and
90% relative humidity. Based on an exposed surface area of 50 cm2, the mass change
within 24 h cannot exceed 0.001 g. The general-purpose sealant is sealing wax, and the
common formulas are as follows:
9.1.2.3 When encapsulating the sample into a circular moisture-permeable cup without
sealant, first place the sample on the inner tray of the cup, and then press the O-ring
tightly on the upper surface of the sample to ensure that the sealing ring is in contact
with the test sample sufficiently. Place the polytetrafluoroethylene gasket over the seal
and tighten the pressing cup. The area of the tray in the cup is the test area.
9.1.2.4 When encapsulating the sample into a square moisture-permeable cup, place the
sample on the supporting inner wall of the cup, and clamp the sample with a fixed mold
to achieve close contact with the sample. Pour molten sealant into the groove between
the outside of the mold and the cup wall, remove the mold after the sealant solidifies,
and remove the sealant attached to the cup wall. The area where the inner wall of the
mold is in contact with the sample is the test area.
9.1.2.5 When the sealant is injected into the moisture-permeable cup, it shall be ensured
that no cracks or air bubbles will occur after the sealant solidifies.
9.1.3 Constant temperature and humidity chamber method
9.1.3.1 Weigh the mass of the encapsulated moisture-permeable cup, and record it as
the initial mass.
9.1.3.2 Place the moisture-permeable cup in the constant temperature and humidity
chamber under stable test conditions with the mouth of the cup facing up, and weigh
the moisture-permeable cup intermittently, that is, weigh the moisture-permeable cup
at regular intervals. When the difference between the two adjacent increments of the
weighed mass of the moisture-permeable cup is not greater than 5%, the test ends. The
common weighing intervals are as follows: the first weighing is carried out after 16 h
(initial balance time), and then the interval between each subsequent weighing can be
24 h, 48 h, or 96 h. The interval between two weighings can be properly selected
according to the amount of transmission of the sample. If the amount of transmission
of the sample is too large, the initial balance time and interval time can be reduced
accordingly. However, the mass change of the moisture-permeable cup shall be
controlled by not less than 0.005 g.
9.1.3.3 For samples with low water vapor transmission or high precision requirements,
another one or two samples shall be taken for a blank test, that is, no desiccant shall be
placed in the moisture-permeable cup.
9.1.3.4 Before each weighing of the moisture-permeable cup, the moisture-permeable
cup shall be placed in a desiccator at 23 °C±2 °C to balance for 30 minutes, and then
weighed at the standard environment of 23 °C±2 °C after it is taken out. Immediately
after each weighing, the moisture-permeable cup shall be placed in a constant
temperature and humidity chamber in which the test environment has been maintained.
9.1.3.5 For each weighing, the order of moisture-permeable cups shall be consistent,
and the weighing time shall not exceed 1% of the interval between two weighings. After
each weighing, slightly vibrate the desiccant in the cup to mix it up and down evenly.
The total increment of the desiccant after absorbing water shall not exceed 10% of its
initial mass, otherwise, the test shall be discontinued.
9.1.4 Water vapor transmission performance tester method
9.1.4.1 Place the moisture-permeable cup encapsulating the sample in the test chamber
with the mouth of the cup facing up, and close the chamber door.
9.1.4.2 Through the software interface, set the test conditions such as temperature,
humidity and wind speed, the weighing interval time, and the mass increment ratio at
the end of the test, and start the test.
9.1.4.3 First, weigh the mass of the moisture-permeable cup with the tester, and records
it as the initial mass. After the test chamber reaches the set test environment, the
moisture-permeable cup is automatically weighed intermittently in the test chamber.
During the test, it is not necessary to take out the moisture-permeable cup and vibrate
the desiccant after each weighing. For the relevant test parameters, refer to 9.1.3.2. For
other test procedures, follow 9.1.3.3 and 9.1.3.5.
9.1.4.4 After the test is over, the instrument will automatically issue the test results and
related graphs.
9.2 Water method
9.2.1 Addition of distilled water
Add distilled water into the dry and clean moisture-permeable cup, the elevation of the
water surface shall be at least 3 mm to ensure that the distilled water can cover the
bottom of the cup and not contact with the sample during the whole test. In order to
prevent water vapor from condensing and adhering to the sample when it is placed in
the instrument, the temperature of the distilled water shall be controlled within a
deviation range not exceeding the test temperature ±1 °C before the sample is
encapsulated.
9.2.2 Encapsulation of samples
Encapsulate the sample according to 9.1.2.
9.2.3 Constant temperature and humidity chamber method
Carry out the test according to the steps described in 9.1.3.1, 9.1.3.2, and 9.1.3.3. Each
time the moisture-permeable cup is taken out, it must be weighed immediately in a
standard environment of 23 °C±2 °C. After each weighing, the moisture-permeable cup
shall be immediately placed in a constant temperature and humidity chamber in which
t -- the time difference between two intervals after the mass change is stabilized, in
hours (h).
If the corresponding blank test for the sample is carried out, the mass change within the
time t in the blank test shall be deducted from Δm. The test results are expressed as the
arithmetic mean of each group of samples and retained to three significant figures. If
necessary, the standard deviation and 95% confidence interval for the mean can be
calculated according to the provisions of ISO 2602:1980.
10.2 Water vapor permeability
The water vapor permeability of the sample is calculated according to formula (2).
where:
Pv -- the water vapor permeability of the sample, the unit is gram centimeter per
square centimeter second Pascal [g • cm /(cm2 • s • Pa)];
WVT -- the water vapor transmission of the sample, the unit is gram per square
meter 24 hours [g/(m2 • 24 h)];
d -- the thickness of the sample, in centimeters (cm);
Δp -- the water vapor pressure difference between both sides of the sample, in
Pascal (Pa).
The test results are expressed as the arithmetic mean of each group of samples, retained
to two significant figures.
NOTE: Generally, the thickness of plastic composite film, embossed film, and artificial leather is not
uniform, so it is not suitable for the calculation of water vapor permeability.
11 Test report
The test report shall include the following contents:
a) the executed document number;
b) the name and model of the test instrument;
c) the structure of the moisture-permeable cup;
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.