GB/T 42694-2023 PDF in English
GB/T 42694-2023 (GB/T42694-2023, GBT 42694-2023, GBT42694-2023)
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Textiles -- Testing and evaluation for surface wetting resistance -- Contact angle and rolling angle method
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Standards related to: GB/T 42694-2023
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GB/T 42694-2023: PDF in English (GBT 42694-2023) GB/T 42694-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.30
CCS W 04
Textiles - Testing and evaluation for surface wetting
resistance - Contact angle and rolling angle method
ISSUED ON: MAY 23, 2023
IMPLEMENTED ON: DECEMBER 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Principle ... 5
5 Apparatus and reagents ... 6
6 Specimen preparation ... 8
7 Test procedure ... 9
8 Expression and evaluation of results ... 10
9 Test report ... 11
Textiles - Testing and evaluation for surface wetting
resistance - Contact angle and rolling angle method
1 Scope
This document describes the method for determination of surface wetting resistance of
fabrics using contact angle and rolling angle tests; provides an evaluation of wetting
resistance.
This document applies to all types of fabrics.
2 Normative references
The contents of the following documents, through normative references in this text,
constitute indispensable provisions of this document. Among them, for dated references,
only the edition corresponding to that date applies to this document. For undated
references, the latest edition (including all amendments) applies to this document.
GB/T 6529 Textiles - Standard atmospheres for conditioning and testing
GB/T 6682 Water for analytical laboratory use - Specification and test methods
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Contact angle
The angle containing the droplet BETWEEN the tangent (the tangent to the gas-liquid
interface drawn at the intersection of the gas, liquid, and solid phases) AND the solid-
liquid boundary, when the liquid forms droplets on the solid surface and reaches
equilibrium.
Note: It is as shown in Figure 1.
5.1.4 Optical imaging device
It shall be able to acquire clear images of the droplet and specimen. The acquired images
can be viewed on the measurement system.
5.1.5 Liquid supply device
The liquid supply device with injection head shall be able to quantitatively add (5±1)μL
of liquid. For the injection head, it is recommended to use a flat-headed needle with a
diameter of 0.21 mm~0.52 mm. Stainless-steel needles are mostly used; other types
such as Teflon-coated needles can also be used.
5.1.6 Measurement system
It can control the light source, optical imaging device, liquid supply device and other
components to complete the test operation. It can record and analyze the data of
different droplet volume, shape and contact angle, which are obtained from the optical
imaging system. The calculation is accurate to 0.1°.
Note: Contact angle calculation methods include Young-Laplace method, width-height method,
circle method, ellipse method, tangent method, etc.
5.2 Rolling angle meter
The rotating device of the rolling angle meter shall be able to drive the specimen stage
to rotate axially continuously, to measure the rotating angle. Its rotation axis is on the
surface of the specimen stage. The rotating device has a graduated line showing the
rotating angle with an accuracy of 0.1°. It is equipped with a micropipette or dropper
capable of dropping about 50 μL. The schematic diagram of rolling angle meter is
shown in Figure 4.
7 Test procedure
7.1 General
The standard atmospheres for conditioning and testing shall be carried out in
accordance with the provisions of GB/T 6529. Before the test, the sample shall be
conditioned and balanced. After consultation with relevant parties, conditioning and
testing can be carried out under other test conditions; but shall be noted in the test report.
Note: The test results under different environmental conditions are not comparable. The evaluation
indicators may not be applicable.
7.2 Determination of contact angle
7.2.1 Adjust the liquid supply device to absorb an appropriate amount of reagent (5.3).
If there are bubbles at the injection head, it is necessary to discharge the bubbles, to
ensure that there are no bubbles in the liquid supply device.
7.2.2 Use a spirit level to level the specimen stage; fix the instrument debugging
specimen with the testing surface facing upwards and flat on the specimen stage.
7.2.3 Set the injection liquid volume to 5 μL. The injection head is approximately 2 mm
away from the surface of the specimen to be tested.
7.2.4 After dropping (5±1)μL of liquid on the surface of the instrument debugging
specimen, remove the injection head. Adjust the camera and the specimen stage so that
the droplet image has a clear contour and appropriate size. When the droplet is
hemispherical or nearly spherical, the droplet diameter accounts for approximately 1/3
of the length of the image window.
7.2.5 Remove the instrument debugging specimen; wipe the specimen stage to keep it
dry; install the test specimen. After adding (5±1)μL of droplets to the surface of the
specimen, remove the injection head. When the contact time is 30 s, take photos of the
specimen and the droplets above it. Use the measurement system to calculate the left
and right contact angles of the droplets; take the average of the two contact angles as
the contact angle of the specimen.
7.2.6 Repeat 7.2.5, to measure the contact angle of the remaining warp (longitudinal)
and weft (transverse) specimens. If there are significant differences in the results of the
5 specimens, they shall be rejected and made up.
Note: The warp (longitudinal) contact angle is the contact angle formed by the droplet on the warp
(longitudinal) section of the specimen. The weft (transverse) contact angle is the contact
angle formed by the droplet on the weft (transverse) section of the specimen.
7.3 Determination of rolling angle
Use a spirit level to adjust the rolling angle meter to the horizontal position; then rotate
the specimen stage to 0 scale; fix the specimen in the center position of the specimen
stage. Use a micropipette or dropper to drop about 50 μL of liquid (5.3) at a distance of
5 mm from the specimen surface; immediately rotate the rotating device slowly (at a
speed of about 0.2 r/min), to drive the specimen stage to rotate. Measure the angle at
which the droplet rotates just as it rolls (i.e., the rolling angle). Measure the rolling
angles of 5 specimens in the warp direction and weft direction respectively; record the
measured results of the rolling angles of each specimen in turn. If there are significant
differences in the results of the 5 specimens, they shall be rejected and made up.
8 Expression and evaluation of results
8.1 Expression of results
For the contact angle, the average values θ1 and θ2 of 5 measurements in the warp
(longitudinal) and weft (transverse) directions respectively are taken as results; round
off to 0.1° according to the rounding principle. If the droplet contacts the surface of the
specimen and is completely absorbed by the specimen within 30 s, the contact angle of
the specimen is directly recorded as 0°.
For the rolling angle, the average values α1 and α2 of 5 measurements in the warp
(longitudinal) and weft (transverse) directions respectively are taken as results; round
off to 0.1° according to the rounding principle. When the rolling angle is >90°, or when
the droplet is completely absorbed by the specimen after addition, it can be recorded as
" >90°".
8.2 Evaluation of wetting resistance
If necessary, according to Table 1, evaluate the wetting resistance of the sample. The
contact angle shall be evaluated based on the smaller values in the warp (longitudinal)
and weft (transverse) directions. The rolling angle shall be evaluated based on the larger
values in the warp (longitudinal) and weft (transverse) directions. The contact angle and
rolling angle shall both comply with the corresponding wetting resistance grade.
Note: The contact angle evaluation index is determined based on the Young-Laplace calculation
method. If other calculation methods are used, it is necessary to verify whether there are
differences with the Young-Laplace method.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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