GB/T 42999-2023 English PDF (GBT42999-2023)

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GB/T 42999-2023: Home textiles - Determination of the light blocking effect of fabric - Illuminometer method
GB/T 42999-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.080.30
CCS W 55
GB/T 42999-2023
Home textiles - Determination of the light
blocking effect of fabric - Illuminometer method
ISSUED ON: SEPTEMBER 7, 2023
IMPLEMENTED ON: APRIL 01, 2024
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 Principle ... 5
5 Test method ... 5
6 Test report ... 7
Bibliography ... 9
Home textiles - Determination of the light
blocking effect to fabric - Illuminometer method
1 Scope
This document describes the test method for determination of the light blocking effect
to fabric using an illuminometer.
This document applies to home textile fabrics and their products.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 6529 Textiles - Standard atmospheres for conditioning and testing
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
3.1
light blocking effect
The ability of textiles to prevent the transmission of light.
NOTE: It is expressed as blocking rate.
3.2
illuminance
The quotient of the luminous flux incident on the surface element containing the point
divided by the area of the surface element.
NOTE: The unit is lux (lx).
[Source: GB 50034-2013, 2.0.6, modified]
4 Principle
Irradiate stable light with a certain intensity on the surface of the sample, measure the
illuminance after the light passes through the sample, compare it with the illuminance
without the sample, and characterize the light blocking effect of the fabric by
calculating the light blocking rate of the sample.
5 Test method
5.1 Test apparatus
5.1.1 The light blocking effect test apparatus shall include: a test chamber for placing
the sample, with a round hole in the center of the top; a light source simulating sunlight
is placed directly above the test chamber and vertically corresponding to the round hole
of the test chamber; an illuminometer is placed at the bottom of the test chamber to
measure changes in illuminance. Figure 1 shows a schematic diagram of a light
blocking effect test apparatus. Other apparatuses with the same effect can also be used.
5.1.2 Test chamber: The size is approximately 40 cm × 40 cm × 10 cm. The diameter
of the round hole at the top that exposes the sample to the light source shall be 10 cm.
The internal surface of the test chamber shall be covered with black coating material to
avoid light reflection inside the chamber that will affect the test results.
5.1.3 Light source: Halogen lamp, the illuminance can reach up to 199000 lx, installed
on a height-adjustable shelf.
5.1.4 Illuminometer: It shall be located at the center position below the round hole of
the test chamber. The test range is 0.01 lx ~ 199000 lx. The measurement accuracy of
the illuminometer is ±2 %.
5.4 Test procedures
5.4.1 Turn on the power switch of the test apparatus and the power indicator light will
light up.
5.4.2 Calibrate the illuminometer.
5.4.3 Set the illuminance of the light source. Set the illuminance of the light source of
the apparatus to 100000 lx, and read the illuminance value (i0) in this state.
5.4.4 Measure the illuminance value of the sample. Place the sample on the upper part
of the apparatus, with the test surface facing the light source, the surface of the sample
is flat and wrinkle-free, and read the illuminance value (i1) passing through the sample.
5.5 Result calculation
5.5.1 Calculate the blocking rate (%) according to formula (1). The test result is the
average of three samples, rounded to single digits.
where:
T - the blocking rate, %;
i1 - the illuminance value after installing the sample, in lux (lx);
i0 - the illuminance value when the sample is not installed, in lux (lx).
5.5.2 For homogeneous samples, use the average of three samples as the test result; for
samples with different colors or fabric structures, report the average of the test results
for each color or structure.
6 Test report
The test report shall include the following content:
a) Indicate that the test is conducted in accordance with this document;
b) Description of the sample;
c) Test temperature and relative humidity;
d) If necessary, indicate the test surface of the sample;
e) Test results;