GB/T 42923-2023 English PDF (GBT42923-2023)

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GB/T 42923-2023: Glass-fibre-reinforced plastic products - Determination of fibre length
GB/T 42923-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.120
CCS Q 23
GB/T 42923-2023 / ISO 22314:2006
Glass-fiber-reinforced Plastic Products - Determination of
Fiber Length
(ISO 22314:2006, Plastics - Glass-fiber-reinforced Products - Determination of
Fiber Length, IDT)
ISSUED ON: AUGUST 6, 2023
IMPLEMENTED ON: MARCH 1, 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 Test Principle ... 5
5 Test Equipment ... 5
6 Test Procedures ... 6
7 Test Report ... 8
Bibliography ... 10
Glass-fiber-reinforced Plastic Products - Determination of
Fiber Length
1 Scope
This document describes the method for determining fiber length in glass-fiber-reinforced
plastic products.
This document is applicable to discontinuous glass-fiber-reinforced thermoplastic molding
compounds and molded parts. Before molding, the fiber length is less than or equal to 7.5 mm;
after molding, the fiber length is less than 1 mm.
NOTE: fiber-reinforced polymer matrix composites of other lengths 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 the 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.
ISO 472 Plastics - Vocabulary
NOTE: GB/T 2035-2008 Terms and Definitions for Plastics (ISO 472:1999, IDT)
ISO 1172 Textile-glass-reinforced Plastics - Prepregs, Molding Compounds and Laminates -
Determination of the Textile-glass and Mineral-filler Content - Calcination Methods
NOTE: GB/T 2577-2005 Test Method for Resin Content of Glass Fiber Reinforced Plastics (ISO
1172:1996, MOD)
3 Terms and Definitions
The terms and definitions defined in ISO 472 are applicable to this document.
Addresses of the terminology database maintained by ISO and IEC for standardization are as
follows:
---ISO online browsing platform: http://www.iso.org/obp;
---IEC electronic open platform: http://www.electropedia.org/.
6 Test Procedures
6.1 Specimen Preparation
Take a certain amount of sample from the calcined ash. Its fiber concentration is such that each
image displayed on the screen contains approximately 100 fibers. The amount of sample
depends on the fiber content and test conditions, especially the diameter of the crystallizing
dish (since fibers are deposited on a horizontal plane, the water depth in the crystallizing dish
has no effect on the concentration of fibers deposited on the glass slide).
EXAMPLE: for a glass-fiber-reinforced polyamide composite material with a content of 30%,
when using a crystallizing dish with a diameter of 90 mm, approximately 0.006 g of
sample is required.
NOTE 1: it is assumed that the fiber length is less than 1 mm.
In accordance with the requirements of ISO 1172, at 625 C, calcinate the material for 1 hour
and 30 minutes, then, cool it.
NOTE 2: the obtained ash consists mainly of glass fibers and may also include mineral fillers. Since
the fibers are extremely fragile, all subsequent treatment must be done with extreme care,
so as to avoid breakage and invalid measurement results.
NOTE 3: after cooling, transfer the ash in the crucible to a watch glass.
NOTE 4: choose the material of an appropriate mass and size. If the material is not sufficiently
calcined, properly extend the calcination time.
Place the previously degreased glass slide into the crystallizing dish (5.2) and pour an
appropriate amount of demineralized water (containing a small amount of surfactant) to cover
the glass slide. In accordance with the mass and size of the fibers, determine the amount of
water, so as to avoid the formation of convection currents during subsequent evaporation.
Pour the ash in the watch glass onto the glass slide in the crystallizing dish (or use the tip of the
scraper to transfer a sufficient amount of ash).
Place the crystallizing dish containing the ash into the ultrasonic equipment to disperse the
fibers without any mechanical action. The time required for dispersion ranges from a few
seconds to one minute.
NOTE 5: reasonably choose the power and frequency of the ultrasonic equipment, so as to avoid
fiber breakage.
Place the crystallizing dish into the oven (5.8) preheated to 130 C for about 1 h, so as to remove
moisture. Then, let it cool. If heating causes fiber bonding, then, this step can be omitted.
Place the crystallizing dish next to the microscope or stereoscope (5.4). Place the fiber-covered
glass slide under the lens of a microscope or stereoscope.
If necessary, wipe away all fibers from the bottom of the glass slide.
6.2 Calibration
Use a reference scale to calibrate the system. It is recommended to use a calibration glass slide
with a length of 1 mm or 1.5 mm.
Calibrate by measuring the length of the calibration glass slide. In accordance with the method
of measuring fiber length, use the mouse to click on both ends of the calibration glass slide, and
compare the reading with the length of the calibration glass slide. The tolerance should be 0.01
mm.
If necessary, increase the frequency of microscope calibration.
6.3 Examination and Measurement
In the pattern of brightfield illumination or darkfield illumination (circular illumination), use
reflected light or transmitted light to directly examine the fibers, and it is unnecessary to use
coverslips or mounting fluid.
Adjust the magnification area (optical and projection) to obtain an image magnified 50 ~ 100
 on the screen. The magnification shall be such that (100  20) intact fibers can be displayed
on the screen.
Use the mouse to click on both ends of each fiber and manually measure the length of all intact
fibers displayed on the screen. Adopt the method of manual measurement to respectively
measure (100  20) fibers from three images and measure a total of (300  60) fibers.
NOTE 1: this manual measurement method can be replaced by a semi-automatic measurement
method. However, semi-automatic measurement method tends to measure fibers with a
relatively small length, and the measurement results obtained will be systematically
smaller than those obtained by the manual measurement method.
NOTE 2: beyond the scope of this method, if relatively long fibers with a length not exceeding 5
mm are measures, as long as the quality of the optical system is good enough to obtain
satisfying measurement data, then, the magnification can be reduced to 15 times.
NOTE 3: if the measurement results of the three images are significantly different, then, increase
the number of fibers for the measurement.
6.4 Result Expression
The expression of the test results is as follows.
---The average fiber length is calculated in accordance with Formula (1):