ISO 21915-2:2020

INTERNATIONAL ISO
STANDARD 21915-2
First edition
2020-04
Textiles — Qualitative and
quantitative analysis of some cellulose
fibres (lyocell, cupro) and their
blends —
Part 2:
Blend quantification using light
microscopy method
Textiles — Analyses qualitative et quantitative de certaines fibres
cellulosiques (lyocell, cupro) et leurs mélanges —
Partie 2: Quantification du mélange par une méthode de
microscopie optique
Reference number
ISO 21915-2:2020(E)
©
ISO 2020

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ISO 21915-2:2020(E)

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Published in Switzerland
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ISO 21915-2:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 2
7 Procedure. 3
7.1 Prior identification . 3
7.2 Preparation of test specimen . 3
7.3 Decolouring . 3
7.4 Pre-treatment for re-dyeing . 3
7.5 Re-dyeing . 3
7.6 Measurement of fibres. 4
7.6.1 Preparation for counting. 4
7.6.2 Measurement . 4
8 Accuracy . 4
9 Test report . 5
Annex A (informative) Observation of fibres by the re-dyeing method . 6
Annex B (informative) Determination of re-dyeing temperature . 9
Annex C (informative) Interlaboratory test result .10
Bibliography .21
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ISO 21915-2:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 38, Textiles.
A list of all parts in the ISO 21915 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 21915-2:2020(E)

Introduction
The qualitative and quantitative determination of fibres is important for the distribution of textile
products. In many countries, it is legally obligatory for producers to attach information on the type of
fibres used and their mixing ratio to textile products.
Therefore, it is desirable that qualitative methods of all fibres used in textile products and quantitative
methods in the case where fibres are mixed (all combinations that can be assumed) exist as test
standards.
Cupro and lyocell described in this document are regenerated fibres made from plants and can be said
to be materials that contribute to a sustainable society in that raw materials are not derived from
petroleum.
However, cupro and lyocell are difficult to qualify. Because the characteristics of appearance, chemical
resistance, infrared spectroscopy (IR) spectrum, etc. are almost the same, the qualitative property
according to ISO/TR 11827 and the quantification by the ISO 1833 series cannot be performed in some
cases. That is, even if we know that unknown fibre is a cupro or lyocell, we cannot identify which one is.
Therefore, it is difficult to distinguish cupro or lyocell if the cupro or lyocell exists in the textile product
or the possibility that cupro and lyocell are mixed completely cannot be denied.
ISO 21915 is composed of three parts. ISO 21915-1 specifies the identification method of cupro and
lyocell by scanning electron microscope and infrared spectrum analysis. Those may be the time-
consuming methods to use the composition analysis. This document and ISO 21915-3 specify methods
for the composition analysis. The method to be used is determined by the instrument availability and
experience.
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INTERNATIONAL STANDARD ISO 21915-2:2020(E)
Textiles — Qualitative and quantitative analysis of some
cellulose fibres (lyocell, cupro) and their blends —
Part 2:
Blend quantification using light microscopy method
1 Scope
This document specifies the quantitative analysis of cupro and lyocell mixtures using the microscopical
analysis as described in ISO 20705 after re-dyeing cupro and lyocell mixtures.
This testing method is applied only for cupro and lyocell, or those blends. If other fibres are present,
those are identified using the test method of ISO/TR 11827 and removed using the relevant parts of the
ISO 1833 series.
This method is not applicable for the fibre surface is damaged during the process (e.g. chemically or
physically).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 1833 (all parts), Textiles — Quantitative chemical analysis
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 20705:2019, Textiles — Quantitative microscopical analysis — General principles of testing
ISO 21915-1, Textiles — Qualitative and quantitative analysis of some cellulose fibres (lyocell, cupro) and
their blends — Part 1: Fibre identification using scanning electron microscope and spectral analysis methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
cupro
cellulose fibre obtained by the cuprammonium process
[SOURCE: ISO 2076:2013, 4.1]
3.2
lyocell
cellulose fibre obtained by an organic solvent (3.3) spinning process (3.4)
[SOURCE: ISO 2076:2013, 4.2]
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ISO 21915-2:2020(E)

3.3
organic solvent
mixture of organic chemicals and water
3.4
solvent spinning
dissolving and spinning without the formation of a derivative
3.5
re-dyeing
process of decolouring and dyeing again fibres
Note 1 to entry: Identification of cupro and lyocell is based on the difference of their dye affinity. Usually, an
alkali treatment is applied after the decolouration.
Note 2 to entry: If the fibre mixtures have not been dyed, decolouration stage may be omitted.
4 Principle
Decolour the testing sample consisting of cupro and lyocell or either cupro or lyocell, then dye again the
decoloured sample by using the specified stain solution and the condition. Observe the re-dyed sample
by the microscopical analysis described in ISO 20705 on longitudinal views of fibre. Count the numbers
of cupro or lyocell based on the colour shade difference.
5 Reagents
The reagents to be used shall be as follows.
5.1 Water, grade 3 quality as specified in ISO 3696.
5.2 Sodium hydrosulphite solution 5 %.
Boil 50 ml of water (5.1) and add 2,5 g of sodium hydrosulphite.
SAFETY PRECAUTIONS — The harmful effects of this regent shall be borne in mind, and full
precautions shall be taking during use.
5.3 Sodium hydroxide solution of 1,8 %.
5.4 Hydrochloric acid solution of approximately 2 %, diluted by water (5.1).
5.5 Stain solution
— dyestuff (C.I. Direct Blue 71 or C.I. Direct Blue 78): 1 g;
— sodium sulfate: 1 g;
— make up to 100 ml by adding water (5.1).
Information of other dyestuff is shown in Annex A.
6 Apparatus
6.1 Water bath, capable of heating up to 40 °C ± 2 °C.
6.2 Thermometer, capable of measurement of 40 °C.
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ISO 21915-2:2020(E)

6.3 Specimen cutting tool.
6.4 Microtome, capable of cutting fibre from 0,4 mm to 0,8 mm in length and is composed of fibre
holder, fibre fixing metal fittings and fibre pusher for setting of fibre to the specified length, or this
microtome with similar functions.
6.5 Razor blade.
6.6 Light microscope and tools, as specified in ISO 20705:2019, 5.1 and Clause 6.
7 Procedure
7.1 Prior identification
Fibres present in the sample are identified according to ISO/TR 11827, and other fibres shall be removed
using the relevant parts of ISO 1833 series as stated in ISO 21915-1.
7.2 Preparation of test specimen
Prepare the specimen with a mass of 1 g and cut to approximately 1 cm × 1 cm or unravel to yarn.
7.3 Decolouring
Decolour the specimen if the sample is dyed as follows.
7.3.1 Dip the specimen in water (5.1) to wet, then extract water by absorbent paper.
7.3.2 Soak the specimen into the boiled 5 % sodium hydrosulphite solution (5.2).
7.3.3 Stir the solution until the specimen is decolourised.
NOTE A stirring duration of about 1 min has been found suitable.
7.3.4 Wash the specimen by water (5.1) and then extract water by absorbent paper.
7.4 Pre-treatment for re-dyeing
The pre-treatment shall be performed to improve the dyeability as the following procedure.
7.4.1 Dip the specimen in water (5.1) to wet, then extract water by absorbent paper.
7.4.2 Add the specimen into 50 ml of 1,8 % sodium hydroxide solution (5.3) and stir for 15 min.
7.4.3 Take out the specimen from 7.4.2 and transfer the specimen to another glass beaker with about
25 ml of approximately 2 % dilute hydrochloric acid solution (5.4), then,
7.4.4 Wash the specimen, then extract water by absorbent paper and dry up naturally.
7.5 Re-dyeing
7.5.1 Prepare the specimen a mass of 0,5 g from the pre-treated specimen.
7.5.2 Dip the specimen in water (5.1) to wet, then extract water by absorbent paper.
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ISO 21915-2:2020(E)

7.5.3 Prepare a beaker and pour 15
...