Nanotechnologies — Clay nanomaterials — Part 2: Specification of characteristics and measurements for clay nanoplates used for gas-barrier film applications

This document specifies characteristics to be measured and measurement methods for clay nanoplate samples in powder and suspension forms used for gas-barrier films. In addition, measurement protocols for the individual characteristics are described. This document does not deal with characteristics of post-manufacturing modification of clay nanoplates. This document does not cover considerations specific to health and safety issues either during manufacturing or use.

Nanotechnologies — Nano argiles — Partie 2: Spécification des caractéristiques et des mesures pour les argiles en nanofeuillets utilisées dans des applications de films barrières aux gaz

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Published
Publication Date
06-May-2021
Current Stage
6060 - International Standard published
Start Date
07-May-2021
Due Date
07-Mar-2021
Completion Date
07-May-2021
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TECHNICAL ISO/TS
SPECIFICATION 21236-2
First edition
2021-05
Nanotechnologies — Clay
nanomaterials —
Part 2:
Specification of characteristics and
measurements for clay nanoplates
used for gas-barrier film applications
Nanotechnologies — Nano argiles —
Partie 2: Spécification des caractéristiques et des mesures pour
les argiles en nanofeuillets utilisées dans des applications de films
barrières aux gaz
Reference number
ISO/TS 21236-2:2021(E)
©
ISO 2021

---------------------- Page: 1 ----------------------
ISO/TS 21236-2:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/TS 21236-2:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Characteristics and measurement methods . 2
5.1 General . 2
5.2 Mineral composition . 3
5.3 Chemical composition . 3
5.4 Cation exchange capacity . 3
5.5 Particle size . 4
5.6 Loss on ignition . 4
5.7 Methylene blue adsorption capacity . 4
5.8 Aspect ratio . 4
5.9 Film formability. 5
5.10 Viscosity . 5
6 Reporting . 5
Annex A (informative) Measurement protocols . 7
Annex B (informative) Principles of a gas barrier using clay nanoplates .12
Annex C (informative) Value chains of clay nanoplate materials.16
Annex D (informative) Example of reporting sheet .17
Bibliography .18
© ISO 2021 – All rights reserved iii

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ISO/TS 21236-2:2021(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 229, Nanotechnologies.
A list of all parts in the ISO 21236 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.
iv © ISO 2021 – All rights reserved

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ISO/TS 21236-2:2021(E)

Introduction
The barrier property in polymeric materials has become progressively more important in recent years
with the widespread use of plastic films and rigid plastics for food packaging, medical packaging,
electronic devices, construction, agriculture and so on. All polymeric materials have varying degrees
of gas permeability. Therefore, the required level of gas barrier performance varies depending on the
application. Barrier films often consist of multilayers or coated films designed to be impervious to
gas and moisture migration, as single-layer films are in general quite permeable to most gases. Food
packaging films are required to have oxygen gas barrier properties and water vapour barrier properties.
A transparent gas barrier film obtained by applying a silica or alumina vapour deposition method on a
PET or nylon film is generally used for food packaging, pharmaceutical packaging, industrial product
packaging and so on. Recently, a film with a higher level of gas barrier properties has been required for
organic light emitting diode displays. These high gas-barrier properties cannot be achieved by simply
using conventional barrier film for food packaging.
High gas-barrier films are expected to be used in a wide range of fields, such as electronics,
pharmaceutical packaging and hydrogen storage. Various approaches can be taken to improve barrier
properties in plastics packaging. There is a method of adding gas-impermeable nano-objects to plastic
to make nanocomposites. One of the most common types of polymer nanocomposites contains clay
nanoplates. These clay nanomaterials improve barrier properties. Many reports predict the market
expansion of nanocomposite materials.
There are many scientific papers and patents on gas barrier composite material using clay nanoplate.
Gas barrier properties are improved by mixing clay nanoplates into the polymer. The high gas-barrier
phenomenon is described in Nielsen's tortuous model. There are lots of clay products in suspension or
powder forms and the effect of loading is different in each. Different production processes bring various
characteristics to clay-containing materials. Various clay products are available to buy, including
smectite, talc, kaolinite and mica. Some are suitable for gas barrier properties while others are not.
Among them, clay products having a high aspect ratio and high affinity with plastic are preferable.
Users of clay nanoplate products should check the characteristic data described in the catalogue, as
these are important for selecting high-quality clay nanoplates for gas-barrier films.
ISO/TS 21236-1 specifies characteristics of layered clay nanomaterials in powder form, as well as
chemically modified ones, and describes their relevant measurement methods.
This document specifies the characteristics to be measured of clay nanoplate and specifies industrially
available measurement methods used to determine these characteristics. In addition, measurement
protocols are described. It provides a sound basis for the research, development and commercialization
of clay nanoplate materials for the application of barrier films for water vapour and dry gases.
© ISO 2021 – All rights reserved v

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TECHNICAL SPECIFICATION ISO/TS 21236-2:2021(E)
Nanotechnologies — Clay nanomaterials —
Part 2:
Specification of characteristics and measurements for clay
nanoplates used for gas-barrier film applications
1 Scope
This document specifies characteristics to be measured and measurement methods for clay nanoplate
samples in powder and suspension forms used for gas-barrier films. In addition, measurement protocols
for the individual characteristics are described.
This document does not deal with characteristics of post-manufacturing modification of clay
nanoplates. This document does not cover considerations specific to health and safety issues either
during manufacturing or use.
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/TS 80004-6, Nanotechnologies — Vocabulary — Part 6: Nano-object characterization
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TS 80004-6 and the following
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
gas barrier film
film that reduces gas diffusion
3.2
nanoplate
nano-object with one external dimension in the nanoscale and the other two external dimensions
significantly larger
[SOURCE: ISO/TS 80004-2:2015, 4.6, modified]
3.3
clay nanoplate
nanoplate composed of clay
© ISO 2021 – All rights reserved 1

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ISO/TS 21236-2:2021(E)

3.4
polymer clay nanocomposite
polymer matrix nanocomposite with a nanostructured clay phase
[SOURCE: ISO/TS 80004-4: 2011, 3.2.1.1]
3.5
film formability
capability of forming a film without additives from a suspension
Note 1 to entry: See Reference [10].
4 Abbreviated terms
AAS atomic absorption spectroscopy
AFM atomic force microscopy
DLS dynamic light scattering
EPMA electron probe micro analysis
ICP inductively coupled plasma spectrometry
SEM-EDX scanning electron microscopy-energy dispersive X-ray spectroscopy
TEM transmission electron microscopy
TGA thermogravimetric analysis
UV-Vis ultraviolet-visible spectrophotometry
XRD X-ray diffraction
XRF X-ray fluorescent analysis
5 Characteristics and measurement methods
5.1 General
The characteristics of clay nanoplate samples to be measured or identified and the applicable
measurement methods are listed in Tables 1 and 2. The characteristics listed in Table 1 shall be
measured by using the listed measurement methods. The characteristics listed in Table 2 should be
measured by using the listed measurement methods. The middle columns in Tables 1 and 2 indicate the
form of test specimen, powder or suspension used for measurements of the individual characteristics.
Test specimens in the specified form are prepared from the suspension or powder sample of clay
nanoplates.
See Annex A for measurement protocols of individual characteristics.
Table 1 — Required characteristics of clay nanoplate samples for measurement or
identification
Characteristics Test specimen form Measurement methods
Mineral composition content Powder XRD, Polarization microscopy
Chemical composition content Powder ICP, AAS, XRF, SEM-EDX or EPMA
[12]
Cation exchange capacity Powder Schollenberger method
2 © ISO 2021 – All rights reserved

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ISO/TS 21236-2:2021(E)

Table 1 (continued)
Characteristics Test specimen form Measurement methods
Particle size Suspension Laser diffraction method or DLS
Loss on ignition Powder Weight measurement or TGA
Table 2 — Recommended characteristics of clay nanoplate samples for measurement or
identification
Characteristics Test specimen form Measurement methods
Methylene blue adsorption capacity Powder Filter paper method or UV-Vis
Aspect ratio Powder AFM, TEM or SEM
Film formability Powder Suspension casting method
Viscosity Suspension Viscometry
See Annex B for principles of a gas barrier using clay nanoplates. See Annex C for value chains of clay
nanoplate materials.
5.2 Mineral composition
A clay nanoplate sample is usually composed of various minerals. Natural smectite clay can contain
quartz, mica, feldspar and calcite. The mineral composition contents of a clay nanoplate test specimen
are the ratios of masses of minerals in a clay nanoplate test specimen to that of the whole test specimen.
The minerals shall be identified and the individual contents shall be measured. The measurement results
of the mineral composition contents shall be expressed as wt % for individual mineral compositions.
[11]
The mineral composition shall be measured by XRD, EPMA or polarization microscopy for a clay
nanoplate sample in powder form. EPMA is a complementary method for clay nanoplate samples.
Polarization microscopy is a supplementary technique, giving mineral phase information and not
information on composition. This measurement is used as a complementary method to increase the
reliability of mineral identification. A thin film sample is prepared for measurement by suspension
casting or similar. When a sample is provided in suspension form, a test specimen in powder form is
prepared from the suspension sample by drying at 100 °C. In cases of XRD, the mineral composition
content is calculated from the peak intensity ratio of minerals. It is common practice to use internal
standards such as reference materials. For measurement, a compacted sample with a flattened surface
or a fixed oriented sample is prepared by suspension casting.
5.3 Chemical composition
The chemical composition consists of the elements contained in a clay nanoplate sample. The chemical
composition shall be measured and the results expressed as wt % for individual elements.
The chemical composition shall be identified and its contents shall be measured by ICP, AAS, XRF, SEM-
EDX or EPMA for a clay nanoplate sample in powder form. SEM-EDX is a complementary method for
clay nanoplate samples. When a sample is provided in suspension form, a test specimen in powder form
is prepared from the suspension sample by drying at 100 °C. For ICP and AAS measurement, proper
concentration of aqueous suspension is to be prepared. For XRF measurement, proper size of dried
solid specimen is prepared.
5.4 Cation exchange capacity
The cation exchange capacity is the number of exchangeable cations per defined mass of a clay nanoplate
[12]
dry sample. The cation exchange capacity shall be measured by the Schollenberger method and
the results expressed in the unit of milliequivalent of hydrogen per 100 g of dry powder sample
(meq+/100g), or in the SI unit centi-mol per kg (cmol+/kg). The Schollenberger method has been most
commonly used in the measurement of cation exchange capacity of soils. The ion concentration can be
[13]
calculated based on elemental analysis by ICP or AAS.
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ISO/TS 21236-2:2021(E)

5.5 Particle size
[14]
Dynamic light scattering (DLS) is a generally accepted method for particle size distribution.
ISO 22412 lists DLS as a method for the estimation of an average hydrodynamic particle size and the
measurement of the broadness of the size distribution. The applicability to nanomaterials depends
on several factors, both related to the material and to the test setup. DLS can give good information
in a narrow size range and provides three-dimensional information instead of the two-dimensional
information from microscopy techniques. The laser diffraction method is also applicable to the particle
size measurements (ISO 13320). In the suspension, primary and agglomerate particles both exist.
Care should be taken that larger agglomerates are formed when the concentration of the suspension is
high. The applicability is limited to stable particle suspensions of monomodal and relatively narrowly
dispersed size distributions, and the shape of the particles plays a role in the interpretation of the
results. Clay samples whose lateral size is enlarged from their original size are often useful to improve
[15]
the film property due to the large aspect ratio. Suspension is made using a proper method such as
stirrer mixing, shaking, rotating or revolution mixing.
The average particle size shall be measured by the laser diffraction method or the DLS method for a
clay nanoplate sample. The analytical value obtained by these measurement methods is hydrodynamic
size. The results shall be expressed in the unit of nm. ISO 13320 and ISO 22412 specify measurement
protocols for general application of the laser diffraction method and DLS, respectively.
When the sample is provided in suspension form, the particle size is measured as it is. When the sample
is provided in powder form, a test specimen in suspension form is prepared by dispersing the sample in
a dispersion liquid.
5.6 Loss on ignition
The loss on ignition is the ratio of the difference between the mass of a clay nanoplate sample in
dried powder form before and after a heat treatment up to 1 000 °C to the mass of the sample before
the heat treatment. It attributes to decompositions of organic impurity and organic modifier, loss of
structural water and phase changes of the clay minerals with mass loss. When the sample is provided
in suspension form, a test specimen in powder form is prepared from the suspension sample by drying.
The loss on ignition shall be measured by the weight measurement method or TGA. The results shall be
expressed as wt %.
The adsorbed water content in the nanoplate sample is indicated by moisture content (see Clause 6).
5.7 Methylene blue adsorption capacity
The methylene blue adsorption capacity of a clay nanoplate powder sample is the ratio of the maximum
amount of methylene blue dye adsorbed to the dried powder sample having been dispersed in water
to the mass of the dried powder sample before dispersing. When the sample is provided in suspension
form, a test specimen in powder form is prepared from the suspension sample by drying.
The methylene blue adsorption capacity should be measured by using the filter paper method or the
[17]
UV-Vis method (see ISO/TS 80004-6) depending on the required measurement accuracy. The results
should be expressed in the unit of mmol/100g.
5.8 Aspect ratio
The aspect ratio of a clay nanoplate sample is the ratio of the circle equivalent diameter of the planar
object contained in clay nanoplate sample to its thickness.
[8,9]
The diameter and thickness should be measured by selecting appropriate methods from AFM ,
[6,10] [20]
TEM and SEM and the results should be expressed in the unit of nm. For accurate measurements,
it is recommended that sufficiently diluted test specimens are prepared so that there is no overlapping
between planar objects on the image. A sample is prepared as follows: a sufficiently diluted suspension,
−5
such as 5 × 10 wt %, is prepared from the sample in powder or suspension form. The dilution is cast
4 © ISO 2021 – All rights reserved

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ISO/TS 21236-2:2021(E)

and dried on a flat substrate at the sub-nanometer level. Casting is performed by dropping droplets of
the suspension with a pipette or similar. Drying is performed under as mild a condition as possible, not
exceeding 100 °C.
The average diameter and the average height of the planar objects are measured. The aspect
ratio is calculated by dividing the former by the latter. The data number of diameter and thickness
measurements can be decided by agreement between buyer and seller.
5.9 Film formability
[10]
The film formability is the capability of forming a film without additives. The film formability should
be evaluated by visual observation and mandrel bend test of the obtained precipitate. The results
should be expressed in the way defined by the method used. For evaluation protocols, see A.9.
5.10 Viscosity
The viscosity of a fluid is the rheological property that expresses resistance to shearing flows. Viscosity
of a clay nanoplate sample in a suspension form should be measured by the viscometry and the results
expressed in the unit of Pa·s. The dry matter content of the suspension sample should be reported
and expressed in the unit of unity by mass. The name of suspension liquid and the measurement
temperature should be reported.
When a sample is provided in suspension form, viscosity is measured as it is. When a sample is provided
in powder form, a test specimen in suspension form is prepared by dispersing the powder sample in an
appropriate dispersion liquid. Viscosity is sensitive to clay concentration. Therefore, if the sample is in
powder form, the concentration shall be mentioned.
The type of viscometer used and measurement conditions can be adopted as agreed between buyer and
seller.
6 Reporting
The reporting shall include the following. An example of the reporting format is shown in Annex D.
— Sample identification:
— sample name;
— manufacturer’s name;
— lot number;
— sample source;
— storage conditions prior to testing.
— Name of the suspension liquid for a suspension sample. In the case of hydrophilic clay, the suspension
liquid is water. In the case of organoclay, the suspension liquid is organic solvent.
— Dry matter content: the ratio of the mass of residues of a clay nanoplate sample in suspension or
powder form after drying to reach constant mass to that of the sample before drying. For aqueous
suspension samples, the drying temperature is 105 ± 2 °C (ISO 11465). The measurement results
are expressed as wt %.
— Moisture content: the moisture content of a clay nanoplate sample in a powder form is measured by
the weight loss method where the sample is heated or by TGA. The appropriate heating temperature
is 105 ± 5 °C. The measurement results are expressed as wt % (ISO 15512).
— Name of additives, if any, such as surfactant and thickening agent.
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ISO/TS 21236-2:2021(E)

— Morphology: representative pictures showing clearly the structure and formation, such as shape
and agglomeration state of clay nanoplates taken by microscopy. The measurement method used
shall be indicated as AFM, TEM or SEM. The magnification scale shall be shown on each picture. The
appropriate number of pictures may be agreed between buyer and seller.
— The pH value of a clay nanoplate sample when it is provided in aqueous suspension form. The pH of
an aqueous suspension is measured by the glass electrode method and the results are expressed as
dimensionless. The measurement temperature is also reported.
— The International Standard used (including its year of publication).
— Name of characteristics measured or identified that are listed in Table 1. When any characteristics
listed in Table 2 are measured, the results can be reported in this test report.
— Measurement methods used for individual characteristics determination.
— Date of measurement and name of organization that made the measurements for individual
characteristics.
— Quantitative and/or qualitative results of measurements for individual characteristics, including a
reference to the clause which explains how the results were calculated.
— Information on the uncertainty of measurement results. Repeatability and reproducibility are
recommended.
— Any unusual features observed.
— Additional information, if any, supporting the measurement results.
— If there are deviations from this document, give the name of and detailed information on the
measurement methods used and their justification.
6 © ISO 2021 – All rights reserved

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ISO/TS 21236-2:2021(E)

Annex A
(informative)

Measurement protocols
A.1 General
Sample preparations, measurement procedures and data analyses generally used for characterizing
clay nanoplate samples in powder and suspension forms are informatively provided in this annex for
individual characteristics.
A.2 Mineral composition
The powder X-ray diffraction method is most often used for the determination of mineral compositions
and their contents of clay nanoplate samples. The obtained pattern is compared with each mineral
pattern file and the minerals are identified. The d spacing is calculated from the peak value of the
[12]
obtained pattern. It is common to use internal standards.
The d spacing is calculated from Bragg's law:
d = nλ/(2 sin θ)
where
n is an integer;
θ is the angle of incidence (or reflection) of the X-ray beam;
λ is the X-ray wavelength.
Most X-ray machines use Cu-Kα1 radiation with λ = 0,154 056 2 nm. For the principal reflection, n = 1.
Typical measurement conditions are as follows: Cu X-ray, tube voltage of 40kV, tube current of 40 mA,
measurement angle from 2 degrees to 60 degrees.
The mineral composition is calculated from the peak intensity ratio of minerals.
A.3 Chemical composition
The chemical composition contents are most frequently measured by XRF or SEM-EDX for powder
samples. Usually, instruction manuals of instrument manufacturers can be used for the measurement
procedures.
A.4 Cation exchange capacity
[16]
The measurement procedure of cation exchange capacity is as follows :
The equipment used is a leachate container, a leaching pipe and a receiver. A small amount of absorbent
cotton is placed on the lower part of the leaching pipe so that the upper surface is flat, and an emulsified
paper is laid on the leaching pipe to a thickness of 2 mm to 3 mm as the supporting layer of the sample.
A sample of 0,4 g to 0,5 g and 10 times the mass of the quartz powder is uniformly mixed. Weigh the
sample to a precision of 0,1mg.
© ISO 2021 – All rights reserved 7

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ISO/T
...

TECHNICAL ISO/TS
SPECIFICATION 21236-2
First edition
Nanotechnologies — Clay
nanomaterials —
Part 2:
Specification of characteristics and
measurements for clay nanoplates
used for gas-barrier film applications
Nanotechnologies — Nano argiles —
Partie 2: Spécification des caractéristiques et des mesures pour
les argiles en nanofeuillets utilisées dans des applications de films
barrières aux gaz
PROOF/ÉPREUVE
Reference number
ISO/TS 21236-2:2021(E)
©
ISO 2021

---------------------- Page: 1 ----------------------
ISO/TS 21236-2:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/TS 21236-2:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Characteristics and measurement methods . 2
5.1 General . 2
5.2 Mineral composition . 3
5.3 Chemical composition . 3
5.4 Cation exchange capacity . 3
5.5 Particle size . 4
5.6 Loss on ignition . 4
5.7 Methylene blue adsorption capacity . 4
5.8 Aspect ratio . 4
5.9 Film formability. 5
5.10 Viscosity . 5
6 Reporting . 5
Annex A (informative) Measurement protocols . 7
Annex B (informative) Principles of a gas barrier using clay nanoplates .12
Annex C (informative) Value chains of clay nanoplate materials.15
Annex D (informative) Example of reporting sheet .16
Bibliography .17
© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii

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ISO/TS 21236-2:2021(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 229, Nanotechnologies.
A list of all parts in the ISO 21236 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.
iv PROOF/ÉPREUVE © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/TS 21236-2:2021(E)

Introduction
The barrier property in polymeric materials has become progressively more important in recent years
with the widespread use of plastic films and rigid plastics for food packaging, medical packaging,
electronic devices, construction, agriculture and so on. All polymeric materials have varying degrees
of gas permeability. Therefore, the required level of gas barrier performance varies depending on the
application. Barrier films often consist of multilayers or coated films designed to be impervious to
gas and moisture migration, as single-layer films are in general quite permeable to most gases. Food
packaging films are required to have oxygen gas barrier properties and water vapour barrier properties.
A transparent gas barrier film obtained by applying a silica or alumina vapour deposition method on a
PET or nylon film is generally used for food packaging, pharmaceutical packaging, industrial product
packaging and so on. Recently, a film with a higher level of gas barrier properties has been required for
organic light emitting diode displays. These high gas-barrier properties cannot be achieved by simply
using conventional barrier film for food packaging.
High gas-barrier films are expected to be used in a wide range of fields, such as electronics,
pharmaceutical packaging and hydrogen storage. Various approaches can be taken to improve barrier
properties in plastics packaging. There is a method of adding gas-impermeable nano-objects to plastic
to make nanocomposites. One of the most common types of polymer nanocomposites contains clay
nanoplates. These clay nanomaterials improve barrier properties. Many reports predict the market
expansion of nanocomposite materials.
There are many scientific papers and patents on gas barrier composite material using clay nanoplate.
Gas barrier properties are improved by mixing clay nanoplates into the polymer. The high gas-barrier
phenomenon is described in Nielson's tortuous model. There are lots of clay products in suspension or
powder forms and the effect of loading is different in each. Different production processes bring various
characteristics to clay-containing materials. Various clay products are available to buy, including
smectite, talc, kaolinite and mica. Some are suitable for gas barrier properties while others are not.
Among them, clay products having a high aspect ratio and high affinity with plastic are preferable.
Users of clay nanoplate products should check the characteristic data described in the catalogue, as
these are important for selecting high-quality clay nanoplates for gas-barrier films.
ISO/TS 21236-1 specifies characteristics of layered clay nanomaterials in powder form, as well as
chemically modified ones, and describes their relevant measurement methods.
This document specifies the characteristics to be measured of clay nanoplate and specifies industrially
available measurement methods used to determine these characteristics. In addition, measurement
protocols are described. It provides a sound basis for the research, development and commercialization
of clay nanoplate materials for the application of barrier films for water vapour and dry gases.
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TECHNICAL SPECIFICATION ISO/TS 21236-2:2021(E)
Nanotechnologies — Clay nanomaterials —
Part 2:
Specification of characteristics and measurements for clay
nanoplates used for gas-barrier film applications
1 Scope
This document specifies characteristics to be measured and measurement methods for clay nanoplate
samples in powder and suspension forms used for gas-barrier films. In addition, measurement protocols
for the individual characteristics are described.
This document does not deal with characteristics of post-manufacturing modification of clay
nanoplates. This document does not cover considerations specific to health and safety issues either
during manufacturing or use.
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/TS 80004-6, Nanotechnologies — Vocabulary — Part 6: Nano-object characterization
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TS 80004-6 and the
following 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
gas barrier film
film that reduces gas diffusion
3.2
nanoplate
nano-object with one external dimension in the nanoscale and the other two external dimensions
significantly larger
[SOURCE: ISO/TS 80004-2:2015, 4.6, modified]
3.3
clay nanoplate
nanoplate composed of clay
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3.4
polymer clay nanocomposite
polymer matrix nanocomposite with a nanostructured clay phase
[SOURCE: ISO/TS 80004-4: 2011, 3.2.1.1]
3.5
film formability
capability of forming a film without additives from a suspension
Note 1 to entry: See Reference [10].
4 Abbreviated terms
AAS atomic absorption spectroscopy
AFM atomic force microscopy
DLS dynamic light scattering
EPMA electron probe micro analysis
ICP inductively coupled plasma spectrometry
SEM-EDX scanning electron microscopy-energy dispersive X-ray spectroscopy
TEM transmission electron microscopy
TGA thermogravimetric analysis
UV-Vis ultraviolet-visible spectrophotometry
XRD X-ray diffraction
XRF X-ray fluorescent analysis
5 Characteristics and measurement methods
5.1 General
The characteristics of clay nanoplate samples to be measured or identified and the applicable
measurement methods are listed in Tables 1 and 2. The characteristics listed in Table 1 shall be
measured by using the listed measurement methods. The characteristics listed in Table 2 should be
measured by using the listed measurement methods. The middle columns in Tables 1 and 2 indicate the
form of test specimen, powder or suspension used for measurements of the individual characteristics.
Test specimens in the specified form are prepared from the suspension or powder sample of clay
nanoplates.
See Annex A for measurement protocols of individual characteristics.
Table 1 — Required characteristics of clay nanoplate samples for measurement or
identification
Characteristics Test specimen form Measurement methods
Mineral composition content Powder XRD, Polarization microscopy
Chemical composition content Powder ICP, AAS, XRF, SEM-EDX or EPMA
[12]
Cation exchange capacity Powder Schollenberger method
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Table 1 (continued)
Characteristics Test specimen form Measurement methods
Particle size Suspension Laser diffraction method or DLS
Loss on ignition Powder Weight measurement or TGA
Table 2 — Recommended characteristics of clay nanoplate samples for measurement or
identification
Characteristics Test specimen form Measurement methods
Methylene blue adsorption capacity Powder Filter paper method or UV-Vis
Aspect ratio Powder AFM, TEM or SEM
Film formability Powder Suspension casting method
Viscosity Suspension Viscometry
See Annex B for principles of a gas barrier using clay nanoplates. See Annex C for value chains of clay
nanoplate materials.
5.2 Mineral composition
A clay nanoplate sample is usually composed of various minerals. Natural smectite clay can contain
quartz, mica, feldspar and calcite. The mineral composition contents of a clay nanoplate test specimen
are the ratios of masses of minerals in a clay nanoplate test specimen to that of the whole test specimen.
The minerals shall be identified and the individual contents shall be measured. The measurement results
of the mineral composition contents shall be expressed as wt % for individual mineral compositions.
[11]
The mineral composition shall be measured by XRD, EPMA or polarization microscopy for a clay
nanoplate sample in powder form. EPMA is a complementary method for clay nanoplate samples.
Polarization microscopy is a supplementary technique, giving mineral phase information and not
information on composition. This measurement is used as a complementary method to increase the
reliability of mineral identification. A thin film sample is prepared for measurement by suspension
casting or similar. When a sample is provided in suspension form, a test specimen in powder form is
prepared from the suspension sample by drying at 100 °C. In cases of XRD, the mineral composition
content is calculated from the peak intensity ratio of minerals. It is common practice to use internal
standards such as reference materials. For measurement, a compacted sample with a flattened surface
or a fixed oriented sample is prepared by suspension casting.
5.3 Chemical composition
The chemical composition consists of the elements contained in a clay nanoplate sample. The chemical
composition shall be measured and the results expressed as wt % for individual elements.
The chemical composition shall be identified and its contents shall be measured by ICP, AAS, XRF, SEM-
EDX or EPMA for a clay nanoplate sample in powder form. SEM-EDX is a complementary method for
clay nanoplate samples. When a sample is provided in suspension form, a test specimen in powder form
is prepared from the suspension sample by drying at 100 °C. For ICP and AAS measurement, proper
concentration of aqueous suspension is to be prepared. For XRF measurement, proper size of dried
solid specimen is prepared.
5.4 Cation exchange capacity
The cation exchange capacity is the number of exchangeable cations per defined mass of a clay nanoplate
[12]
dry sample. The cation exchange capacity shall be measured by the Schollenberger method and
the results expressed in the unit of milliequivalent of hydrogen per 100 g of dry powder sample
(meq+/100g), or in the SI unit centi-mol per kg (cmol+/kg). The Schollenberger method has been most
commonly used in the measurement of cation exchange capacity of soils. The ion concentration can be
[13]
calculated based on elemental analysis by ICP or AAS.
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5.5 Particle size
[14]
Dynamic light scattering (DLS) is a generally accepted method for particle size distribution.
ISO 22412 lists DLS as a method for the estimation of an average hydrodynamic particle size and the
measurement of the broadness of the size distribution. The applicability to nanomaterials depends
on several factors, both related to the material and to the test setup. DLS can give good information
in a narrow size range and provides three-dimensional information instead of the two-dimensional
information from microscopy techniques. The laser diffraction method is also applicable to the particle
size measurements (ISO 13320). In the suspension, primary and agglomerate particles both exist.
Care should be taken that larger agglomerates are formed when the concentration of the suspension is
high. The applicability is limited to stable particle suspensions of monomodal and relatively narrowly
dispersed size distributions, and the shape of the particles plays a role in the interpretation of the
results. Clay samples whose lateral size is enlarged from their original size are often useful to improve
[15]
the film property due to the large aspect ratio. Suspension is made using a proper method such as
stirrer mixing, shaking, rotating or revolution mixing.
The average particle size shall be measured by the laser diffraction method or the DLS method for a
clay nanoplate sample. The analytical value obtained by these measurement methods is hydrodynamic
size. The results shall be expressed in the unit of nm. ISO 13320 and ISO 22412 specify measurement
protocols for general application of the laser diffraction method and DLS, respectively.
When the sample is provided in suspension form, the particle size is measured as it is. When the sample
is provided in powder form, a test specimen in suspension form is prepared by dispersing the sample in
a dispersion liquid.
5.6 Loss on ignition
The loss on ignition is the ratio of the difference between the mass of a clay nanoplate sample in
dried powder form before and after a heat treatment up to 1 000 °C to the mass of the sample before
the heat treatment. It attributes to decompositions of organic impurity and organic modifier, loss of
structural water and phase changes of the clay minerals with mass loss. When the sample is provided
in suspension form, a test specimen in powder form is prepared from the suspension sample by drying.
The loss on ignition shall be measured by the weight measurement method or TGA. The results shall be
expressed as wt %.
The adsorbed water content in the nanoplate sample is indicated by moisture content (see Clause 6).
5.7 Methylene blue adsorption capacity
The methylene blue adsorption capacity of a clay nanoplate powder sample is the ratio of the maximum
amount of methylene blue dye adsorbed to the dried powder sample having been dispersed in water
to the mass of the dried powder sample before dispersing. When the sample is provided in suspension
form, a test specimen in powder form is prepared from the suspension sample by drying.
The methylene blue adsorption capacity should be measured by using the filter paper method or the
[17]
UV-Vis method (see ISO/TS 80004-6) depending on the required measurement accuracy. The results
should be expressed in the unit of mmol/100g.
5.8 Aspect ratio
The aspect ratio of a clay nanoplate sample is the ratio of the circle equivalent diameter of the planar
object contained in clay nanoplate sample to its thickness.
[8,9]
The diameter and thickness should be measured by selecting appropriate methods from AFM ,
[6,10] [20]
TEM and SEM and the results should be expressed in the unit of nm. For accurate measurements,
it is recommended that sufficiently diluted test specimens are prepared so that there is no overlapping
between planar objects on the image. A sample is prepared as follows: a sufficiently diluted suspension,
−5
such as 5 × 10 wt %, is prepared from the sample in powder or suspension form. The dilution is cast
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and dried on a flat substrate at the sub-nanometer level. Casting is performed by dropping droplets of
the suspension with a pipette or similar. Drying is performed under as mild a condition as possible, not
exceeding 100 °C.
The average diameter and the average height of the planar objects are measured. The aspect
ratio is calculated by dividing the former by the latter. The data number of diameter and thickness
measurements can be decided by agreement between buyer and seller.
5.9 Film formability
[10]
The film formability is the capability of forming a film without additives. The film formability should
be evaluated by visual observation and mandrel bend test of the obtained precipitate. The results
should be expressed in the way defined by the method used. For evaluation protocols, see A.9.
5.10 Viscosity
The viscosity of a fluid is the rheological property that expresses resistance to shearing flows. Viscosity
of a clay nanoplate sample in a suspension form should be measured by the viscometry and the results
expressed in the unit of Pa·s. The dry matter content of the suspension sample should be reported
and expressed in the unit of unity by mass. The name of suspension liquid and the measurement
temperature should be reported.
When a sample is provided in suspension form, viscosity is measured as it is. When a sample is provided
in powder form, a test specimen in suspension form is prepared by dispersing the powder sample in an
appropriate dispersion liquid. Viscosity is sensitive to clay concentration. Therefore, if the sample is in
powder form, the concentration shall be mentioned.
The type of viscometer used and measurement conditions can be adopted as agreed between buyer
and seller.
6 Reporting
The reporting shall include the following. An example of the reporting format is shown in Annex D.
— Sample identification:
— sample name;
— manufacturer’s name;
— lot number;
— sample source;
— storage conditions prior to testing.
— Name of the suspension liquid for a suspension sample. In the case of hydrophilic clay, the suspension
liquid is water. In the case of organoclay, the suspension liquid is organic solvent.
— Dry matter content: the ratio of the mass of residues of a clay nanoplate sample in suspension or
powder form after drying to reach constant mass to that of the sample before drying. For aqueous
suspension samples, the drying temperature is 105 ± 2 °C (ISO 11465). The measurement results
are expressed as wt %.
— Moisture content: the moisture content of a clay nanoplate sample in a powder form is measured by
the weight loss method where the sample is heated or by TGA. The appropriate heating temperature
is 105 ± 5 °C. The measurement results are expressed as wt % (ISO 15512).
— Name of additives, if any, such as surfactant and thickening agent.
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— Morphology: representative pictures showing clearly the structure and formation, such as shape
and agglomeration state of clay nanoplates taken by microscopy. The measurement method used
shall be indicated as AFM, TEM or SEM. The magnification scale shall be shown on each picture. The
appropriate number of pictures may be agreed between buyer and seller.
— The pH value of a clay nanoplate sample when it is provided in aqueous suspension form. The pH of
an aqueous suspension is measured by the glass electrode method and the results are expressed as
dimensionless. The measurement temperature is also reported.
— The International Standard used (including its year of publication).
— Name of characteristics measured or identified that are listed in Table 1. When any characteristics
listed in Table 2 are measured, the results can be reported in this test report.
— Measurement methods used for individual characteristics determination.
— Date of measurement and name of organization that made the measurements for individual
characteristics.
— Quantitative and/or qualitative results of measurements for individual characteristics, including a
reference to the clause which explains how the results were calculated.
— Information on the uncertainty of measurement results. Repeatability and reproducibility are
recommended.
— Any unusual features observed.
— Additional information, if any, supporting the measurement results.
— If there are deviations from this document, give the name of and detailed information on the
measurement methods used and their justification.
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Annex A
(informative)

Measurement protocols
A.1 General
Sample preparations, measurement procedures and data analyses generally used for characterizing
clay nanoplate samples in powder and suspension forms are informatively provided in this annex for
individual characteristics.
A.2 Mineral composition
The powder X-ray diffraction method is most often used for the determination of mineral compositions
and their contents of clay nanoplate samples. The obtained pattern is compared with each mineral
pattern file and the minerals are identified. The d spacing is calculated from the peak value of the
[12]
obtained pattern. It is common to use internal standards.
The d spacing is calculated from Bragg's law:
d = nλ/(2 sin θ)
where
n is an integer;
θ is the angle of incidence (or reflection) of the X-ray beam;
λ is the X-ray wavelength.
Most X-ray machines use Cu-Kα1 radiation with λ = 0,154 056 2 nm. For the principal reflection, n = 1.
Typical measurement conditions are as follows: Cu X-ray, tube voltage of 40kV, tube current of 40 mA,
measurement angle from 2 degrees to 60 degrees.
The mineral composition is calculated from the peak intensity ratio of minerals.
A.3 Chemical composition
The chemical composition contents are most frequently measured by XRF or SEM-EDX for powder
samples. Usually, instruction manuals of instrument manufacturers can be used for the measurement
procedures.
A.4 Cation exchange capacity
[16]
The measurement procedure of cation exchange capacity is as follows :
The equipment used is a leachate container, a leaching pipe and a receiver. A small amount of absorbent
cotton is placed on the lower part of the leaching pipe so that the upper surface is flat, and an emulsified
paper is laid on the leaching pipe to a thickness of 2 mm to 3 mm as the supporting layer of the sample.
A sample of 0,4 g to 0,5 g and 10 times the mass of the quartz powder is uniformly mixed. Weigh t
...

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