ISO/TS 21236-1:2019

Nanotechnologies — Clay nanomaterials — Part 1: Specification of characteristics and measurement methods for layered clay nanomaterials

This document specifies characteristics to be measured of layered clay nanomaterials in powder form and chemically modified ones, and describes their relevant measurement methods. This document does not deal with health, safety and environmental issues.

Nanotechnologies — Nano argiles — Partie 1: Spécification des caractéristiques et des méthodes de mesure des nano argiles en couches

General Information

• Status: Published
• Publication Date: 22-Oct-2019
• ICS: 07.120 - Nanotechnologies
• Technical Committee: ISO/TC 229 - Nanotechnologies
• Drafting Committee: ISO/TC 229/WG 4 - Material specifications
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 07-Mar-2023

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 21236-1
First edition
2019-10
Nanotechnologies — Clay
nanomaterials —
Part 1:
Specification of characteristics and
measurement methods for layered
clay nanomaterials
Nanotechnologies — Nano argiles —
Partie 1: Spécification des caractéristiques et des méthodes de mesure
des nano argiles en couches
Reference number
ISO/TS 21236-1:2019(E)
©
ISO 2019

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ISO/TS 21236-1:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
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ISO/TS 21236-1:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 3
5 Characteristics and measurement methods . 4
5.1 General . 4
5.2 Fundamental characteristics . . 4
5.3 Optional characteristics . 5
5.4 Descriptions on characteristics and measurement methods . 6
5.4.1 Chemical composition content . 6
5.4.2 Mineral composition content . 6
5.4.3 Interlayer distance . 7
5.4.4 Thickness . 8
5.4.5 Aspect ratio . 9
5.4.6 Bulk density . 9
5.4.7 Cation exchange capacity . 9
5.4.8 Loss on ignition . 9
5.4.9 Water absorption capacity .10
5.4.10 Moisture content .10
5.4.11 Brightness .10
5.4.12 Colour .10
5.4.13 Methylene blue adsorption capacity .11
5.4.14 Cohesion coefficient .11
5.4.15 Tap density .11
5.4.16 Specific surface area .11
5.4.17 Film formability .12
5.4.18 Electrical resistivity .12
5.4.19 Modifier type .13
6 Reporting .14
6.1 General .14
6.2 Information .14
6.3 Measurement results .14
6.4 Example of table format .14
Annex A (informative) Basic information on layered clay nanomaterials .16
Annex B (informative) Organo-modified layered clay nanomaterials (Organoclay).18
Bibliography .20
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ISO/TS 21236-1:2019(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/TS 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.
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ISO/TS 21236-1:2019(E)

Introduction
Layered clay nanomaterials are a subgroup of clay materials with the external dimension (thickness) or
the internal structural dimension (interlayer distance) in the nanoscale. Clay itself, as most important
group of layered nanostructured silicates, refers to naturally occurring or synthetic material composed
primarily of fine-grained minerals, which show plasticity through a variable range of water content
and will harden when fired or dried. The minerals found in clay are generally silicates of less than
2 micrometres in lateral size. Clays are very abundant at the earth's surface; they form rocks known
as shales and are a major component in nearly all sedimentary rocks. The small size of the particles
and their unique crystal structures give clay materials special properties, including cation exchange
[1]
capabilities, plastic behaviour when wet, catalytic abilities, swelling behaviour, and low permeability .
Other than the structure and composition, there are several additional factors which are important in
determining the properties and applications of clays and clay nanomaterials (see Annex A). These are
the mineral impurities, the presence of organic materials, the type and amount of exchangeable ions
[2]
and soluble salts, and the morphological aspects .
Natural and modified clays as layered structured minerals are very important industrial materials.
In pristine form, clay materials are normally subnano spaced layers, structured in bundles and in
exfoliated state; they are nano-objects with thickness in the nanoscale while in intercalated form they
are structured nanomaterials with interlayer space in nanoscale.
Modification of clay with change in its characteristic such as its hydrophobicity, interlayer distance,
exchangeable ion, and surface connected groups leads to the extension of its applications e.g. for high
performance nanocomposites, effective rheological modifier, or biomedical applications. A small
quantity of well dispersed intercalated or exfoliated organo-modified layered clay nanomaterials in
polymeric composites (see Annex B) is proved to show superior impacts on properties such as barrier,
tensile modulus, mechanical strength, and flame retardancy.
There are numerous industrial applications for layered clay nanomaterials. Purified and modified
clays are used as; coatings on paper to enhance whiteness and to allow the proper absorption of ink,
the life time extender of rubber in tires, in concrete, as catalysts in many industries. Moreover, they
can also be used in oil purification, pharmaceuticals, ceramic industry, soil stabilization, porcelains
and barriers for nuclear and chemical wastes because of their cation-exchange capabilities, low
permeability, and long-term structural stability. In addition, layered clay nanomaterials are utilized in
purification industries, in agricultural and food engineering applications, polymeric nanocomposites,
deodorizer, insecticide carrier, pesticides carrier, drilling fluids, desiccant, detergents, plasticizer,
emulsion stabilizer, food additives, cosmetic applications, environmental remediation and many other
[1][2]
miscellaneous applications .
For such a wide range of clay nanomaterial applications, various fundamental characteristics (as
shown in Table 1) play undeniable roles. These characteristics are measured and reported by the
provider of the layered clay nanomaterials. In fact, the determinations of these fundamental and basic
characteristics will facilitate the communication between sellers and buyers of these nanomaterials for
different applications. These characteristics are considered for all industrial layered clay nanomaterial
applications such as nanocomposites, paper, ink, purification, and catalysts. In addition to fundamental
characteristics, presented in Table 1, some other optional characteristics of layered clay nanomaterials
as shown in Table 2 are measured and reported subject to the agreement between sellers and buyers.
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TECHNICAL SPECIFICATION ISO/TS 21236-1:2019(E)
Nanotechnologies — Clay nanomaterials —
Part 1:
Specification of characteristics and measurement methods
for layered clay nanomaterials
1 Scope
This document specifies characteristics to be measured of layered clay nanomaterials in powder form
and chemically modified ones, and describes their relevant measurement methods.
This document does not deal with health, safety and environmental issues.
2 Normative references
There are no normative references in this document.
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
aspect ratio
ratio of the sheet length to the sheet width
[SOURCE: ISO 8336:2017,3.13]
3.2
bulk density
ratio of the mass of an untapped powder sample and its volume including the contribution of the
interparticulate void volume
3.3
cation exchange capacity
amount of exchangeable cations per defined mass of clay nanomaterial sample
3.4
clay
naturally occurring or synthetically manufactured material composed primarily of fine-grained
minerals, which is generally plastic at appropriate water contents and will harden when dried or fired
Note 1 to entry: Taken from Reference [3].
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Note 2 to entry: Although clay usually contains phyllosilicates, it may contain other materials that impart
plasticity and harden when dried or fired. Associated phases in clay may include materials that do not impart
plasticity and organic matter. Different disciplines have uniquely defined the size of clay particles, and it is for
this reason that “fine grained” is used in the definition rather than a precise value. However, because of these
size variations from discipline to discipline, it is important that the particle size be specified in the context of the
application.
3.5
clay nanomaterials
material composed predominately of clay with any external dimension in the nanoscale or having
internal structure or surface structure in the nanoscale
3.6
exchangeable ion
ions bearing in clays which can be exchanged with other ions
Note 1 to entry: See Reference [4].
3.7
exfoliated clay
state of separating clay layers and distributing individual layers
Note 1 to entry: Usually exfoliation of layered clay nanomaterials is conducted in liquid suspension by giving
shear forces.
Note 2 to entry: See Reference [5].
3.8
film formability
ability of clay to form self-standing films (uniform and ordered lamination of clay layers)
Note 1 to entry: See Reference [6].
3.9
gallery thickness
distance between clay layers
3.10
intercalated clay
clay in which heterogeneous material (atoms, molecules and nanoparticles) is inserted into a host
structure (crystal lattice or other macromolecular structure)
3.11
interlayer distance
distance between identical adjacent layers of clay which is sum of gallery thickness (height) and
thickness of a single sheet of clay (d )
s
3.12
layer
discrete material restricted in one dimension, within or at the surface of a condensed phase
[SOURCE: ISO/TS 80004-11:2017, 3.1.2]
3.13
layered clay nanomaterial
clay nanomaterial composed of one or more structural layer
3.14
loss on ignition
dried sample’s weight loss during a heat treatment up to 1 000 °C
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ISO/TS 21236-1:2019(E)

3.15
moisture content
ratio of the mass of water contained in a sample to that of the sample
3.16
nanocomposite
solid comprising a mixture of two or more phase-separated materials, one or more being nanophase
[SOURCE: ISO/TS 80004-4:2011, 3.2]
3.17
nanostructured
having internal or surface structure in the nanoscale
[SOURCE: ISO/TS 80004-11:2017, 3.1.8]
3.18
organoclay
modified clay by exchanging the original interlayer cations for organic cations
3.19
phyllosilicate
silicate mineral, such as mica, the tetrahedral silicate groups of which are linked in sheets
Note 1 to entry: See Reference [7].
3.20
smectite
clay mineral (e.g. bentonite) which undergoes reversible expansion on absorbing water
3.21
specific surface area
absolute surface area of the sample divided by sample mass
[SOURCE: ISO 9277:2010, 3.15]
3.22
tap density
mass of the powder divided by its volume after tapping the sample in powder form
3.23
total surface area
sum of external and internal surface area
4 Abbreviated terms
AFM Atomic force microscopy
BET Brunauer-Emmett-Teller
FESEM Field emission scanning electron microscopy
FTIR Fourier transform infrared spectrometry
ICP-MS Inductively coupled plasma - mass spectrometry
ICP-OES Inductively coupled plasma - optical emission spectrometry
LOI Loss on ignition
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ISO/TS 21236-1:2019(E)

SEM Scanning electron microscopy
TEM Transmission electron microscopy
TGA Thermogravimetric analysis
UV-Vis Ultraviolet-visible spectrophotometry
XPS X-ray photoelectron spectrometry
XRD X-ray diffraction
XRF X-ray fluorescence
5 Characteristics and measurement methods
5.1 General
This clause provides both fundamental and optional characteristics of layered clay nanomaterials
and their relevant measurement methods. Relevant standards describing measurement protocols for
individual characteristics are also listed in this clause. However, it should be noted that these standards
have not yet been fully validated for application to layered clay nanomaterials.
5.2 Fundamental characteristics
Table 1 lists the fundamental characteristics that are commonly used for material specifications of
layered clay nanomaterials. The characteristics for measurements shall be selected from Table 1
based on the agreement between sellers and buyers. Table 1 additionally provides information on
units suggested to be used for expressing the measurement results of individual characteristics,
measurement methods recommended to be used, and other measurement method suggested to
use when the recommended measurement methods are not available and existing standards for
measurement protocols.
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Table 1 — Fundamental characteristics and the relevant measurement methods
Recommended meas- Other measure- Relevant measure-
Characteristic Units
urement method(s) ment methods ment protocols
Chemical
1–1 composition kg/kg ICP-MS ICP-OES or XRF —
content
Mineral
1–2 composition kg/kg XRD — —
content
1–3 Interlayer distance Nm XRD TEM or FESEM —
XRD, TEM or
1–4 Thickness Nm AFM —
FESEM
SEM, FESEM or
1–5 Aspect ratio — AFM —
TEM
Gravimetry and Japanese Pharmaco-
3
1–6 Bulk density kg/m —
[14]
volumetry poeia: 3.01
Cation exchange
1–7 cmol+/kg Schollenberger method — ISO 23470:2018
capacity
Heating and
1–8 Loss on ignition kg/kg Thermogravimetry ISO/TR 18230:2015
weighing method
Water absorption Water absorption Enslin-Neff
1–9 kg/kg ISO 10769:2011
capacity method method
Oven-drying
1–10 Moisture content kg/kg Thermogravimetry ISO 10769:2011
method
5.3 Optional characteristics
In addition to the fundamental characteristics which shall be measured (Table 1), there are some other
important characteristics which could be related to specific applications. The optional characteristics
listed in Table 2 should be measured subject to the agreement between buyers and sellers. Table 2
additionally provides information on units suggested to be used for expressing the measurement results
of individual characteristics, measurement methods recommended to be used, other measurement
method suggested to use when the recommended measurement methods are not available and existing
standards for measurement protocols.
Table 2 — Optional characteristics of layered clay nanomaterials and relevant measurement
methods
Recommended
Other measurement Relevant measure-
Characteristic Units measurement
methods ment protocols
method(s)
2–1 Brightness — Reflectometry — TAPPI T646
2–2 Colour — Colorimetry — —
Methylene blue
UV-Vis spectrophotom-
2–3 adsorption mmol/100g Filter paper method ASTM C837 – 09 (2014)
etry
capacity
Cohesion ISO 17892-7:2017/
2–4 kPa Direct Shear test —
coefficient ASTM D3080/D3080M
Japanese
Gravimetry and Pharmacopoeia:
3
2–5 Tap density kg/m —
[14]
volumetry 3.01 and European
[15]
Pharmacopoeia
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Table 2 (continued)
Recommended
Other measurement Relevant measure-
Characteristic Units measurement
methods ment protocols
method(s)
Ethylene glycol
Specific Gas adsorption
2
2–6 m /g monomethyl ether ISO 9277: 2010
surface area method
absorption method
Film Film casting and
2–7 — — —
formability visual inspection
Electrical Four-point probe
2–8 Ω·m — —
Resistivity method
Raman spectrometry,
2–9 Modifier Type — IR or FTIR —
XPS or UV-Vis
5.4 Descriptions on characteristics and measurement methods
Below, descriptions of the characteristics as well as of the measurement methods listed in Tables 1
and 2 are presented.
5.4.1 Chemical composition content
Chemical composition content is defined as the ratio of the mass of a constituent element included in
a layered clay nanomaterial sample to that of the dried sample. The chemical composition content of a
layered clay nanomaterial sample shall be measured using an appropriate measurement method. The
measurement results are usually expressed as wt%.
Wet chemical analysis using ICP-MS can be applied to chemical composition content measurements for
elements even at an impurity level. The method is such that ions are generated at a high temperature
under the atmospheric pressure in argon plasma and detected using a mass spectrometer.
Layered clay nanomaterial samples can be decomposed using various dissolving agents, including
mixtures of strong acids and or hydrogen fluoride. Lithium metaborate (LiBO2) fusion is one of the main
options to decompose silicate material, because it is effective even in dissolving the most refractory
minerals. A plasma source could be also used to dissociate the sample into its constituent atoms or
ions, and the analysis of the atoms is done either with mass spectrometry or by detecting the optical
emission from the excited atoms (ICP-OES). In chemical composition report in addition to report of
major elements, it is required to report impurities, too.
The XRF spectrometry is also a method for the qualitative and quantitative determination of the
elemental composition content of a layered clay nanomaterial sample in both laboratory and industrial
environments. This method is less time consuming but it has some limitation on minimum content
detection and so it cannot be recommended for chemical composition content measurements at an
impurity level.
5.4.2 Mineral composition content
The mineral composition content is the ratio of the mass of a mineral composition included in a layered
clay nanomaterial sample to that of the dried sample. The mineral composition content shall be measured
using an appropriate measurement method. The measurement results are usually expressed as wt%.
The contents of major mineral composition of a layered clay nanomaterial sample can be determined
using XRD spectra of the dried sample. This technique could provide crystallographic information
[8][9]
about a sample by observing the diffraction pattern due to an X-ray beam hitting the sample .
Although many quantification methods based on the XRD technique are highly accurate, sample
preparation, data processing and the selection of standards are essential for the XRD quantification of
[10]
layered clay nanomaterial samples .
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5.4.3 Interlayer distance
In Figure 1, the thickness, length and some other structural parameters of layered clay nanomaterial
are schematically presented.
Key
L lateral size of layered clay
t layered clay nanomaterial thickness
d layer thickness
s
d gallery thickness
g
d interlayer distance
(001)
a layered clay nanomaterial
b multilayer structure of intercalated clay nanomaterial
c repetitive lattice cell
Figure 1 — Structural parameters of layered clay nanomaterial — (a) a layered clay
nanomaterial, (b) the dark grey area represents a single sheet of clay material and the light
grey area represents the spacing between two adjacent sheets, and (c) a , b and c represent
0 0 0
the lattice cell parameters
The interlayer distance of clay and clay nanomaterials can be calculated from Bragg’s equation
(nλ = 2d sin θ) using XRD spectrum, where in Bragg’s equation d is the spacing between layers of the
clay, λ the wavelength of X-ray, θ the angle at the peak and n is the layer number. In the Bragg’s equation
for case of n = 1 d is d which is the interlayer distance of a layered clay nanomaterial sample. A
001
typical XRD spectrum of layered clay nanomaterial is shown in Figure 2.
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Key
Y intensity
Figure 2 — Typical low angle XRD spectrum for a layered clay nanomaterial sample
XRD method is a preferable method for determination of the interlayer distance of a layered clay
nanomaterial sample due to its simplicity and accessibility. However other methods such as TEM
and FESEM, could be used for complementary and more detailed structural analysis of layered clay
nanomaterials. TEM could be used for structural analysis of layered clay nanomaterials. This method
produces images and diffraction patterns with a resolution in atomic scale by using an electron beam
which passes through the sample and interacts with the sample to a detector.
FESEM is another technique that examines and analyses the surface of samples by scanning with a
primary electron beam, which causes the ejection of secondary electrons, backscattered electrons,
absorbed electrons and X-ray radiation. The images constructed by these signals can be used to
determine the interlayer distance of a layered clay nanomaterial.
5.4.4 Thickness
Thickness of a layered clay nanomaterial is defined as the distance between the two edges on a cross-
sectional line orthogonal to the layer surface. When the thickness varies over the surface of the
nanomaterial, the largest value is recorded as the thickness. The thickness of a layered clay nanomaterial
shall be measured using an appropriate method. There are two options
...