ISO/TS 21237:2020

Nanotechnologies — Air filter media containing polymeric nanofibres — Specification of characteristics and measurement methods

This document specifies the characteristics to be measured of air filter media containing polymeric nanofibres on the surfaces of a substrate. It also describes measurement methods for determining the individual characteristics. This document does not cover characteristics specific for health and safety issues. NOTE The properties/performances assessment of air filter media related to applications requires the use of relevant published standards. The physical properties and performances of filtration media, such as pressure drop, and the particle removal efficiency of air filter media are measured with test methods suitable for specific applications.

Nanotechnologies — Milieux filtrants de l'air contenant des nanofibres polymères — Spécification des caractéristiques et des méthodes de mesure

General Information

• Status: Published
• Publication Date: 30-Mar-2020
• 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: 26-Jun-2023

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 21237
First edition
2020-03
Nanotechnologies — Air filter media
containing polymeric nanofibres —
Specification of characteristics and
measurement methods
Reference number
ISO/TS 21237:2020(E)
©
ISO 2020

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ISO/TS 21237:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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ii © ISO 2020 – All rights reserved

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ISO/TS 21237:2020(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 to be measured and their measurement methods .3
5.1 General . 3
5.2 Mandatory and optional characteristics and their measurement methods. 3
5.3 Descriptions on characteristics and their measurement methods . 4
5.3.1 General. 4
5.3.2 Fibre diameter . 4
5.3.3 Morphology . 4
5.3.4 Specific surface area . 4
5.3.5 Chemical composition content . 5
5.3.6 Thermal stability. 5
5.3.7 Crystalline structure . 5
5.3.8 Crystallinity . 5
5.3.9 Crystallite size . 6
6 Reporting . 6
Annex A (informative) Typical structures of air filter media containing nanofibres .7
Annex B (informative) Test report format for mandatory characteristics . 9
Annex C (informative) Test report format for optional characteristics .10
Bibliography .11
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ISO/TS 21237:2020(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 229, Nanotechnologies.
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 21237:2020(E)

Introduction
Air filter media play an important role in the performance and efficiency of different types of air filters.
In this respect, most air filter media take advantage of nonwovens to separate solid or liquid particles.
Air filter media have a wide range of applications such as gas turbine inlet air, industrial dust collectors,
respiratory masks, personal protective equipment, heating, ventilation and air conditioning systems,
cleanrooms, etc.
In recent years, air filter media containing nanofibres have been commercialized and widely used by
different industries due to their high filtration efficiency along with a low pressure drop created by the
[6]
slip flow effect . Air filter media containing nanofibres are normally produced by depositing one or
more types of polymer-based nanofibres directly on the surface of a suitable porous substrate during
spinning.
Since the diameter of nanofibres is significantly smaller than that of conventional microfibres employed
in filters, it offers a higher chance of inertial impaction and interception, i.e. a more optimum filtration
efficiency. The slip flow also results in a reduced pressure drop and more contaminants passing near
the surface of the nanofibres. Hence, the inertial impaction and interception efficiencies rise. As a result,
the filtration capability of the nanofibres layer increases for the same pressure drop as compared with a
conventional fibre layer. Additionally, the very high surface area of nanofibres facilitates the adsorption
of contaminants from the air. All these desirable features have led to a wide range of air filter media
[6][7][8]
containing nanofibres being used for air filtration applications .
Different techniques such as electrospinning, force spinning and other methods have been used to
produce air filter media containing nanofibres. The deposited nanofibres form a web-like nonwoven
layer on the surface of the substrate. Nanofibres can exhibit different crystalline structures, morphology
and diameter. The surface area and crossed-fibres porosity of the formed nonwoven layer is mainly
affected by the nanofibre diameter as well as the morphology. Polymeric nanofibres such as polyamide,
polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and polyurethane (PU) are normally used for
air filter media. Nanofibres can be deposited on different kinds of woven and nonwoven substrates.
Annex A shows a schematic of the cross-section of an air filter medium (see Figure A.1) and SEM images
relating to the morphology of the nanofibres (see Figures A.2 and A.3).
This document facilitates the communication between sellers and buyers and supports the growing
trade of this new class of air filter media.
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TECHNICAL SPECIFICATION ISO/TS 21237:2020(E)
Nanotechnologies — Air filter media containing polymeric
nanofibres — Specification of characteristics and
measurement methods
1 Scope
This document specifies the characteristics to be measured of air filter media containing polymeric
nanofibres on the surfaces of a substrate. It also describes measurement methods for determining the
individual characteristics.
This document does not cover characteristics specific for health and safety issues.
NOTE The properties/performances assessment of air filter media related to applications requires the use
of relevant published standards. The physical properties and performances of filtration media, such as pressure
drop, and the particle removal efficiency of air filter media are measured with test methods suitable for specific
applications.
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
air filter
filter
device for separating solid or liquid particles (3.6) or gaseous contaminant from an air stream passing
through the device
Note 1 to entry: The device is generally formed of a layer or layers of porous, fibrous or granular material.
Note 2 to entry: Air being cleaned by a filter must pass through the filter, whereas an air cleaner can reduce air
contamination by any method.
[SOURCE: ISO 29464:2017, 3.1.16, modified — The preferred term has been changed to “air filter”.]
3.2
air filter medium
porous permeable material employed in filtration (3.3) within which the filtrate is trapped or deposited
Note 1 to entry: The filter medium is composed of a nanofibre (3.5) layer(s) and substrate (3.7).
[SOURCE: ISO 9912-1:2004, 2.27, modified — “air” has been added to the term and Note 1 to entry has
been added.]
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ISO/TS 21237:2020(E)

3.3
filtration
separation of contaminants from a fluid stream in which they are suspended through retention
of the contaminants (by extension, also the whole of the activities involved in the construction and
commissioning of a filter installation)
[SOURCE: ISO 29464:2011, 3.5.29]
3.4
nanoscale
length range approximately from 1 nm to 100 nm
Note 1 to entry: Properties that are not extrapolations from larger sizes are predominantly exhibited in this
length range.
[SOURCE: ISO/TS 80004-1:2015, 2.1]
3.5
nanofibre
nano-object with two external dimensions in the nanoscale (3.4) and the third dimension
significantly larger
Note 1 to entry: The largest external dimension is not necessarily in the nanoscale.
Note 2 to entry: The terms nanofibril and nanofilament can also be used.
Note 3 to entry: If the dimensions differ significantly (typically by more than 3 times), terms such as nanofibre or
nanoplate may be preferred to the term nanoparticle.
[SOURCE: ISO/TS 80004-2:2015, 4.5]
3.6
particle
minute piece of matter with defined physical boundaries
Note 1 to entry: A physical boundary can also be described as an interface.
Note 2 to entry: A particle can move as a unit.
Note 3 to entry: This general particle definition applies to nano-objects.
[SOURCE: ISO/TS 80004-2:2015, 3.1]
3.7
substrate
base layer for depositing nanofibres (3.5) on the surface
4  Abbreviated terms
AFM atomic force microscopy
FESEM field emission scanning electron microscopy
FTIR Fourier transform infrared
IR infrared
SEM scanning electron microscopy
STM scanning tunnelling microscopy
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ISO/TS 21237:2020(E)

TEM transmission electron microscopy
TGA thermo gravimetric analysis
UV-Vis ultraviolet-visible
XRD X-ray diffraction
5  Characteristics to be measured and their measurement methods
5.1 General
This clause provides both mandatory and optional characteristics to be measured of air filter media
containing nanofibres and their measurement methods. The purpose, definition and measurement
methods are described for each characteristic in the following individual subclauses.
For all measurements of the characteristics, pieces of the air filter media sample combining a nanofibre
layer(s) and a substrate are used as test specimens.
5.2  Mandatory and optional characteristics and their measurement methods
The characteristics of air filter media containing nanofibres listed in Table 1 shall be measured.
The relevant measurement methods listed in Table 1 should be taken for the determination of the
individual characteristics. The other listed measurement methods can be also used. The characteristic
measurements listed in
...