ISO/TR 22293:2021
(Main)Evaluation of methods for assessing the release of nanomaterials from commercial, nanomaterial-containing polymer composites
Evaluation of methods for assessing the release of nanomaterials from commercial, nanomaterial-containing polymer composites
This document reviews and evaluates the utility of available methods to assess material released from commercial polymer composites in support of product use and safety decisions, and describes what revised or additional methods are needed. The document is not focused on describing methods per se; rather the goal is to describe information that is appropriate for consideration in the selection of methods to support decision-making.
Évaluation des méthodes de détermination d'émission de nanomatériaux par des polymères composites commerciaux, contenant des nanomatériaux
General Information
Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 22293
First edition
2021-07
Evaluation of methods for assessing
the release of nanomaterials from
commercial, nanomaterial-containing
polymer composites
Évaluation des méthodes de détermination d'émission de
nanomatériaux par des polymères composites commerciaux,
contenant des nanomatériaux
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviations. 3
5 Understanding the nano-enabled products . 4
5.1 Pathway analysis for the supply chain . 4
5.2 Matrix and MNM characteristics affecting rate and form of release. 8
5.2.1 General. 8
5.2.2 Consideration of the polymer used in the composite . 9
5.2.3 Polymer degradation .10
5.2.4 Consideration of MNM used in the composite .10
5.2.5 Polymer nanocomposites .11
5.2.6 Application areas and use phase (or lifecycle) processes .12
6 Factors affecting release measurement method selection .15
6.1 General .15
6.2 Forms of release .16
6.3 Decision support framework to determine which transformations need
consideration with examples .21
7 Approaches to detecting and quantifying the released material associated with
added manufactured nanomaterials .23
7.1 General .23
7.2 Methods for sampling released material .23
7.2.1 General.23
7.2.2 Sampling material released into air .24
7.2.3 Sampling material released into water, solids, and biological fluids .25
7.3 Methods for preparing samples of released material for subsequent analysis .26
7.3.1 General.26
7.3.2 Preparation and analysis of air samples .26
7.3.3 Preparation and analysis of waters, solids and biological fluid samples .27
7.4 Measurement challenges .28
7.4.1 General.28
7.4.2 Surface functionalization and transformations.28
7.4.3 Sample collection artefacts .29
7.4.4 Applicability of a measurement method for a given release media .29
7.4.5 Sample preparation artefacts.29
7.4.6 Capability of a measurement method .29
7.4.7 Representativeness of measurements .30
7.4.8 Composition measurements .30
7.4.9 Polymer stability .30
7.4.10 Commercial practices .30
7.5 Considerations for detection, quantification, and determination of properties of
released materials .31
7.6 Applicable measurement methods .32
8 Identification of needs for standards, methods, instrumentation, decision
frameworks, and research .32
8.1 General .32
8.2 Potential improved/new methods .32
8.3 Inter-laboratory studies .33
8.4 Protocols and assays .34
8.5 Opportunities for standardization of methods .34
8.6 Decision frameworks .35
Annex A (informative) Example case studies.38
Bibliography .57
iv © ISO 2021 – All rights reserved
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
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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
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on the ISO list of patent declarations received (see www .iso .org/ patents).
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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.
Introduction
0.1 General
The use of manufactured nanomaterials (MNM) in consumer products and applications is growing as
manufacturers exploit the unique properties of nanomaterials. MNMs are an increasingly common
feature of a growing variety of commercial applications and consumer products — from computer chips
to golf clubs. So too are concerns over what is or can be released from products containing MNMs, and
the risk and potential impacts of exposure to such releases. These unique properties offer significant
commercial value, enabling the manufacture of products that that offer novel characteristics. The MNM
might be embedded in solids, might be suspended in fluid, or might be bound to the surface of solid
products. An understanding of what is released from products containing MNMs is critical to planning
and managing safe development and use of those products.
This document aims to contribute to that understanding by providing a guide to the information to
be taken into account in determining the methods for identifying and evaluating releases of MNMs
from matrices; providing a framework for understanding how these methods and the information they
produce can support decision-making; and identifying opportunities for developing standards in this
area.
This document provides practical support for decisions related to product development and use through
early consideration of the potential for release of MNM and through focus on realistic use scenarios
where exposures to the released MNM might occur.
The intended users of this document would include:
— those planning to develop or adapt technical specifications for MNM use in commercial products;
— risk managers, product developers, exposure measurement practitioners or other stakeholders
seeking guidance on the availability and utility of methods to measure releases that could occur
from uses of specific MNMs in composites;
— methods and instrumentation developers seeking to identify needs of the risk management
community;
— those planning basic and applied research programs for measurement and modelling to support
decisions around sustainably safe uses of MNMs.
The structured review of the information regarding the selection of MNM measurement methods
provided in this document is needed because technologies to produce MNMs, their uses, and MNM
measurement methods are often developing at the same time, and the development of measurement
methods can in some cases lag behind product development needs. Furthermore, the need to measure
particular characteristics of the released MNM might also evolve as greater understanding of what
might cause toxicity for a particular kind of MNM is gained. This relationship between emerging
measurement methods and emerging information about toxicity makes a structured approach to review
of measurement needs even more important, so that data are assembled to support decisions using the
most up-to-date and fit-to-purpose measurement methods. Finally, the selection process for choosing
a particular MNM-composite for a product should include the consideration of whether the available
measurement methods are feasible for the evaluating the conditions of use of that MNM-composite.
This consideration is needed because many methods available for research or for controlled conditions
in industrial hygiene settings are not useful for realistic measurement needs where consumers might
be exposed. In some cases, those methods are too difficult to conduct outside of the laboratory, and in
other cases the methods are too labour-intensive to be feasible for routine decision support.
The development of the decision-making framework presented in this document is based in large part
on initial analyses that focused on releases from polyamide or epoxy polymers to which multi-wall
carbon nanotubes (MWCNT) have been added. Nonetheless, the framework can be used to inform the
selection of methods for identifying and evaluating the releases for a wide range of MNMs and types of
matrices, as illustrated by the case studies in Annex A. The case studies have been chosen because of
the availability of information and methods relevant for actual MNM-polymer composite uses.
vi © ISO 2021 – All rights reserved
Release from polymer nanocomposites can occur through processes such as physical, chemical, or
thermal degradation of a polymer matrix, resulting in particles that might include a mixture of free
MNM, free polymer, and matrix-bound MNM. This document focuses on the first release to human
exposure or to an effluent pathway. While acknowledging that subsequent MNM fate and transport
could follow from this initial release, the primary concern of this document is whether and where
release of MNMs can occur in the context of consumer or commercial use, and the need to monitor
likelihood of human exposure potential. Although other stages of the lifecycle of products containing
MNMs are discussed briefly to provide context, subsequent fate and transport events are not addressed
in detail.
The ultimate goal is to use the report structure of this document as a foundation for addressing releases
of other MNMs from other matrices in subsequent versions of the document.
0.2 Decision-Making Framework
0.2.1 General
In developing the decision-making framework set out in this document two key concepts that have
proven useful in addressing the relevant risk management issues in support of decision-making have
[1]
been applied. The first is “problem formulation” . This describes the purpose and context of the
analysis, and the nature of the decision that the analysis aims to support. By making it clear the analysis
is being conducted to support a specific decision, this approach helps to ensure the analysis remains
focused on methods that have practical application in making that decision. The second key concept
is “fit for purpose.” In other words, the nature of the analytical approach used should be sufficient for
and appropriate to addressing the specific risk management decision. This includes assuring that the
depth of analysis - including consideration of the sources and potential magnitude of uncertainty – is
consistent with the information needed to support the decision. In the context of this document, this
means that feasibility is an important consideration in the choice of analytical methods.
0.2.2 Application of concepts
In applying these concepts to the selection of methods for identifying and evaluating releases of
MNMs from matrices, the problem formulation would include an evaluation of the potential for human
exposure to the component of the nano-enabled product (NEP) that contains the MNM and the potential
for MNM release from that component.
To evaluate the potential for human exposure, an understanding of the product design and the potential
use scenarios is required. If, for example, the component containing the MNM is fully encased within a
consumer product, or is part of a machine where it is accessible only during maintenance, there are
limited opportunities for human exposure as part of the release event. Description of potential use
scenarios is also critical for understanding the potential nature of human exposure (e.g. direct dermal
contact vs. inhalation of released MNM), as well as relevant conditions of potential wear and aging (e.g.
potential and nature of abrasion, temperature, presence or absence of water and UV light).
Together, these elements of the problem formulation can aid in determining which potential release
scenarios need to be tested, as well as the nature of the analytical methods needed and, thus, aid in
determining whether it is feasible to evaluate the risk of a given choice of product composition without
substantial investment in analytical methods development.
0.2.3 Tiered approach
In some situations, a tiered approach — such as those described in Clause 8 — can be useful. For
example, if release outside of a confined structure is not expected (e.g. if the MNM is contained within
a phone, and release would not result in consumer exposure), an analytical method that simply detects
the MNM could be sufficient. In other cases, a qualitative description might be useful to predict the
potential for further interactions with other materials, and ultimately the fate and transport of the
MNM. Such information could be used, for example, in deciding between alternative designs or products
0.2.4 Quantitative risk assessment presents challenges
Finally, in some cases it could be necessary to quantitatively evaluate the MNM release in order to feed
into a quantitative risk assessment. In such cases, it is important to ensure that exposure measurements
are made in a way that facilitates integration with hazard data to evaluate risk. Such integration
includes evaluating the MNM characteristics with regard to key determinants of toxicity (e.g. degree of
aggregation and functionalization), and reporting exposure in relevant dose units. Currently completing
an evaluation of this kind presents a significant challenge, as the key determinants of toxicity and
appropriate dose units are still being identified in many situations.
0.2.5 Data requirements
As described in this document, key data needs to support a decision related to product development
and use include:
— a description of the NEP and where in the product the MNM is found;
— a description of common use scenarios, including frequency of use and relevant populations;
— a description of potential degradation mechanisms that can lead to release under the use scenario(s)
of interest;
— a description of the nanomaterial;
— a description of the composite matrix and its resistance to degradation under the use scenario(s) of
interest.
Based on this information, the assessor can determine the potential for release (including the release
rate) and the likely media into which the release might occur. These parameters in turn inform the
nature of sampling and analytic methods that might be needed.
0.3 Document structure and use
After a brief discussion of how the topic of this document relates to Lifecycle analysis, the document
addresses the structure of the polymer and the embedded MNM, and how those structures inform
measurement methods needs through their effect on the release rate and the form of the release
(Clause 5). Clause 6 describes how the relative resilience of the polymer matrix and the embedded MNM
inform measurement methods needs through their effect on the nature of the resulting release and
proposes a tiered (stepwise) decision framework for deciding if or which transformations at the release
point need to be considered. Worked examples applying the decision framework outlined in 6.3 are
presented in Annex A. Clause 7 addresses methods for measuring and describing the characteristics of
the released material, including sampling methods in various media, methods for sample preparation
and analysis, and measurement challenges. Clause 8 addresses remaining gaps and data needs, and
briefly reviews several available decision frameworks to support risk managers in determining the
information and sampling methods needed to support product design and development decisions.
It is anticipated that the information presented in this document will find application in assisting
manufacturers and regulatory agencies to more clearly identify products and scenarios with low
consumer exposure potential (e.g. where the MNM is part of a component that is fully encased) and
those products and scenarios with higher exposure potential (e.g. the MNM is in continuous contact
with human skin or is used under conditions subject to severe weathering). This document is also
intended to aid in evaluating — at the product design stage — how variation in adducts, coatings, or
MNM composition would affect MNM release rates and measurement needs.
viii © ISO 2021 – All rights reserved
TECHNICAL REPORT ISO/TR 22293:2021(E)
Evaluation of methods for assessing the release of
nanomaterials from commercial, nanomaterial-containing
polymer composites
1 Scope
This document reviews and evaluates the utility of available methods to assess material released from
commercial polymer composites in support of product use and safety decisions, and describes what
revised or additional methods are needed. The document is not focused on describing methods per
se; rather the goal is to describe information that is appropriate for consideration in the selection of
methods to support decision-making.
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 (all parts), Nanotechnologies — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TS 80004 (all parts) 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 https:// www .electropedia .org/
3.1
manufactured nanomaterial
MNM
nanomaterial intentionally produced to have selected properties or composition
[SOURCE: ISO/TS 80004-1:2015, 2.9]
3.2
nanocomposite
solid comprising a mixture of two or more phase-separated materials, one or more being nanophase
Note 1 to entry: Gaseous nanophases are excluded [they are covered by nanoporous material].
Note 2 to entry: Materials with nanoscale phases formed by precipitation alone are not considered to be
nanocomposite materials.
[SOURCE: ISO/TS 80004-4:2011, 3.2]
3.3
carbon nanotube
CNT
nanotube composed of carbon
Note 1 to entry: Carbon nanotubes usually consist of curved graphene layers, including single-wall carbon
nanotubes and multiwall carbon nanotubes.
[SOURCE: ISO/TS 80004-3:2010, 4.3]
3.4
multi-wall carbon nanotube
MWCNT
carbon nanotube composed of nested, concentric or near-concentric graphene sheets with interlayer
distance similar to those of graphite
Note 1 to entry: The structure is normally considered to be many single-wall carbon nanotubes nesting each
other, and would be cylindrical for small diameters but tends to have a polygonal cross-section as the diameter
increases.
[SOURCE: ISO/TS 80004-3:2010, 4.6]
3.5
lifecycle
consecutive and interlinked stages of a product system, from raw material acquisition or generation
from natural resources to final disposal
[SOURCE: ISO 14044:2006, 3.1, modified — the term has been modified from "life cycle" to "lifecycle".]
3.6
nano-enabled
exhibiting function or performance only possible with nanotechnology
[SOURCE: ISO/TS 80004-1:2015, 2.15]
3.7
single wall carbon nanotube
SWCNT
carbon nanotube consisting of a single cylindrical graphene layer
Note 1 to entry: The structure can be visualized as a graphene sheet rolled into a cylindrical honeycomb
structure.
[SOURCE: ISO/TS 80004-3:2010, 4.4]
3.8
nano-enhanced
exhibiting function or performance intensified or improved by nanotechnology
[SOURCE: ISO/TS 80004-1:2015, 2.16]
3.9
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]
2 © ISO 2021 – All rights reserved
3.10
agglomerate
collection of weakly or medium strongly bound particles where the resulting external surface area is
similar to the sum of the surface areas of the individual components
Note 1 to entry: The forces holding an agglomerate together are weak forces, for example van der Waals forces or
simple physical entanglement.
Note 2 to entry: Agglomerates are also termed secondary particles and the original source particles are termed
primary particles.
[SOURCE: ISO 26824:2013, 1.2]
3.11
graphene oxide
GO
chemically modified graphene prepared by the oxidation of graphite causing extensive oxidative
modification of the basal plane
[SOURCE: ISO/TS 80004-13:2017, 3.1.2.13, modified — "and exfoliation" has been deleted.]
3.12
additive
substance added to polymers to improve or modify one or more particles
Note 1 to entry: In a narrow sense, the term additive includes only ingredients added in small amounts; in such
cases the term modifier is used for an ingredient added in relatively large amounts.
[SOURCE: ISO 472:1999, Clause 2]
4 Abbreviations
AC article category
AFM atomic force microscopy
AUC analytical ultracentrifugation
CRM certified reference material
ECHA European Chemicals Agency
EC elemental carbon
EM electron microscopy
ERC environmental release category
ES exposure scenario
ESD emissions scenario document
ICP inductively coupled plasma
ICP-MS inductively coupled plasma mass spectrometry
ILS inter-laboratory studies
LCA Lifecycle analysis
LCS lifecycle stage
MCE mixed cellulose ester
NEP nano-enabled or nano-enhanced product
PC polycarbonate
PP polypropylene
PROC process category
PVC polyvinyl chloride
RM reference material
RTM representative test material
SEM scanning electron microscopy
SL service life
SU sector of use
TEM transmission electron microscopy
TO thermal optical
UDS use descriptor system
UV ultraviolet
UV-VIS ultraviolet-visible spectroscopy
WWTP waste water treatment plants
5 Understanding the nano-enabled products
5.1 Pathway analysis for the supply chain
The focus of this document is on release of the MNM in the use phase of the lifecycle, including both
consumer and commercial use. However, the design of NEPs needs to consider the potential for MNM
release, and ultimately MNM exposure, throughout the lifecycle. Therefore, this clause briefly discusses
considerations for the broader NEP lifecycle. The first step in the identification of potential releases
along the lifecycle of NEPs is to provide a comprehensive pathway analysis along and beyond their
value chain. The basis of this pathway analysis will be the information available about the product and
the processes the product passes through during its whole lifecycle. This information might include
product composition (nanomaterial and matrix type and composition), production and use volumes for
each application, knowledge on fabrication and other lifecycle processes, use profiles (market details)
and disposal options. Furthermore, MNM releases in industries strongly depend on the risk mitigation
measures applied for waste management and uncontrolled processes.
The estimation of the concentration of chemicals released from products and ending up in the different
environmental compartments could be based on the information provided in documents such as OECD
Emission Scenario Documents (ESDs). The OECD Working Party on Exposure Assessment develops
ESDs in order to reflect conditions on production, use, etc., that are different between countries, and so
avoiding duplicative efforts by Member countries and industry. ESDs have been widely used in national
and regional contexts. For example, ECHA’s guidance document on environmental exposure estimation
refers to existing ESDs developed by both OECD and the European Commission. Other OECD member
countries have developed their own ESDs and the US EPA has developed several generic scenarios to
be used as default release scenarios in risk assessment. The OECD describes an emission scenario as a
4 © ISO 2021 – All rights reserved
set of conditions about sources, pathways, production processes, and uses patterns that quantify the
emissions (or releases) of a chemical from production, formulation, processing, use and recovery, and
disposal into water, air and solid waste. An emission rate is used to quantify releases. Default values
are established in a way that reflect an average number for the whole lifecycle considering the emission
rate remains constant over time. However, this is not applicable to most of the cases since the rate will
decrease over time for most additives.
Furthermore, to support the identification of uses and facilitate effective communication up and down
the supply chain, as well as quantification of releases, ECHA has developed a standardized description
of uses in the supply chain called the use descriptor system. The UDS was based on six separate
descriptors: lifecycle stage, sector of use, process category, product category, article category, and ERC.
There are four basic stages in the lifecycle of a substance to which a use can be assigned: manufacture,
formulation or repacking, end-use (use in industrial sites, professional use, and consumer use) and
(article) SL. A brief description of the product use(s) can be obtained by using these descriptors.
— Lifecycle stage: Reflects the stage of the chemical/ nanomaterial in its lifecycle. It is structured
in such a way that it indicates the type of organizations using the chemical (or nanomaterial) after its
manufacture (e.g. formulators, industrial end users).
— Sector of use: Describes in which sector or market area the substance (nanomaterial) is used.
EXAMPLE 1 SU4: manufacture of textiles, leather, fur; SU11: manufacture of rubber products.
— Process category: Describes the application techniques or process types defined from an
occupational perspective; the PROC, in combination with the operational conditions and risk
management measures, is the prime determinant for the level of occupational exposure. It is a required
descriptor for worker uses.
EXAMPLE 2 PROC1: Production in closed process without likelihood of exposure or processes with equivalent
containment conditions; PROC5: Mixing or blending in batch processes; PROC7: Industrial spraying.
— Chemical product category: Describes the types of products in which a substance/ nanomaterial
is used. The chemical product category in combination with the operational conditions and risk
management measures primarily determines the level of consumer exposure. It is a required descriptor
for consumer uses.
EXAMPLE 3 PC9a: Coatings and paints, thinners, paint removers, PC24: Lubricants, greases, release products;
PC31: Polishes and wax blends.
— AC: Describes the type of article in which the substance/nanomaterial has been processed. The AC
is only relevant and used for the lifecycle stage SL.
EXAMPLE 4 AC2b: Other machinery, mechanical appliances, electrical/electronic articles; AC8e: Paper
articles: Furniture and furnishings; AC13a: Plastic articles: large surface area articles.
— ERC: Describes the broad conditions of use from an environmental perspective, based on those
characteristics that give a first indication of the potential release of the substance to the environment.
The default is to select only one ERC per use.
EXAMPLE 5 ERC2: Formulation into mixture; ERC6a: Use of intermediate; ERC8a: Widespread uses of non-
reactive processing aid (no inclusion into or onto article, indoor).
Table 1 provides an example of the UDS for polymeric nanocomposites. Scenarios for each lifecycle stage
are listed, along with a brief description of relevant processes and activities. The table then identifies
the process, product, article, and environmental release categories, to provide an overview of uses
across the supply chain.
Table 1 — Example of the ECHA use descriptor system of CNT in polymeric nanocomposites
Short descrip-
Product
LCS ES tion of process PROC SU AC ERC
category
or activity
Synthesis PROC1
Recovery PROC2
Packing PROC9
Production/
synthesis of ERC1 Manu-
Internal trans- PROC8b
CNTs using — — — facture of the
port
chemical va- substance
Cleaning and PROC8b
pour deposition
maintenance
Storage and dis- PROC8b
tribution
Synthesis PROC1
Recovery PROC2
Packing PROC9
Production/
ERC1 Manu-
Internal trans- PROC8b
synthesis of
— — — facture of the
port
CNT using
substance
arc-vapour
Cleaning and PROC8b
maintenance
Storage and dis- PROC8b
tribution
Synthesis PROC1
Recovery PROC2
Packing PROC9
Production/
ERC1 Manu-
Internal trans- PROC8b
synthesis of
— — — facture of the
port
CNT using laser
substance
ablation
Cleaning and PROC8b
maintenance
Storage and dis- PROC8b
tribution
Weighing, mixing, PROC5 SU12 Man-
loading ufacture
of plastics
Extrusion and PROC14
products,
granulation
Manufacturing
including
Packing PROC21
of intermedi- ERC1 Manu-
compounding
ate composite — — facture of the
and conver-
Internal trans- PROC21
materials con- substance
sion
port
taining CNTS
Cleaning and PROC8b
maintenance
Storage and dis- PROC21
tribution
6 © ISO 2021 – All rights reserved
LCS 2: CNT Incorporation
into products
LCS 1: CNT synthesis
Table 1 (continued)
Short descrip-
Product
LCS ES tion of process PROC SU AC ERC
category
or activity
Weighing, mixing
PROC5
and loading
SU12 Man-
Extrusion, mould-
Manufactur- ufacture PC32
PROC14
ing and forming
ing of solid of plastics Polymer
AC13 ERC3 Formula-
products with Shaping and fin- products, prepara-
PROC24 Plastic tion into solid
composite ishing including tions and
articles matrix
materials con- compounding com-
Cleaning and
PROC8b
taining CNTs and conver- pounds
maintenance
sion
Storage and dis-
PROC21
tribution
Professional PC32
use (service Polymer ERC11a Wide-
life) of solid Cutting, shaping, prepara- spread use of
PROC24 — —
composite drilling, sanding tions and articles with low
materials con- com- release (indoor)
taining CNT pounds
Sorting (mechan-
ical, electromag-
PROC21
netical and manu-
PC32
al separation)
Recycling and Polymer ERC12a Process-
disposal of prepara- ing of articles at
Processing (me-
— —
products con- tions and industrial sites
chanical and ther- PROC24
taining CNTs com- with low release
mal processes)
pounds
Landfill PROC21
Incineration PROC2
The descriptors for all of these categories are requested under the registration, evaluation,
authorization and restriction of chemicals (REACH) regulation in Europe for the safety assessment of
chemical substances (including nanomaterials) and their uses. The information from this assessment
is summarized in the REACH chemical safety report (CSR). One key component of that CSR is the
ES in which manufacturers or importers set out the conditions for safe use of their substance. This
information is essential to many actors in the chemical supply chain in their day-to-day handling of
substances (including nanomaterials). For the identification of the ESs associated with a nano-enabled
product, the generation of conceptual maps for the product lifecycle is proposed (general diagram in
Figure 1). This diagram links the lifecycle stages of a product with potential exposure/release scenarios
(defined as those activities from which release is highly probable to occur), receptors (human, water,
soil, air, biota) and technological compartments (WWTPs, incinerators, landfill sites). The five lifecycle
stages considered are:
a) MNM synthesis,
b) incorporation of MNM into the product (nano-enabled product manufacturing),
c) manufacturing of products containing MNM,
d) use and service life phase, and
e) recycling and end of life.
A full description of the lifecycle, particularly potential use scenarios, can aid in focusing release
testing on conditions that are potentially relevant to the product. During the use phase, intended and
unintended release of MNM can occur. The unintended release of MNM typically results from non-point
sources such as washed off sunscreens in the ocean water or release from other consumer products,
while the intended release results from point sources such as a WWTP that uses MNM for groundwater
LCS 4: Use
LCS 5: Recycling and LCS 3: Manufacturing of
and service
end of life products containing CNTs
life
remediation. In Figure 1, green arrows indicate releases to the environment (generally uncontrolled)
and possibly resulting in human exposure (workers and consumers) and red arrows indicate MNM
release pathways ending up in waste management or end-of-life treatments.
Figure 1 — Lifecycle of a nano-enabled product
5.2 Matrix and MNM characteristics affecting rate and form of release
5.2.1 General
Variations in matrix materials, and MNM types and compositions of nanocomposites can affect the
likelihood of nanomaterial release, form of release (e.g. particles containing filler, free filler, degraded
filler), and in general the magnitude of materials release, which in turn can each affect measurement
[2]
method selection. Understanding the physicochemical properties of the neat polymeric matrix
material, MNM additive, and composite material is critical in understanding the release behaviour
of nanocomposites in their use cases. Potential exposure is often application-specific and is highly
dependent on MNM physicochemical properties, the way the MNM is incorporated into the product,
and the way the product is being used. Subclause 5.2 briefly reviews key aspects of the physicochemical
properties and other key characteristics of the major matrices and MNM additives relevant to
nanocomposites to help frame evaluation of the effect of MNM-matrix differences on MNM release
characteristics in Clause 6 and the need for particular sampling and measurement methods in Clause 7.
The key topics discussed include:
— release of mnm throughout lifecycle;
— standardized descriptors of nep use, quantification of releases;
— factors affecting MNM release:
— mnm type,
— structure/composition of matrix, and
— product use.
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5.2.2 Consideration of the polymer used in the composite
5.2.2.1 General
To fabricate industrial and consumer NEPs the MNM is usually integrated in a matrix. This matrix
is often a designated plastic, i.e. a synthetic material made from a wide range of organic polymers.
Plastics are broadly classified as thermosetting or thermoplastic polymers; the classification reflects
the post-manufacturing malleability and flexibility. Thermosetting polymers are irreversibly hardened
via curing by, for example, heat. Thermoplastic polymers are pliable or moldable at a certain elevated
temperature and solidifies upon cooling. The thermal properties depend on the chemical structure
and molecular units that form polymer chains and backbones. Thermosetting polymers are often
crosslinked forming resins and rubbers (duromers). Understanding the performance differences can
help making better sourcing decisions and improve product design.
5.2.2.2 Thermosetting polymers
Thermosetting polymers are made from polymer chains that cross-link together during the curing
process to form a permanent chemical bond. Cross-linking that occurs during the curing process
prevents movement of individual polymer chains after curing. Because of thi
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