ISO 23832:2021

INTERNATIONAL ISO
STANDARD 23832
First edition
2021-06
Plastics — Test methods for
determination of degradation
rate and disintegration degree of
plastic materials exposed to marine
environmental matrices under
laboratory conditions
Plastiques — Méthodes d'essai pour l'évaluation de la vitesse de
dégradation et du degré de désintégration des matériaux plastiques
exposés aux matrices environnementales marines dans des conditions
de laboratoire
Reference number
ISO 23832:2021(E)
©
ISO 2021

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ISO 23832:2021(E)

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© ISO 2021
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Published in Switzerland
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ISO 23832:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 3
6 Environmental matrix . 3
6.1 Sampling . 3
6.2 Preparation of the sediment and seawater . 4
7 Apparatus . 4
8 Materials . 6
8.1 Test material . 6
8.2 Reference material . 6
8.3 Negative control . 6
9 Sample preparation and measurements . 7
9.1 Acclimatisation of samples . 7
9.2 Conditioning before measurements . 7
9.3 Marking of samples . 7
9.4 Protective net . 7
9.5 Tensile properties . 7
9.6 Thickness . 8
10 Test set-up . 8
10.1 Incubation . 8
10.2 Sampling times and replicates . 8
10.3 Start of the test . 8
10.3.1 General. 8
10.3.2 Test Method A (sand burial degradation test) . 9
10.3.3 Test method B (sediment/seawater interface degradation test) . 9
10.3.4 Test method C (Seawater degradation test) .10
10.4 End of the test .10
11 Degradation rate .10
12 Degree of disintegration .11
12.1 General .11
12.2 Surface area analysis .11
12.3 Mass loss .11
13 Validity of the test .12
14 Test report .12
Annex A (informative) Determination of degradation rate — Example .13
Bibliography .15
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ISO 23832:2021(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 61, Plastics, Subcommittee SC 14,
Environmental aspects.
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 23832:2021(E)

Introduction
Plastics are potentially susceptible to ultimate biodegradation, i.e. to be decomposed by the actions
of microorganisms under aerobic conditions into CO , water and biomass as can be proven with
2
specific test methods. In most cases, biodegradation occurs at the surface of the plastics materials, i.e.
at the solid-liquid interface. Microbes and enzymes cannot penetrate the solid plastic item, thus only
the exposed surface is generally available to biodegradation. The physical effect of biodegradation
on a solid plastic item is erosion leading to a thinning and weakening of the item. This process leads
the item to lose mass, physical properties, and ultimately physical integrity by fragmentation into
biodegradable particles whose ultimate fate is to be biodegraded. The term disintegration is used
when the degradation process is extended until a total fragmentation of the original item into particles
below a defined size is reached. When microorganisms cause degradation processes biodegradation,
biofragmentation, biodisintegration are the proper terms, etc. as suggested by CEN/TR 15351. However,
when the physical breakdown rather than the chemical breakdown is measured, the generic term
“degradation” is preferably used, reserving the term “biodegradation” to the assessment of the ultimate
biodegradation, i.e. the conversion into CO , H O and biomass.
2 2
The assessment of specific degradation rates occurring when plastics materials are exposed to marine
matrices is needed for designing products intended for marine applications (e.g. biodegradable plastic
fish and mussel farming, floating devices) and for assessment of the risk caused by leakage of products
into the sea.
In this document three test methods for testing degradation are described. Plastics samples can be
exposed to three different test conditions and different marine matrices:
— buried into a wet sandy marine sediment;
— at the interface between a marine sandy sediment and the water column;
— to seawater.
The conditions applied in these test methods are designed to determine the degradation rates of
plastics materials and give an indication of their propensity to physical degradation and disintegration
in natural environments.
Degradation rates considered in this document are mass loss rate, erosion rate, and mechanical
properties loss. Disintegration, i.e. physical breakdown of a sample into very small fragments (<2mm),
can also be assessed.
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INTERNATIONAL STANDARD ISO 23832:2021(E)
Plastics — Test methods for determination of degradation
rate and disintegration degree of plastic materials exposed
to marine environmental matrices under laboratory
conditions
1 Scope
This document specifies test methods for the measurement of the physical degradation of samples made
with plastics materials when exposed to marine environmental matrices under aerobic conditions at
laboratory scale.
This document is not suitable for the assessment of degradation caused by heat (thermo-degradation)
or light exposure (photo-degradation).
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 527-1, Plastics — Determination of tensile properties — Part 1: General principles
ISO 527-2, Plastics — Determination of tensile properties — Part 2: Test conditions for moulding and
extrusion plastics
ISO 527-3, Plastics — Determination of tensile properties — Part 3: Test conditions for films and sheets
ISO 4593, Plastics — Film and sheeting — Determination of thickness by mechanical scanning
ISO 16012, Plastics — Determination of linear dimensions of test specimens
ASTM D 638-14, Standard Test Method for Tensile Properties of Plastics
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
biodegradation
degradation caused by biological activity, especially by enzymatic action, leading to a significant change
in the chemical structure of a material
[SOURCE: ISO 472:2013, 2.1680]
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ISO 23832:2021(E)

3.2
degradation
irreversible process leading to a significant change in the structure of a material, typically characterized
by a change of properties (e.g. integrity, molecular mass or structure, mechanical strength) and/or by
fragmentation, affected by environmental conditions, proceeding over a period of time and comprising
one or more steps
[SOURCE: ISO 472:2013, 2.262]
3.3
disintegration
physical breakdown of a material into very small fragments
[SOURCE: ISO 14855-1:2012, 3.3]
3.4
total dry solids
amount of solids obtained by taking a known volume of test material or inoculum and drying at about
105 °C to constant mass
[SOURCE: ISO 13975:2019, 3.5]
3.5
volatile solids
amount of solids obtained by subtracting the residues of a known volume of test material or inoculum
after incineration at about 550 °C from the total dry solids (3.4) content of the same sample
Note 1 to entry: The volatile solids content is an indication of the amount of organic matter present
[SOURCE: ISO 13975:2019, 3.6]
4 Principle
This document describes three laboratory test methods:
a) Method A: Sand burial degradation test;
b) Method B: Sediment/seawater interface degradation test; and
c) Method C: Seawater degradation test.
These three test methods are based on the exposure of plastic samples to environmental matrices
taken from the sea and on the measurement of physical degradation.
These three test methods differ for the exposure conditions.
In Method A, the plastic samples are buried in a wet sandy sediment (a condition similar to the sandy
shoreline where beach is maintained wet by the waves and tides).
In Method B, the plastic samples are laid at the interface between a sandy sediment bed and a water
column (a condition similar to the seabed where most debris sinks, accumulates, and undergoes
degradation).
In Method C, the plastic samples are exposed to seawater.
The degradation rate of the plastic material can be measured as:
a) mass loss and/or
b) erosion and/or
c) tensile properties decay.
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ISO 23832:2021(E)

The three test methods can also be used to determine the time for disintegration, i.e. the time needed to
get the plastic samples fragmented into pieces below 2 mm, as determined by the surface area loss and/
or mass loss determination.
The three test methods can be performed together or independently.
Claims of performance shall be limited to the numerical result obtained in the test and not be used for
unqualified “biodegradable in marine environment” claims and similar. The results obtained are solely
referred to the propensity to physical degradation caused by exposure to environmental matrices. The
results do not give information regarding the ultimate biodegradability in the marine environment.
The test design (i.e. the total number of tested samples, the number of replicates and of repeated
measurements) of the test methods is flexible. The complexity of test design and the cost of testing
can be modulated according to the requests and purposes of the client. For example, tests planned for
results delivered under statistically optimal conditions can be arranged for certification purposes,
while simpler tests can be arranged for screening purposes.
5 Reagents
5.1 Distilled or deionized water, free of toxic substances (copper in particular) and containing less
than 2 mg/l of DOC.
5.2 Artificial seawater
Dissolve:
Sodium chloride (NaCl) 22 g
Magnesium chloride hexahydrate (MgCl . 6 H O) 9,7 g
2 2
Sodium sulfate (Na SO ) 3,7 g
2 4
Calcium chloride (CaCl ) 1 g
2
Potassium chloride (KCl) 0,65 g
Sodium hydrogen carbonate (NaHCO ) 0,20 g
3
in water (5.1) and make up to 1 000 ml
6 Environmental matrix
6.1 Sampling
Take a sample of a sandy sediment with a shovel beneath the low-water line at the shoreline and/or
seawater with a bucket. Record location and date of sampling. The wet sediment together with seawater
is transferred into sealed containers for transport and fast delivered to the laboratory. After delivery,
conserve the sediment and seawater at low temperature (approximately 4 °C) until use. The seawater/
sediment sample should preferably be used within 4 weeks after sampling. Record storage time and
conditions. More detailed instructions about sampling, preservation, handling, transport and storage
of marine matrices are given in ISO 5667-3.
Measure the total dry solids, total organic carbon [(TOC) or, as an alternative, ashes and volatile solids],
pH, and nitrogen content of the sediment and of the natural seawater.
The pH can be measured by applying ISO 10523 with seawater or ISO 10390 with marine sediments.
ISO 10694 can be applied to determine the TOC and ISO 11261 can be applied to determine nitrogen
content. A description on how to measure total dry solids, volatile solids and ashes of a solid
environmental matrix (e.g. marine sediment or compost) is given in ISO 20200 and ISO 16929.
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ISO 23832:2021(E)

6.2 Preparation of the sediment and seawater
Remove, manually or by sieving, stones, pebbles and other materials until a clean marine sediment is
obtained .
Filter the sediment in a funnel with a coarse filter paper to eliminate excess seawater. Sediment is ready
for testing when seawater dripping stops. Sediment after filtering is named “wet sediment” hereafter
and ready for Method A and Method B.
Natural seawater is directly used without filtration.
7 Apparatus
7.1 General
Polypropylene boxes or domestic aquariums (i.e. fish tanks for hobbyists) are suitable for the purposes
of this document. However, if the test material is made with plastics expected to have degradation
properties similar to the plastics used in the aquarium, glass should be used. See Figure 1 for a schematic
representation of the tanks, which can be used to carry out the test methods.
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ISO 23832:2021(E)

Key
A sand burial degradation test 3 wet sediment
B sediment/seawater interface degradation test 4 plastic sample
C seawater degradation test 5 aeration system
1 lid 6 seawater
2 5 mm hole for gas exchange
Figure 1 — Apparatus
7.2 Test Method A (Sand burial degradation test)
Polypropylene (or other suitable material) boxes with a minimum dimension approximately of
30 cm × 20 cm × 10 cm (length, width, height) are appropriate. Alternatively, test devices as described
in 7.3 can be used to perform the sand burial degradation test. Each box shall be provided with a lid
assuring a tight closing to avoid an excessive vapour release. The closing between box and lid can be
sealed with an adhesive tape to limit the water evaporation. In the middle of the two 20 cm wide sides,
a hole of 5 mm of diameter shall be done at a height of about 6,5 cm from the bottom. The two holes
provide gas exchange between the inner atmosphere and the outside environment. Attention shall be
paid not to cover them with the adhesive tape, or in other way.
7.3 Test Method B (Sediment/seawater interface degradation test)
Tanks/aquariums (made with polypropylene or other suitable materials) with a minimum volume of
12 l (e.g. with dimension of 30 cm × 20 cm × 20 cm length, width, height) are appropriate. The dimension
of the aquarium should be decided on the basis of the experimental design established by the operator,
i.e. form and size of the plastic material to be tested and the number of replicates.
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ISO 23832:2021(E)

Aeration of seawater shall be applied with an appropriate aeration system. The typical systems used in
domestic aquariums are appropriate.
7.4 Test Method C (Seawater degradation test)
See 7.3.
7.5 Analytical balance
7.6 pH meter
8 Materials
8.1 Test material
Test the material in the form of film, sheet or other forms. Prepare samples of adequate dimensions (e.g.
5 cm × 5 cm) from films and sheets. Measure the thickness of samples and register in final report (see
Clause 11). Prepare the samples with a minimum thickness of 1 mm to 3 mm when thickness loss is
measured. Standard “dumbbell-shaped” test samples made as reported in ISO 527-2 or ASTM D638 are
suitable for the purpose.
When testing the degree of disintegration (see Clause 12), samples can be obtained from the product
of interest or prepared from the plastic material of interest. Samples of 25 μm to 30 μm are suitable for
testing the degree of disintegration.
8.2 Reference material
The following can be used as a reference material:
1)
a) polycaprolactone (PCL) , or
2)
b) ashless cellulose filter (e.g. filter paper Whatman® n. 42 ), or
c) pure cotton (for example 100 % cotton gauze),
d) or poly-ß-hydroxybutyrate.
Prepare and characterize samples using the same procedure used for test materials (see 8.1). Form,
size, and thickness of samples should be comparable to that of the test material. Report characteristics
of reference material (density, etc.) in the test report.
8.3 Negative control
Optionally, a non-biodegradable polymer (e.g. polyethylene) can be tested as a negative control. Prepare
samples using the same procedure used for test materials (see 8.1).
TM TM
1) PCL products of the CAPA series (e.g. CAPA 6800) from Ingevity (USA) have been found satisfactory for
this purpose. This information is given for the convenience of users of this document and does not constitute an
endorsement by ISO of the product named. Equivalent products may be used if they can be shown to lead to the
same results.
®
2) Whatman quantitative filter paper is the trade name of a product supplied by Aldrich. This information is
given for the convenience of users of this document and does not constitute an endorsement by ISO of the product
named. Equivalent products may be used if they can be shown to lead to the same results.
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ISO 23832:2021(E)

9 Sample preparation and measurements
9.1 Acclimatisation of samples
An acclimatisation phase of samples in seawater shall be carried out in order to simulate their initial
exposure to seawater. This phase permits soluble components to leach out and not to concentrate in the
close, static, and small-scale laboratory aquarium. Immerse the samples in seawater for at least 5 days
at the same temperature that will be used for conducting the test prior to start the test.
9.2 Conditioning before measurements
Soak the exposed samples in freshwater/distilled water for 1 h, then rinse with distilled water to clean
them, i.e. remove sediment particles, microbial biofilm, and sea salts. Condition the samples in an oven
at (40 ± 2) °C until constant weight is reached. Then, measure and record the characteristic of interest
(e.g. surface area, mass, thickness, tensile properties) of each individual sample. Apply conditioning
before measurements to any sample both before acclimatisation and after exposure.
9.3 Marking of samples
When samples used for testing do not differ for more than 2 % for the characteristic of interest, i.e. the
mass, or thickness or tensile properties or surface area, then all samples are considered as equal. Equal
samples do not need to be individually identified because they are assumed to be equivalent, i.e. have
the same original characteristic.
For practical reasons, it is suggested to prepare and test samples with equal physical characteristics
(deviation < 2 %).
If samples are not equivalent, then mark each sample with appropriate means to ensure a clear
permanent identification during the incubation time until final measurement and comparison with the
initial measurement is performed.
9.4 Protective net
For assessment of disintegration degree, test each sample within a protective pocket made with
a ≤2 mm mesh non-degradable net (e.g. a vinyl-coated fibreglass mosquito net or a polyester gauze).
If degradation of the test material is expected to be similar to that of the net, then use alternative
materials, more resistant to degradation. The purpose of the pocket is to cover the sample, preventing
the loss of material with dimensions >2 mm during the exposure period, still allowing the exposure
with the test environment. Particles with dimensions <2 mm can leak out. Duct tape can be used to close
the pocket after introduction of the sample. Non-biodegradable plastic frames placed inside or outside
the pocket can be used to prevent the pocket from folding back on itself, decreasing the exposure of the
sample.
At sampling, the pocket is recovered and the plastic sample carefully removed.
NOTE The pocket made with the net can act as a barrier between the sample and the test environment and
affect the degradation.
9.5 Tensile properties
Preferably, measure tensile strength at break. Other mechanical properties can be measured if deemed
to be more suitable for the type of material and intended applications.
Apply ASTM D638 and/or ISO 527-1, ISO 527-2, ISO 527-3 for the determination of the tensile properties
of the samples.
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ISO 23832:2021(E)

9.6 T
...