ISO 16636:2025

International
Standard
ISO 16636
First edition
Plastics — Disintegration field
2025-04
test of plastics under water
environmental conditions
Plastiques — Essai sur site de désintégration des plastiques dans
les conditions d'un environnement aquatique
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
4 Principle . 2
5  Test procedure . 3
5.1 Test material .3
5.2 Reference material .3
5.3 Preparation of test and reference materials .3
5.4 Number of replicates .4
5.5 Immersion in water .5
5.6 Water conditions .6
5.6.1 General .6
5.6.2 Determination of number of microorganisms in water .6
5.6.3 Analysis of microbial community composition in seawater (optional) .6
5.6.4 Properties of water .6
5.7 Termination of the field test and sampling interval .6
6  Analysis and monitoring of the field test . 7
6.1 Photographic documentation .7
6.2 Determination of disintegration .7
6.2.1 General .7
6.2.2 Calculating degree of disintegration of test material based on weight
determination .7
6.2.3 Calculating degree of disintegration rate (film thickness decrease rate) of film
sample .8
6.2.4 Calculating degree of disintegration rate (weight loss rate) of the sample other
than film .8
6.3 Analysing characteristics of plastic materials (optional) .9
6.4 Monitoring environmental parameters (recommended) .9
7 Test report .10
Annex A (informative)  Example of results for disintegrated plastic materials in real sea .11
Annex B (informative)  Microbial counts in sea water .15
Bibliography .16

iii
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
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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 document 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).
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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.

iv
Introduction
Marine plastic litter has been continuously increasing. Plastic waste released in the environment eventually
reaches the rivers, the lakes and the sea, floats on the water surface, and some of them sink to the riverbed,
lakebed and seabed. Floating plastic litter has a significant negative impact on aquatic life due to accidental
ingestion or entangling. To minimize the risk of plastic waste, it is recommended that plastics become low
molecular weight by microbial action, lose strength, and disintegrate. Biodegradable plastics are designed to
disintegrate in this way. The biodegradation of plastics in the marine environment is defined in laboratory
tests, such as ISO 18830, ISO 19679, ISO 22404, ISO 23977-1 and ISO 23977-2. ISO 23832 describes a test
method for the determination of the degradation rate and disintegration degree. However, these test
methods do not measure disintegration under environmental conditions. ISO 22766 applies to disintegration
only in the sandy sublittoral and the sandy eulittoral zone.
This document provides a test method for determining the disintegration degree of biodegradable plastic
materials floating on the water surface. It can only apply if the biodegradation test according to the ISO
standard, for example ISO 18830, ISO 19679, ISO 23977-1 and ISO 23977-2, has been carried out and has
given a positive result. This test method is simplified so that it can be conducted in various coastal area.
The disintegration is thought to be due to combination of bio-action, non-biochemical action, and physical
degradation, but it is not specified by this method.

v
International Standard ISO 16636:2025(en)
Plastics — Disintegration field test of plastics under water
environmental conditions
1 Scope
This document specifies test methods for the determination of the degree of disintegration of plastic
materials floating in water.
NOTE The disintegration test is a field test performed under natural environmental conditions in a part of the
sublittoral zone, the shores of lakes or rivers, and the test samples are immersed to a depth between 1,5 m to 3 m from
water surface.
This document specifies the general requirements of the apparatus and the procedures for using the test
methods described.
This document is not suitable for the assessment of disintegration caused by heat or light exposure.
The described field test is a disintegration test and not a biodegradation test. Therefore, it cannot be used
for demonstrating biodegradation or for making unqualified claims such as “biodegradable in marine
environment” and similar.
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 4591, Plastics — Film and sheeting — Determination of average thickness of a sample, and average thickness
and yield of a roll, by gravimetric techniques (gravimetric thickness)
ISO 4593, Plastics — Film and sheeting — Determination of thickness by mechanical scanning
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
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 https:// www .electropedia .org/
3.1
biodegradation
degradation (3.2) 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]

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 small fragments
[SOURCE: ISO 472:2013, 2.1757]
3.4
sublittoral zone
coastal seafloor that is permanently immersed and extends from the low-water line to the continental shelf
edge at 200 m water depth
Note 1 to entry: The seafloor can consist of solid rock, or fragments that form sediments of different particle size, from
coarse blocks and pebbles, to permeable sands, silt and clay. Sediments can form from fragmented rock or consist of
fragments of biogenic origin (algae, shells, coral, etc.), or be a mixture of these compounds.
[SOURCE: ISO 22766:2020, 3.5]
3.5
dissolved organic carbon
DOC
part of the organic carbon in water which cannot be removed by specified phase separation methods, for
-2
example by centrifugation at 40 000 ms for 15 min or by membranes with pores of 0,2 μm to 0,45 μm
diameter
[SOURCE: ISO 22404:2019, 3.4]
4 Principle
The disintegration test is a field test performed under natural environmental conditions in the sublittoral
zones especially in the coast, the shores of lakes or rivers, and the test samples are immersed to a depth
between 1,5 m to 3 m from water surface. This test is a short-term immersion method with the goal to
reduce the probability of coastal microorganisms inhibiting microbial surface contact to the test material
or damaging the sample as it was observed for long-term immersion tests. Therefore, the sample used
in this test is preferably a film, a fibre, or the like, and is not suitable for a film so thin that it disappears
quickly. The sample is used uncovered or covered with a mesh or wrapped in a nonwoven fabric and put in a
specially designed perforated plastic container which is immersed in the sea and which allows the samples
to move freely. The degree of disintegration of the sample is determined by the weight loss or the film
thickness reduction (μm). The film thickness decrease can be obtained by multiplying the film thickness
before immersion by the weight loss rate (%). When films of different thicknesses are immersed for the
same period, the apparent weight loss rate is greater for thin films because in principle both thick and thin
films are disintegrated from the surface to the same depth. On the other hand, the film thickness decrease is
essentially constant for both thick and thin films, therefore, it is preferred to use the film thickness decrease
rate as an index of disintegration in case the sample films are of different thickness. As the disintegration
progresses, it becomes impractical to collect all the fragmented samples that causes variation, therefore,
the test condition needs to be adjusted to maintain the weight retention ratio of 50 % or more to prevent
fragmentation of the test sample in order to obtain reliable data. In the case of weight retention of 50 % or
less, further fragmentation occurs during the cleaning process because the film strength is greatly reduced.
Since it is impractical to completely collect these fragments, it is recommended to recover them before
they fragmentate too much. In this way, a reliable weight reduction rate or film thickness decrease rate
can be obtained. In order to recover samples with a weight retention rate of 50 % or more, it is efficient
and recommended to immerse samples with different film thicknesses. Further, since the disintegration

degree varies greatly depending on the immersion sea location (e.g. sea temperature and the number of
microorganisms), it is also recommended to take samples multiple times with different periods so that the
weight retention rate remains at 50 % or more, and then calculate the weight loss rate from these samples
to evaluate the degree of disintegration. In addition, when immersion is performed for the purpose of
collecting data on physical properties, strength, or shape changes after immersion, observing the progress
of disintegration, comparing data between samples, etc., immersion may be continued until significant
disintegration occurs. The immersion period is preferably within 3 months. The immersion for a longer
period is possible if the disintegration rate is slow. If there is a large amount of sludge or marine organisms
in the container, it is advisable to remove samples at appropriate intervals, rinse lightly, and then transfer
them to a new container to continue the test.
5  Test procedure
5.1 Test material
Use the test material preferably in the form of film in an identical form (e.g. shape, thickness) as for the
intended final use. The thickness of the film shall be either determined in accordance with ISO 4591 or
ISO 4593.
Other forms than films, for instance articles such as fibres, nonwoven fabrics, or foams, can also be tested if
test procedure and test evaluation are in accordance with this document.
5.2 Reference material
1) 1)
A poly(3-hydroxybutyrate-co-hexanoate) (PHBH) film and/or a polycaprolactone (PCL) film of 50 μm
to 500 μm thickness and/or ashless cellulose filters shall be used as a positive control as these materials
are thought to be biodegradable. Low-density polyethylene (LD-PE), high-density polyethylene (HD-PE),
polypropylene, polystyrene and polyvinylchloride are thought to be non-biodegradable and these film of
20 μm to 100 μm thickness shall be used as a negative control. Use pellets to blow or to extrude a film, or
dissolve pellets in a solvent and cast to make a film of desired thickness.
5.3  Preparation of test and reference materials
Test samples shall not be subjected to conditions or procedures, such as a pretreatment by heat and/or an
exposure to radiation, designed to accelerate disintegration prior to testing according to this document.
A plastic material preferably in the form of a film having a thickness of 100 μm, the same thickness as the
positive control, and at least two other film thickness, for example, 35 μm and 200 μm, is cut into pieces of
30 mm × 40 mm in size.
NOTE By using a sample with three thicknesses of 35 µm, 100 µm, and 200 μm, even if the 35 μm sample is lost
due to more collapse than expected, the 100 μm and 200 μm samples can be recovered and the test will be completed.
In the case of immersion tests using thin films, it might be difficult to distinguish whether the film has
completely disintegrated or whether only a portion of it has disintegrated and flowed out. By using a thick
film and calculating film thickness decrease rate from the weight loss and initial thickness, the disintegration
behaviour of a thin film due to immersion can be determined. Record the weight and thickness of each cut
film and take a photograph of the film. The film can be used as it is for the test, or can be covered with non-
biodegradable plastic mesh of 40 mm × 50 mm in size with 1 mm × 1 mm mesh size on both sides. Typical
non-biodegradable meshes are made of polyamide, polyethylene, or polypropylene. If the test sample is a
fibrous material or a fragile material and is easily lost through the mesh, it may be wrapped in a nonwoven
fabric (see A.1).
1) PHBH-pellets from KANEKA (https:// www .kaneka .co .jp/ en/ solutions/ phbh/ ) and PCL-pellets (Mn 80,000) from
Sigma-Aldrich(https:// www .sigmaaldrich .com/ US/ en/ product/ aldrich/ 440744) are examples of a suitable reference
material. This information is given for the convenience of users of this document and does not constitute an endorsement
by ISO of the suppliers named. Equivalent products may be used if they can be shown to lead to the same results.

Figure 1 shows, from left to right, a film as it is, a film covered with non-biodegradable plastic mesh, and a
fibrous material wrapped in a nonwoven fabric.
Figure 1 — Test samples
The film samples thus prepared are put in a non-biodegradable plastic container having a perforated or
mesh structure on each surface with an opening rate of over 25 % to allow ambient water flows freely from
all directions. The container has, for example, three rooms (see Figure 2) and each room hold one sample,
and the largest cross-section of the room is more than twice the film area to allow the film moves freely in
the room.
Example of the container
Outer size: 190 × 65 × 55 mm Inner size: (53 × 55 × 50) mm × 3 rooms
Pore diameter: 8 mm Opening ratio: 26 %
2 2
Largest cross section of a room: 40 cm Sample area: 12 cm

NOTE Film sample: 30 mm × 40 mm
Figure 2 — Perforated plastic container with 3 rooms
5.4 Number of replicates
Provide a sufficient number of samples prepared according to 5.3, at least:
— three replicates of each test material;

— three replicates of the positive control material;
— three replicates of the negative control material.
Positive and negative controls are described in 5.2.
It is recommended to make one more replicate of each material as a blank sample for physical, mechanical,
and chemical analysis, to have a baseline of spectroscopic analysis.
Since disintegration in sea varies greatly depending on the location and season, it is recommended to
prepare a few sets of samples to immerse and take the sample set out at certain period, for example, after
1 month, 2 months, 3 months immersion. The same number of replicates is requested if other forms than
film, for instance fibres, nonwoven fabrics, or foams, are tested for each thickness selected.
The above number of replicates is a minimum requirement for this test. For more effective field test, it is
recommended to test samples with varying film thicknesses because the thinner the initial film thickness,
the smaller the weight retention ratio, and the thicker the initial film thickness, the higher the weight
retention ratio.
As this is a field test in various marine locations, damage of test samples in the container cannot be excluded
during the immersion period, possibly due to the erosive power of tides and sediment and activity of sea life.
Hence, it is recommended to increase the number of replicates for
...