ISO/DTR 20470-1
(Main)New weatherable topcoats as part of an associated protective coating system — Part 1: Weathering of FEVE type fluoropolymer topcoat
New weatherable topcoats as part of an associated protective coating system — Part 1: Weathering of FEVE type fluoropolymer topcoat
Titre manque — Partie 1: Titre manque
General Information
Standards Content (Sample)
FINAL DRAFT
Technical
Report
ISO/TC 35/SC 14
New weatherable topcoats as part
Secretariat: DIN
of an associated protective coating
Voting begins on:
system —
2025-11-26
Part 1:
Voting terminates on:
2026-01-21
Weathering of FEVE type
fluoropolymer topcoat
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
Technical
Report
ISO/TC 35/SC 14
New weatherable topcoats as part
Secretariat: DIN
of an associated protective coating
Voting begins on:
system —
Part 1:
Voting terminates on:
Weathering of FEVE type
fluoropolymer topcoat
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General introduction of FEVE type fluoropolymer . 2
4.1 Chemical structure of FEVE type fluoropolymer .2
4.2 Chemical curing system .2
5 Weatherability of fluoropolymer topcoats . 3
5.1 Weatherability by fluorescent UV condensation cycle testing .3
5.2 Fifteen years weatherability test of FEVE type fluoropolymer topcoats .4
5.3 Actual bridges situation .6
6 Durability of fluoropolymer topcoat system . 6
6.1 Results of collaboration study .6
6.2 Evaluation of the durability .9
6.2.1 Weatherability test during 29 years of fluoropolymer topcoat system .9
6.2.2 Test method .9
6.3 Summary . 12
7 Health and safety .12
Annex A (informative) Examples of bridges with FEVE type fluoropolymer topcoat systems .13
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
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 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 35, Paints and varnishes, Subcommittee SC 14,
Protective paint systems for steel structures.
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
In ISO 12944-5:2019, 6.2.5, fluoroethylene vinyl ether (FEVE) fluoropolymer topcoats are characterized as
a specialized type of polyurethane based on fluoropolymers. This document describes the characteristics
of the fluoropolymer topcoats with the intention of helping users understand both their advantages and
limitations. Joint research on enhancing the weatherability and durability for a variety of coatings was
launched in 1983 managed by the Public Works Research Institute of the Ministry of Construction in Japan
and was continued until the publication of this document. The fluoropolymer topcoat systems were included
in the joint research and results were obtained on the durability and weatherability over 30 years. These
[1]-[9]
fluoropolymer topcoats systems were reported at several international conferences. This document
incorporates valuable findings from the joint research on weathering tests conducted over the past 30 years,
which are beneficial for users. Moreover, users are encouraged to contribute their own results to enhance
the comprehensiveness of this document. FEVE type waterborne fluoropolymer topcoats and their coating
systems have been developed and used in the market since around 2015, but long-term outdoor weathering
data as has been obtained for the solvent borne type have not been achieved at present.
This document contains weathering performance data such as the rate of gloss retention and chalking
resulting in film thickness loss of the topcoat system, along with chemical analysis data focusing on the
coating film deterioration of fluoropolymer topcoat. All data has been obtained from the outdoor exposure
testing. The chemical analysis relating to coating film deterioration was conducted using FTIR spectroscopy,
covering analysis of both the surface and the cross-section (depth direction from the surface).
Users of this document can use the results of the long-term outdoor exposure test to predict the durability
of the coating system.
Finally, this document points to the technological development of coating materials with state-of-the-art
weathering performance in future, such as extremely slow chalking deterioration. This coating can be the
standard reference for observing and evaluating short-, medium- and long- term weatherable coatings using
the outdoor exposure data of these topcoats.
By using the data in this document, the real time durability of the coating film can be efficiently estimated
using a short-term exposure test or an accelerated weathering test, or both.
v
FINAL DRAFT Technical Report ISO/DTR 20470-1:2025(en)
New weatherable topcoats as part of an associated protective
coating system —
Part 1:
Weathering of FEVE type fluoropolymer topcoat
1 Scope
This document describes the basic characteristics of fluoroethylene vinyl ether copolymer (FEVE) type
fluoropolymer topcoats and their coating systems. Information on the weathering performance of the
[1]-[9]
fluoropolymer topcoats and associated coating systems for over 30 years is also provided.
This document covers:
— weathering data of FT (FEVE fluoropolymer topcoat);
— chemical analysis of outdoor exposed coated panels focusing on the paint surface and their cross-
sections.
This document does not include FEVE type waterborne fluoropolymer topcoats and their coating systems.
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 terminology 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
imaging infrared
imaging IR
method of measuring and imaging the in-plane distribution of functional groups specific to a compound
using a detector composed of multiple elements
Note 1 to entry: Since it is possible to measure the molecular structure over a wide area, imaging IR is effective for
investigating the cross-sectional structure of surface deterioration due to ultraviolet irradiation and the cross-
sectional layer structure of multilayer films.
3.2
fluoroethylene vinyl ether copolymer
FEVE
resin which consist of fluoro-olefin units, various hydrocarbon vinyl ether units and has pendant OH-groups
Note 1 to entry: Along the polymer chain each vinyl ether unit alternates with fluoro-olefine unit. This sequence is
responsible for weather resistance.
4 General introduction of FEVE type fluoropolymer
4.1 Chemical structure of FEVE type fluoropolymer
Fluoroethylene vinyl ether copolymer (FEVE) used for coating systems of steel structures as topcoats is
an amorphous polymer, soluble in organic solvents and curable at ambient temperature. Waterborne type
FEVE fluoropolymer has also been developed. As shown in Figure 1, FEVE consists of fluoro-ethylene units,
various hydro-carbon vinyl ether units and has pendant hydroxy group (OH) groups. Along the polymer
chain, each vinyl ether unit alternates with fluoroethylene units which protects the rather unstable vinyl
ether unit, chemically and sterically, which can be easily attacked by bases at the hydrogen on the tertiary
carbon and by acids at the oxygen in the ether linkage. The hardness of FEVE coatings is due mainly to
the fluoroethylene units, but the other properties are desired, such as solubility in organic solvents,
compatibility with pigments and dyestuffs and curing reagents such as isocyanates. Gloss, flexibility and
adhesion can be optimized by choosing the appropriate amount of vinyl ether unit. The OH and COOH values
of the polymer are set to be like those of the general polymers with free hydroxyl groups such as polyester,
acrylic and polyether resin.
Key
X F, CF , Cl
R , R alkyd group
1 2
R , R alkylene group
2 4
1 weatherability, durability
2 gloss, hardness, solvent, solubility
3 flexibility
4 adhesion, pigment dispersion
Figure 1 — Molecular structure of the FEVE type fluoropolymer
FEVE resins have characteristics of both fluoropolymers and hydrocarbons. The fluoroethylene groups
are the strength of the FEVE resin. These groups are responsible for the polymer’s high resistance to UV
degradation. The C-F bond is very strong (see Table 1). The energy of this bond is higher than the energy of
UV radiation at 290 nm which is ~411 KJ/mol. The alternating pattern, shown in Figure 1, is critical for the
extreme UV resistance properties. The chemically stable and UV resistant fluoroethylene units sterically
and chemically protect the neighbouring vinyl ether units.
Table 1 — Bond energy of fluoro-chemicals and commodity chemicals
Resin C-C Chain KJ/mol C-F. C-H KJ/mol
Fluoro compound CF3-CF3 414 [F]-CF2-CH3 523
Fluoro compound CF3-CH3 424 CF3CH2-[H] 447
Commodity chemical CH3-CH3 379 CH3CH2-[H] 411
4.2 Chemical curing system
Compatibility of FEVE with curing agents is essential for paint formulation to ensure weather resistant
coatings. FEVE is a fluoropolymer that has free hydroxyl groups which react with suitable isocyanate curing
agents. Aromatic or aliphatic poly-isocyanates can be used as the curing agent component. Almost three days
are required for curing at room temperature when an isocyanate is used with a molar ratio of NCO:OH = 1:1,
though the coating is tack-free after only three hours and blocking-free after eight hours.
5 Weatherability of fluoropolymer topcoats
5.1 Weatherability by fluorescent UV condensation cycle testing
Surface degradation of the fluoropolymer coating and the polyurethane coating was measured using the
IR-ATR (attenuated total reflection) method before and after the fluorescent UV-condensation cycle test.
The fluoropolymer resin cures at normal temperature by reacting with an isocyanate similarly to the
polyurethane. So, the degradation behaviour of the fluoropolymer coating was regarded as decomposition of
−1
the urethane bond. The decrease of the inherent IR absorption for a chemical bond of amide(II)(1 530 cm )
was measured to estimate the degradation.
The degradation mechanism of the urethane bond is considered to be as follows:
Hydrolysis of urethane bonding
R’ NHCOOR” + H O → R’ NH + CO + HOR”
2 2 2
The absorbance was measured to compare the degradation before and after the fluorescent UV-condensation
cycle test.
A
A�= (1)
rat
B
where
A is the absorbance ratio;
rat
-1
A is the absorbance of amide(II) (1 530 cm );
-1
B is the absorbance of methylene (1 470 cm ).
Absorption of amide (II) depends on the degree of degradation. Absorption of methylene did not change and
was independent of degradation time. So, the amide (II) retention was obtained from the absorbance ratio
at the same initial value to that after the fluorescent UV-condensation cycle
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ISO/FDIS TRDTR 20470-1 .
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ISO /TC 35/SC 14/WG 12
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Secretariat: DIN .
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Date: 2025-07-0711-11
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ISO/FDIS TR 20470-1: New weatherable topcoats as part of an .
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associated protective coating system — — .
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Part 1:
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Weathering of FEVE type fluoropolymer topcoat
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This document is not an ISO International Standard. It is distributed for review and comment. It is subject to
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change without notice and may not be referred to as an International Standard.
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Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of
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© ISO/AWI TR 20470-1(X) – All rights reserved
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ISO #####-#:####(X)
A model document of an International Standard (the Model International Standard) is available at:
https://www.iso.org/drafting-standards.html
2 © ISO #### – All rights reserved
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© ISO/AWI TR 20470-1(X) – All rights reserved
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
Formatted: Indent: Left: 0 cm, Right: 0 cm, Adjust
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
space between Latin and Asian text, Adjust space
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
between Asian text and numbers
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (Switzerland)
EmailE-mail: copyright@iso.org
Formatted: French (Switzerland)
Website: www.iso.orgwww.iso.org
Formatted: German (Germany)
Published in Switzerland
Formatted: English (United Kingdom)
iv
Foreword . 3
Introduction . 4
1. Scope . 5
3 Terms and definitions . 5
4. General introduction of FEVE type fluoropolymer . 6
4.1 Chemical structure of FEVE type fluoropolymer . 6
4.2 Chemical curing system . 6
5. Weatherability of fluoropolymer topcoats . 7
5.1 Weatherability by fluorescent UV condensation cycle testing . 7
5.1.1 Surface analysis by FT-IR after the fluorescent UV-condensation cycle test(QUV) . Fehler!
Textmarke nicht definiert.
5.2 Fifteen years weatherability test of FEVE type fluoropolymer topcoats . 8
5.3 Actual bridges situation . 9
6. Durability of fluoropolymer topcoat system . 10
6.1 The results of collaboration study organized by Public Works Research Institute of
Ministry of Construction of Japan. . 10
6.2 Evaluation of the durability . 12
6.2.1 Twenty nine years weatherability test of fluoropolymer topcoat system. 12
6.2.2 Test method . 12
6.2.2.1 Preparation of test panel . 12
6.2.2.2 Weatherability test method . 13
6.3 Summary . 15
7 Health and safety . 16
8 Some typical examples of track records [coated by FEVE topcoat system] Fehler! Textmarke
nicht definiert.
Bibliography . 20
v
Contents
Foreword . vii
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General introduction of FEVE type fluoropolymer . 2
4.1 Chemical structure of FEVE type fluoropolymer . 2
4.2 Chemical curing system . 3
5 Weatherability of fluoropolymer topcoats . 3
5.1 Weatherability by fluorescent UV condensation cycle testing . 3
5.2 Fifteen years weatherability test of FEVE type fluoropolymer topcoats . 5
5.3 Actual bridges situation . 8
6 Durability of fluoropolymer topcoat system . 9
6.1 Results of collaboration study . 9
6.2 Evaluation of the durability . 13
6.3 Summary . 17
7 Health and safety . 18
Annex A (informative) Examples of bridges with FEVE type fluoropolymer topcoat systems . 19
Bibliography . 26
vi
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 Intendedintended for Itsits further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documentsdocument 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 2 (see
www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
Formatted: English (United Kingdom)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
Formatted: Font: Not Italic, English (United Kingdom)
which may be required to implement this document. However, implementers are cautioned that this may not
Formatted: English (United Kingdom)
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
Formatted: English (United Kingdom)
patent rights.
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’sISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
Formatted: Font color: Auto
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 14,
Protective paint systems for steel structures.
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.
Formatted: English (United Kingdom)
Field Code Changed
vii
Introduction
In section 6.2.5 of ISO 12944-5:2019, FEVE (6.2.5, fluoroethylene vinyl ether (FEVE) fluoropolymer topcoats
are characterized as a specialized type of polyurethane based on fluoropolymers. This document describes the
characteristics of the fluoropolymer topcoats with the intention of helping potential users understand both
their advantages and limitations. Joint research on enhancing the weatherability and durability for a variety
Formatted: Font color: Auto
of coatings was launched in 1983 managed by the Public Works Research Institute of the Ministry of
Formatted: Font color: Auto
Construction in Japan and was continued until the publication of this document. The fluoropolymer topcoat
systems were included in the joint research and results were obtained on the durability and weatherability
over 30 years. These fluoropolymer topcoats systems were reported at several international conferences [1-
[ ]-[ ]
9]. Incorporating and sharing. 1 9 This document incorporates valuable findings from the joint research on
weathering tests conducted over the past 30 years in this document will be, which are beneficial for potential
users. Moreover, users are encouraged to contribute their own results to enhance the comprehensiveness of
the report.this document. FEVE type waterborne fluoropolymer topcoats and their coating systems have been
developed and used in the market since around 2015, but long-term outdoor weathering data as has been
obtained for the solvent borne type have not been achieved at present.
TheThis document contains weathering performance data such as the rate of gloss retention and chalking
resulting in film thickness loss of the topcoat system, along with chemical analysis data focusing on the coating
film deterioration of fluoropolymer topcoat. All data has been obtained from the outdoor exposure testing.
The chemical analysis relating to coating film deterioration was conducted using FTIR spectroscopy, covering
analysis of both the surface and the cross -section (depth direction from the surface) ).
Users of this document can use the results of the long-term outdoor exposure test to predict the durability of
the coating system.
Finally, this document points to the technological development of coating materials with state-of-the-art
weathering performance in the future, such as extremely slow chalking deterioration. This coating can be the
standard reference for observing and evaluating short-, medium- and long- term weatherable coatings using
the outdoor exposure data of these topcoats.
By using the data in this document, the real time durability of the coating film can be efficiently estimated
Formatted: Body Text
using a short time by a short-term exposure test and/or by an accelerated weathering test, or both.
viii
Technical report of new
ix
Formatted: Font: Bold
Formatted: HeaderCentered
New weatherable topcoats as part of an associated protective coating
system – —
Formatted: Main Title 2, Space After: 0 pt
Part 1: The weathering of solvent borne type
Weathering of FEVE type fluoropolymer topcoat
1.1 Scope Formatted: Font: 13 pt
Formatted: Font: 13 pt
This document describes the basic characteristics of fluoroethylene vinyl ether copolymer (FEVE) type
Formatted: No bullets or numbering
fluoropolymer topcoats and their coating systems. TheInformation on the weathering performance of the
[ ]-
fluoropolymer topcoats and associated coating systems for over 30 years is also explained. (1-9) provided. 1
[ ]
Formatted: Font: Not Bold
This document covers the following, :
— ・Weatheringweathering data of FT (FEVE fluoropolymer topcoat), ); Formatted: List Continue 1
— ・Chemicalchemical analysis of outdoor exposed coated panels focusing on the paint surface and their
cross-sections.
When new high weathering-resistant paint materials are developed in the future, the data in this document
can provide useful suggestions for estimating the life of the developed coatings, and the FEVE type
fluoropolymer topcoats can be used as the standard reference (model).
This document does not include FEVE type waterborne fluoropolymer topcoats and their coating systems.
2 2 Normative references
Formatted: Font: 13 pt
Formatted: Font: 13 pt, Not Bold
There are no normative references in this document.
Formatted: Heading 1
3 Terms and definitions
Formatted: Font color: Auto
Formatted: No bullets or numbering
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
Formatted: English (United Kingdom)
Formatted: Font: 11 pt, English (United Kingdom)
— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
Formatted: English (United Kingdom)
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
Formatted: English (United Kingdom)
3.1 3.1
Formatted: TermNum2
imaging infrared (
imaging IR)
Formatted: Note
method of measuring and imaging the in-plane distribution of functional groups specific to a compound using
Formatted: Font: 10 pt
a detector composed of multiple elements
Formatted: Font: 10 pt
Note 1 to entry: Since it is possible to measure the molecular structure over a wide area, imaging IR is effective for
Formatted: FooterCentered, Left, Line spacing: single
investigating the cross-sectional structure of surface deterioration due to ultraviolet irradiation and the cross-sectional
Formatted: Font: 11 pt
layer structure of multilayer films.
Formatted: FooterPageNumber, Left, Space After: 0 pt,
Line spacing: single
© ISO/ TR 20470-1 2025 – All rights reserved
Formatted: Font: Bold
Formatted: HeaderCentered
3.2
3.2 Fluoroethylene
fluoroethylene vinyl- ether copolymer (
FEVE)
resin which consist of fluoro-olefin units, various hydrocarbon vinyl ether units and has pendant OH-groups.
Note 1 to entry: Along the polymer chain each vinyl ether unit alternates with fluoro-olefine unit. This sequence is
Formatted: Note
responsible for weather resistance.
4.4 General introduction of FEVE type fluoropolymer
Formatted: No bullets or numbering
4.1 4.1 Chemical structure of FEVE type fluoropolymer
Formatted: Heading 2, None
Fluoroethylene vinyl- ether copolymer (FEVE) used for coating systems of steel structures as topcoats is an
amorphous polymer, soluble in organic solvents and curable at ambient temperature. Waterborne type FEVE
fluoropolymer washas also been developed. As shown in Figure 1,Figure 1, FEVE consists of fluoro-ethylene
units, various hydro-carbon vinyl ether units and has pendant hydroxy group (OH) groups. Along the polymer
chain, each vinyl ether unit alternates with a fluoro-ethylenefluoroethylene units which protects the rather
unstable vinyl ether unit, chemically and sterically, which can be easily attacked by bases at the hydrogen on
the tertiary carbon and by acids at the oxygen in the ether linkage. The hardness of FEVE coatings is due mainly
to the fluoro-ethylenefluoroethylene units, but the other properties are desired, such as solubility in organic
solvents, compatibility with pigments and dyestuffs and curing reagents such as isocyanates. Gloss, flexibility
and adhesion can be optimized by choosing the appropriate amount of vinyl ether unit. The OH and COOH
values of the polymer are set to be like those of the general polymers with free hydroxyl groups such as
polyester, acrylic, and polyether resin.
Key
X F, CF3, Cl
R1, R2 alkyd group
R , R alkylene group Formatted: Font: 10 pt
2 4
1 weatherability, durability
Formatted: Font: 10 pt
2 gloss, hardness, solvent, solubility
Formatted: Font: 11 pt
3 flexibility
Formatted: FooterPageNumber, Space After: 0 pt, Line
4 adhesion, pigment dispersion
spacing: single
2 © ISO #### 2025 – All rights reserved
Formatted: Font: Bold
Formatted: HeaderCentered
Figure 1 — Figure 1 — Molecular structure of the FEVE type fluoropolymer
Formatted: Font color: Auto
Formatted: Figure title
FEVE resins have characteristics of both fluoropolymers and hydrocarbons. The fluoroethylene groups are the
strength of the FEVE resin. These groups are responsible for the polymer’s high resistance to UV degradation.
The C-F bond is very strong (see Table 1).Table 1). The energy of this bond is higher than the energy of UV
radiation at 290nm290 nm which is ~411KJ411 KJ/mol. The alternating pattern, shown in Figure 1,Figure 1,
is critical for the extreme UV resistance properties. The chemically stable and UV resistant fluoroethylene
Formatted: English (United Kingdom)
units sterically and chemically protect the neighbouring vinyl ether units.
Formatted: English (United Kingdom)
Formatted: Indent: Left: 0 cm
Table 1 — Bond energy of Fluoro-Chemicalsfluoro-chemicals and Commodity Chemicalscommodity
Formatted: English (United Kingdom)
chemicals
Formatted: Font: Bold, Font color: Auto
Resin C-C Chain KJ/mol C-F. C-H KJ/mol
Formatted: Font color: Auto
Fluoro
Formatted: Font: Bold, Font color: Auto
Compoundcompound CF3-CF3 414 [F]-CF2-CH3 523
Formatted: Font color: Auto
Fluoro
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Compoundcompound CF3-CH3 424 CF3CH2-[H] 447
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Commodity
Chemicalchemical CH3-CH3 379 CH3CH2-[H] 411 Formatted: Font: Bold, Font color: Auto
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4.2 4.2 Chemical curing system
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Compatibility of FEVE with curing agents is essential for paint formulation to ensure weather resistant
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coatings. FEVE is a fluoropolymer that has free hydroxyl groups which react with suitable isocyanate curing
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agents. Aromatic or aliphatic poly-isocyanates can be used as the curing agent component. Almost three days
are required for curing at room temperature when an isocyanate is used with a molar ratio of NCO:OH= = 1:1, Formatted Table
though the coating is tack-free after only three hours and blocking- free after eight hours.
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5.5 Weatherability of fluoropolymer topcoats
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5.1 Weatherability by fluorescent UV condensation cycle testing
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Surface degradation of the fluoropolymer coating and the polyurethane coating was measured using the IR-
ATR (attenuated total reflection) method before and after the fluorescent UV-condensation cycle test. The
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fluoropolymer resin cures at normal temperature by reacting with an isocyanate similarly to the polyurethane.
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So, the degradation behaviour of the fluoropolymer coating was regarded as decomposition of the urethane
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bond. The decrease of the inherent IR absorption for a chemical bond of amide(Ⅱ)(1530cm (II)(1 530 cm )
was measured to estimate the degradation. Formatted: Body Text
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The degradation mechanism of the urethane bond is considered to be as follows:
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Hydrolysis of urethane bonding
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H2O
R’ NHCOOR”→ ” + H2O → R’ NH2 + CO2 + HOR”
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The absorbance was measured to compare the degradation before and after the fluorescent UV-condensation
cycle test.
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A 𝐴𝐴
A = 𝐴𝐴 = (1)
𝑟𝑟𝑟𝑟𝑟𝑟 𝑟𝑟𝑟𝑟𝑟𝑟
𝐵𝐵 𝐵𝐵
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where
Arat Absorbance ratio
A is the absorbance of amide(II) (1530cm-1)
B is the absorbance of methylene (1470cm-1)
A is the absorbance ratio;
rat
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A is the absorbance of amide(II) (1 530 cm );
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B is the absorbance of methylene (1 470 cm ).
Absorption of amide (II) depends on the degree of degradation. Absorption of methylene did not change and
was independent of degradation time. So, the amide (II) retention was obtained from the absorbance ratio at
the same initial value to that after the fluorescent UV-condensation cycle test (QUV). The larger the value, the
smaller was the degree of degradation.
The amide (II) retention ratio is shown in Figure 2. Figure 2.
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X exposure time (×10 hours)
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Figure 2 — Y retention of amide(II) in %
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fluoropolymer coating
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polyurethane coating
Figure 2 — retention of amide(II)
Key
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Fluoropolymer coating
Polyurethane coating
Y Retention of amide(II) in %
X exposure time (x10 hours)
Judging from the results obtained from the measurement after 1 000 hours of fluorescent UV-condensation
cycle test, surface degradation of the polyurethane coating was progressing steadily. On the other hand,
fluoropolymer coating showed little or no surface degradation. The reason why the fluoropolymer coating did
not show degradation was thought to be because the fluorine atom was in a skeleton structure with strong
bonding, which makes it difficult to produce the free radicals which cause decomposition.
5.2 Fifteen years weatherability test of FEVE type fluoropolymer topcoats
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Figure 3Figure 3 shows cross -sections of the fluoropolymer topcoats coatings system, which had been
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outdoor exposed outdoors for 15 years in a marine environment. This test panel was cut with a highly -
accurate slicing machine to obtain a side view of the coating films. The white part is the topcoat layer. Under
this layer, there are layers consisting of MIO epoxy resin coating film, epoxy resin coating film, zinc rich coating
film, and steel as substrate. A portion of the coating was covered with tape and thus was not exposed to
sunlight. Under the tape the film was not damaged by the UV light from the sunshine. The film thickness of the
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topcoat after 15 years outdoor exposure can be compared to the original film thickness under the tape. Figure
2Figure 3 shows that there is almost no deterioration in the part of the fluoropolymer topcoat film. After
15 years, the fluoropolymer fluoropolymer topcoat has lost about 1,1 μm total, the average annual
consumption was about 0,1 μm /year. The figure of erosion was very small judging from a general
understanding in paint technology. The polyurethane coating system as reference showed 28 µm of film
thickness loss after 15 years of outdoor exposure testing in the marine environment.
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Key
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A, B areas for imaging IR measurement as below
a 1/20 scale horizontal axis
1 FEVE coating
2 MIO epoxy resin coating
3 epoxy resin coating
4 zinc rich coating
5 steel as substrate
6 film consumption: 0 μm ∼ 1,1 μm
Figure 3 — Figure 3 — Consumption of topcoat in film thickness
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after exposure for 15 years (cross -section)
Key
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A, B A, B area are for Imaging IR measurement as below
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a 1/20 scale horizontal axis
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1 FEVE coating
2 MIO epoxy resin coating
3 epoxy resin coating
4 zinc rich coating
5 steel as substrate
6 film consumption: 0 ∼ 1,1 μm
Two points marked in Figure 3Figure 3 are measured area by Imagingimaging IR (Specialspecial resolution;
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12.,5 µm). That measurement can trace amide (II) absorbance as distribution for cross-section area
comparing with C-H band C-F band. In Figure 4, the isocyanate in the protected area of each coating is shown
in black. TheFigure 4, the FEVE coating shows no decomposition of the isocyanate.
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A: light sealed area B: light irradiated area
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FEVE coating
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Polyurethane coating
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