ISO/TS 19392-5:2023

Paints and varnishes - Coating systems for wind-turbine rotor blades - Part 5: Measurement of transmittance properties of UV protective coatings

This document specifies a test method to measure the ultraviolet (UV) and visible (VIS) spectral transmittance in the wavelength range from 280 nm to 700 nm of coatings for wind turbine rotor blades. Single and multilayer coatings or coating systems can be tested. From the spectral transmittance the transmittance of UV, VIS and the combined UV and VIS wavelength range can be calculated. It is applicable to free coatings films or coatings applied on a UV-transparent quartz substrate.

Matériaux de revêtement pour pales de turbines éoliennes — Partie 5: Mesurage des propriétés du facteur de transmission des revêtements de protection anti UV

General Information

• Status: Published
• Publication Date: 09-Mar-2023
• ICS: 87.040 - Paints and varnishes
• Technical Committee: ISO/TC 35/SC 9 - General test methods for paints and varnishes
• Drafting Committee: ISO/TC 35/SC 9/WG 32 - Coating materials for wind-turbine rotor blades
• Current Stage: 6060 - International Standard published
• Start Date: 10-Mar-2023
• Due Date: 21-Sep-2024
• Completion Date: 10-Mar-2023

Overview

ISO/TS 19392-5:2023 defines a test method for measuring the UV and visible (UV/VIS) spectral transmittance of coatings used on wind‑turbine rotor blades. The specification covers single and multilayer coatings, permitting testing of free coating films or coatings applied to a UV‑transparent quartz substrate. Measurements are carried out across the spectral range 280 nm to 700 nm, enabling calculation of transmittance for UV, VIS and combined UV+VIS bands to assess UV‑protective performance.

Key topics and technical requirements

• Spectral range and output: Measurement of spectral transmittance τ(λ) from 280–700 nm, reported in defined wavelength increments (instrument dependent).
• Instrumentation: Use of a UV/VIS spectrophotometer equipped with a radiation source (e.g., deuterium or halogen), limiting aperture, integrating sphere, and spectroradiometer/diffraction detector.
• Instrument performance: Requirements include stray‑light suppression, dark‑current correction, higher‑order wavelength correction, wavelength calibration and a resolution/step capability around 2 nm.
• Sample preparation: Coatings may be tested as free films or on quartz substrates; typical dry film thicknesses referenced and thickness measurement per ISO 2808.
• Environmental conditioning: Specimens conditioned per ISO 3270 or supplier instructions before measurement.
• Checks and validation: Use of a long‑pass (cut‑on) filter to verify spectrophotometer performance (50% cut‑on between about 320–360 nm and very low transmittance in the absorption region).
• Data and calculations: Spectral transmittance recorded across the band and integrated to give band transmittance values (UV, VIS, UV+VIS); software to compute τ(λ) is required.
• Precision and reporting: Test precision, number of specimens (minimum three), and required test report details are specified.

Applications and users

• Coating manufacturers and formulators assessing UV protective coatings for rotor blades.
• Wind‑turbine OEMs and blade manufacturers specifying or verifying coating performance to protect composite substrates from UV/VIS degradation.
• Independent test laboratories and certification bodies performing quality control, R&D evaluation, and comparative performance testing.
• Material scientists and durability engineers using spectral transmittance data to predict weathering, color change and substrate protection.

Related standards

• ISO 2808 - Determination of film thickness
• ISO 3270 - Temperatures and humidities for conditioning and testing
• ISO 4618 - Paints and varnishes vocabulary

ISO/TS 19392-5:2023 provides a reproducible, instrument‑based method to quantify how well blade coatings block damaging UV and short‑wavelength visible light - a critical input for improving blade lifetime and reducing UV‑driven failure modes.

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 19392-5
First edition
2023-03
Paints and varnishes — Coating
systems for wind-turbine rotor
blades —
Part 5:
Measurement of transmittance
properties of UV protective coatings
Matériaux de revêtement pour pales de turbines éoliennes —
Partie 5: Mesurage des propriétés du facteur de transmission des
revêtements de protection anti UV
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus and materials .2
5.1 Film applicator for coating material . 2
5.2 Substrate for free coating film preparation . 2
5.2.1 Preparation of free film and test specimen . 2
5.2.2 Coating application . . 3
5.3 Film thickness measurement . 3
5.4 UV/VIS spectrophotometer . 3
5.5 Long pass specification for check . 4
6 Test procedure .4
6.1 Test procedure with spectrophotometer . 4
6.2 Check of spectrophotometer with long pass filter . 5
6.3 Spectral transmittance of the specimen (film). 6
6.4 Calculation of transmittance . 6
7 Precision . 6
8 Test report . 6
Annex A (normative) Check of the spectral transmittance of the long pass filter .8
Annex B (informative) Application and evaluation references . 9
Bibliography .11
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 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 on 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 the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee
SC 9, General test methods for paints and varnishes.
A list of all parts in the ISO/TS 19392 series can be found on the ISO website.
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 the wind energy industry, coatings are applied to rotor blades surface to protect the glass fibre
reinforced polymer composite substrate from environmental stresses. Rain drops and hailstones can
damage these coatings in such a way that individual layers come off or the whole coating delaminates
from the substrate. This applies mostly to the leading edge. Glass fibre reinforced polymer composites
and other blade materials can be also sensitive to UV degradation and thus can be damaged during
outdoor operation, if not protected accurately against irradiation by solar radiation. Failure of
protection can lead to delamination and a subsequent failure of the full blade.
An important function of the rotor blade coating is therefore to protect the blade material from UV
radiation. This applies to the leading edge, but also to the other surface areas of the blade.
The damage by solar radiation is mainly induced by the most energetic ultraviolet (UV) radiation, but
also visible (VIS) radiation (e.g. violet or blue radiation) is still energetic enough to have a negative
input on the appearance and durability of the blade.
Pigments and organic or inorganic UV absorbers can be used to reduce the coating film transmittance
against UV (and visible) radiation and cause a positive effect on lifetime and functional aspects of the
blade material. Pigments and UV absorbers can affect the transmittance in the visible range. This may
lead to colour change of the coated blade.
This document, as part of the ISO/TS 19392 series on rotor blade coatings, describes a method to
measure the spectral transmittance or the transmittance in a specific wavelength range. This allows
evaluating the UV and VIS radiation protection quality of a coatings film on the sensitive blade substrate
below. The focus is to avoid damage of the blade by natural solar radiation especially caused by the
most energetic part, the ultraviolet and short wavelength visible radiation.
v
TECHNICAL SPECIFICATION ISO/TS 19392-5:2023(E)
Paints and varnishes — Coating systems for wind-turbine
rotor blades —
Part 5:
Measurement of transmittance properties of UV protective
coatings
1 Scope
This document specifies a test method to measure the ultraviolet (UV) and visible (VIS) spectral
transmittance in the wavelength range from 280 nm to 700 nm of coatings for wind turbine rotor
blades. Single and multilayer coatings or coating systems can be tested.
From the spectral transmittance the transmittance of UV, VIS and the combined UV and VIS wavelength
range can be calculated.
It is applicable to free coatings films or coatings applied on a UV-transparent quartz substrate.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 2808, Paints and varnishes — Determination of film thickness
ISO 3270, Paints and varnishes and their raw materials — Temperatures and humidities for conditioning
and testing
ISO 4618, Paints and varnishes — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4618 and the following 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
transmittance
τ
Φ
t
quotient of transmitted radiant flux, Φ , and incident radiant flux, Φ , τ =
t m
Φ
m
Note 1 to entry: Transmittance is also defined spectrally in terms of wavelength, in which case, “spectral” is
added before the quantity name.
Note 2 to entry: Due to energy conservation, α + ρ + τ = 1 except when polarized radiation is observed, where α is
absorptance and ρ is reflectance.
Note 3 to entry: Transmittance, τ, is the sum of regular transmittance, τ , and diffuse transmittance, τ : τ = τ + τ .
r d r d
Note 4 to entry: The transmittance has unit one.
[SOURCE: CIE S 017:2020; 17-24-065]
3.2
ultraviolet radiation
UV
radiation in a wavelength range from 280 nm to 400 nm
3.3
visible radiation
VIS
radiation in a wavelength range from 400 nm to 700 nm
4 Principle
The UV and VIS transmittance through a coating film is measured using an UV/VIS spectrophotometer
equipped with a radiation source, a limiting aperture, an integrating sphere, and a spectroradiometer
with a diffraction element and a detector. See Annex B for application and evaluation references.
A beam of optical radiation, limited by an aperture, with an incident radiant flux, Φ , is directed on a
m
film specimen. The transmitted radiant flux, Φ , enters an integrating sphere. The sphere is equipped
t
with the input optics of a spectroradiometer with which spectrally resolved measurements of the
unfiltered radiant flux Φ (λ) and the filtered (transmitted) radiant flux Φ (λ) can be performed. The
m t
quotient Φ (λ)/Φ (λ) is the spectral transmittance τ(λ).
t m
NOTE τ(λ) multiplied by 100 represents the percentage of the transmitted radiant flux at a specific
wavelength or wavelength range passing through the film compared to the incident radiant flux Φ (λ).
m
From the spectral transmittance, the transmittance in a specific wavelength range can be calculated as
described in 6.4.
The spectral transmittance is recorded in wavelength increments over the entire wavelength range of
280 nm to 700 nm continuously during a wavelength scanning (e.g. in 2 nm to 10 nm steps depending
on the apparatus used and the resolution needed). Depending on the application the transmittance of
the specific wavelength ranges for UV, VIS and UV + VIS can be calculated.
5 Apparatus and materials
5.1 Film applicator for coating material
A suitable blade or spatula to apply coatings fi
...