ISO/FDIS 877-3

ISO/TC 61/SC 6
Secretariat: DIN
Date: 2026-01-0802-05
Plastics — Methods of exposure to solar radiation — —
Part 3:
Intensified weathering using concentrated solar radiation
Plastiques — Méthodes d'exposition au rayonnement solaire — —
Partie 3: Exposition intensifiée par rayonnement solaire concentré
FDIS stage
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ii
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
5.1 General requirements . 2
5.2 Apparatus for measurement of climatic factors . 6
6 Test specimens . 6
7 Exposure conditions . 6
7.1 Orientation of mirrors . 6
7.2 Exposure site . 6
7.3 Temperature control . 6
7.4 Irradiance level . 9
8 Exposure stages . 10
8.1 General . 10
8.2 Solar radiant exposure . 10
9 Procedure . 11
9.1 Mounting of test specimens . 11
9.2 Mounting of reference materials (if used) . 11
9.3 Climatic observations . 11
9.4 Exposure of test specimens . 11
10 Expression of results . 12
10.1 Determination of changes in properties . 12
10.2 Climatic conditions and observations . 12
11 Test report . 13
Bibliography . 14

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).
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 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 61, Plastics, Subcommittee SC 6, Ageing,
chemical and environmental resistance, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 877--3:2018), which has been technically
revised.
The main changes are as follows:
— — size requirements in 7.37.3 have been added;
— — in 10.2.410.2.4,, a second formula has been added;
— — a new 10.2.510.2.5 “Radiation measurement” has been added and subsequent clauses have been
renumbered.
A list of all parts in the ISO 877 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.
© ISO #### 2026 – All rights reserved
iv
FINAL DRAFT International Standard ISO/FDIS 877-3:2026(en)

Plastics — Methods of exposure to solar radiation — —
Part 3:
Intensified weathering using concentrated solar radiation
1 Scope
This document specifies a method for exposing plastics to concentrated solar radiation using reflecting
concentrators to accelerate the weathering processes. The purpose is to assess property changes produced
after specified stages of such exposures. The reflecting concentrators used in these exposures are sometimes
referred to as “Fresnel reflectors” because, in cross-section, the array of mirrors used to concentrate the solar
radiation resembles the cross-section of a Fresnel lens.
General guidance concerning the scope of the ISO 877 series is given in ISO 877--1.
NOTE Additional information about solar concentrating exposures, including a partial list of standards in which they
are specified, is given in the Bibliography.
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 877--1, Plastics — Methods of exposure to solar radiation — Part 1: General guidance
ISO 877--2:2025, Plastics — Methods of exposure to solar radiation — Part 2: Direct weathering and exposure
behind window glass
ISO 4892--1, Plastics — Methods of exposure to laboratory light sources — Part 1: General guidance and
requirements
ASTM G90, Standard Practice for Performing Accelerated Outdoor Weathering of Nonmetallic Materials Using
Concentrated Natural Sunlight
ASTM G179, Standard Specification for Metal Black Panel and White Panel Temperature Devices for Natural
Weathering Tests
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Principle
This document describes a method for performing accelerated weathering on plastics using intensified solar
radiation. General guidance is given in ISO 877--1.
5 Apparatus
5.1 General requirements
General requirements shall be in accordance with ISO 877--1.
All requirements for the solar concentrating device, operation of the device and measurement of the solar
radiation within the specimen exposure area shall be in accordance with ASTM G90. See Figures 1Figures 1
and 22 for schematic diagrams of the two types of test apparatus.
© ISO #### 2026 – All rights reserved
Key
1 air plenum
2 air blower
3 rotor assembly
4 air deflector
5 A-frame assembly
6 mirror
7 gear box
8 mast for manual elevation adjustment
9 air flow switch
10 water spray nozzles
11 clutch disc for elevation drive
12 solar cells with shadow hat
13 specimen protection door
14 door release mechanism
Figure 1 — Schematic diagram of test apparatus with single-axis tracking
and manual elevation adjustment
© ISO #### 2026 – All rights reserved
Key
1 air plenum
2 air blower
3 rotor assembly
4 turntable assembly
5 A-frame assembly
6 mirror
7 gear box for elevation drive
8 control box
9 gear box for azimuth drive
10 air flow switch
11 water spray nozzles
12 clutch disc for elevation drive
13 solar cells with shadow hat
14 specimen protection door
15 door release mechanism
16 air deflector
Figure 2 — Schematic diagram of test apparatus with dual-axis tracking
5.2 Apparatus for measurement of climatic factors
The apparatus for measurement of climatic factors shall be in accordance with ISO 877--1.
6 Test specimens
Test specimens shall be in accordance with ISO 877--1.
NOTE When irregularly shaped specimens are used, air flow and specimen cooling can be adversely affected. In
addition, irradiance will not be uniform on all surfaces of a shaped specimen.
7 Exposure conditions
7.1 Orientation of mirrors
The orientation of the mirrors shall be in accordance with ASTM G90.
7.2 Exposure site
Fresnel-reflecting solar concentrating devices operate most effectively at locations that receive at least 3 500 h
of sunshine per year and where the average daytime relative humidity is less than 30 %. ASTM G90 provides
requirements for the exposure site’s average ratio of direct solar radiation to global normal solar radiation.
NOTE In regions that receive 3 500 h of solar radiation and where the average daytime relative humidity is less than
30 %, the average ratio of direct solar radiation to global normal solar radiation is at least 0,75. Areas that meet these
criteria have a minimum diffuse component of solar radiation (sky radiation). The use of reflecting solar concentrator
devices in regions of moderate to high diffuse solar irradiance will substantially reduce the amount of UV radiation at the
specimen target board. Moderate to high levels of humidity and urban aerosols result in scattering of the direct
component of solar radiation so that ultraviolet radiation is scattered into the hemispherical sky dome and is not
available to be focused by the mirrors on to the specimen target board. This is shown in Figure 3Figure 3. In addition,
the use of reflecting solar concentrator devices in regions of moderate to high diffuse solar irradiance can give different
stability rankings for materials compared to exposures conducted in accordance with ISO 877--2 because of the
differences in UV radiation.
7.3 Temperature control
Solar concentrating devices are equipped with a blower to cool the specimens. Specimen temperatures for
most materials are typically 10 °C higher than the maximum temperature which would be reached if an
identical specimen was exposed directly to solar radiation (without concentration) at normal incidence at the
same time.
© ISO #### 2026 – All rights reserved
If more precise control of specimen temperature is required, the temperature of a black or white panel, the
temperature of a black or white standard thermometer, the temperature of a particular specimen, the air
temperature or the temperature indicated by a remote sensor may be monitored and used as an input to
control the specimen temperature. If used, report the controlled temperature and any observed deviations in
the test report.
Use of this method of temperature control can produce results that are not equivalent to typical solar
concentrating exposures and can require longer radiant exposures to produce the same amou
...