ISO 26723:2020
(Main)Plastics — Determination of total luminous transmittance and reflectance
Plastics — Determination of total luminous transmittance and reflectance
This document specifies the determination of total luminous transmittance and total luminous reflectance on clear, translucent or opaque plastics. Specimen shapes include moulded plaque or discs, films and sheets. Fluorescent plastics and chromatic colour plastics are not covered by this document. NOTE The scope of ISO 13468-1 shows that ISO 13468-1 covers planar transparent and substantially colourless plastics. The method in this document provide the way to trap diffused light and covers to measure translucent and opaque plastics.
Plastiques — Détermination de la transmission lumineuse totale et de la réflectance
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 26723
First edition
2020-04
Plastics — Determination of total
luminous transmittance and
reflectance
Plastiques — Détermination de la transmission lumineuse totale et de
la réflectance
Reference number
ISO 26723:2020(E)
©
ISO 2020
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ISO 26723:2020(E)
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ISO 26723:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Specimen . 3
7 Conditioning . 4
8 Procedure. 4
9 Calculation procedure . 5
10 Precision . 5
11 Expression of results . 5
12 Test report . 6
Annex A (informative) Measurement examples of total luminous transmittance and total
luminous reflectance. 7
Annex B (informative) Derivation of formulae .10
Bibliography .11
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ISO 26723:2020(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
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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).
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
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 26723:2020(E)
Introduction
This document specifies not only the total luminous transmittance of colourless and transparent
plastics that have been covered by ISO 13468-1, but also specifies the transmittance of translucent
materials such as opal sheets and the reflectance of materials such as translucent and/or opaque sheets
or films.
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INTERNATIONAL STANDARD ISO 26723:2020(E)
Plastics — Determination of total luminous transmittance
and reflectance
1 Scope
This document specifies the determination of total luminous transmittance and total luminous
reflectance on clear, translucent or opaque plastics. Specimen shapes include moulded plaque or discs,
films and sheets.
Fluorescent plastics and chromatic colour plastics are not covered by this document.
NOTE The scope of ISO 13468-1 shows that ISO 13468-1 covers planar transparent and substantially
colourless plastics. The method in this document provide the way to trap diffused light and covers to measure
translucent and opaque plastics.
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 291, Plastics — Standard atmospheres for conditioning and testing
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observers
ISO 11664-2, Colorimetry — Part 2: CIE standard illuminants
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
total luminous transmittance
τ
t
ratio of the transmitted luminous flux to the incident luminous flux when a collimated beam of light
passes through a specimen
3.2
total luminous reflectance
ρ
t
ratio of the reflected luminous flux to the incident luminous flux when a collimated beam of light
reflected on a specimen
4 Principle
When evaluating the total luminous transmittance of light diffusing material, the scattered light will go
toward the edge of the specimen by its light diffusing property. This method intends to collect scattered
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ISO 26723:2020(E)
light from the edge of the specimen toward inside of the integrating sphere. This method is suitable for
not only light diffusing materials but also clear materials.
This method can also evaluate total luminous reflectance of clear, translucent or opaque materials.
NOTE When evaluating the specimen which has almost zero absorption of light such as PMMA milky white,
sum of total luminous transmittance and total luminous reflectance will be 100 % or around.
5 Apparatus
5.1 The apparatus shall consist of a stabilized light source, an associated optical system, an integrating
sphere with ports, and a photometer comprising a photo-detector, signal processor and display unit or
recorder (see Figure 1).
5.2 The light source and the photometer shall be used in conjunction with a filter to provide an output
corresponding to the photopic standard luminous efficiency V(λ) (as defined in ISO/CIE 11664-1), which
is identical to the colour-matching function y (λ) specified in ISO/CIE 11664-1 under CIE standard
illuminant D65 as specified in ISO 11664-2. The output of the photodetector shall be proportional to the
incident flux, to within 1 % of the incident flux, over the range used. The spectral and photometric
characteristics of the light source and photometer shall be kept constant during measurements.
5.3 The total port area (sum of area of the port a, b, c and d) shall not exceed 4,0 % of the internal
reflecting area of the sphere. It is desirable for the diameter of integrating sphere to be not less than
150 mm to be big enough for a specimen to pull together the scatter light to the thickness direction of the
specimen enough.
5.4 Ports a, b and c shall be centred on the same great circle of the sphere. The angle between line ac
and line bc shall be 14 °. Where the line ac means the line which links the centre of port c to the centre of
port a, and the line bc means the line which links the centre of port b to the centre of port c. Port d shall
not be in the great circle on the sphere with port a, b and c.
5.5 The light source and its associated optical system shall produce a collimated light beam, no ray
of which makes an angle of more than 0,05 rad (3°) with the beam axis. The centre of light flux shall be
matched up precisely with the centre of the port a. The cross-section of light flux shall be circular and
have sharp image. The diameter of light flux at the por
...
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