ISO 13468-2:2021 Plastics — Determination of the total luminous transmittance of transparent materials —Part 2: Double-beam instrument

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Plastics — Determination of the total luminous transmittance of transparent materials —Part 2: Double-beam instrument是于2021-06发布的ISO标准，适用于世界范围。

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Plastics — Determination of the total luminous transmittance of transparent materials —

Part 2: Double-beam instrument

1 Scope

This document covers the determination of the total luminous transmittance, in the visible region of the spectrum, of planar transparent plastics and substantially colourless plastics, using a double-beam scanning spectrophotometer. This document cannot be used for plastics which contain fluorescent materials.

This document is applicable to transparent moulding materials, films and sheets not exceeding 10 mm in thickness.

NOTE 1 Total luminous transmittance can also be determined by a single-beam instrument as in ISO 13468-1.

NOTE 2 Substantially colourless plastics include those which are faintly tinted.

NOTE 3 Specimens more than 10 mm thick can be measured provided the instrument can accommodate them, but the results cannot be comparable with those obtained using specimens less than 10 mm thick.

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 291, Plastics — Standard atmospheres for conditioning and testing

CIE Publication No 15, Colorimetry

1)

CIE Publication No 17, International lighting vocabulary

3 Terms a nd definiti ons

For the purposes of this document, the terms and definitions given in CIE Publication No. 17 and the following 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://w ww .electropedia .org/ 1) Also published as IEC 60050-845, International Electrotechnical Vocabulary (IEV) International electrotechnical vocabulary — Chapter 845: Lighting.

3.1

transparent plastic

plastics in which the transmission of light is essentially regular and which have a high transmittance in the visible region of the spectrum

Note 1 to entry: Provided their geometrical shape is suitable, objects will be seen distinctly through plastic which is transparent in the visible region.

3.2

total spectral transmittance

ratio of the transmitted radiant flux (regular and diffuse) to the incident radiant flux when a parallel beam of monochromatic radiation of a given wavelength passes through a specimen

3.3

total luminous transmittance

ratio of the transmitted luminous flux to the incident luminous flux when a parallel beam of light passes through a specimen

4 Apparatus

4.1 The apparatus shall consist of the following elements:

— a stabilized light source;

— a monochromator;

— an optical system that forms two parallel beams of monochromatic radiation of equal wavelength λ and approximately equal radiant flux from the output of the monochromator (called the sample and the reference beam);

— and an integrating sphere fitted with ports and a photodetector.

The sample beam enters the sphere through the entrance port. The reference beam enters the sphere through the reference port. The photodetector is mounted on the photodetector port in a manner that allows it to view with equal efficiency all parts of the sphere. Ingress of external light into the integrating sphere shall be prevented. A schematic arrangement of the integrating sphere is shown in Figure 1.

4.2 The value of the total luminous transmittance determined by the instrument shall be accurate to ±1,0 %. To fulfil this requirement, the response of the photodetector shall be sufficiently linear in the visible region of the spectrum and the spectral bandwidth at half power of the monochromator shall be sufficiently small. The measurement conditions shall be such that the specimen temperature does not increase while measurements are made.

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