Overview
CEN ISO/TR 18486:2018 (ISO/TR 18486:2018) defines a calculation method to compare the spectral irradiance of a laboratory radiation source (solar simulator) used for weathering tests with a reference solar spectral irradiance. The Technical Report provides objective, repeatable parameters to quantify how well a solar simulator fits a chosen reference sun spectrum or a specific action spectrum relevant to polymer/photo‑chemical responses.
Key Topics and Requirements
- Purpose: Provide objective factors (characterizing parameter f) that quantify the spectral fit between a laboratory source and a reference solar spectrum or an action spectrum.
- Calculation method: Scale the laboratory source spectrum to the reference within a chosen wavelength range, then compute a deviation parameter f. An ideal fit yields f = 0; larger f values indicate worse fitting.
- Wavelength selection: Choose a wavelength range (λ1 to λ2) relevant to the test or material; ranges should be larger than 10 nm. Annex A lists typical ranges for different applications.
- Action spectra: When the polymer’s action spectrum s(λ) is known, scale and compare weighted spectral irradiances to assess photochemical relevance.
- Spectral resolution: Measurements and calculations require 1 nm spectral resolution.
- Reference spectra: The document recommends using solar spectra calculated with the SMARTS2 model (ISO/TR 17801, ASTM G177) because older references (e.g., CIE 85:1989) have limitations.
- Informative content: Examples for commercial solar simulators and typical parameters are provided in Annex A.
Applications and Who Uses It
- Materials scientists and polymer test laboratories evaluating artificial weathering and photochemical ageing.
- Manufacturers and users of solar simulators and laboratory radiation sources who need to validate spectral performance.
- Quality assurance and R&D teams selecting or qualifying lamps for accelerated weathering tests, photochemistry, photo‑dermatology, or thermal-stress experiments.
- Standards bodies and test method authors integrating objective spectral-fit metrics into test procedures.
Practical benefits include clearer acceptance criteria for solar simulators, consistent reporting of spectral fitness, and improved alignment of laboratory weathering to real-world solar exposure.
Related Standards
- ISO/TR 17801 - reference on solar spectral irradiance modeling (SMARTS2)
- ASTM G177 - reference solar spectra using SMARTS2
- CIE 85:1989 - historic reference spectrum (noted as limited; under revision)
Keywords: ISO/TR 18486:2018, CEN ISO/TR 18486, spectral irradiance, solar simulator, laboratory radiation source, weathering, action spectrum, plastics, SMARTS2, accelerated weathering.
