A novel facility for ageing materials with narrow-band ultraviolet radiation exposure

Abstract

A facility for exploring wavelength dependencies in ultraviolet (UV) radiation induced degradation in materials has been designed and constructed. The device is essentially a spectrograph separating light from a lamp to spectrally resolved UV radiation. It is based on a 1 kW xenon lamp and a flat-field concave holographic grating 10 cm in diameter. Radiation at the wavelength range 250-500 nm is dispersed onto the sample plane of 1.5 cm in height and 21 cm in width. The optical performance of the device has been characterized by radiometric measurements. Using the facility, test samples prepared of regular newspaper have been irradiated from 1 to 8 h. Color changes on the different locations of the aged samples have been quantified by color measurements. Yellowness indices computed from the color measurements demonstrate the capability of the facility in revealing wavelength dependencies of the material property changes in reasonable time frames.

High-resolution setup for measuring wavelength sensitivity of photoyellowing of translucent materials

“…1. This spectrograph, UVEMA2, is an improved version of the spectrograph developed and reported by Kärhä et al 8 Its general operating principle is similar to the original version, but the optical configuration and the exposure wavelength region are slightly different.…”

“…anna.vaskuri@aalto.fi tors and spectrographs, [7][8][9] or lasers. 10 The source-dependent techniques include, e.g., exposing samples under the solar radiation 11 and using a weathering chamber 12 equipped with xenon (Xe) or mercury (Hg) lamps.…”

“…The action spectrum of a material cannot be derived using source-dependent techniques only. Kärhä et al 8 have developed and reported a spectrograph, a compact version of the Okazaki large spectrograph 7 that uses spectrally dispersed radiation to expose samples in order to measure the wavelength sensitivity of the photodegradation. The spectrograph disperses the radiation of 1-kW Xe lamp spectrally from 250 nm to 500 nm and spatially onto the sample plane of 21 × 1.5 cm 2 by using a flat-field concave holographic grating.…”

“…To overcome the challenges in measuring color changes in translucent samples, we have developed and constructed a high-resolution measurement setup that uses 14 laser lines with wavelengths between 325 nm and 933 nm for scanning the transmittances across UV exposed material samples. This measurement setup is used together with our earlier developed spectrograph 8 to obtain high-resolution transmittance data on regions exposed to different UV wavelengths that can be used to derive the action spectrum.…”

Facility for determining action spectra of UV photodegradation

“…We have developed a facility for exposing material samples to spectrally dispersed UV radiation with different exposure times [7] and for measuring the wavelength sensitivity of photodegradation with lasers [8]. We use the facility for exposing and measuring a set of atactic polystyrene sheets, and derive a nonlinear action spectrum for the photoyellowing.…”