2 December 1985 Specularity and Stability of Silvered Polymers
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Abstract
Silvered polymers have been studied for possible mirror applications in concentrators for solar thermal systems. The polymeric mirrors were prepared by vacuum evaporating or dc-sputtering silver onto several candidate polymers for use as second surface mirrors. Specularities were measured at 7 and 15 mrad acceptance angles at 660 nm. The specularity of silvered polymers depends strongly on the topography and bulk properties of the polymer used. It is independent both of the deposition rate from 0.1 to 7 nm/s and from thermal evaporation and dc-sputtering processes. Silvered glass specularities are also independent of deposition rates from 0.1 to 45 nm/s and are typically 93% at 7 mrad. The specularity does not depend on the substrate temperatures during depositions for the range of 5° to about 100°C. In some cases, a metallic film was deposited onto the silver before mounting onto a Corning 7809 glass substrate. Inconel backing of films from 35 to 150 nm thick does not reduce the specularity of silvered polymers at 15 mrad, but does accelerate the degradation of the multilayer combination during accelerated or real-time weathering. After measuring the solar-weighted hemispherical reflectance and the second surface specularity at 660 nm for acceptance angles of 15 and 7 mrad, the silvered polymeric specimens were subjected to accelerated testing in a Weather-Ometer at 60°C, 80% relative humidity, and UV irradiation, or in a QUV at 40°C, UV irradiation, and condensation cycles. Real-time testing has also been carried out in the suburban Denver atmosphere. With exposure, all mirrors prepared show evidence for some or extensive optical and/or visual degradation. The relative durabilities of the various combinations studied are discussed in terms of the silvering method, polymer used, metallic backing for the silver, and adhesive used for mounting the silvered polymer onto a test substrate.
© (1985) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
A. W. Czanderna, A. W. Czanderna, Paul Schissel, Paul Schissel, } "Specularity and Stability of Silvered Polymers", Proc. SPIE 0562, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IV, (2 December 1985); doi: 10.1117/12.966292; https://doi.org/10.1117/12.966292
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