Polymer reflectors research during FY 1986

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Abstract
The long-term objectives of the Silvered Polymer Reflectors subtask within the SERI Solar Thermal Research Program are to develop silvered polymers that have a high specular reflectance and to develop modifications of polymers that will protect the silver and maintain the reflectance in outdoor environments for many years. Major progress has been made toward the specific long-term targets of a specularity resulting in 90% of the solar flux being contained within a cone angle of 4 to 10 mrad, and a useful life of at least 5 years. We have shown that silvered polymers can have an initial specular reflectance well over 90% into an acceptance angle of 1 to 2 mrad, significantly better than our long-range goals. It was further shown that these results could be obtained when the silvered polymer was mounted with an adhesive onto a smooth, flat substrate or stretched as a membrane without a firm support as in the membrane mirror configuration. Thus, the initial optics exceeds our goals, and the focus of our work is now directed to the durability of silvered polymers. Durability studies using industrial silvered polymers are conducted in accelerated weathering devices and outdoors. Outdoor tests in Colorado show that silveredmore » polymers can maintain reflectances in excess of our long-range goals (>90%, 4 mrad) for at least 48 weeks (18% of our durability goal) and the tests are continuing. Materials placed into test earlier, before we attained the full optical performance, are also providing encouraging results. Samples outdoors in Golden, Colo., for 2 1/2 years maintain reflectances near 90% at 12 mrad while other samples here avoided silver corrosion as determined by visual inspection for nearly 3 years. 39 refs., 56 figs., 11 tabs.« less

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