Solar Thermal Technology Program: polymer synthesis and characterization subtask. Annual progress report, FY 1983
Initial candidate methods for protecting the polymeric glazing and the metallic layer from degradation by ultraviolet light (uv) and candidate new polymeric materials have been identified. The characteristics of photodegradation permit the application of methods involving both photon absorption and transfer of electronic energy. Generally, photostabilizers for polymers are classified according to their mode of action: uv light absorbers, excited state quenchers, antioxidants, and hydroperoxide decomposers. We have selected the radical copolymerization of monomeric uv absorbers with methylmethacrylate and related monomers for our initial system. The first step is to evaluate absorbers mixed with the polymethylmethacrylate system. Mirrors are made using Corning 7809 glass as a substrate onto which a thin silver film is deposited, and the modified polymeric films are then cast from solution onto the silver. Mirrors are characterized by measuring the hemispherical reflectance as a function of wavelength and by determining the solar-weighted hemispherical reflectance. Mirrors are exposed to environmental degradation using accelerated weathering devices and outdoor exposure. We have demonstrated that uv absorbers added to polymethylmethacrylate can improve the weathering performance of mirrors. A benzotriazole absorber has performed best. Experiments on the present task also show that benzotriazole absorbers stabilize polyester films. Unstabilized polyacrylonitrile glazings have also performed well. We have observed that prior treatment of the mirror with uv light can improve the adhesion. We have also observed that the process for silver deposition influences the initial reflectivity of silver mirrors.
- Research Organization:
- Solar Energy Research Inst., Golden, CO (USA)
- DOE Contract Number:
- AC02-83CH10093
- OSTI ID:
- 5488467
- Report Number(s):
- SERI/PR-255-2148; ON: DE84000094
- Resource Relation:
- Other Information: Portions are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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