Effect of Exposing Two Commercial Manufacturers' Second-Surface Silver/Glass Mirrors to Elevated-Temperature, Mechanical Loading, and High-Humidity Environments

摘要

A preliminary examination of the effect of three accelerated exposure parameters on second surface silver/glass mirrors was performed. The variables studied were temperature (elevated and sub-zero), humidity and mechanical loading. One test consisted of exposing mirror coupons to dry heat (80 exp 0 C) and heat plus water vapor (80 exp 0 C, approx. 100% RH) environments. Another test consisted of subjecting mechanically loaded mirror strips to sub-zero temperature (-20 exp 0 C), dry heat (80 exp 0 C), and heat plus water vapor. Samples were evaluated qualitatively using dark field microscopy (1X and 100X). Quantitative determination of the effects of exposure testing on the mirrors was done with spectrophotometer spectral hemispherical and diffuse reflectance measurements. Degradation that was progressive with time was observed for mirrors exposed to dry heat and heat plus water vapor. The degradation did not have the same visual appearance for the two environments. Mechanical loading at -20 exp 0 C produced no degradation after three months' exposure time. Mechanical loading in dry heat and heat plus water vapor environments resulted in mirror degradation that was the same as that found in unloaded mirrors exposed to the same temperature and humidity. These preliminary tests indicate that the dry heat and heat plus water vapor accelerated tests may provide useful information about mirror degradation, while the mechanical load tests do not. The microscopy and spectrophotometer reflectance measurements were both useful techniques for determining the extent of degradation. (ERA citation 07:056610)