Ultra-Accelerated Weathering System I: Design and Functional Considerations

By Henry K. Hardcastle, Gary J. Jorgensen , Carl E. Bingham

Ultra-accelerated approaches to weathering testing differ significantly from prior approaches of “real time” (not accelerated) and “moderately accelerated” weathering test methods. In real-time weathering, test specimens are directly exposed to weather in end use or worst-case end use environmental conditions. Test specimens mounted on racks that directly face the sun in South Florida or Arizona represent real-time, unaccelerated exposures.

The ASTM G71 test method represents an example of a real-time exposure method. Moderately accelerated exposures can be categorized into natural and artificial classes. Artificial accelerated methods utilize artificial light sources to simulate natural sunlight (typically filtered xenon arc or fluorescent light sources).

Many of the developments in artificial weathering technologies have been focused on getting the light right—achieving good spectral match with natural sunlight in order to produce the same balance of photochemical degradation observed in real-time exposures.2 ASTM G1553 and SAE J25274 test methods represent examples of moderately accelerated artificial exposures.