Exposure Study on the Aging of PTFE and Ceramic Diffusers
Benjamin K. Tsai, Catherine C. Cooksey, David W. Allen, Christopher C. White, Walter E. Byrd, Deborah S. Jacobs
This paper describes efforts to quantify the effects of aging in the ultraviolet (UV) on polytetrafluoroethylene (PTFE) and ceramic samples. Long term UV aging may significantly alter the reflectance factor and cause an error in the calibration of reflectance standards. A large integrating sphere was used to irradiate the samples for an extended period of time equivalent to about 4.3 solar units. Samples were qualified and measured for reflectance, bidirectional reflectance distribution function (BRDF), and fluorescence data, before and after the year-long measurements, as well as in between the 3-month aging periods. This study revealed significant differences between the aging behavior of ceramic and PTFE samples.