Service Life Prediction Using Accelerated Degradation Data from Laboratory Testing and Outdoor Weathering Data

• Activity Number: 573
• Type: Contributed
• Date/Time: Wednesday, August 3, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Section on Quality and Productivity
• Author(s): Yili Hong*+ and William Q. Meeker
• Companies: Virginia Tech and Iowa State University
• Keywords: Coatings ; Photodegradation ; Reliability ; UV exposure

Abstract

Photodegradation caused by ultraviolet (UV) radiation is a primary cause of failure for coatings, as well as many other products made from organic materials exposed to sunlight. Other environmental factors includes temperature and humidity. Service life prediction of such coatings is difficult because UV radiation from the sun are highly variable. Both indoor and outdoor experiments were conducted at the US NIST to generate necessary experimental data. Accelerated laboratory tests were conducted on a device in which spectral UV wavelength and intensity, temperature, and relative humidity (RH) can be precisely and accurately controlled over time. Outdoor exposure experiments were conducted on the roof of a NIST laboratory. The chemical degradation of coatings was measured every few days. Longitudinal information on temperature, RH and solar spectrum for outdoor specimens were also recorded. In this paper, a physically motivated model is fitted to indoor data. Outdoor data were used to validate the model fitted to the indoor data. Service life prediction was obtained based on the fitted model and prediction intervals were obtained to quantify the statistical uncertainties.