A NOVEL APPROACH TO YELLOWING PROCESS AND FORMATION OF CHROMOPHORES IN EVA SHEETS BY TWO UV-AGING METHODS

摘要

Accelerated degradation tests by a UV pulsed laser and fluorescence tubes for ethylene vinyl acetate (EVA) encapsulants were applied at ITRI. The glass/EVA/glass samples were prepared and irradiated by a 10 mJ, 355 nm UV pulsed laser with a repetition rate of 10 Hz and 5 ns pulse-duration. Both of the UV pulsed laser and fluorescence tubes induced the change of yellowness index (ΔYI). Our results showed that ΔYI = 10 could be achieved in 20 to 30 hours by a UV pulsed laser; Instead, ΔYI value was still less than 2 by fluorescence rubes (60 °C, 40 W/m~2) in a chamber over 600 hours. Transmittance and Raman spectrum of the samples were investigated, and the essential difference of polymer degradation in EVA films after accelerated tests by two UV methods were also discussed in this work.