SYNOPSISThe wavelength sensitivity for decrease in percent elongation at break of ethylene carbon monoxide copolymer (ECO) and a low density polyethylene containing a metal compound prooxidant (LDPE/MX) on exposure to a borosilicate-filtered xenon-arc source was determined using a set of sharp cut-on filters. The spectral region primarily responsible for the degradation at 60°C is 323-328 nm for ECO and 323-338 nm for LDPE/MX. At 77"C, the sensitivity shifts about 10 nm to longer wavelengths. Based on the wavelength sensitivity of these materials to solar simulated radiation and the transmission properties of window glass, these materials can be expected to lose desirable mechanical properties when exposed to window-glass-filtered sunlight.

The wavelength sensitivity of unpigmented 100 mil thick ABS exposed to sunlight and filtered xenon are radiation was determined by the sharp cut filter technique based on three types of photochemical changes: bleaching, yellowing and loss in impact strength. Bleaching of the yellow‐colored species formed in the processed material is caused by wavelengths between 380 and 525 nm with maximum color change by the 475–485 nm region. Photochemical yellowing is due to wavelengths between 300 and 380 nm with all wavelengths being almost equally effective. The spectral sensitivity based on change in impact strength shifts from the UV to the visible region as photochemical yellowing progresses. Addition of two stabilizers, a benzotriazole ultraviolet absorber and a hindered amine stabilizer, shifts the wavelength sensitivity based on yellowing to wavelengths shorter than 330 nm, but has no influence on the spectral effects based on impact strength. It is postulated that the rate of yellowing is reduced mainly by the ultraviolet absorber and stabilization against loss in impact strength is due largely to the hindered amine. Differences in rates and spectral response of the three types of photochemical changes indicate that they are due to different initiating mechanisms and thus require different types of stabilization. The significance to stability testing is discussed.