Rapid assessment of weathering stability from exposure of polymer films. I. Real and simulated weathering of commercial ABS terpolymers

Changes in the infared transmission spectra of thin films were used to follow the natural and artificial weathering of ABS terpolymers. Photo‐oxidation of the polybutadiene moiety, which is the major process involved, occurs only after a well‐defined amount of ultraviolet energy has been absorbed. Therafter, unsaturation decreases in a first‐order manner with respect to UV energy absorbed. Under artificial conditions with constant UV intensity, energy absorbed is synonymous with time, but this is not so in natural exposure because of the variability of solar energy and its UV content. The method permits rapid comparison of commercial grades of ABS with the advantage of using natural conditions. It has been shown that pigmentation (3.6 phr brown and 1.25 phr carbon black) increases weathering stability two‐ and fourfold respectively, as assessed by induction energy and rate of disappearance of unsaturation.