Spectroscopic methods, UV/Vis and Fourier Transform Infrared with an attenuated total
reflectance (ATR) accessory, were applied to evaluate the influence of light stabilizers
on ABS samples exposed to accelerated and natural weathering conditions up to 600h
and 360 days, respectively.
Some important differences in the formation rate of carbonyl compounds were found
when comparing accelerated to natural weathering exposure. While stabilized samples
exposed to accelerated weathering reveals slower formation of carbonyl groups than
unstabilized ABS, the carbonyl absorption of samples exposed to natural weathering is
comparable to the unstabilized ones.
The behaviour of light stabilizers during natural exposure is somewhat surprising and
cannot be only associated to its stabilizing effect. The disappearance of light stabilizers
only after one month of exposure could be due to molecular scission of light stabilizers
with consequence volatilization and diffusion of these fragments on the surface, while
under acceleration conditions seems to occur by photochemical reactions.
The results obtained are interesting showing that sometimes the material behavior
under real weathering conditions cannot be predicted from the results of accelerated
laboratory experiments.Fundação para a Ciência e a Tecnologia (FCT) - SFRD/BD/48512/200
