Fotodegradação natural e artificial de filmes de poli (tereftalato de etileno) (PET).

Abstract

In this work. the effects of photodegradation was investigated in conunereial films of pol\(elh\Iene lerephlhalale) produeed by exlrusion. Samples with diííerenl ihickness (12. 36 and lOOum) were exposed in the natural environment as well as in the laboratory. After various exposure times they were characterized for meehanical propeilies and modifications in the chemical structure using Fourier transform infrared spectroscopy. A comparison of the data obtained for the three thickness and for the two exposures types (natural and artificial) showed that the photodegradation sensitix ity depends on the film thickness, exposure time and procedure. The thinnest film, with a higher degree of orientation. showed higher tensile strength and elongation in the unexposed state but it was the most sensitive towards the degradation effects. This is probably because the degradation is concentrated at the surface layers. A comparison between the two exposure types showed the accelerating factor varicd with the type of films. The thicker ones had a higher deterioration in the laboratory whereas the thinner ones degraded much more during natural exposure. It is possible that meehanical effects during natural exposure caused by rain and wind cause failure of the degraded films. This finding poses a qucstion in the validity of comparison the two types of exposures for thin PET films if environmental components that result in stress are not reproduced in the laboratory.