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Conclusions

The lack of reliable wavelength sensitivity data and dose-response information has always been a serious limitation in efforts to assess the increased damage to materials from enhanced UV levels resulting from ozone layer depletion. In recent years, however, this need has been partly addressed with several relevant action spectra for at least the common polymeric materials reported in the literature. More importantly some of this data pertains to formulations typically used in outdoor applications in the building industry. Also significant is the availability of spectral sensitivity data for several biopolymers during the recent years.

    However, very limited dose-response data is available for these same compositions and the information reported is somewhat inconsistent. Furthermore, the photostabilizer effectiveness (or even their own photostability under exposure to UV-enhanced solar radiation) still remains unclear. These limitations do not allow reliable damage estimates for polymers typically used in building applications to be reliably estimated. The various assumptions typically employed in damage assessment for materials have not yet been validated for a great majority of polymers.

    An important aspect of the problem is the role of temperature in exacerbating the effects of an increase in solar UV radiation. In regions with high ambient temperatures the assessment process must take into account the very high bulk temperatures polymers are subjected to during their service life. To do so effectively a better understanding of UV induced degradation processes at the lower temperatures will be particularly useful. Again the data available on this topic are very limited.

    While the relevent information is begining to appear in the research literature, there is as yet inadequate data to conduct reliable damage estimates for most common polymers.


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