Photogeneration of carbon dioxide from polypropylene film stabilized by hindered amines

Infrared spectrometric measurements have been used to measure the amount of carbon dioxide generated by UVA irradiation of polypropylene film stabilized with 0.5% of three different hindered amine light stabilizers (HALS). The measurements were made in situ, using a specially constructed glass cell fitted with CaF₂ windows. In each case the amount of photogenerated carbon dioxide was less than that from a HALS-free polypropylene film of similar thickness. The amount of photogenerated CO₂ was greatest in oxygen that had been pre-saturated with water and the amount of CO₂ evolved depended on the grade of HALS. In dry oxygen, although the differences between the films containing different HALS were much reduced the amount of CO₂ continued to be smaller than that from the HALS-free polymer. The sensitivity of CO₂ photogeneration to the presence of HALS provides new evidence of the relevance of the CO₂ photogeneration method to the diagnosis of photosensitivity of polymers and the influence of stabilizing additives.