Wavelength dependence of the surface photo-oxidation of Bisphenol A polycarbonate

ESCA and difference uv techniques have been used to monitor the changes which take place in the surface and bulk chemistry, during photo-oxidation of Bisphenol A polycarbonate, as a function of irradiation wavelength over the range 280–330 nm. Whereas for the surface, the maximum change is observed at 280 nm, in the bulk this occurs at 290 nm. Irradiation at 310 nm, which gives bulk changes similar to natural weathering, does not involve the carbonate group in the surface so that the initial photo-instability of polycarbonate cannot be attributed to a photo-Fries rearrangement of this moiety. The surface photo-reactions are consistent with photo-oxidation.