Spectroscopic Properties of HALS Doped Polycarbonate by Fluorescence Spectroscopy

The fluorescence and fluorescence excitation spectra of pure and doped polycarbonate (PC) depending on hindered-amine light stabilizers (HALS: Tinuvin 770 and Tinuvin 123) concentration and different processing conditions have been studied. Non-processed PC has no emission band in the visible range but processed PC with additives show visible fluorescence bands between 400–470 nm. It suggested that PC undergoes a kind of degradation process which lead to the fluorescence emission caused by the transitions from the new distortion-related localized states (defect states) created by processing and the additives. Such defects lead also to the emergence of a new band in the excitation and emission spectra at lower energies, where the symmetry of the bands break near. The intensity of these bands drastically depends on the sample treatment where the luminescence intensity quantitatively characterizes the concentration of defect radicals. An increase in screw speed resulted in an increase in specific mechanical energy (SME), higher SME led to a remarkable macromolecular degradation.