Degradation Monitoring of Hindered Amine Light Stabilizer Doped Polymers | Chapter 10 | Advances and Trends in Physical Science Research Vol. 2
Polycarbonate (PC) is
the most widely used aromatic polymer in various industrial applications. It is
a condensation polymer in which benzene rings plus quaternary carbon atoms form
bulky stiff molecules that promote rigidity and strength. The bulky chains
crystallize with great difficulty, so the polymer is normally amorphous with
excellent characteristics such as optical clarity, heat stability and
mechanical resistance. The fluorescence and fluorescence excitation spectra of
pure and doped 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. The fluorescence spectroscopy 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 shown that
pure non-processed PC has no emission band in the visible range but have an
absorption band at 290 nm. Processing under excessive conditions is most likely
to produce chains and general degradation which leads to a fluorescence
emission. Processed PC with additives shows visible fluorescence bands between
400–470 nm. The intensity of these bands drastically depends on the sample
treatment where the luminescence intensity quantitatively characterizes the
concentration of defect radicals. PC becomes considerably yellow discolored
with higher concentration of Tinuvin 770 or Tinuvin 123 and the PC gets more
brittle (higher degradation grade).
Biography
of author(s)
Read full article: http://bp.bookpi.org/index.php/bpi/catalog/view/25/68/156-1
View Volume: https://doi.org/10.9734/bpi/atpsr/v2
Biography
of author(s)
Roushdey Salh
Department of physics, Umeå University, 901 87 Umeå, Sweden.
Department of physics, Umeå University, 901 87 Umeå, Sweden.
Read full article: http://bp.bookpi.org/index.php/bpi/catalog/view/25/68/156-1
View Volume: https://doi.org/10.9734/bpi/atpsr/v2
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