The photosensitizing action of aromatic compounds in translucent polymers

Initiation of Polypropylene Photooxidation. 1. Polynuclear Aromatic Compounds

“…Xe Arc Irradiation ( h ) Polynuclear Aromatics and PPH Photoinitiation. Pivovarov et al 5 have previously reported that naphthalene and phenanthrene can photosensitize radical formation in PPH and polyoxymethylene, whereas anthracene retards radical formation. However, these results, which were attributed to biphotonic processes, were obtained for film samples at 77 K with full mercury arc irradiation in the absence of oxygen.…”

“…The accumulation of these compounds in polyolefins is now well established.3-5 They are apparently absorbed from the urban atmosphere up to equilibrium concentrations of ~1 X 10-3 M naphthalene, ~1 X 10~4 M phenanthrene, and ~1 X 10-5 M anthracene. 5 From fluorescence spectroscopy, the absorbed compounds may be alkylsubstituted derivatives or the unsubstituted parent aromatics. 5 All can be removed by hexane washing but reaccumulate to their equilibrium levels within ~10 days storage in air.…”

“…5 From fluorescence spectroscopy, the absorbed compounds may be alkylsubstituted derivatives or the unsubstituted parent aromatics. 5 All can be removed by hexane washing but reaccumulate to their equilibrium levels within ~10 days storage in air. [3][4][5] These compounds absorb strongly or intensely (in the case of anthracenes) in the near uv to give excited states.…”

“…5 All can be removed by hexane washing but reaccumulate to their equilibrium levels within ~10 days storage in air. [3][4][5] These compounds absorb strongly or intensely (in the case of anthracenes) in the near uv to give excited states. Quenching of these triplet states by atmospheric oxygen is efficient and gives singlet oxygen (1Ag, 1026-8).…”

Photostabilization of macromolecules by excited state quenching

“…Polynuclear aromatics (PNA), which are present in the atmosphere, are known to concentrate in polyolefins (Ref. 25,26,27); naphthalene, phenanthrene and anthracene have been detected in commercial PP films from their characteristic fluorescence emission spectra (Ref. 24).…”