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J. Zieliński, B. Osowiecka, W. Ciesińska, B. Liszyńska, T. Brzozowska



The effect of a polyester resin or polyoxyethylene glycols as coal-tar pitch modifiers

on pitch's benzo[a]pyrene content

Polimery 1998, No 3, 175


DOI: dx.doi.org/10.14314/polimery.1998.175


Summary

Prolonged (<5 h) heating of a coal-tar pitch with an unsaturated polyester resin (Polimal 138) or with polyoxyethylene glycols (PEG) at elevated temperatures (140—150°C) resulted in nearly 90% reduction of the content of benzo[a]pyrene (BAP) in the pitch. The modified pitch contained novel systems involving essentially altered group and elementary compositions and had a reduced content of free radicals and a reduced degree of aromaticity. The modifications observed are believed to be due to strong molecular interactions and chemical transformations of pitch constituents with the polar modifiers added, presumably with polyester chains' terminal groups (e.g. hydroxyls) as inferred from studies conducted with PEG. 13C-NMR spectra changes observed suggest both O- and C- alkylation mechanisms to be operative in BAP—polyester and BAP—PEG interactions.


Keywords: coal-tar pitch, benzo[a]pyrene, unsaturated polyesters, polyoxyethylene glycols, modifications


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