| Abstract
| - The results of studies of the effect of air-blowing treatment on the molecular size and structureof coal-tar pitch components are examined. Four air-blown pitches, obtained after treatment at275 °C for 10, 18, 25, and 30 h, and the commercial parent pitch were studied using techniques,such as SEC, MALDI, UV-F, GC, NMR, and thermal analysis, to monitor the chemical changesundergone by pitch components under the air-blowing conditions. The results showed theformation of larger molecules due to polymerization induced by the oxygen, with the subsequentincreases in the excluded peaks in the SEC analysis. The polymerization involved mainly aliphatichydrogens in −CH2− bridges and “bay” zones, promoting the formation of side-bonds betweenthe molecules. Only the pitch treated for 30 h showed stronger signals at long wavelengths ofthe UV-F spectrum, indicating an increase of the condensed aromatic units. Evidence of theseside-bonds was obtained by thermogravimetric analysis, which showed a new band of weightloss around 400 °C being developed with the air-blowing treatment, and also by the evolution ofthe band associated to the glass transition detected by differential scanning calorimetry.
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