Initial degradation processes of cellulose at elevated temperatures revisited - chemiluminescence evidence

The initial processes governing degradation of cellulose at elevated temper atures are re-examined. The influences of moisture, alkali-earth metal carb onates, and atmosphere at 180 degreesC, were studied. The various effects w ere studied both conventionally, by determining the changes in the degree o f polymerisation by viscometry, and by chemiluminescence measurements. The moisture initially contained in the sample was shown to have no effect on d egradation in dry nitrogen although the chemiluminescence of moist samples is initially considerably higher. It was associated with production of sing let oxygen. On the other hand, presence of moisture in oxygen atmosphere en hances oxidation. Some initial degradation occurs during rapid heating and was attributed to mechanical degradation, though no chemiluminescent phenom enon could be associated with it. The degradation rates during the more adv anced phases were shown to be related to the presence of earth-alkali metal cations. It is suggested that complex formation between a metal cation and glycosidic oxygen might play an important role in the degradation mechanis m. (C) 2001 Published by Elsevier Science Ltd. All rights reserved.