Thermal degradation behavior and kinetic analysis of spruce glucomannan and its methylated derivatives

• We studied the thermal behavior and kinetics of spruce and konjac glucomannanan.
• The konjac glucomannan was more thermal stable than the spruce glucomannan.
• The pyrolysis of both glucomannans was modeled using a Dn- and Fn-type reaction.
• Higher DS leads to higher volatile yields and a more resistant material.
• Methylation of the glucommanans can be introduced to suit specific applications.

The thermal degradation behavior and kinetics of spruce glucomannan (SGM) and its methylated derivatives were investigated using thermogravimetric analysis to characterize its temperature-dependent changes for use in specific applications. The results were compared with those obtained for commercial konjac glucomannan (KGM). The SGM and the KGM exhibited two overlapping peaks from 200 to 375 °C, which correspond to the intensive devolatilization of more than 59% of the total weight. Differences in the pyrolysis-product distributions and thermal stabilities appeared as a result of the different chemical compositions and molecular weights of the two GMs. The Friedman and Flynn-Wall-Ozawa isoconversional methods and the Coats–Redfern were adopted to determine the kinetic triplet of the intensive devolatilization region. Both GMs can be modeled using a complex mechanism that involves both a Dn-type and an Fn-type reaction. The comparative study of partially methylated GM indicated higher homogeneity and thermal resistance for the material with the higher degree of substitution.