Thermal and kinetics of the degradation of chitosan with different deacetylation degrees under oxidizing atmosphere

Abstract

The degradation process of chitosan with degrees of deacetylation (DD) varying from 54 to 84% was investigated by thermogravimetric analysis at different heating rates under air atmosphere. The chitosan with DD of 54% presented the highest thermal stability and slower changes in its structure as the temperature was increased, according to the infrared spectroscopy analyses. The activation energies (Ea) of the degradation process were estimated by the Flynn-Wall-Ozawa and the Vyazovkin isoconversional methods, obtaining values between 90 and 319 kJ/mol. The 3R-Gaussian distributed activation energy (3R-Gaussian DAEM) model was applied and adjusted successfully to the experimental data. In addition, DAEM model allowed to determine the Ea associated to each degradation reaction stage of chitosan (between 163–346.3 kJ/mol), in contrast to isoconversional methods. Consequently, the 3R-Gaussian DAEM model is a suitable option to describe the kinetics of chitosan degradation process.