Kinetics of the thermal degradation of chitosan

The thermal degradation of chitosan, degree of acetylation 12%, was studied by using TG in nitrogen atmosphere in isothermal and dynamic conditions. Temperatures ranging from 240 degrees C to 280 degrees C were studied in isothermal conditions while heating rates in the interval 2.5-15.0 degrees C/minwere employed when using dynamic conditions. The data issued from the dynamic experiments were treated by the methods proposed by Ozawa-Flynn-Wall and Kissinger, resulting in apparent activation energy of 149.6 kJ/mol and 138.5 kJ/mol, respectively. The approach proposed by MacCallum was used to treat the data issued from the isothermal experiments, resulting in E-a = 153 kJ/mol in good agreement with the results issued from the dynamic experiments. The use of the isoconvertional method due to Vyazovkin also showed a good agreement with the value of the activation energy issued by applying the method of Ozawa-Flynn-Wall. It was also observed that regardless of using isothermal or dynamic experimental conditions, the kinetic model best suited to describe the thermal degradation of chitosan is the catalytic Sestak-Berggren model. (C) 2007 Elsevier B.V. All rights reserved.