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 °C to 280 °C were studied in isothermal conditions while heating rates in the interval 2.5–15.0 °C/min were 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 Ea = 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 Šesták–Berggren model.