A comparison study on non-isothermal decomposition kinetics of chitosan with different analysis methods

A thermal degradation study of chitosan in air atmosphere has been carried out in detail through Fourier transform infrared (FTIR) analysis, thermogravimetric (TG) analysis and differential thermal analysis (DTA) measurements. FTIR spectra reveal the variations of chemical structures of chitosan in the course of thermal degradation. The mass loss data were collected under the heating rates of 5-30 K min(-1). Kinetic analysis of chitosan thermal degradation has been performed through isoconversional FWO, CR, MKN and Tang methods, and the calculated results are basically comparable for these four different methods. With the Arrhenius parameters obtained, the four methods have been attempted to reconstruct the temperature-dependent mass conversion curves and have resulted in generally acceptable results. The TG and DTA results suggest that two-stage thermal degradation processes may be better assumed. For more accurately describing the thermal degradation process of chitosan, the most probable reaction functions have thus been determined for these two stages, leading to greatly improved calculation performance over the entire conversion range. On the basis of the Arrhenius parameter values obtained, the changes in entropy, enthalpy and Gibbs free energy, and lifetime predictions have been estimated concerning the thermal degradation processes of chitosan.