Kinetic study of thermal degradation of chitosan as a function of deacetylation degree

Abstract

Thermal degradation of chitosan with varying deacetylation degree (DD) ranging between 50 and 85% was analyzed by dynamic thermogravimetric analysis at different heating rates. The present study focused on the temperature range between 500 and 800 K, above water evaporation. Thermal degradation for the samples with the highest DD content showed a single degradation stage in this temperature interval while a second stage appeared in the weight derivative curves as a shoulder in the high temperature side of the main peak for the samples with the lowest DD. The Kissinger and isoconversional Ozawa-Flynn-Wall models were employed to evaluate the Ea of both thermal degradation processes. Different kinetic models were evaluated to simulate the thermogravimetry traces calculating the model parameters with a non-linear least squares fitting routine. The Sestack-Berggren model allowed reproducing accurately the overlapping of the two degradation mechanisms and calculating the mass fraction lost in each of them.