Kinetic studies on the pyrolysis of chitin and chitosan

The thermal degradation of chitin and chitosan have been studied by using simultaneous TG and DSC in nitrogen atmosphere. The model-free iso-conversional method has been employed to evaluate the activation energies as a function of the extent of degradation. The obtained dependencies are interpreted in terms of degradation mechanisms. Under nitrogen, the thermal degradation of chitin and chitosan follows a random scission pathway, which is initiated at weak links. The activation energies of thermal degradation of chitin are constant and this process follows 1.23 order reaction. As for chitosan, the activation energies of thermal decomposition are obviously dependent on the extent of conversion. The pyrolysis reaction of chitosan is analysed by using a distributed activation energy model (DAEM) because the residual N-acetylated side-chains are randomly distributed on the chitosan main chains. Also, the parameters of the DAEM are evaluated.