A kinetic study on the thermal degradation of N,N,N-trimethylchitosan

The thermal degradation of chitosan and N,N,N-trimethylchitosan, degrees of quaternization 5%, 21% and 33%, was studied by using TG in nitrogen atmosphere. The methylation of chitosan decreased its thermal stability, the decrease being more important the greater the degree of quaternization attained. The absolute values of the activation energy of chitosan and N,N,N-trimethylchitosan calculated from different methods, Broido's and MacCallum's methods, do not agree but they do show the same general trend. The activation energy for the less methylated derivative is higher than that of chitosan but it decreases as the degree of quaternization increases, independently of the method used for its determination. The use of the MacCallum's method reveals that the activation energy increases with increasing degree of conversion for chitosan but no clear trend is observed for the N,N,N-trimethylchitosans. The occurrence of a more complex set of reactions is suggested for the N,N,N-trimethylchitosan samples, including acid-catalyzed processes. (C) 2004 Elsevier Ltd. All rights reserved.