Thermographs of the chitosan and EHCs are shown in
Fig. 5. The chitosan shows slow weight loss starting from
140.0 C to 200.0 C due to the decomposition of polymer
with low molecular weight, followed by more obvious loss
of weight starting from 200 C to 310 C, which could be
attributed to a complex process including dehydration of
the saccharide rings, depolymerization and decomposition
of the acetylated and deacetylated units of the polymer
(Peniche & SanRoman Arguelles-Monal, 1993). A fast process
of weight loss appears in TG curve for EHCs decomposing
from 170 C to 300 C. The results demonstrate the
loss of the thermal stability for EHCs to the original chitosan.
Introduction of –OH and –NH2 group into polysaccharide
structure should disrupt the crystalline structure
of chitosan, especially through the loss of the hydrogen
bonding