Fig. 4a shows the heat flow curves of RH cellulose analysed by
MDSC. Considering total and non-reverse heat flow curves, they
show two main events. The first endothermic peak observed below
150 ◦C is due to loss of water. The second endothermic transition
starts around 270 ◦C with a peak at 320 ◦C and is related to cellulose
melting. A smooth exothermic transition can be detected
near 340 ◦C. This event has its onset overlapped with the end of the
endothermic region and can be related to the depolymerization of
cellulose as supported by the equivalent peak in the non-reverse
heating curve. Such conclusion is also corroborated by the TGA
study which shows a maximum of weight loss for RH cellulose in the
same temperature region. On the other hand, an important change
in the heat capacity of the medium can also be seen between 300 ◦C
and 330 ◦C in the reverse heat flow curve. This indicates a change
in chemical composition as a result of the depolymerization reaction.
The absence of an endotherm in reversing signal indicates that
this thermal event is a kinetic transformation. By visual inspectionof the pan, very few solid residues were found at this stage and charring process was evident.