3.3.3. Thermogravimetric analysisFig. 6 shows the thermal degradation of the GS, ATGS, BGS andCNC-GS. All TG curves showed an initial small drop between 25 and150◦C, which correspond to the absorbed moisture on the surfacesof these materials, including chemisorbed water and/or the inter-molecularly H bonded water.Thermal degradation of the CNC-GS started at approximately200◦C in a N2atmosphere, while for the BGS degradation beganat approximately 220◦C. The increased thermal stability of BGSmight be attributed to the removal of amorphous hemicelluloses,as evidenced above by FT-IR and XRD results. However, the CNC-GS showed lower thermal stability than BGS and the untreated GS(Fig. 6). This was probably due to the replacement of hydroxylgroups by sulfate groups (O SO3H) during the hydrolysis step,which clearly decreased the activation energy for the degradationof CNC, making the sample less resistant to pyrolysis. Therefore,