*3.3. Thermal Properties*

Crystallinity is an important parameter, which can greatly affect the physical properties of biodegradable polymers. The identification of neat polymers, copolymers, polymer blends, and composites, as well as the determination of their purity and stability, are generally described by DSC. Amorphous polymers exhibit a glass transition temperature while crystalline or semi-crystalline polymers may possess glass transition temperature, a freezing and melting temperature with various freezing, and melting enthalpies [56]. In this work, the glass transition temperature, Tg, melting point, T m, and decomposition temperature, Td were investigated to interpret thermal behaviors of the extracted celluloses. The DSC thermograms for the BC, DP-BC, BC-NC and the reference materials, commercial Microcrystal Cellulose, MCC and Nanocrystal Cellulose, NCC were registered at a heating rate of 10 ◦C/min and depicted in Figure 3. The thermograms revealed that BC exhibited different pattern from DP-BC and BC-NC. The heat-flow curve of BC displayed a small inflection of the baseline around 105–110 ◦C, which is the glass transition temperature, Tg, and is followed by an endothermic peak with the onset, T m = 113.8 ◦C. In the treated celluloses, DP-BC and BC-NC, with the increased in crystalline content (CrI), the endothermic peak shifted toward a higher temperature. This slightly marked peak could be attributed to the presence of an amorphous region [57]. The curve of DP-BC showed an endothermic peak at 310–370 ◦C, which appeared to be a melting temperature at T m = 348.7 ◦C. The peak was followed by a degradation temperature at Td = 381.3 ◦C of the cellulosic material. A similar result was found for BC-NC: an endothermic peak was detected around 260–290 ◦C with the onset temperature at T m = 282.8 ◦C then followed by degradation at Td = 318.6 ◦C. The Tg of both samples, DP-BC and BC-NC disappeared or became difficult to detect because of the partial removal of the amorphous regions.

**Figure 3.** Differential Scanning Calorimetry (DSC)-Thermograms of: 1. BC; 2. depolymerized cellulose, DP-BC; 3. extracted nanocrystalline cellulose, BC-NC.
