## 3 Results and Discussions
### Thermogravimetric Analysis Results (TGA)  
Graphical representations of the mass loss as a function of temperature for the designed polymeric materials are illustrated in Figure 3. The thermal decompositions of the raw SB and HC fillers were also investigated, with the corresponding TGA/DTG curves being plotted in Figure 4.  
Figure 3: TGA/DTG curves for the (**a**,**b**) HC-based materials and (**c**,**d**) SB-based materials in oxidative environment, heating at 10 \({}^{\circ}\)C/min. Generally, wood biomass is constituted mainly by hemicellulose, cellulose, lignin and small percentages of other organic and inorganic extractives [41]. Based on the literature study [42; 43], softwood is composed of 18-38% cellulose, 15-33% hemicellulose and about 30-60% lignin. The TGA/DTG thermograms (Figure 4) of raw SB and HC present several mass losses. The first mass loss observed for both raw SB and HC is presented from 35-40 \({}^{\circ}\)C to 120-140 \({}^{\circ}\)C and is attributed to the evaporation of the absorbed water. Thermal treatment applied to obtain the HC particles influenced the mass loss at this stage, which is only 1%, compared to the raw SB, which loses about 7%. TGA analyses (Figure 4) show that the thermal stability of SB is divided into two distinct and complex stages, while in the case of HC, this behaviour appears as a broad and complex degradation mechanism step. According to the literature [44; 45; 46], the thermal behaviour of the lignocellulosic biomass is characterized by a two-step process, the first one (200-370 \({}^{\circ}\)C) being attributed to the depolymerization of hemicellulose and the breaking of glycosic bonding of cellulose, while the main thermal degradation stage (340-370 \({}^{\circ}\)C) is characteristic of the degradation of \(\alpha\)-cellulose. Due to its complex structure, the thermal degradation of lignin takes place at a large range of temperatures (200-500 \({}^{\circ}\)C) interposing with that of cellulose and hemicellulose. For the raw SB, the second degradation stage is ranged between 170 and 390 \({}^{\circ}\)C, with a mass loss of about 56%, while the cellulose and lignin degradation for this natural filler appears as a double broad peak from 400 \({}^{\circ}\)C to 540 \({}^{\circ}\)C, having a mass loss around 37%. Knowing that hemicellulose are less thermally stable than cellulose and lignin, starting their decomposition at about 160 \({}^{\circ}\)C [47], the thermal treatment at 280 \({}^{\circ}\)C applied for HC manufacturing led to the degradation and partial removal of the hemicellulose. Therefore, the thermal decomposition of raw HC appears as a single broad peak, ranged from 250 \({}^{\circ}\)C to 580 \({}^{\circ}\)C, with a mass loss of -95%. Studying the DTG curves (Figure 3b,d), it can be seen that the thermal decompositions of the ELO-based resins and composites are divided into two major stages. Before the main degradation step, a small mass loss of about 3-6% appears for all the systems in the temperature interval of 140-260 \({}^{\circ}\)C, typical for the gradual evaporation of absorbed water and the release of volatiles present in the materials' compositions. The first major degradation step shows up as a complex exothermic peak with a double peak shoulder. This principal thermal step is ranged in the 260-500 \({}^{\circ}\)C temperature interval, with a maximum  
Figure 4: TGA and DTG curves for raw HC (black line) and raw SB (red line). temperature of degradation at about 365 \({}^{\circ}\)C and a mass loss of ~75-90%, and is characteristic of the thermolysis of network structure [48]. The thermo-oxidative degradations take place in the last stage of decomposition, ranged from 500 to 700 \({}^{\circ}\)C with a maximum at ~540-590 \({}^{\circ}\)C, presenting a mass loss of about 7-22%. As can be seen, the thermal stability of the developed materials is improved with the addition of filler; as the amount of HC or SB increases, the mass loss in the first stage decreases and increases in the second, which occurs at higher temperatures.