# Integrating Cork Biochar as a Green Filler via Photopolymerization
## 3 Results and Discussion
### Thermal Analysis of Cork Biochar-Based Composites
#### 3.2.2 Differential Scanning Calorimetry Analysis  
As is well known, DSC is a powerful technique for analyzing the thermal properties of materials. It measures the difference in heat flow between a sample and a reference material as a function of temperature. DSC analysis offers a comprehensive understanding of CBPCs, allowing for informed decisions regarding the selection of materials and the processing parameters for 3D printing. The photocurable resin is a type of photopolymer that can be used in comparison with heat-resistant polymers. While the idea of glass transition also relates to thermosetting materials; in this case, the alterations in the properties during the glass transition are not significant. However, DSC analysis can still provide valuable information about the transition temperatures and thermal behaviors of photocurable CBPCs.  
Regarding the DSC of this work, Figure 4 shows the DSC curves for the neat resin and CBPCs printed. The DSC curves show four differentiated points, as shown in Figure 4A. For better clarity in visualizing these temperature ranges, Figure 4B-D display these ranges separately.  
The first one (No. 1 Figure 4B), located at the beginning of the DSC analysis, around \(\sim\)40 \({}^{\circ}\)C, can be attributed to the heat deflection temperature (HDT) of the photocurable resin. This endothermic peak was observed in all CBPCs because the resin matrix was the same. The second highlighted area (No. 2 Figure 4B) in the DSC graph, which occurs in the temperature range of 80-260 \({}^{\circ}\)C. In this range, a glass transition (Tg) characteristic of the amorphous region of the polymer occurs. The DSC graph shows that this amorphous region is more pronounced for samples with a higher biochar content, indicating greater heterogeneity of the material, which will unequivocally affect both the thermal and me  
Figure 4: DSC of cork biochar photopolymer composites and neat photocurable resin. Overview of (**A**) stages 1 and 2 (**B**), stage 3 (**C**), and stage 4 (**D**).  
chanical properties. The endothermic peak around 310 \({}^{\circ}\)C, (No. 3 Figure 4C), which is present in all CBPCs and in the pristine resin, is attributed to the fusion temperature (T\({}_{\text{m}}\)). The presence of this peak confirms the existence of a crystalline phase in the composites. The next area of interest (No. 4 Figure 4D) occurs at a high temperature, around \(\sim\)450 \({}^{\circ}\)C. This peak is directly linked to the decomposition of the photopolymer resin, which acts as a matrix in the developed CBPCs. This high-temperature endothermic phenomenon occurs due to the extensive cross-linking present in photopolymer resin, which results in highly interconnected structures that require high decomposition energy.  
It should also be noted that no secondary polymerization reactions of the monomers of the photocurable resin were observed, as has been reported on other occasions for this type of composite [44; 45; 46]. Thus, subsequent curing with a UV chamber was effective for completely curing the photocurable resin. The exothermic peaks around \(\sim\)500 \({}^{\circ}\)C is attributed to the final mass loss due to total photocurable resin bond rupture.