# Integrating Cork Biochar as a Green Filler via Photopolymerization
## 3 Results and Discussion
### Mechanical Properties of Cork Biochar Polymer Composites (CBPCs)
#### 3.4.3 Percentage Elongation at Break of CBPCs  
Regarding the elongation at break of the studied CBPCs (Figure 9), the incorporation of cork biochar into the neat photocurable resin drastically decreased the ductility of all the printed CBPCs, and it can be concluded that the CBPCs were more rigid than the neat photocurable resin. The reduction in \(\%\) elongation at break is primarily attributed to the incorporation of cork biochar into the matrix, which restricted the mobility and relaxation of photopolymer chains under tension, leading to lower ductility in the sample. This behavior has been previously reported for composites with carbon-based fillers [57; 58].  
Figure 8: Tensile strength of the photocurable resin and CBPCs. The blue and red bars correspond to the standard deviations and the standard error of the mean, respectively.  
Figure 9: Percentage elongation at break of the photocurable resin and CBPCs. The blue and red bars correspond to the standard deviations and the standard error of the mean, respectively.  
3.4.4. Discussion of the Mechanical Properties of the Cork Biochar-Integrated Materials and Interpretation of the Results  
The data in Table 2 reveal that the mechanical performance significantly declined with increasing biochar content. The elongation at break decreased progressively, indicating reduced material ductility. The tensile strength also decreased considerably from 58 MPa (pure resin) to 14 MPa at \(1.5\%w/w\) biochar, demonstrating a substantial weakening of the material. Additionally, Young's modulus declined as the biochar content increased, suggesting reduced stiffness.  
A typical trend in material mechanics is that a decrease in Young's modulus often corresponds to an increase in elongation at break as the material becomes more flexible. However, in this case, the opposite trend was observed: both [PERSON]'s modulus and elongation at break decreased simultaneously. This suggests that the addition of biochar particles introduces stress concentrators or defects within the matrix, leading to premature failure rather than increased flexibility.  
Despite the reduction in mechanical properties, biochar incorporation may offer other functional benefits that justify its use in specific applications. For example, regarding sustainability and environmental impact, biochar is derived from biomass, making it a sustainable additive that may contribute to eco-friendly material formulations. Another advantage of using cork biochar in some polymer composites is that biochar can enhance thermal stability and barrier properties against moisture or gases, potentially benefiting applications in packaging or insulation. Furthermore, as a bio-based filler, biochar may reduce material costs while providing acceptable performance for non-load-bearing applications.  
If mechanical performance is a primary concern, the observed reductions in strength, elongation, and stiffness may limit the applicability of biochar-based composites in structural or high-performance mechanical applications. Future research should explore strategies to mitigate these drawbacks, such as surface modification of biochar, optimization of filler dispersion, and hybrid reinforcement approaches.  
Overall, although biochar affects the mechanical properties of the resin matrix, its potential benefits in terms of sustainability and functional improvements may justify its use in targeted applications. Further studies are needed to balance mechanical performance with the advantages that biochar offers.