## 3 Results and Discussion
### Cure Evaluation  
In order to establish an optimum cure schedule for the fatty acid resins prepared, the cure evolution of a crude resin containing 50 wt % of tung oil fatty acids, 30 wt % of BMA, and 20 wt % of DVB was monitored through dielectric analysis (DEA) at different temperatures as shown in Figure 5A, where the log of ion viscosity (an artificial property derived from the permittivity of the resin) is plotted against time at each chosen temperature. This resin composition was selected based on previous studies with similar bio-based systems [12]. The initial decrease in ion viscosity observed in the first 50 min of each run (Figure 5A) corresponds to the initial increase in temperature before polymerization starts. Indeed, the increase in temperature prior to extensive polymerization leads to greater molecular mobility, which translates into a decrease in ion viscosity (Figure 5A). At approximately 50 min, the polymerization process reaches a significant rate, resulting in an increase in ion viscosity due to a decrease in molecular mobility, as the crosslinked polymer network grows. Once the ion viscosity plateaus, it is accepted that no further changes occur in the material's electrical and physical properties, indicating cure completion. When the fatty acid resin is cured at 140 \({}^{\circ}\)C, a significant amount of shrink cracks can be easily noticed in the sample, indicating an inappropriate cure temperature. Additionally, the DEA curve obtained at 140 \({}^{\circ}\)C (Figure 5A) displayed a secondary decrease in ion viscosity at approximately 12 h, which could be attributed to exposure of the DEA sensor to air after formation of shrink cracks in the polymer, affecting the permittivity measured. For the DEA curve of the fatty acid resin cured at 120\({}^{\circ}\)C (Figure 5A), the ion viscosity continuously increases throughout the duration of the experiment (20 h). In order to obtain a clearer comparison between the cure at 120 and 130 \({}^{\circ}\)C, the derivative of ion viscosity with respect to time was plotted against cure time in Figure 5B. Close inspection of Figure 5B reveals that the derivative approaches zero (indicating the change in electrical and physical properties is zero and the cure is completed) at approximately 18 h (dashed line added as a guide to the eye, Figure 5B) when the resin is heated at  
Figure 5: (**A**) DEA curves of fatty acid resin cured at 120, 130, and 140 \({}^{\circ}\)C for 20 h; (**B**) Derivative of the DEA curves of the fatty acid resin cured at 130 and 120 \({}^{\circ}\)C with respect to time. 130 \({}^{\circ}\)C. When the resin is heated at 120 \({}^{\circ}\)C, the derivative of the DEA curve never reaches zero for the duration of the experiment, indicating an incomplete cure after 20 h (Figure 5B). A comparison of the Raman spectra of a crude fatty acid resin and a cured sample (Figure 6A) provides further evidence that cure completion was achieved for the fatty acid resin after heating at 130 \({}^{\circ}\)C for 18 h. Indeed, the presence of a signal at approximately 1630 cm\({}^{-1}\) in the spectrum of the crude resin (Figure 6A) is indicative of unreacted carbon-carbon double bonds from the various resin components. That signal is absent in the spectrum of the cured resin (Figure 6A), indicating that the polymer was fully cured as previously supported by the DEA results. In order to validate the DEA and Raman results and to confirm cure completion, a tung oil fatty acid resin cured at 130 \({}^{\circ}\)C for 18 h was subjected to a DSC experiment (Figure 6B). The same cure schedule was applied to similar resins prepared from tung oil and from tung oil methyl esters. The DSC curves of all three samples are presented in Figure 6B(a-c). The DSC results indicate that the cure schedule used is adequate for tung oil and fatty acid resins since no exothermic peaks are observed for these two samples (Figure 6B).