## 3 Results and Discussion
### Microwave Cure in the Presence of CNTs  
One of the most common limitations for the preparation of good CNT composites is the tendency for agglomeration and precipitation of this carbon species in a variety of solvents. It can be seen in Figure 4, however, that a negligible precipitation of CNTs is observed after 60 min of its suspension in tung oil and in the crude resin (Figure 4). When DMSO is used as the solvent, CNTs start precipitating almost instantly after suspension, and the majority of CNTs have completely precipitated after 60 min (Figure 4). Besides the higher viscosity of tung oil in comparison to DMSO, which helps to keep the CNTs suspended, it is believed that the polarity of the solvent greatly affects its interaction with the CNTs. In the case of triglycerides, the long chain fatty acids confer a strong non-polar character to the molecule, which favors van der Waals interactions with CNTs, helping to achieve a good dispersion for at least 60 min in the crude resin. In this project, achieving a good dispersion of CNTs in vegetable oil is crucial for maximizing the heat transfer from CNTs to the resin under microwaves. As indicated in Figure 4 and as suggested by the examination of composites after the cure (Figure 5--discussed later in the text), the CNT suspensions generated in this work are stable enough for sufficient time to allow for consolidation of the thermoset, potentially resulting in a composite with well-dispersed CNTs. When the initiator for the cationic polymerization is added to the crude mixture of co-monomers and CNTs, gellation happens within 30 min, potentially maintaining the original suspension of CNTs. During the subsequent cure stages, the polymer is consolidated and a final material, which most likely contains evenly dispersed CNTs, is obtained. Indications of a good CNT dispersion in the final composites can be seen in Figure 5.  
The extraordinary heat generated by the microwave irradiation of CNTs is the result of localized Joule heating from the interaction of RF electromagnetic waves and the nanostructured carbon material. Table 1 shows the heating rates obtained for suspensions of CNTs in tung oil irradiated under different microwave powers. As expected, an increase in microwave power results in an increase of the heating rates, regardless of the CNT concentration (Table 1). Moreover, for microwave powers between 100 and 500 W, increasing the CNT concentration results in an increase of the heating rates. It is interesting to notice, however, that a greater increase in the heating rate with CNT concentration, in proportional terms, is observed at lower powers. For instance, when irradiated at 100 W, the measured heating rate of a  
Figure 3: Differential scanning calorimetry (DSC) curves of tung oil-based thermosetting resins cured for 1.5 h, 3.5 h, 5.5 h, and 6 h at 140 \({}^{\circ}\)C. The resin is composed of 70 wt % of tung oil, 15 wt % of DVB, 10 wt % of ST, 3 wt % of soybean oil, and 2 wt % of BF\({}_{3}\cdot\)OEt\({}_{2}\). suspension with 0.25 wt % of CNT is approximately 1.8 times higher than that of pure tung oil (Table 1). At 500 W, the heating rate of a suspension with 0.25 wt % of CNTs is only approximately 1.3 times higher than that of pure tung oil (Table 1). The heating rates discussed here were determined in a short time interval in comparison to the cure of the tung oil resins discussed next. It is possible, therefore, that over the course of the extended cure times under microwaves, the average heating rates may differ from the ones reported in Table 1. However, the results in Table 1 are still representative of the effect of adding CNTs to triglyceride-based resins cured under microwaves.