# Emulsion Polymerization of Tung Oil-Based Latexes with Asolectin as a Biorenewable Surfactant
## 3 Results and Discussion
When comparing the peak max temperatures in Table 1, there is an apparent trend of decrease in the temperature with increases in the percentage of tung oil in the sample for samples containing up to 70 wt.% of oil. This behavior could be related to the overall number of carbon-carbon double bonds per monomer molecules. With increasing amounts of tung oil, there is a natural increase in the number of carbon-carbon double bonds that remain unreacted in the resin after cure. With a larger number of carbon-carbon double bonds, it is expected that the residual polymerization during the DSC experiments will start more easily, requiring a lower temperature. This trend, however, doesn't hold true for the sample containing 80 wt.% of tung oil, which exhibits a slightly higher peak max than the sample with 70 wt.% of tung oil. At this stage, after repeating these experiments three times and preparing new samples with consistent results, it is unclear why the sample containing 80 wt.% of tung oil exhibits a different behavior than the other ones. The answer could be in micro-phase separation phenomena happening at a very small scale within the sample, but further investigation would be needed in order to fully understand this behavior. Overall, the DSC results suggest that the sample containing 40 wt.% of tung oil is the one with the highest extent of polymerization after the 24 h curing process, but the implementation of a post-cure step is needed for full polymerization of the sample. In a previous work [13], it had been demonstrated that the bulk polymerization of a resin with the same monomer composition as the sample containing 40 wt.% of tung oil had been completed after heating at 140 \({}^{\circ}\)C for 2 h and 50 min. Therefore, in order to obtain a completely cured system, a post-cure step at 140 \({}^{\circ}\)C was implemented here after drying the emulsions. DSC was used to assess any residual cure in the dried emulsions after post-curing at 140 \({}^{\circ}\)C for 1.5 h and 2 h (Figure 7). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Tung Oil (wt.\%)** & **Enthalpy (J/g)** & **Peak Max (\({}^{\circ}\)C)** \\ \hline
40 & 50 & 168 \\
55 & 63 & 160 \\
70 & 97 & 155 \\
80 & 99 & 159 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Enthalpy associated to exothermic peak and peak max temperatures for differential scanning calorimetry (DSC) curves of products containing 40 wt.%, 55 wt.%, 70 wt.%, and 80 wt.% of tung oil. Figure 7: DSC curves of dried emulsions containing 200 mg of total monomer weight with 40 wt.% of tung oil (**A**) before post-cure, (**B**) post-cured at 140 \({}^{\circ}\)C for 1.5 h, and (**C**) post-cured at 140 \({}^{\circ}\)C for 2 h.  
When comparing the DSC curves of samples post-cured for 0 h, 1.5 h, and 2 h (Figure 7), it becomes evident that the exothermic event at approximately 160 \({}^{\circ}\)C decreases with post-cure time. Indeed, the peak is obvious and prominent in the sample that wasn't post-cured (Figure 7A). After a post-cure time of 1.5 h (Figure 7B), the peak is very subtle. When the sample is subjected to a post-cure of 2 h (Figure 7C), no peaks can be detected at 160 \({}^{\circ}\)C. The appearance of a change in the baseline at approximately 70 \({}^{\circ}\)C for the post-cured samples (Figure 7B,C) may be indicative of a glass transition temperature. The absence of considerable exothermic peaks after a post-cure of 2 h suggests that no residual cure takes place during the DSC experiment, indicating that the polymerization process is complete. Therefore, a post-cure step of 2 h at 140 \({}^{\circ}\)C is crucial in order to complete the polymerization of the system. Raman spectroscopy was also used to verify the completion of the reaction after a 2 h post-cure at 140 \({}^{\circ}\)C (Figure 8). The spectra corresponding to asolectin, tung oil, and BMA components (Figure 8A-C) exhibit a peak in the 1630-1650 cm\({}^{-1}\) range corresponding to C=C streches.