The polyesterification could initially be followed by H NMR, until the newly formed polyester was no longer soluble in chloroform, which occurred after more than 50 minutes of reaction. Even if the 1 H NMR analysis is limited to the initial phase of the reaction, it confirms the direct esterification between two EFA monomers, with the rising signal at 4.07 ppm assigned to the new ester bond. Meanwhile, the depletion of the epoxide signal (2.93 ppm), as well as the formation of a secondary alcohol (3.60 ppm), and the growing signal from the secondary ester bond (4.85 ppm) prove the ring opening esterification. The absence of any signal associated with the epoxide group after only 50 minutes of reaction suggests that in such conditions, the epoxide is consumed leading to the formation of new ester bonds and secondary alcohols. As observed in the FT-IR spectra, the 1 H NMR confirms that the mid-chain unsaturation is not involved in any reaction, with the peaks at 2.02 ppm and 5.36 ppm not being affected by the process. approximately 100 °C and 260 °C, which are not present for PEFA or for the final PEFA film. The former may be explained by moisture uptake during the storage phase, consistent with the presence of free hydroxyl groups in the sample, and the latter by the boiling of more volatile suberin components deriving from the heterogeneity of the sample. Following 3 h and 15 min of thermal treatment, only a smaller signal in the DTG (275 °C) can be identified before the main degradation of the sample. Again, more volatile suberin components are considered responsible for this. For all samples, the main weight loss occurs in a two-step decomposition which peaks at 427 °C and 462 °C. This has been observed in polyesters with a similar structure. The first step is associated with the degradation of the backbone, which leads to the release of volatile products and the production of a carbonaceous char, readily decomposed in the second step. During the synthesis of the PEFA film, the temperature does not exceed 150 °C, thus the components seen to evaporate above such temperature would still be present in the sample. They participate in the esterification reaction, being potentially shorter hydroxy fatty acids or diacids, thus molecules bearing hydroxyl and carboxyl functionalities. This is also evident from the thermal stability of the PEFA film, which has no weight loss before the main degradation. There are no unreacted monomers left, an important feature in packaging materials intended to be used in contact with food, where migration of monomers from the package is unwanted.