The 18-hydroxy-9,10-epoxy octadecanoic acid can undergo a self-catalyzed polymerization which leads to the formation of a cross-linked polyester thanks to its triple functionality. Following direct esterification, the condensation reaction occurs between the hydroxyl group and the carboxylic group of two different monomers. Additionally, it can also undergo a ring-opening esterification, where the epoxide ring is protonated by the COOH leading to the formation of an ester bond and a secondary alcohol (Figure ). The carboxylic group is involved in both reactions; thus, it represents the limiting functionality that inevitably leads to remaining unreacted OH groups. Furthermore, the ratio between the functionality involved in the polyesterification is affected by the known heterogenous nature of the EFA fraction.