Epoxy Monomers Derived from Tung Oil Fatty Acids and Its Regulable Thermosets Cured in Two Synergistic Ways

A novel biobased epoxy monomer with conjugated double bonds, glycidyl ester of eleostearic acid (GEEA) was synthesized from tung oil fatty acids and characterized by 1H and 13C NMR. Differential scanning calorimeter analysis (DSC) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the curing process of GEEA with dienophiles and anhydrides. DSC indicated that GEEA could cross-link with both dienophiles and anhydrides through Diels–Alder reaction and epoxy/anhydride ring-opening reaction. Furthermore, Diels–Alder cross-link was much more active than the ring-opening of epoxy and anhydride in the curing process. FT-IR also revealed that GEEA successively reacted with dienophiles and anhydrides in both cross-linking methods. Dynamic mechanical analysis and mechanical tensile testing were used to study the thermal and mechanical properties of GEEA cured by maleic anhydride, nadic methyl anhydride and 1,1′-(methylenedi-4,1-phenylene)bismaleimide. Due to the independence between the curing agents, dienophile and anhydride, a series of thermosetting polymers with various properties could be obtained by adjusting the composition of these two curing agents.