Bio-based thermosetting epoxy foams from epoxidized soybean oil and rosin with enhanced properties

Bio-based thermosetting epoxy foams were synthesized via an epoxide ring opening reaction of epoxidized soybean oil (ESO) with fumaropimaric acid (FPA) by using N, N-dimethylbenzylamine as the catalyst and sodium bicarbonate as the foaming agent. The reactivity of the ESO/FPA polymeric matrix became stronger as the proportion of FPA increased. Thermal gravimetric (TG) analysis showed that these thermosetting epoxy foams had high thermal stability. The introduction of the rigid hydrogenated phenanthrene ring structure of FPA improved the viscosity of the ESO/FPA polymeric matrix and the cell wall structure of the foams. Therefore, the apparent density of foams decreased from 361 to 231 kg/m3 with the increase in FPA content in the ESO/FPA polymeric matrix. The compressive modulus (E*) and compressive strength (σc) of the foams improved due to the rigid hydrogenated phenanthrene ring structure of FPA. Furthermore, the foam could be adjusted to become flexible foam or rigid foam by changing the molar ratio of the ESO/FPA polymeric matrix. Foams with low apparent density, high porosity, and closed cells had a lower thermal conductivity coefficient which decreased to 0.031 W/(m·K).