RECUPERAÇÃO DE ÓLEO DE SOJA RESIDUAL PARA DESENVOLVIMENTO DE REDE EPÓXI/ÁCIDO CATALISADA POR Al(OTf)3

Abstract

Due to the growing demand for materials that combine high performance with environmental responsibility, this study proposes creating a new generation of innovative polymeric systems. For this purpose, cross-linked thermosets were synthesized from epoxidized virgin soybean oil (ESO) and epoxidized residual soybean oil (RESO) by reacting them with fumaric acid (FMA) in the presence of aluminum triflate (Al(OTf)3) as a catalyst. The influence of Al(OTf)3 content, ranging from 0 to 1.5% by weight, was evaluated, evidencing a significant reduction in curing temperatures—up to 100 °C lower than formulations without catalyst—through the determination of curing enthalpy via DSC under non-isothermal conditions in an inert atmosphere. Additionally, kinetic modeling of the systems was performed by regressing data obtained from four heating rates using the Friedman and Flynn-Wall-Ozawa models (with R2 > 0.96) and the Borchardt-Daniels model (with R2 > 0.99), which allowed for the estimation of key parameters such as activation energy, frequency factor, reaction half-life, and reaction order. In particular, the formulation containing 0.5% Al(OTf)3 demonstrated peak performance, as evidenced by the highest dα/dt values and complete curing below 120 °C, with curing enthalpies of 280 J/g for the ESO-based system and 190 J/g for the RESO-based system. The nonlinear profiles observed in the reaction enthalpies of the systems without catalyst were attributed to the precipitation of unreacted FMA, exacerbated by high heating rates, thermal gradients, and delays in heat transfer, which compromise the uniformity of the cure. Regarding the reaction mechanisms, the results indicated that for catalyst contents up to 0.5%, the models corresponding to consecutive mechanisms (Cnm→An) provided a better fit, while formulations with 1.0% and 1.5% Al(OTf)3 were better described by consecutive mechanisms under simultaneous control of diffusion and autocatalysis (An→Cnm); notably, the compositions with 0.5% catalyst exhibited the greatest thermal stability due to enhanced crosslinking density. Finally, despite the inclusion of Al(OTf)3, degradation of the samples results predominantly in the formation of CO2—accompanied by hydrocarbons, esters, and ethers—without any traces of sulfur, thereby highlighting the environmental safety of the process. This detailed investigation into the kinetics, curing mechanisms, thermal stability, and volatile formation consolidates the technical and scientific viability of these formulations for industrial applications.