The curing reaction of epoxidized methyl esters of corn oil with Diels–Alder adducts of resin acids. The kinetic study and thermal characterization of crosslinked products

Abstract

The methyl esters of corn oil (COE) obtained by the optimized transesterification reaction using Ba(OH)2 as catalyst, in presence of diethyl ether as solvent were converted in monomer by in situ epoxidation using peracid method (H2O2/acetic acid solutions). The epoxidation was carried out in presence of Amberlite IR 120H as catalyst and cyclohexane as solvent, at molar ratio 0.5/1.5/1 (acetic acid/hydrogen peroxide/ethylenic double bonds) resulting epoxy methyl esters with an epoxide number (E.N.)=0.39mol100g−1).The kinetic analysis of the curing reaction of epoxidized methyl esters of corn oil (ECOE) with Diels–Alder adducts of resin acids (D–A) and thermal characterization of crosslinked products were achieved using nonisothermal differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The obtained data were processed using the Thermokinetics software (Netzsch). Depending on the chemical structure of curing agent, the crosslinking and thermal degradation reactions have took place in three steps. Taking into account of the chemical structure of the evolved gases obtained at the thermal decomposition and identified with the FT-IR and MS techniques, a schematic mechanism for the thermal degradation process was proposed.