Properties of Bio-based Epoxy Resins from Rosin with Different Flexible Chains

Triglycidyl ester FPAE and glycidyl ethers FPEG1, FPEG2, and FPEG3, listed in order of increasing flexible chain amounts, were obtained from rosin and characterized by 1H nuclear mangetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectroscopy. The effects of a harder dose on cured resin properties were studied by determining the tensile strength and water absorption. The results indicated that the optimum harder dose of the FPEG system was higher than the stoichiometric ratio. The effects of flexible chains on cured resin properties were studied by tensile strength characterization, differential scanning calorimetry, thermogravimetric analysis, water absorption, and acetone absorption. The results showed that the cured resin FPAE1C exhibited the best thermal properties, water resistance, and acetone resistance. FPAEC did not display the best tensile properties, because of its brittleness, but the tensile strength was improved by introducing the flexible chain. Moreover, FPAE, FPEG1, and FPEG2 displayed tensile strength similar to that of petrochemical E44, and FPAE exhibited a high glass-transition temperature (Tg), compared to E44.