The novel potential epoxy resins, epoxidized soybean oil (ESO) and epoxidized castor oil (ECO), were synthesized and characterized. The cationic polymerization of ESO and ECO with a latent thermal catalyst, N-benzylpyrazinium hexafluoroantimonate (BPH), was initiated at 80 and 50degreesC, respectively. The cured ECO samples showed a higher T-g and lower coefficient of thermal expansion that those of ESO, due to the higher intermolecular interaction in the ECO/BPH system.