Synthesis of bio-based hydrogel from epoxidized palm oil catalyzed by fluoroantimonic acid hexahydrate

Abstract

An epoxidized palm oil-based hydrogel (HPEPO) was synthesized by using ring opening polymerization (ROP) in the presence of fluoroantimonic acid hexahydrate catalyst (HSbF6·6H2O), followed by chemical hydrolysis catalyzed with sodium hydroxide (NaOH). The structural characterization and thermal property of synthesized hydrogel were studied. The successful ring opening of EPO was confirmed by disappearing of epoxy functional group at 833 cm-1 in the Fourier transform infrared (FTIR) spectrum. The formation of HPEPO was detected at 2500 cm-1 to 3400 cm-1 which represents the O-H stretching of carboxylic acid. Based on nuclear magnetic resonance (NMR), the disappearance of epoxy ring group at 2.8 - 3.0 ppm has indicated the completely reacted oxirane ring with the presence of peak at 3.7 ppm corresponded to hydroxyl group. Meanwhile, HPEPO exhibited low thermal stability by having melting temperature around 45 °C to 60 °C in Differential scanning calorimetry (DSC) and as showed by the great percentage of weight loss in thermogravimetric analysis (TGA) curve. However, the formation of char residue was slow, probably due to the formation of hydrogen linkages in hydrogel.