Preparation and Characterization of Epoxy Soybean Oil Modified Polylactic Acid Reinforced with Straw Fibers

Natural fiber-reinforced biogenic polymer composites have been promising materials for packaging, furniture, and other applications due to their environmentally friendly and cost-effective characteristics. However, certain properties, including mechanical properties, still need to be improved. In this work, polylactic acid (PLA) was modified with a range of epoxy soybean oil (ESO) concentrations, and straw fibers were added to the plasticized PLA. The functional groups of various compositions were investigated via FTIR and the effects of SF and ESO on the impact, flexural, and tensile intensities were evaluated. The composites’ thermal stability performance was examined via TG and DSC analysis. The results showed that chemical bonds were formed between PLA and ESO, with the possibility of H-bonding between the -OH group on the molecular chains of SF and PLA and the ethylene oxide group of ESO. The mechanical intensity of material can be enhanced after adding a small amount of ESO (< 4%), while the SF addition has the opposite result. The addition of both ESO and straw fibers decreased the thermal transition temperature (Tg, Tc, and Tm) and the degree of PLA crystallinity. Meanwhile, SF was beneficial for improving the thermal decomposition temperature.