Influence of Ozonized Soybean Oil as a Biobased Plasticizer on the Toughness of Polylactic Acid

This work aimed to study the mechanism of toughness improvement of polylactic acid (PLA) by using a biobased plasticizer. Ozonized soybean oil (OSBO), acting as a biobased plasticizer, was prepared by the ozonolysis reaction. The functional groups and chemical structure of OSBO were characterized by FTIR and NMR techniques, respectively. Plasticized PLA specimens were prepared by compounding using a corotating twin-screw extruder and sheet forming using a compression molding machine. The influences of OSBO contents, varying from 0 to 15 wt%, on PLA were evaluated via mechanical and thermal testing and morphological analysis. After the ozonolysis reaction, there was an increase in ester groups and the formation of hydroxyl groups in OSBO. With increasing OSBO content, it was found that elongation at break and impact strength tended to increase, whereas tensile strength decreased. The glass transition, crystallization and melting temperatures of PLA continuously decreased as a function of OSBO content. The presence of OSBO enhanced crystallization of PLA. OSBO at low content acted as a plasticizer for PLA, whereas OSBO at 15 wt% formed fine oil droplets acting as an impact absorber by energy dissipation.