Esters of Cinnamic Acid as Green Plasticizers for Polylactide Formulations with Improved Ductility

Abstract

[EN] This study demonstrates the potential of different cinnamate esters, namely methyl trans-cinnamate (MC), isobutyl cinnamate (IBC), allyl cinnamate (AC), and ethyl cinnamate (EC), as environmentally friendly plasticizers for polylactide (PLA). Plasticized PLA formulations with a constant nominal wt% of 20 of each plasticizer are compounded in a twin-screw co-rotating extruder and subsequently processed by injection molding. The results show exceptional plasticization efficiency of AC with an increase in elongation at break from 3.9% (neat PLA), up to 339.4% and a remarkable increase in impact strength, thus showing great potential to overcome the main drawback related to PLA intrinsic brittleness. The incorporation of cinnamates in a PLA matrix leads to a decrease in Tg from 61.7 °C down to 36.1 °C for the plasticized PLA formulation containing 20 wt% AC. Thermogravimetry analysis reveals that a slight plasticizer loss occurs during processing, as it happens with other monomeric plasticizers, but this phenomenon does not limit their plasticization efficiency. Therefore, the results obtained in this study confirm the suitability of a new family of organic compounds derived from the esterification of cinnamic acid as green plasticizers for PLA with improved toughness, with comparable, or even superior, ductile properties of typical plasticizers for PLA.