Tuned flexibility with phenethyl esters plasticized polylactic acid

This study explores improving polylactic acid (PLA) by incorporating phenethyl-based plasticizers. PLA is a biobased polymer that tends to be rigid and has limited flexibility. To address this, 20 wt% phenethyl esters were added through extrusion and injection molding. These esters are formed by esterifying carboxylic acids of various chain lengths with phenol, and both reactants can be sourced from nature, making this a sustainable approach. Including phenethyl plasticizers greatly increased PLA's elongation at break from 3.4 % to over 130 %, though tensile strength fell from 70.5 MPa to between 20 and 25 MPa. This change was evident in the fracture surfaces, which showed signs of plastic deformation. Thermal and thermomechanical tests revealed a lower glass transition temperature, improving chain mobility and allowing PLA to become ductile at room temperature. Although initial thermal degradation began at a lower temperature, the maximum degradation temperature rose slightly, suggesting enhanced thermal stability due to possible antioxidant effects of the plasticizers. Regarding shape memory, phenethyl plasticizers improved the recovery rate of the samples, expanding potential applications. Overall, these findings demonstrate the effectiveness of phenethyl-based plasticizers in improving PLA's flexibility and shape memory behavior, making it a more versatile material.