Ferulic acid derivatives used as biobased powders for a convenient plasticization of polylactic acid in continuous hot-melt process

Plasticizers are additives used to soften polymers, but most of them are oily or waxy and are difficult to process in a continuous hot-melt process. The plasticizing effect of four functionalized ferulic acid derivatives designed with controlled solubility parameters was investigated upon the study of both the thermal stability and the mechanical properties of polylactic acid (PLA) blends. The synthesized powders were incorporated into PLA through a continuous hot-melt process (extrusion) allowing the derivatives to turn from crystalline to an amorphous state. Such phase transition permitted the derivatives to act as plasticizers, reaching a reduction of the Young's modulus of PLA by 40% for one of the derivatives blended at 20 wt%. Another derivative decreased the glass transition of the PLA from 56.6 degrees C to 26.3 degrees C at the same content. These works demonstrate the interest of using phase transition additives to ease the mixing of efficient plasticizers by hot-melt processing.