Synergistic effect of lactic acid oligomers and laminar graphene sheets on the barrier properties of polylactide nanocomposites obtained by the in situ polymerization preincorporation method

Nanocomposites of polylactide (PLA) and functionalized graphene sheets (FGS) were obtained via melt compounding. Preincorporation of the FGS fillers into lactic acid oligomers (OLLA) by in situ melt polycondensation was performed with the aim of improving the FGS dispersion and distribution into the polymeric matrix. To evaluate the effect of the preincorporation step, a comparison with direct addition of the filler to the melt mixing process was carried out. Addition of OLLA and FGS led to enhanced better barrier properties. Specifically, reductions of up to 45% and 41% in oxygen and water vapor permeability were achieved, respectively. Mechanical and electrical properties of the PLA and its nanocomposites were also studied and correlated with both the addition of oligomers and the incorporation method.