Influence of different type of impermeable phase on the permeability of PLA films: Nanofillers versus crystalline phase

Different amorphous PLA-based nanocomposites series allowing to vary the nanofiller shape from spherical (hydrophobic/hydrophilic silica, silver), to tubular (halloysites) and lamellar (montmorillonite, graphene) have been prepared for filler content up to 15 vol%. In parallel, a semi-crystalline PLA films series has been prepared by annealing amorphous PLA films from the glassy state with the aim to achieve different degree of crystallinity. The polymer chains mobility and the impermeable domains (either filler domains or crystalline phase) contained in each membrane have been characterized in detail. Membranes water vapor and oxygen permeability coefficients have been determined with the aim to evidence the governing factors for barrier properties. For nanocomposite membranes, the matrix microstructure and chain mobility were not significantly affected by the addition of fillers, so the barrier properties were mainly governed by the filler domains size and dispersion. For semi-crystalline membranes, the increase in crystallinity led to a decrease of the amorphous chains mobility ( MAF ) which was found to also influence the permeability. Theoretical models were used to describe the evolution of the experimental relative permeability and an equivalence diagram was proposed to have a direct comparison of the effect of fillers and crystallinity on the permeability. • A wide range of PLA-based nanocomposites films were prepared by melt-blending. • Semi-crystalline PLA films were obtained by annealing at 110 °C and 120 °C. • The factors governing the barrier properties were identified for each film series. • Permeability models were adapted to each membrane series. • An equivalence diagram was proposed to compare crystallinity and fillers effects.