Effect of an organo-modified montmorillonite on PLA crystallization and gas barrier properties

Amorphous nanocomposite films were prepared from melt-blending of polylactide (PLA) and an organo-modified montmorillonite (O-MMT). The filler amount was varied in the range from 0 to 8 wt.%. The gas permeability decrease measured as a function of the clay content was accurately described by Nielsen law. The influence of O-MMT was studied on PLA non isothermal and isothermal crystallisation. The incorporation of small amounts of OMMTs within PLA favoured the polymer matrix crystallisation by decreasing the cold crystallisation temperature for heating thermal treatments and the crystallisation half-time for isothermal ones. Optimised annealing conditions allowing to obtain high crystallinity degrees combined with high melting crystalline lamellae were proposed. The permeability decrease observed for the annealed nanocomposite with respect to the amorphous reference PLA film was shown to result from the respective contribution of the clays and the crystalline phase.

Research highlights
► We analyse and model the permeability decrease measured on amorphous nanocomposite.
► We examine the influence of clay on PLA crystallisation.
► We propose annealing conditions for optimised morphology and gas barrier properties.
► We discuss and model the permeability of semi-crystalline nanocomposites.