Open Volumes Structure and Molecular Transport in Biopolymer Nanocomposites

We discuss gas barrier mechanisms in biopolymer nanocomposite in which fillers of different natures and concentrations are added. The kinetics of gas transport is studied by gas phase permeation techniques and free volumes are analyzed by positron annihilation lifetime spectroscopy. Gas barrier properties of two biopolymer nanocomposite films are presented in relation to their free volume. The first film is poly(3-hydroxybutyrate-co-3- hydroxyhexanoate) (PHBH) containing 0.25 wt% of graphene oxide (GO) filler nanoparticles. The second film is poly(lactic acid) (PLA) in which cellulose nanofibrils have been dispersed with content from 4.1 to 12.4 vol.%. It is shown that in both biopolymer films the filler addition improves their gas barrier properties but with different mechanism.