Effect of Nanosilica Aggregates/Agglomerates on Functional Properties of Poly(Butylene 2,5-Furandicarboxylate)-Based Nanocomposites

The nanofillers inclusions in poly(butylene 2,5-furandicarboxylate) (PBF)/SiO2 nanocomposites were found to consist of aggregates and agglomerates of nanosilica particles. The estimated density of the nanosilica aggregates/agglomerates attested to the presence of empty spaces within them. The thermal, permeability, mechanical, and viscoelastic properties of PBF/SiO2 nanocomposites were investigated as a function of the nanosilica aggregation status. The analysis of the thermal properties revealed that weak interactions were established between PBF and the nanosilica. Gas permeability was found to be strongly influenced by the morphological features. Oxygen permeability increased with SiO2 content due to the additional free volume introduced by the nanofillers aggregates/agglomerates. In contrast, water vapor permeability decreased as nanosilica content increased in parallel with diffusivity reduction. This behavior was attributed to the filling of the voids within the silica aggregates by bonded water molecules and the consequent more tortuous diffusion path for the free water molecules. Mechanical tests revealed a good load transfer between the PBF matrix and nanosilica, with a progressive increase in elastic modulus, particularly in semi-crystalline samples. In the melt state, the PBF/SiO2 nanocomposites displayed a viscosity increase due to the restriction in polymer chain mobility induced by the nanofillers.