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Composites composed of polyesters, poly(butylene succinate) (PBS) or poly[(butylene succinate)-co-(butylene adipate)] (PBSA), and 5 wt% of montmorillonite (CNa) or organo-modified montmorillonite (C30B) were melt-processed and transformed into films by either compression-molding or extrusion-calendering. XRD, rheological measurements and TEM images clearly indicated that films containing CNa are microcomposites, while nanocomposites were observed for those containing C30B. Using Flash DSC, it was possible, for the first time, not only to measure the heat capacity step at the glass transition of these two materials in their amorphous state, but also to investigate whether the preparation technique influenced the Rigid Amorphous Fraction (RAF) in our PBS- and PBSA-based nanocomposites. In this work, we have successfully shown the correlation between the microstructure of the films and their barrier properties, and especially the role played by the RAF. Indeed, the lowest permeabilities to gases and to water were determined in the films containing the highest RAF in both PBS- and PBSA-based materials. [ABSTRACT FROM AUTHOR]

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB-co-4HB) films containing various contents of organo-modified montmorillonite C30B nanoclays were prepared by melt intercalation. Wide angle X-ray diffraction measurements and transmission electron microscopy observations evidenced aggregated and intercalated structures with individual nanoclay platelets in the nanocomposites and an orientation of nanoclays. Differential scanning calorimetry measurements showed that the nanoclay did not influence the crystalline structure of the matrix because it is mainly located in the polymer amorphous phase. The influence of the filler on the barrier properties of the film was evaluated by water diffusion, gas permeation (CO2, N2, O2) and liquid water sorption measurements. A decrease of the N2 permeability was measured due to the tortuosity effect of the filler associated with a decrease of the solubility within the matrix. The influence of the filler was more marked for O2 due to the larger decrease of O2 solubility. In contrast, the CO2 permeability increased whatever the filler content because of a facilitated transport mechanism due induced by the presence of quaternary ammonium cations on the C30B surface. The decrease of the water permeability with the filler was explained by a competition between the kinetic (diffusivity) and thermodynamic (solubility) contributions defining the permeability process. [ABSTRACT FROM AUTHOR]

Poly(vinylidene difluoride) (PVDF) displays attractive ferroelectric/piezoelectric properties and its polar β-crystals are specifically targeted for achieving electroactive applications. However, their direct crystallization from the melt state represents a challenging task that has never been addressed using melt-state processes. The use of poly(methyl methacrylate) (PMMA) is herein investigated to promote the PVDF polar β-phase using melt-blending and extrusion-calendering technologies. The presence of the β-phase is here confirmed by ATR-FTIR and WAXS experiments with blends at a PMMA content as low as 5 wt%. The key role of PMMA for the β-phase crystallization from the melt state was unambiguously highlighted with the help of Flash DSC experiments in non-isothermal cooling mode from the melt state. PMMA is able to efficiently shift the α-to-β crystal transition to lower cooling rates (>100-200 °C s-1), making the achievement of the PVDF polar β-phase for these blends compatible with conventional processing tools. A crystal phase diagram is proposed for the PVDF/PMMA blends to highlight the dual effects of both PMMA and cooling rate on the PVDF crystallization during melt-processing. Ferroelectric properties were even observed for the blends containing PMMA up to 10 wt% with the highest remanent polarization obtained at 5 wt% PMMA. After 10 wt% PMMA, a progressive transition from ferroelectric to pseudo-linear dielectric behavior is observed more likely due to the presence of PMMA in the interlamellar amorphous phase of the polar PVDF spherulites as shown by SAXS experiments. In this work, we successfully demonstrated that PMMA plays a key role in the crystallization of PVDF polar crystals from the melt state, enabling large-scale and continuous extrusion processing of PVDF-based materials with attractive dielectric properties for sensing and harvesting applications.