Water sorption behavior of two series of PHA/montmorillonite films and determination of mean water cluster size

International audienceBiodegradable polyester-based films constituted of poly(hydroxyalkanoates) (PHA) were successfully extruded with various Cloisite 30B contents. The morphology was highly dependent on the matrix, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate), the polymer crystalline phase fraction, the matrix/nanoclay interfacial regions as well as the nanoclay content. Water vapour resistance was investigated through sorption kinetics, isotherms, modelling aspect, and diffusivity. A typical sigmoid-shaped isotherm was obtained in every case. It emerges that the nanoclay highly contributed to the increase of water solubility of matrices. The dependence of polymer crystallinity on the affinity of the nanocomposite films for water was highlighted. Thermodynamic and kinetic contributions of the sorption process were also correlated with the film morphology. According to the matrix used, water diffusivity in films was differently impacted by the sorbed water amount. The access of sorbed water molecules within films was examined through a mathematical modelling approach and the deduced mean cluster size of water vs. its activity was corroborated by sorption kinetics

Dielectric relaxations in polyhydroxyalkanoates/organoclay nanocomposites

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Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) based nanocomposites: influence of the microstructure on the barrier properties

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Microstructure and barrier properties of PHBV/organoclays bionanocomposites

International audienceThe impact of organomodified montmorillonite on morphology, thermal and barrier properties of PHBV-based nanocomposites prepared by melt intercalation was investigated. XRD analyses and TEM observations have shown the presence of aggregated and intercalated structures with individual nanoclay platelets and a significant orientation of nanoclays into the nanocomposites. No nucleating effect induced by nanoclays was detected in DSC measurements, which indicates that the crystalline phase of the PHBV copolymer was not impacted. The improvement of barrier properties to gas and water was found to be dependent not only on the dispersion and orientation of nanoclays but also the nature of permeated molecules, the quality of the matrix/nanoclays interface and degradation effects induced during melting process. A competition between kinetic and thermodynamic contributions of the permeation process was highlighted. A dependence of the water diffusion coefficient with water concentration was observed as a result of water plasticization effect

Structure and Barrier Properties of Biodegradable Polyhydroxyalkanoate Films

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