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"Les polyhydroxyalcanoates  PHAs    tudi  s sont des polyesters biod  gradables et biocompatibles synth  tis  s par fermentation bact  rienne de produits d  riv  s de la canne    sucre  Ces biopolym  res pr  sentent notamment une bonne rigidit   et un taux de cristallinit   tr  s important  Cependant  leur comportement m  canique fragile et leur faible stabilit   thermique limitent encore leur d  veloppement  L   laboration de nano-biocomposites  i e  l incorporation et la dispersion de charges de taille nanom  trique telles que les montmorillonites dans la matrice PHA vise donc    pallier ces d  ficiences  L analyse des relations proc  d  -structure-propri  t  s ont montr   que les facteurs cl  s contr  lant l   laboration de ces mat  riaux nanostructur  s sont l affinit   polym  re-argile  le taux de charge et la voie d   laboration  voie  solvant  vs   fondu    Par ailleurs  une   tude sp  cifique a montr   que les organomodifiants utilis  s pour compatibiliser le polym  re et la charge  et dans une moindre mesure  les r  sidus de fermentation  affectent la stabilit   thermique et thermom  canique des PHAs  Diff  rentes approches  enrobage des feuillets d argile par greffage de biopolyester  redispersion de masterbatch   ont donc   t   explor  es afin de limiter la d  gradation de la matrice mais   galement d am  liorer la dispersion de la charge et de mieux compatibiliser la charge et la matrice  Ces   tudes ont montr   que la dispersion directe d un faible taux de Cloisite  30B    3 pds  dans le PHA    l   tat fondu pr  sente le meilleur compromis en terme de d  gradation limit  e  de qualit   de dispersion et donc de propri  t  s du mat  riau final    Polyhydroxyalkanoates  PHAs  are biodegradable and biocompatible polyesters produced from renewable resources by bacterial fermentation  These biopolymers are stiff and highly crystalline  Nevertheless  they are not fully competitive compared to conventional polymers since they exhibit brittleness and poor thermal stability  Therefore  to improve their properties  PHA-based nano-biocomposites were prepared by adding nano-sized fillers such as montmorillonites  a clay layered silicate   The process-structure-properties relationships have been investigated  They have shown that the polymer-clay affinity  the filler content and the elaboration route  solvent vs  melt intercalation  are key factors for elaboration of these nanostructured materials  Moreover  a specific study evidenced that organomodifiers used as polymer-clay compatibilizers and  in a less extent  the fermentation residues affect the thermal and thermo-mechanical PHAs stability  Different approaches  biopolyester grafting on the clay surface  masterbatch route    were thus considered to limit the matrix degradation  but also to improve the clay nanodispersion and the polymer-clay affinity  This work has revealed that melt mixing of less than 3 wt  of Cloisite  30B with PHA leads to better results in terms of limited degradation  clay dispersion and thus properties of the final material    STRASBOURG-Sc  et Techniques  674822102    Sudoc   Sudoc   France   FR"
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