Résumé
The objective of the present work was to develop fully bio-sourced and biodegradable composite materials based on polyhydroxybutyrate (PHB) and hemp fibers. It is well-known that the improvement of the final functional properties of composite materials is not only related to the filler content and intrinsic properties of constituents, but also to the filler dispersion state and to the properties at the filler/matrix interface. Hence, the lack of favourable interactions between the apolar PHB matrix and the polar hemp fibers has been overcome by adding a green compatibilizer which was previously synthetized using a solvent-free process, i.e. reactive extrusion. The modulation of the extrusion processing conditions (screw profile and speed) was tested in combination with the previous compatibilizing route in order to optimize the performances of the materials. The impact of processing and formulation on the structure and thermal properties of biocomposites (filler content of 20 wt%) has been discussed in relation to their mechanical properties and water vapour sensitivity. A strong nucleating effect provided by the fibers has been highlighted, making it unnecessary the recourse to mineral nucleating agents. Mechanical performances exhibited by the materials revealed a fiber-matrix load transfer, confirming the effectiveness of the prepared compatibilizer.