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Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was blended with poly(lactic acid) (PLA) using various reactive processing agents in order to decrease its brittleness and enhance its processability. Three diisocyanates, namely, hexamethylene diisocyanate (HMDI), poly(hexamethylene) diisocyanate (polyHMDI) and 1,4-phenylene diisocyanate (PDI), were used as compatibilizing agents. The morphology, thermomechanical properties and rheological behavior were investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile tests, dynamo-mechanical thermal analysis in torsion mode (DMTA) and oscillatory rheometry with a parallel plate setup. The presence of the diisocyanates resulted in an enhanced polymer blend compatibility, thus leading to an improvement in the overall mechanical performance without affecting the thermal stability of the system. A slight reduction in PHBV crystallinity was observed with the incorporation of the diisocyanates. The addition of diisocyanates to the PHBV/PLA blend resulted in a notable increase in the final complex viscosity at low frequencies when compared with the same system without compatibilizers.2

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Poly(3-hydroxybutyrate-co-3-valerate), PHBV, is a bacterial thermoplastic biopolyester that possesses interesting thermal and mechanical properties. As it is fully biodegradable, it could be an alternative to the use of commodities in single-use applications or in those intended for composting at their end of life. Two big drawbacks of PHBV are its low impact toughness and its high cost, which limit its potential applications. In this work, we proposed the use of a PHBV-based compound with purified α-cellulose fibres and a thermoplastic polyurethane (TPU), with the purpose of improving the performance of PHBV in terms of balanced heat resistance, stiffness, and toughness. Three reactive agents with different functionalities have been tested in these compounds: hexametylene diisocianate (HMDI), a commercial multi-epoxy-functionalized styrene-co-glycidyl methacrylate oligomer (Joncryl® ADR-4368), and triglycidyl isocyanurate (TGIC). The results indicate that the reactive agents play a main role of compatibilizers among the phases of the PHBV/TPU/cellulose compounds. HMDI showed the highest ability to compatibilize the cellulose and the PHBV in the compounds, with the topmost values of deformation at break, static toughness, and impact strength. Joncryl® and TGIC, on the other hand, seemed to enhance the compatibility between the fibres and the polymer matrix as well as the TPU within the PHBV.