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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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A study concerning the incorporation of sepiolite in blends of biopolyesters (PHBV/PLA) to obtain clay/ polymer nanocomposites (CPN) was performed to improve the gas barrier performance of the final materials and achieve a well dispersed morphology by means of an increase in the melt viscosity during melt blending. The latter is relevant to increase the stability of the PHBV sheets during thermoforming. The samples were analyzed using scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile tests at room and high temperatures, dynamo-mechanical thermal analysis in torsion mode (DMTA), oscillatory rheometry with a parallel plate setup, Vicat softening temperature system and oxygen barrier properties. The resulting Sepiolite/PHBV/PLA nanocomposites not only improved the compatibility between the biopolymers and reduced the oxygen permeability, but also improved the mechanical properties at room temperature, showing an increase in the elongation at break, as well as increasing the rigidity and stability of the CPN at higher temperatures, which could make them very attractive for uses in thermoforming applications for food packaging. POLYM. COMPOS., 00:000-000, 2017.

The influence of the incorporation of tris(nonylphenyl) phosphite (TNPP) as a chain extender on the morphology and thermal stability of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV)/clay nanocomposites obtained by melt mixing has been studied. Two different clays have been used: a laminar organomodified montmorillonite (Cloisite® 30B) and a tubular unmodified halloysite (HNT). The morphology of the so‐obtained nanocomposites has been assessed by transmission electron microscopy, scanning electron microscopy, and wide angle X‐ray diffraction, showing a partially exfoliated structure for PHBV/Cloisite® 30B nanocomposites, as well as a good dispersion of the HNT in the PHBV matrix. The crystallinity of the resulting nanocomposites, determined by DSC, does not change when clays or TNPP are added. An increase in the onset temperature of thermal degradation of PHBV has been obtained with the addition of TNPP, as determined by TGA. With regard to the effect of the nanoclays on the thermal stability of PHBV, the onset temperature of the PHBV/HNT nanocomposites is higher than that of the pure PHBV, while this trend is not observed for the nanocomposites containing Cloisite® 30B. The addition of TNPP to the PHBV/Cloisite® 30B nanocomposites resulted in an improved thermal stability; however, for the HNT nanocomposites, the TNPP does not seem to have a significant effect. For all studied systems, it was shown that the variation of mechanical properties of the nanocomposites is due to the reinforcing effect of the nanoclays on the PHBV matrix. In the case of TNPP, it is due to the increased molecular weight and formation of a long‐chain branching structure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42390.