Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Poly(propylene carbonate) Blends: an Efficient Method to Finely Adjust Properties of Functional Materials

Polyhydroxyalkanoate (PHA) and poly(propylene carbonate) (PPC) are blended in order to investigate their mutual contributions in terms of functional properties. A wide range of blend composition is processed through extrusion from dry blends. Droplet-matrix morphology is observed for all samples. Thermal investigations reveal the PPC effect on the PHA crystallization process with a decrease and broadening of the crystallization temperature window and on the depression of its glass transition temperature. This investigation also confirms the as yet un-reported non-miscibility of this kind of blend. However, a slight phase interaction is expected since thermal behavior of PHA is impacted. The fragile behavior of PHA is balanced by the high ductility of PPC. The weak strain at break of PHA can thus be increased by up to 200% although a significant amount of PPC is needed to start modifying this property. Stress at break and modulus are linearly decreased from pure PHA to pure PPC values. PPC also acts as an impact modifier for PHA. In terms of barrier properties, PHA brings a large contribution even at low content to the initially high oxygen and water vapor permeability of PPC.