Improving the Flowability of Poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) by Blending Techniques

In this study, the rheological properties of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBHHx) were modified by the addition of poly(ε-caprolactone) (PCL) or triethyl citrate. Triethyl citrate was found to be miscible with PHBHHx and act as a plasticizer. As theoretically predicted, the shear viscosity of plasticized PHBHHx clearly decreased in the low shear rate region. In contrast, PCL was immiscible with PHBHHx, and the PHBHHx/PCL blends showed the phase-separated structure. Although the decreases in the oscillatory shear moduli in the linear viscoelastic region were limited, the steady-state shear viscosity greatly decreased by the addition of PCL in a wide range of the shear rate. Furthermore, the addition of PCL also enhanced the crystallization rate of PHBHHx. This technique will be attractive in industry because the molecular weight of PHBHHx should be high to meet the requirements of the mechanical properties in the solid state.