4. Conclusions
The purpose of this work was to investigate the dynamic
mechanical properties of melt-blended PLA/PHBV, PLA/PCL and
PHBV/PCL prepared in the absence and presence of small amounts
of TiO2 nanoparticles. Blending PHBV and PLA increased the
glassy modulus to values above those of the individual neat
polymers, while the presence of nanoparticles had little effect.
Changes in the glass transition temperatures of these two
polymers in the blends indicated partial miscibility at their
interfaces, which was also observed from the reduced maximum
damping values. The cold crystallization transition of PLA shifted
to lower temperatures after blending with PHBV, which was
attributed to more free volume created by the presence of the
more mobile PHBV chains. The dynamic mechanical properties of
PLA/PCL and PHBV/PCL were little influenced by blending and the
presence of TiO2 nanoparticles. The glass transitions of PHBV and
PCL in the blends were, however, seen to be more separated than
those of the individual neat polymers, which we explained as the
immobilization of PHBV chains through the presence of PCL, and
the creation of more free volume for the movement of PCL chains
through the presence of PHBV. The broadness of the PCL glass
transition peaks increased when blended with PHBV, probably
because of the incompatibility between PHBV and PCL in the
blends.