PLA deviates from the terminal behavior markedly (G0
(x)
/ x1.58). The values are in consistency with the results reported
in literatures [16,32]. The G0 of PLA/PBA blends
slightly deviates from the terminal behavior, from G0
(x))
/ x1.51 for the blend with 5 wt.% PBA to G0
(x)) / x1.2 for
the blend with 15% PBA. Molecular weight distribution
strongly affects the shape of the terminal region. Chains
of different sizes relax to equilibrium at different times,
which ‘‘smears out’’ the typical relaxation behavior of a
monosized polymer melt. The relatively broad molecular
weight distribution of PBA (PI = 4.202) likely accounts for
the different relaxation behavior.[33] On the other hand,
the partially miscible characteris of blends might be the
other reason for the deviation.[34] The incorporation of
PBA affected the storage moduli and loss moduli of the
melts at all frequencies; they decreased with the increase
of PBA content as compared with pure PLA, except that
the G0 of BA-15 increased at low frequencies. For the blend
with 15 wt.% PBA, the lower slope values and higher absolute
values of dynamic modulus indicate the formation of
entanglement structures in PLA/PBA melts [16]. It is known
that molecular chain PBA is more flexible than that of PLA
and is easier to entangle. The entanglement density was
higher than that of PLA, leading to high reversible elastic
deformation (G0 Fig. 3. Cole–Cole plot of the PLA/PBA blends at 190 C. ) of the BA-15 melts [16].