Blends of Polyhydroxyalkanoates (PHAs) - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 84

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Figure 4.4 SEMs illustrating the attachment of olfactory ensheathing cells (OECs)

on P(3HB)/EtC blend films with variations in EtC loadings after 24 hours'
cultivation (a, d) P(3HB) films with 0%, (b, e) 20% and (c, f) 40% (w/w)
ETC loadings; (a-c) 250, bar ¼ 200 mm, (d-f) 1500, bar ¼ 30 mm. 65

The P(3HB)/EtC: 20/80 wt% blend had the most irregular surface with a
significantly greater R a value. Despite significant increases in R a, no sig-
nificant changes in morphology and proliferation of olfactory ensheathing
cells were observed with the P(3HB)/EtC blends.
Blending of P(3HB) with cellulose had also been performed by Zhang and
Deng 36 but with a different cellulose derivative, hydroxyethyl cellulose
acetate (HECA). It was found that P(3HB) contents above 20% exhibited zero
influence on the T m of P(3HB) in the P(3HB)/HECA blend. However, an in-
crease in the HECA component had resulted in the decrease of the melting
enthalpy of the blends. The T g of P(3HB) in the blend was constant at about
8 1C. FT-IR analysis showed that the two components did not exhibit specific
interactions. It was found that the hydrogen bonding in HECA was so strong
that the interaction between P(3HB) and HECA became very weak. The
crystallisation of P(3HB) in the P(3HB)/HECA: 20/80 wt% blend was sig-
nificantly affected by the HECA component. The phase transformation of
HECA from an isotropic phase to a mesophase was easier than the crystal-
lisation process, could be found at both lower and higher cooling rates and
was almost independent of the P(3HB) component. However, crystallisation
of P(3HB) was strongly dependent on the cooling rate and blend
composition. Two separate transitions were found for P(3HB)/HECA (80/20),
(60/40) and (40/60) blends during the DSC cooling run at a lower cooling
rate, which corresponded to the crystallisation of P(3HB) and the phase
transition of HECA from an isotropic phase to a mesophase in the blends,
respectively.
Phase behaviour and crystallisation kinetics for the binary blend P(3HB)/
cellulose propionate (CP) were studied by Maekawa and co-workers. 37 A
strong dependence of the measured T g on composition was detected at high
levels of CP. The Flory-Fox equation is one of the best equations to describe
the dependence of T g on composition in miscible blend systems. A good

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