Blends of Polyhydroxyalkanoates (PHAs) - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 67

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Figure 4.1 Classification of the main biodegradable polymers. 1

Polymer blending has attracted the attention of researchers because
polymers with extraordinary properties obtained by chemical synthesis are
more expensive than existing polymers and blending operations. Further-
more, a wise choice and combination of the polymeric materials in specific
amounts may lead to the fabrication of blend materials with desirable
properties. There are various numbers of polymers that can be combined to
form blends with different physical properties. The characteristics of the
polymeric blend are influenced by the nature of the dispersed and disper-
sion phases, the volume ratio of the phases, the sizes and size distributions
of the particles of the dispersed phase and interfacial adhesion. 3 One of the
popular questions being addressed regarding the polymer blend is the
miscibility between the components. The blends formed can be miscible,
partially miscible or fully immiscible. The miscible polymer blend is formed
by choosing polymers with compatible chemical structures which are cap-
able of specific interactions. 4
Polyhydroxyalkanoates (PHAs) are members of a greatly fascinating family
of microbial polyesters of 3-, 4-, 5- and 6-hydroxyacids that show potential for
various industrial and medical applications due to their wide range of
characteristics. 5,6 These polymers with imperative ecosystem roles and high
biotechnological potential are synthesized naturally by a diverse range of
bacterial species from at least 75 different genera. 7,8 The polymers are
usually accumulated as insoluble inclusions in the cytoplasm of bacterial
cells during the depletion of essential nutrients such as nitrogen, mag-
nesium or phosphorus in the presence of abundant carbon sources. 9
Although PHAs are considered to be consumer-oriented and environ-
mentally friendly biopolymers due to their biodegradability and biocompati-
bility, commercialisation of these biopolymers is stringently dependent on
the material properties that satisfy the requirements of the targeted market
application. At present, more than 200 different monomer constituents
are found either as homopolyesters or in combination as copolyesters. 10

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