Blends of Polyhydroxyalkanoates (PHAs) - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 72

cellulose and P(3HB-co-3HV) copolymer were dried under vacuum in order to
remove the moisture. Cellulose was dissolved using 1-butyl-3-methylimida-
zolium chloride ([BMIM]CI). The mixture was then heated and stirred to
obtain a homogeneous solution. The P(3HB-co-3HV) copolymer was then
added and coagulated in water. The mixture was then stirred at 100 1C. In
order to obtain the film, the viscous solution of cellulose and P(3HB-co-3HV)
copolymer was casted in between two glass plates and then soaked in a water
bath to allow the ionic solution to evaporate.
Gilmore et al. 41 reported the preparation of a blend of cellulose acetate
esters and P(3HB-co-3HV) copolymer using a solvent-casting method. P(3HB-
co-3HV) copolymer and cellulose acetate esters were dissolved separately in
chloroform and then dried under vacuum. Lotti and Scandola 42 reported the
preparation of a blend of cellulose acetate butyrate and P(3HB-co-3HV) co-
polymer whereby the components were mixed in an injection molding ma-
chine. The temperature was kept low in order to minimise the thermal
degradation of P(3HB-co-3HV) copolymer.

d n 2 r 4 n g | 6

4.2.4 PHAs/Starch Derivatives
Starch is a renewable resource that comprises a linear polymer (amylose)
and a branched polymer (amylopectin). It is an attractive biopolymer due to
its low cost, low density, non-abrasive nature and biodegradability. It is
readily available from agricultural sources such as maize, potatoes, tapioca,
rice and wheat. Starch is widely used in food and non-food applications.
Starch is therefore classified as inexpensive and a commodity material. The
hydrophilic nature of starch limits the development of starch-containing
materials; therefore, starch is usually blended with other polymers.
Blending the starch with biodegradable and more hydrophobic polymers
produces blends that are completely biodegradable under biologically
active environments. 43 The main reason for adding starch to PHAs is to reduce
the overall cost besides improving its properties. Since PHAs are hydrophobic
and starch is hydrophilic, there will be a poor adhesion between these two
polymers thus contributing to poor mechanical properties. 44
P(3HB)/starch blend was prepared either by a conventional solvent-casting
method or by melt processing methods, such as injection molding and
compression molding after compounding. Two types of maize starch, Starch
1 (containing 70% amylose) and Starch 2 (containing 72% amylopectin)
were blended with P(3HB) using a melt compounding method at a ratio of
70/30 wt% and they were characterised in terms of their morphology,
structure, thermal, rheological and mechanical properties. 45 The thermal
behaviour and morphological structure of solvent-cast films of P(3HB)/
starch acetate (SA) blend with weight ratios of 100/0, 80/20, 60/40, 40/60,
20/80 and 0/100 had been studied by Zhang et al. 46 Ismail and Gamal 47
prepared P(3HB)/starch composites with different starch contents to
investigate their mechanical and swelling in water properties and to evaluate
the capability of Actinomycetes to degrade this polymer under different

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