Nanocomposites of Polyhydroxyalkanoates (PHAs) - Polyhydroxyalkanoate (PHA) Based Blends, Composites and Nanocomposites - page 115

from poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) composited with
nanofillers of silsesquioxane (POSS).
Silver ions are thought to adhere to the negatively charged bacterial cell
wall, changing the permeability of the cell wall and consequently causing
protein denaturation, which induces cell lysis and death. This specific trait
of silver nanoparticles is exploited in food packaging and processing in-
dustries. Nanocomposites of biodegradable polymers containing silver
nanoparticles exhibited antimicrobial activities, which inhibit the growth
of post-processing microbial contaminants, thereby extending the shelf life
of food and improving food safety. 60 In fact, such metal intercalated nano-
particles not only posses antimicrobial properties, but are also reported to
exhibit catalytic, electrical and sensing properties (Table 5.2). 66
The current high demand for portable electronic gadgets warrants the
urgent need of a portable power source to support these appliances. At
present, lithium-ion batteries use a liquid electrolyte that is flammable, and
can cause problems such as gas formation due to overcharging, and release
of toxic and hazardous materials into the environment following end-of-
cycle disposal. 67 An alternative to this liquid electrolyte in electrochemical
cells is a system consisting of a solid polymer electrolyte produced through
incorporation of an electrochemical salt (e.g. lithium salt) in the polymer
matrix. This kind of polymeric cell is expected to show a better charge cycle
than the conventional liquid electrolyte systems in existence today. 68 In this
respect, Reusch and Reusch 69 described an embodiment for the method of
preparing such polymer electrolyte cells using polyhydroxyalkanoate
nanocomposites. 69

d n 2 r 4 n g | 8

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5.5 Conclusions
The increasing use of non-degradable fossil-derived plastics has caused great
concern in terms of environmental pollution and degradation issues. Bio-
degradable polymers such as bacterial polyhydroxyalkanoates (PHAs) are
considered as an alternative to existing petrochemical-based plastics. Despite
their promising commercial potential, most of the PHAs produced exhibit
brittleness, a low heat distortion temperature and poor gas-barrier properties,
thus limiting their applications in vast potential fields. Incorporation of
nanofillers into the biodegradable polymer matrices resulted in nano-
composites that possess significantly improved mechanical and thermal
properties both in solid and melt states along with enhanced gas barrier
properties (O 2 ,CO 2 , water vapor etc.) compared to conventional filler com-
posites. These superior qualities extend the polymeric composites' appli-
cations to aggressive environments where the neat polymers are likely to fail.
However, extensive research on the scarcely explored field of nano-
composite formulation based on polyhydroxyalkanoates is needed in order
to enhance their mechanical, and other, properties, which can be manipu-
lated to suit end-users' requirements in order to meet a wide range of
applications.