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Biodegradable Polymers Due to the increasing
concerns about the preservation of eco systems, it is increasingly being
recognized that the use of long-lasting polymers for short-lived applications
is not entirely justified. Conventional plastics that persist in the
environment due to improper disposal are a significant source of
environmental pollution and a waste management problem. In industrialized EU
nations, plastics represent approximately between 20 - 40% of municipal
waste. Consumption of plastic material in the EU was approximately 40 million
tones in 2000. The need for the development
of polymeric materials based on renewable sources has led to the
development of new materials, such as the poly(lactic acid) (PLA), which is currently being
produced from a feedstock of corn rather than petroleum. PLA has been used
since 1970s for biomedical and pharmaceutical applications, but the only
recently the technology for large scale production has been fully developed,
making it available at low cost for inumerous other applications. Since the
packaging industry, more precisely food
packaging, plays a dominant role in the short term use of cheap plastic
materials, its replacement with PLA could provide a significant step towards
a greener planet. In order to preserve adequately the quality of the food,
the packaging materials have to provide efficient barriers against water
vapor, atmospheric gases and volatile organic compounds (VOC) thus preventing
food degradation and oxidation and preserving aromas and flavours. Thus, the
determination of the permeability (solubility and diffusion) of gases,
flavors and aromas in polymers is of vital importance in the application of
PLA in the food packaging industry. Nanomaterials
Polymer composites are
receiving a great amount of attention in science and technology, due to their
innumerous applications in everyday life, including transportation,
construction, electronics and consumer products. The constituents of
composites are two or more materials possessing complementary physical
chemical properties and they are expected to produce synergistic properties
which are difficult to obtain from the pure components. Nanocomposites are a class of new
promising materials showing better thermal, mechanical and barrier properties
than conventional composites because of the stronger interfacial forces
between the nanometer sized domains. Among the most promising
composite systems, polymer nanocomposites are a class of new reinforced
polymers, with low quantities (>5%) of nanometric sized clay particles,
which show a considerable improvement of their mechanical, thermal and
barrier properties, without damaging their processability, optical properties
and toughness. |
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..2005 © PATh |
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