Biomedical Engineering Reference
In-Depth Information
information, highly effective stabilizers (e.g., radical scavengers, peroxide decom-
posers, UV absorbers) have been developed; they are used extensively in a wide
variety of commercial formulations.
More recently, the demand for polyolefi n products having a shorter lifetime has
arisen, primarily in single-use packaging applications but also for a variety of
agricultural products and in hygiene applications. As a result, oxo-biodegradable
polyolefi ns have been invented and developed. These “clever” products are based
on the following principles. (i) The actual requirement is for polyolefi ns having
controlled lifetimes, that is, shelf life/use life combinations that can be varied
between a few months and several years, depending on the formulation. (ii) In
order to achieve such controlled lifetimes, it is required to enhance the rate of
oxidative degradation - after the polyolefi n articles have been used and dis-
carded - by several orders of magnitude. This cannot be done simply by adding an
oxidizing agent or by omitting the addition of stabilizers. It is being done by adding
transition metal/fatty acid salts in catalytic quantities to conventional polyolefi n
resins prior to product fabrication. These salts catalyze the decomposition of
hydroperoxide groups attached to the polymer molecules, but only after stabilizing
additives in the resins have been depleted. (iii) Polyolefi ns are resistant to biodeg-
radation by naturally occurring microorganisms, but their degradation products
are biodegradable. (iv) The combination of abiotic oxidation and biodegradation
provides for the required shelf life/use life values and suffi ciently rapid bioassimi-
lation to avoid the buildup of discarded plastics in a variety of environments. The
oxo-biodegradation of suitable polyolefi n formulations when buried in soil occurs
at rates which permit the retention and use of as-produced biomass; (v) no toxic
byproducts are produced in either the abiotic or subsequent biotic degradation of
oxo - biodegradable polyolefi ns.
In the immediate future, it is expected that oxo- biodegradable polyolefi ns will
become available for even more eco-compatible products and applications.
References
1
Guillet , J.E. ( 1995 ) Plastics and the
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Wiles , D.M. ( 2005 )
Oxo - biodegradable
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Biodegradable
Polymers for Industrial Applications
, CRC
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3
ASTM (2009) D6400 - 04 Standard
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http://www.astm.org./Standards
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4
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