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Life
Cycle Assessment (LCA):
An objective process to evaluate the environmental
burdens associated with a product, process or activity
by identifying and quantifying energy and materials
used and wastes released to the environment, to assess
the impact of those energy and materials uses and
releases on the environment, and to evaluate and implement
opportunities to affect environmental improvements.
The assessment includes the entire life cycle of the
product, process or activity, encompassing extraction
and processing of raw materials, manufacturing, transportation
and distribution, use/reuse/maintenance, recycling
and final disposal. (A Technical Framework for Life-Cycle
Assessment, Society of Environmental Toxicology and
Chemistry (SETAC), January 1991).
Life Cycle Inventory
(LCI):
An objective, data-based process of quantifying energy
and raw material requirements, air emissions, waterborne
effluents, solid waste, and other environmental releases
incurred throughout the life cycle of a product, process
or activity. (A Technical Framework for Life-Cycle Assessment,
Society of Environmental Toxicology and Chemistry (SETAC),
January 1991).
Linear
Low Density Polyethylene (LLDPE):
A plastic that is used predominantly in film applications
due to its toughness, flexibility and relative transparency.
LLDPE is the preferred resin for injection molding because
of its superior toughness and is used in items such
as grocery bags, garbage bags and landfill liners. (Adapted
from Modern Plastics Encyclopedia 1995; Plastic Packaging
Opportunities and Challenges, APC, February 1992).
Low
Density Polyethylene (LDPE):
A plastic used predominantly in film applications due
to its toughness, flexibility and relative transparency.
LDPE has a low melting point, making it popular for
use in applications where heat sealing is necessary.
Typically, LDPE is used to manufacture flexible films
such as those used for plastic retail bags and garment
dry cleaning and grocery bags. LDPE is also used to
manufacture some flexible lids and bottles, and it is
widely used in wire and cable applications for its stable
electrical properties and processing characteristics.
(Adapted from Modern Plastics Encyclopedia 1995).
Liquid
Rubber
A liquid, usually a viscous low molecular weight polymer
(typical molecular weight being a few thousand), which
may be readily crosslinked to a product similar in behaviour
to that of a normal rubber vulcanizate. The use of a
liquid rubber offers the considerable technological
advantage over conventional rubbers that expensive compounding
and press vulcanization procedures are not required.
Some polyurethane elastomers, silicone rubbers and polysulphide
rubbers may be processed as liquid rubbers. An early
liquid rubber was depolymerised natural rubber and the
term originally applied specifically to this material.
More recently liquid rubbers based on polybutadiene
(of molecular weight about 10000), which may be Crossliked
through functional groups on the chain ends(telechelic
polymer), have been developed, e.g. carboxy-terminated
polybutadiene and hydroxy-terminated polybutadiene and
similar nitrile and styrene-butadiene copolymers.
Liquid
crystalline side chain polymer
A liquid crystalline polymer in which the mesogenic
groups are part of the groups attached to the main chain.
Ordering of the mesogens, and hence liquid crystalline
behaviour, is enhanced by distancing them from the main
chain with flexible groups.
Living
polymerization
A chain polymerization in which the concentration of
kinetic-chain carriers, under the appropriate conditions
for synthesis, remains constant for a period many times
longer than the duration of the synthetic procedure.
Often, the absence of chain transfer is implied in the
term "living polymerization".
Lower
critical solution temperature (LCST)
The critical solution temperature below which a binary
mixture exists as a homogeneous single phase solution
at all compositions. Thus when such a mixture existing
below the LCST is heated, phase separation occurs. Such
behaviour is more unusual than upper critical solution
temperature behaviour and is not accounted for by the
simple theories of solution, e.g. the Flory-Huggins
theory for polymer solutions. However, it does occur
for several polymer/solvent pairs and not at all infrequently
for polymer/polymer pairs, i.e. polymer blends. This
behaviour implies an increase in x(the Flory-Huggins
interaction parameter) with temperature, and can be
accounted for by the corresponding states theory, as
being due to dissimilar thermal expansion coefficients
between polymer and solvent. At high temperatures, the
more highly expanded solvent must fit into a denser
medium and mixing must involve a negative volume change
and negative entropy of mixing.
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Plastic
Brief
