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| Glossary |
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| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
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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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