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Pond Liner
A pond liner is an impermeable geomembrane used for retention of liquids, including the lining of reservoirs, retention basins, hazardous and nonhazardous surface impoundments, garden ponds and artificial streams in parks and gardens. Installation Pond liners need to be protected from sharp objects (for example, stones) below the liner and from being punctured by any objects in the water body. Protection can be provided with layers of sand, geotextiles (particularly needle-punched nonwovens) and other materials. Pond liners are manufactured in rolls or accordion-folded on pallets. When deployed in the field their edges and ends are overlapped and seamed together. Methods are thermal fusion, solvents, adhesives and tapes. The edge of the pond liner is generally rolled over the top of the soil slope and secured in an anchor trench or it can be fixed to a vertical wall made of wood or concrete. Box-shaped pond liners can be made for rectangular structures. The vast majority of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EPDM
EPDM rubber (ethylene propylene diene monomer rubber) is a type of synthetic rubber that is used in many applications. EPDM is an M-Class rubber under ASTM standard D-1418; the ''M'' class comprises elastomers with a saturated and unsaturated compounds, saturated polyethylene chain (the M deriving from the more correct term polymethylene). EPDM is made from ethylene, propene, propylene, and a diene comonomer that enables crosslinking via sulfur vulcanization. Typically used dienes in the manufacture of EPDM rubbers are ethylidene norbornene (ENB), dicyclopentadiene (DCPD), and vinyl norbornene (VNB). Varying diene contents are reported in commercial products, which are generally in the range from 2 to 12%. The earlier relative of EPDM is EPR, ethylene propylene rubber (useful for high-voltage electrical cables), which is not derived from any diene precursors and can be crosslinked only using radical methods such as peroxides. As with most rubbers, EPDM as used is always compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raceway (aquaculture)
A raceway, also known as a flow-through system, is an artificial channel used in aquaculture to culture Aquatic animal, aquatic organisms. Raceway systems are among the earliest methods used for inland aquaculture. A raceway usually consists of rectangular basins or canals constructed of concrete and equipped with an inlet and outlet. A continuous water flow-through is maintained to provide the required level of water quality, which allows animals to be cultured at higher densities within the raceway."Aquatext: Raceways" Aquatext – The Free Online Aquaculture Dictionary. Accessed 29.9.2011. College of Agriculture and Life Sciences, The University of Arizona: Starting An Aquaculture System. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landscape Engineering
Landscape engineering is the application of mathematics and science to shape land and waterscapes. It can also be described as green engineering, but the design professionals best known for landscape engineering are landscape architects. Landscape engineering is the interdisciplinary application of engineering and other applied sciences to the design and creation of anthropogenic landscapes. It differs from, but embraces traditional reclamation. It includes scientific disciplines: agronomy, botany, ecology, forestry, geology, geochemistry, hydrogeology, and wildlife biology. It also draws upon applied sciences: agricultural & horticultural sciences, engineering geomorphology, landscape architecture, and mining, geotechnical, and civil, agricultural & irrigation engineering. Landscape engineering builds on the engineering strengths of declaring goals, determining initial conditions, iteratively designing, predicting performance based on knowledge of the design, monitoring performan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landfill Liner
A landfill liner, or composite liner, is intended to be a low permeable barrier, which is laid down under engineered landfill sites. Until it deteriorates, the liner retards migration of leachate, and its toxic constituents, into underlying aquifers or nearby rivers from causing potentially irreversible contamination of the local waterway and its sediments. Modern landfills generally require a layer of compacted clay with a minimum required thickness and a maximum allowable hydraulic conductivity, overlaid by a high-density polyethylene geomembrane. The United States Environmental Protection Agency has stated that the barriers "will ultimately fail," while sites remain threats for "thousands of years," suggesting that modern landfill designs delay but do not prevent ground and surface water pollution. Chipped or waste tires are used to support and insulate the liner. Types Different types of liquid trash will vary in their chemical properties and threat posed to the local env ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomembranes
A geomembrane is very low permeability (earth sciences), permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (liquid or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with Bitumen, asphalt, elastomer or polymer, polymer sprays, or as Bituminous Geomembranes (BGMs), multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common. Manufacturing The manufacturing of geomembranes begins with the production of the raw materials, which include the polymer resin, and various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants (as a processing aid). These raw materials (i.e., the "formulation") are then processed into sheets of various widths and thickness by extrusion, calendering, and/or spread ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyurea
Polyurea is a type of elastomer that is derived from the reaction product of an isocyanate component and an amine component. The isocyanate can be aromatic or aliphatic in nature. It can be monomer, polymer, or any variant reaction of isocyanates, quasi-prepolymer or a prepolymer. The prepolymer, or quasi-prepolymer, can be made of an amine-terminated polymer resin, or a hydroxyl-terminated polymer resin. The resin blend may be made up of amine-terminated polymer resins, and/or amine-terminated chain extenders. The amine-terminated polymer resins do not have any intentional hydroxyl Moiety (chemistry), moieties. Any hydroxyls are the result of incomplete conversion to the amine-terminated polymer resins. The resin blend may also contain additives or non-primary components. These additives may contain hydroxyls, such as pre-dispersed pigments in a polyol carrier. Normally, the resin blend does not contain a catalyst(s). This is because the reaction between an isocyanate and amine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bituminous Geomembranes (BGMs)
Bituminous geomembrane (BGM) is a type of geomembrane consisting of a reinforcing geotextile to provide mechanical strength and elastomeric bitumen (often called asphalt in American English, U.S.) to provide impermeability. Other components such as sand, a glass fleece, and/or a polyester film can be incorporated into the layers of a BGM. Bituminous geomembranes are differentiated from bituminous waterproofing materials used in buildings due in part to their wide roll width, which can exceed 5m, and their substantial thickness of up to 6.0mm. These properties are designed for environmental protection, civil infrastructure, and mining applications. Properties History The earliest estimated use of bitumen dates back 40,000 years to the Paleolithic age and bitumen#History, the historical use of bitumen as a waterproofing layer is extensive and well documented. In 1926, successful experiments were conducted by the South Carolina Highway Department in which cotton fabric wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LLDPE
Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. Linear low-density polyethylene differs structurally from conventional low-density polyethylene (LDPE) because of the absence of long chain branching. The linearity of LLDPE results from the different manufacturing processes of LLDPE and LDPE. In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The amount of comonomer is typically in the range from 1 to 10%. The copolymerization process produces an LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties. Production and properties The production of LLDPE is initiated by transition metal catalysts, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomembrane
A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (liquid or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common. Manufacturing The manufacturing of geomembranes begins with the production of the raw materials, which include the polymer resin, and various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants (as a processing aid). These raw materials (i.e., the "formulation") are then processed into sheets of various widths and thickness by extrusion, calendering, and/or spread coating. A 2010 estimate cited geomembranes as the largest geosynthetic ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HDPE
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or " polythene" when used for HDPE pipes. With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code. In 2008, the global HDPE market reached a volume of more than 30 million tons. Properties HDPE is known for its high strength-to-density ratio. The density of HDPE ranges from 930 to 970 kg/m3. Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength (38 MPa versus 21 MPa) than LDPE. The difference in strength exceeds the difference in density, giving HDPE a higher specific strength. It is also harder and mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymer
A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compound (chemistry), compounds, produces unique physical property, physical properties including toughness, high rubber elasticity, elasticity, viscoelasticity, and a tendency to form Amorphous solid, amorphous and crystallization of polymers, semicrystalline structures rath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
