Low-density polyethylene: Difference between revisions
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'''Low-density [[polyethylene]]''' ('''LDPE''') is a [[thermoplastic]] made from [[petroleum]]. It was the first grade of polyethylene, produced in 1933 by [[Imperial Chemical Industries]] (ICI) using a high pressure process via [[Radical polymerization|free radical polymerization]].<ref>{{cite web | title = Polyethylene chemical fact sheet | publisher = [http://www.pacia.org.au Plastics and Chemicals Industries Association] | url = http://www.pacia.org.au/_uploaditems/docs/3.polyethylene.pdf | format = PDF }}</ref> Its manufacture employs the same method today. LDPE is commonly recycled{{Citation needed|date=January 2009}} and has the number "4" as its [[resin identification code|recycling symbol]]. Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2009 the worldwide LDPE market reached a volume of 22.2 billion US-Dollars (15.9 billion Euro).<ref>{{cite web | title = Market Study: Polyethylene LDPE | publisher = [http://www.ceresana.com Ceresana Research] | url = http://www.ceresana.com/en/market-studies/plastics/polyethylene-ldpe/ }}</ref> |
'''Low-density [[polyethylene]]''' ('''LDPE''') is a [[thermoplastic]] made from [[petroleum]]. It was the first grade of polyethylene, produced in 1933 by [[Imperial Chemical Industries]] (ICI) using a high pressure process via [[Radical polymerization|free radical polymerization]].<ref>{{cite web | title = Polyethylene chemical fact sheet | publisher = [http://www.pacia.org.au Plastics and Chemicals Industries Association] | url = http://www.pacia.org.au/_uploaditems/docs/3.polyethylene.pdf | format = PDF }}</ref> Its manufacture employs the same method today. LDPE is commonly recycled{{Citation needed|date=January 2009}} and has the number "4" as its [[resin identification code|recycling symbol]]. Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2009 the worldwide LDPE market reached a volume of 22.2 billion US-Dollars (15.9 billion Euro).<ref>{{cite web | title = Market Study: Polyethylene LDPE | publisher = [http://www.ceresana.com/en/ Ceresana Research] | url = http://www.ceresana.com/en/market-studies/plastics/polyethylene-ldpe/ }}</ref> |
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==Properties== |
==Properties== |
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Revision as of 08:34, 19 May 2010
 | This article needs additional citations for verification. (April 2009) |
Low-density polyethylene (LDPE) is a thermoplastic made from petroleum. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization.[1] Its manufacture employs the same method today. LDPE is commonly recycled[citation needed] and has the number "4" as its recycling symbol. Despite competition from more modern polymers, LDPE continues to be an important plastic grade. In 2009 the worldwide LDPE market reached a volume of 22.2 billion US-Dollars (15.9 billion Euro).[2]
Properties
LDPE is defined by a density range of 0.910 - 0.940 g/cm³. It is not reactive at room temperatures, except by strong oxidizing agents, and some solvents cause swelling. It can withstand temperatures of 80 °C continuously and 95 °C for a short time. Made in translucent or opaque variations, it is quite flexible, and tough but breakable.[citation needed]
LDPE has more branching (on about 2% of the carbon atoms) than HDPE, so its intermolecular forces (instantaneous-dipole induced-dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher. Also, since its molecules are less tightly packed and less crystalline because of the side branches, its density is lower. LDPE contains the chemical elements carbon and hydrogen.
Chemical resistance
- Excellent resistance (no attack) to dilute and concentrated acids, alcohols, bases and esters
- Good resistance (minor attack) to aldehydes, ketones and vegetable oils
- Limited resistance (moderate attack suitable for short-term use only) to aliphatic and aromatic hydrocarbons, mineral oils, and oxidizing agents
- Poor resistance, and not recommended for use with Halogenated hydrocarbons.[3]
Applications
LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various molded laboratory equipment. Its most common use is in plastic bags. Other products made from it include:
- Trays & general purpose containers
- Food storage and laboratory containers
- Corrosion-resistant work surfaces
- Parts that need to be weldable and machinable
- Parts that require flexibility, for which it serves very well
- Very soft and pliable parts
- Six-pack soda can rings
- Juice and milk cartons, whose "cardboard" is actually liquid packaging board, a laminate of paperboard and LDPE (as the water-proof inner and outer layer), and often with of a layer of aluminum foil (thus becoming aseptic packaging).[4][5][6]
- Parts of computer hardware, such as hard disk drives, screen cards and optical disc drives.
- Playground Slides
- Plastic Bags
- Plastic Wraps
See also
References
- ^ "Polyethylene chemical fact sheet" (PDF). Plastics and Chemicals Industries Association.
{{cite web}}: External link in|publisher= - ^ "Market Study: Polyethylene LDPE". Ceresana Research.
{{cite web}}: External link in|publisher= - ^ "Plastic Properties of Low Density Polyethylene (LDPE)". Dynalab Corp.
{{cite web}}: External link in|publisher= - ^ [1] Applications for LDPE, Exxon Mobil Corporation, 2002
- ^ DOW LDPE 5004I, by Dow Plastics, is used for fresh milk cartons, liquid/juice containers, IDES - The Plastics Web [2]
- ^ typical aseptic liquid food package may provide a shelf life-time up to one year and a typical laminate structure of the package comprises layers of LDPE-paperboard-LDPE-aluminum foil-adhesive-LDPE[3]