Low-density polyethylene 2138217 222200763 2008-06-28T01:33:13Z 222.154.110.37 /* Physical qualities */ {{Unreferenced|date=February 2008}} {| align=right border="1" cellspacing="1" |- | {| cellpadding="10" border="0" | [[Image:Resin-identification-code-4-LDPE.svg|80px|right|]] |} |- align="center" <!-- | [[SPI]] LDPE [[Resin identification code|Recycling Symbol]] --> | LDPE has [[Society of the Plastics Industry|SPI]] [[resin identification code|resin ID code]] 4 |} '''Low-density [[polyethylene]]''' ('''LDPE''') is a [[thermoplastic]] made from [[petroleum|oil]]. 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 polymerisation]] [http://www.pacia.org.au/_uploaditems/docs/3.polyethylene.pdf|1]. Its manufacture employs the same method today. ==Properties== LDPE is defined by a density range of 0.910 - 0.940 g/cm³. It is unreactive at [[room temperature]]s, except by strong oxidizing agents, and some [[solvent]]s 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 to the degree of being almost unbreakable. It has more [[Branching (chemistry)|branching]] (on about 2% of the carbon atoms) than [[high-density polyethylene|HDPE]], so its [[intermolecular force]]s ([[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. ===Chemical resistance=== * Excellent resistance (no attack) to dilute and concentrated [[acid]]s, [[alcohol]]s, [[Base (chemistry)|bases]] and [[ester]]s * Good resistance (minor attack) to [[aldehyde]]s, [[ketone]]s and [[vegetable oil]]s * Limited resistance (moderate attack suitable for short-term use only) to [[aliphatic]] and [[aromatic]] [[hydrocarbons]], [[mineral oil]]s, and [[oxidizing agent]]s * Poor resistance, and not recommended for use with [[Halogenated hydrocarbons]].[http://www.dynalabcorp.com/technical_info_ld_polyethylene.asp] ==Applications== LDPE is widely used for manufacturing various containers, dispensing bottles, wash bottles, tubing, plastic bags for computer components, and various [[molding (process)|molded]] laboratory equipment. <!-- and many more, care to add? --> Its most common use is in [[plastic bag]]s. 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 [[machining|machinable]] * Parts that require flexibility, for which it serves very well * Very soft and pliable parts * Six-pack soda can rings * Extrusion coating on paperboard and aluminum laminated for beverage cartons. * Computer components, such as hard drives, screen cards and disk-drives. * Playground Slides ==See also== * [[High-density polyethylene]] * [[Linear low-density polyethylene]] * [[Ultra-high-molecular-weight polyethylene]] {{polymer-stub}} [[Category:Polyolefins]] [[Category:Plastics]] [[Category:Packaging materials]] [[nl:LDPE]] [[ja:低密度ポリエチレン]]