Editing Polyethylene (section)

===Ultra-high-molecular-weight (UHMWPE)===
{{main|Ultra-high-molecular-weight polyethylene}}
[[File:Stainless steel and ultra high molecular weight polythene hip replacement (9672239334).jpg|thumb|Stainless steel and ultra-high-molecular-weight polyethylene hip replacement]]
UHMWPE is polyethylene with a molecular weight numbering in the millions, usually between 3.5 and 7.5 million [[Atomic mass unit|amu]].<ref>{{cite book|author=Kurtz, Steven M. |title=UHMWPE Biomaterials Handbook. Ultra-High Molecular Weight Polyethylene in Total Joint Replacement and Medical Devices|edition= 3rd| page=3|isbn=9780323354356 |year=2015|publisher=Elsevier|doi=10.1016/C2013-0-16083-7}}</ref> The high molecular weight makes it a very [[toughness|tough]] material, but results in less efficient packing of the chains into the [[crystal structure]] as evidenced by densities of less than high-density polyethylene (for example, 0.930–0.935&nbsp;g/cm<sup>3</sup>). UHMWPE can be made through any catalyst technology, although Ziegler catalysts are most common. Because of its outstanding toughness and its cut, wear, and excellent chemical resistance, UHMWPE is used in a diverse range of applications. These include can- and [[bottle]]-handling machine parts, moving parts on weaving machines, bearings, gears, artificial joints, edge protection on ice rinks, steel cable replacements on ships, and butchers' chopping boards. It is commonly used for the construction of articular portions of [[implant (medicine)|implants]] used for [[hip replacement|hip]] and [[knee replacement]]s. As [[Ultra-high-molecular-weight polyethylene#UHMWfiber|fiber]], it competes with [[aramid]] in [[bulletproof vests]].