<P> Polymerisation of UHMWPE was commercialised in the 1950s by Ruhrchemie AG, which changed names over the years . Today UHMWPE powder materials, which may be directly moulded into a product's final shape, are produced by Ticona, Braskem, DSM, Teijin (Endumax) and Mitsui . Processed UHMWPE is available commercially either as fibres or in consolidated form, such as sheets or rods . Because of its resistance to wear and impact, UHMWPE continues to find increasing industrial applications, including the automotive and bottling sectors . Since the 1960s, UHMWPE has also been the material of choice for total joint arthroplasty in orthopedic and spine implants . </P> <P> UHMWPE fibres, commercialised in the late 1970s by the Dutch chemical company DSM, are widely used in ballistic protection, defence applications, and increasingly in medical devices . </P> <P> UHMWPE is a type of polyolefin . It is made up of extremely long chains of polyethylene, which all align in the same direction . It derives its strength largely from the length of each individual molecule (chain). Van der Waals bonds between the molecules are relatively weak for each atom of overlap between the molecules, but because the molecules are very long, large overlaps can exist, adding up to the ability to carry larger shear forces from molecule to molecule . Each chain is bonded to the others with so many van der Waals bonds that the whole of the inter-molecule strength is high . In this way, large tensile loads are not limited as much by the comparative weakness of each van der Waals bond . </P> <P> When formed into fibres, the polymer chains can attain a parallel orientation greater than 95% and a level of crystallinity from 39% to 75% . In contrast, Kevlar derives its strength from strong bonding between relatively short molecules . </P>

The approximate number of mers in a single molecule of uhmwpe is