Ultra High Molecular Weight Polyethylene
From 04/07/2014 to 2/7/2012
Ultrahigh Molecular Weight Polyethylene (UHMWPE
Ultrahigh Molecular Weight Polyethylene (UHMWPE) Fibers
Ultrahigh Molecular Weight Polyethylene (UHMWPE) Implants
1. “Ultra-high-molecular-weight polyethylene (UHMWPE or sometimes shortened to UHMW), also known as high-modulus polyethylene (HMPE) or high-performance polyethylene (HPPE), is a subset of the thermoplastic polyethylene. It has extremely long chains, with molecular weight numbering in the millions, usually between 2 and 6 million. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. It is highly resistant to corrosive chemicals with exception of oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating; and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to that of polytetrafluoroethylene (Teflon), but UHMWPE has better abrasion resistance than PTFE. It is odorless, tasteless, and nontoxic.
Polymerisation of UHMWPE was commercialised in the 1950s by Ruhrchemie AG, which changed names over the years; today UHMWPE powder materials are produced by Ticona, Braskem, and Mitsui. UHMWPE is available commercially either as consolidated forms, such as sheets or rods, and as fibers. UHMWPE powder may also be directly molded into the final shape of a product. Because of its resistance to wear and impact, UHMWPE continues to find increasing industrial applications, including the automotive and bottling sectors, for example. Since the 1960s, UHMWPE has also been the material of choice for total joint arthroplasty in orthopedic and spine implants.
(Wikipedia, UHMWPE, 4/18/2012)
2. “Compared to high molecular weight polyolefin used in general, formed articles of ultra-high molecular weight polyolefin represented by ultra-high molecular weight polyethylene, or the like, have excellent mechanical properties, such as, impact resistance, abrasion resistance, low coefficient of friction and tensile strength, and resistance to chemicals. Taking advantage of such characteristics, formed articles of ultra-high molecular weight polyolefin are used in mechanical parts such as gears, pulleys or sprockets, in various linings of guide rails or hopper tank lining materials, and the like.
Meanwhile, since molten viscosity is extremely high and fluidity is poor for ultra-high molecular weight polyolefins compared to polyethylene used in general, which makes forming by extrusion molding and injection molding extremely difficult, there is the disadvantage that forming processes are difficult. Therefore, compression molding, or the like, has been adopted in general as a forming method for ultra-high molecular weight polyethylene, and as part of others, a method has been adopted, called ram extrusion molding, in which molding is under the condition of extremely low molding speed, in order to obtain rod-shaped formed products.”
[Takeyama and Mayama, US Patent 8,303,064 (11/6/2012)]
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Roger D. Corneliussen
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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 4/18/2012.