Ultra high molecular weight polyethylene properties

Many polymer items are designed specifically to make contact with other materials. Where surface contact is concerned, two key properties are coefficient of friction and abrasion resistance. Polymers used in such applications include ultra high molecular weight polyethylene, polyacctal, fluorinated polymers, and natural and synthetic rubbers. Examples that we routinely come across include furniture upholstery, bushings and gears in office equipment, and bicycle tires. Industrial uses include the outer cover of electrical cables, and pipes that convey abrasive liquids such as slurries and powders. 

Polyolefins. Ultra-High-Molecular-Weight Polyethylene.TIus is easily made by conventional low-pressure coordination polymerization. Hercules Hi-fax 1900 has a molecular weight of 2.5-5.0 million. Its outstanding properties are low coefficient of friction (0.11) abrasion-resistance superior to nylon, polyurethane, and steel unbreakable in the Izod notched impact test and high resistance to most inorganic and many organic chemicals. 

Gsell, R.A., H.L. Stein, and J.J. Ploskonka Characterization and Properties of Ultra-High Molecular Weight Polyethylene/ American Society for Testing. Materials, West Conshohocken, PA, 1998. 

Ultra-high molecular weight polyethylene (UHMWPE) has been used in orthopaedic prosthetic surgery for many years due to its excellent mechanical properties and frictional resistance. A large number of studies on both retrieved prostheses and raw material have, however, been necessary in order to understand and prevent degradation of the prostheses. The shape of the prostheses and the compression moulded blocks from which they are cut is usually not suitable for examination. In a number of studies microtomy has therefore been used in order to produce pieces suitable for further studies [112, 113, 114, 115, 116, 117, 118, 119, 120]. However, very often when microtomy is used, it is without any consideration of the fact that the process... 

Muratoglu, O.K. Bragdon, C.R. O Connor, A.S. Jasty, M. Harris, W.H. A novel method of cross-linking ultra-high molecular-weight polyethylene to improve wear reduce oxidation, and retain mechanical properties. J. Arthoplasty 2001, 16, 149-160. 

Blends of LLDPE/PP = 50 50, with or without compatibilizing ethylene-propylene copolymer, EPR, were studied by Dumouhn et al. [1984]. In spite of the expected immiscibihty, the blends showed additivity of properties with good superposition of the stress growth functions in shear and elongation, as well as with the zero deformation rate Trouton ratio, Rj, = 1. In earlier work, blends of medium density PE (MDPE) with small quantities of ultra-high molecular weight polyethylene (UHMWPE) were studied in shear and extension. Again, SH and Rj, = 1 were observed. 

Two sets of experiments were performed. In the first set, three polymers with very different mechanical properties were chosen to determine their response to this experiment. Polycarbonate PC, rigid polyvinyl chloride PVC, and ultra-high molecular weight polyethylene UHMWPE, were loaded with 10, 8.5, and 7.2 N and tested at 0.04 m/s sliding speed. In these tests, the friction force was continuously... 

FIGURE 41.6 Properties of carbon fiber reinforced ultra high molecular weight polyethylene. (Replotted from Sclippa, E. and Piekarski, K. 1973. /. Biomed. Mater. Res., 7,59-70. With permission.)... 

The blood bag case study illustrates the use of polymeric film as a flexible container. It considers the permeability of polymers, plus processes for fabricating plastics film. Plasticised PVC has dominated the market for years, but there could be a changeover to flexible polyolefin films. The case study on replacement joints for implanting in the body illustrates wear and the effects of wear debris. Research continues on improving the wear resistance of the ultra high molecular weight polyethylene (UHMWPE) and mitigating the effects of sterilisation on the implant properties. 

Y. Chen, H. Zou, M. Liang, P. Liu, Rheological, thermal, and morphological properties of low-density polyethylene/ultra-high-molecular-weight polyethylene and linear low-density polyethylene/ultra-high-molecular-weight polyethylene blends. J. Appl. Polym. Sci. 129, 945-953 (2013)... 

X. Wang, B. Mu, Hg Wang, Preparation and properties of thermoplastic polyuiethane/ultra high molecular weight polyethylene blends. Polym. Compos. (2014). doi 10.1002/pc.23009... 

M. Ahmad, M.U. Wahit, M.R.A. Kadir, K.Z.M. Dahlan, Mechanical, iheological, and bioactivity properties of ultra high-molecular-weight polyethylene bioactive composites containing polyethylene glycol and hydroxyapatite. Sci. World J. 13, 474851 (2012)... 

C.M. Chan, C. Chi-Leung, M.F.Y. Matthew, Electrical properties of polymer composites prepared by sintering a mixture of carbon black and ultra-high molecular weight polyethylene powder. Polym. Eng. Sci. 37, 1127-1136 (1997)... 

Della, C.N., Dongwei, S. Mechanical properties of carbon nanotubes reinforced ultra high molecular weight polyethylene. Solid State Phenom. 136, 45-49 (2008)... 

The maximum benefits from this qrproach come when UHMW-PE (ultra high molecular weight polyethylene Mw > 10 ) is used. PE chains tend to crystallize or solidify in a chain-folded or lamellar crystal. To exploit the stififiiess and strength properties intrinsic to the polymer chain the chain-folded ciystallites must be unfolded... 

Zachariades A.E. 1985. The effect of powder particle fusion on the mechanical properties of ultra-high molecular weight polyethylene. Poly Engr Sci 25 747-750. 

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