Ultra High Molecular Weight Polyethylene (UHMWPE)
Ultra high molecular weight polyethylene has molecular weights on the order of a million or more. The long entangled chains form a very tough material with the highest impact strength of any common thermoplastic and is very abrasion resistant. It was commercialized in 1950 by Ruhrchemie AG. UHMWPE fibers were commercialized by DSM. (R.D. Corneliussen 10/19/2009)
“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. It has extremely low moisture absorption, has a very low coefficient of friction, is self-lubricating, and is highly resistant to abrasion (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 Teflon, but UHMWPE has better abrasion resistance than Teflon. It is odorless, tasteless, and nontoxic.” (Wikipedia, UHMWPE, 1/8/2011)
Crosslinked UHMWPE
Polyethylene
Polymers /Resins
UHMWPE Blends
UHMWPW Fibers
UHMWPE Fluorination
UHMWPE Nanocomposites
UHMWPE Orthopedic Implants
Wear of UHMWPE Materials
Recent US Patents
9/20/2011
8,022,115
Anti-fouling ultrahigh molecular weight polyethylene compositions and methods of using the same
Gregg and Yarcich, of Quadrant EPP, Indiana, developed a combination of polychlorophenoxyphenol, a silver-containing biocide, and an organopolysiloxane makes UHMWPE materials resistant to both soft and hard fouling. The polychlorophenoxy phenol is preferably 2.4.4'-trichloro-2'-hydroxy-diphenylether and the metal-containing biocide is preferably a silver zeolite. (RDC 9/25/2011)
1/4/2011
7,863,410
Sintering ultrahigh molecular weight polyethylene
Smith, Visjager and Tervoort of Smith & Nephew Orthopaedics, Switzerland, have developed sinterabile UHMWPE materials by adding small amounts of a co-monomer to the polymer. (RDC 7/18/2011)
Recent Journal Articles
Study on Immobilized Metallocene and Single-Site Catalysts for the Preparation of Ultra-High Molecular Weight Polyethylene at Various Polymerization Conditions
(1557-1563) Polymer - Plastics Technology and Engineering 50 #15 (2011)
Abstract
Woo and Hong of Sejong University, South Korea, immobilized Ti with bis(phenoxy-imine) ligand (FI catalyst) and Me2Si(C5Me4)(N-tBu)TiCl2 (CGC) on silica and tested for the preparation of UHMWPE. Results revealed that soluble FI catalyst and CGC can produce polyethylene having relatively high molecular weight above 106 g/mol, which also can be successfully immobilized on carriers for better adaptability to production processes. (RDC 11/11/2011)
Modeling the tensile behavior of ultra-high-molecular-weight polyethylene with a novel flow rule
(2936–2944)Journal of Applied Polymer Science 121 #5 (2011)
Sweeney, Naz and Coates of the University of Bradford, United Kingdom, found that strain rate sensitivity is a function of the strain. This was related to a flow rule developed for this material in a previous study on compressive behavior. This flow rule is an adaptation of that of Hill, in which the anisotropy coefficients are power-law functions of the extension ratios. It is used in conjunction with an Eyring process. The observed rate dependence of the tensile behavior conformed with that obtained with the power-law flow rule and could be used to derive a value of the power-law coefficient. A constitutive model was developed that incorporates the new flow rule and was implemented in a finite element analysis. When this analysis was used to model the inhomogeneous tensile specimens, it gave predictions of the axial and transverse strain that were consistent with the experiment when the power-law coefficient was the same value as that derived from the study of the rate dependence. (RDC 6/16/2011)
Crystalline Phase in Gelled UHMWPE Reactor Powder
(60 – 66) International Journal of Polymer Analysis and Characterization 16 #1 (2011)
Pakhomov et al of Russia and Germany prepared a dried ultrahigh molecular weight polyethylene gel (xerogel). X-ray and low-frequency Raman scattering techniques, showed the presence of stacked lamellar crystals in the material. The stacks showed equal “long periods” in meridional and equatorial directions. (RDC 2/16/2011)
Ultra high molecular weight polyethylene with improved plasticity and toughness by high temperature melting
(Pages 2721-2731) Polymer 51 #12 (2010)
Fu et al found that melting of consolidated medical-grade UHMWPE at 280, 300, and 320 °C in inert atmosphere improved the elongation at break, work-to-failure and impact strength, presumably due to chain scissioning and structural defect elimination through self-diffusion. An important finding of this study was that the gain in plasticity and toughness did not sacrifice the wear resistance under optimized melting conditions, which may be promising for next generation high performance UHMWPE materials for joint implant bearing surfaces. (RDC 12/22/2010)
Interfacial bond property of UHMWPE composite
(35-44) Polymer Bulletin 65 #1 (2010)
Zhu et al of East China University showed that UHMWPE resins mixed with hydrocarbons has good wettability with the UHMWPE fiber surface. The UHMWPE/PCH composite has excellent transverse tensile strength, interlaminar shear strength, and the pull-out strength together with outstanding interfacial bonding. (RDC 12/16/2010)