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Ultrahigh-molecular-weight Polyethylene (ultrahigh-molecular-weight + polyethylene)
Selected AbstractsProduction of Ultrahigh-Molecular-Weight Polyethylene/Pristine MWCNT Composites by Half-Titanocene CatalystsADVANCED MATERIALS, Issue 8 2009Sungjin Park MWCNT/ Ultrahigh-molecular-weight polyethylene (UHMWPE) composites, where pristine MWCNTs are well dispersed in the UHMWPE matrices, are produced using MWCNT/half-titanocene hybrids as catalysts. The diameter of the UHMWPE-coated MWCNT strands produced is about 30,70,nm, while the diameter of the pristine MWCNTs used is 10,15,nm. UHMWPE composites with a molecular weight greater than 2,×,106 are produced. [source] Investigation of the ultradrawing properties of gel spun fibers of ultra-high molecular weight polyethylene/carbon nanotube blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Jen-Taut Yeh Abstract The carbon nanotubes (CNTs) contents, ultrahigh-molecular-weight polyethylene (UHMWPE) concentrations and temperatures of UHMWPE, and CNTs added gel solutions exhibited significant influence on their rheological and spinning properties and the drawability of the corresponding UHMWPE/CNTs as-prepared fibers. Tremendously high shear viscosities (,s) of UHMWPE gel solutions were found as the temperatures reached 140°C, at which their ,s values approached the maximum. After adding CNTs, the ,s values of UHMWPE/CNTs gel solutions increase significantly and reach a maximum value as the CNTs contents increase up to a specific value. At each spinning temperature, the achievable draw ratios obtained for UHMWPE as-prepared fibers prepared near the optimum concentration are significantly higher than those of UHMWPE as-prepared fibers prepared at other concentrations. After addition of CNTs, the achievable draw ratios of UHMWPE/CNTs as-prepared fibers prepared near the optimum concentration improve consistently and reach a maximum value as their CNTs contents increase up to an optimum value. To understand these interesting drawing properties of the UHMWPE and UHMWPE/CNTs as-prepared fibers, the birefringence, thermal, morphological, and tensile properties of the as-prepared and drawn fibers were investigated. Possible mechanisms accounting for these interesting properties are proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation and tribological properties of polyetheretherketone compositesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010Dangsheng Xiong Abstract Polyetheretherketone (PEEK) is a thermoplastic engineering plastic with excellent mechanical properties. In this article, PEEK and its composites filled with ultrahigh-molecular-weight polyethylene (UHMWPE) were prepared by vacuum hot-pressing method. Tribological properties of these materials were investigated by block-on-ring friction and wear rig. An alloy (CoCrMo) ring and a ceramic (Si3N4) ring were used as friction pairs. The experiments were conducted under deionized water lubrication (DWL), saline lubrication (SL), and calf serum solution lubrication (CSSL). Worn surfaces morphology was observed and analyzed by metallographic microscope. The results indicated that friction coefficients of PEEK/UHMWPE composites were effectively reduced when compared with pure PEEK. When the materials slid against the alloy (CoCrMo) ring, wear rates of PEEK/UHMWPE were also effectively reduced when compared with pure PEEK. Wear mechanisms of PEEK were mainly ploughing and slight scratches under CSSL condition, whereas the quantity of the ploughing and scratches for PEEK/20%UHMWPE were significantly reduced. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] ,-Irradiation of ultrahigh-molecular-weight polyethylene: Electron paramagnetic resonance and nuclear magnetic resonance spectroscopy and imaging studies of the mechanism of subsurface oxidationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2004Todd M. Alam Abstract The shelf aging of irradiated ultrahigh-molecular-weight polyethylene (UHMWPE) causes subsurface oxidation, which leads to failure in UHMWPE orthopedic components, yet the mechanisms causing subsurface oxidation remain unclear. The shelf aging of ,-irradiated UHMWPE bars has been studied with electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) imaging and with microtoming and Fourier transform infrared microscopy. The bars initially contained only allyl radicals, and upon air exposure, a surface layer of peroxyl radicals formed through the reaction of allyl radicals with oxygen. Importantly, a band of low radical intensity just beneath the peroxyl layer became apparent. NMR imaging showed a zone of altered proton relaxation in this zone. With increasing time, surface peroxyl radicals persisted in comparison with the interior allyl radicals, although oxygen did not appear to penetrate any more deeply into the bar. The area of maximal oxidation and mechanical disruption, measured after 3 years, was at the interface between the zone of exterior peroxyl radicals and the zone of low radical intensity. We present a mechanism involving the intermediacy of sterically strained reactive dialkyl peroxides at this interface to explain subsurface oxidation. We also demonstrate that EPR and NMR imaging provides information that could potentially be used to identify subsurface oxidized UHMWPE components before failure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5929,5941, 2004 [source] Preparation, morphology, and adhesive and mechanical properties of ultrahigh-molecular-weight polyethylene/SiO2 nanocomposite fibersPOLYMER COMPOSITES, Issue 4 2010Yi Zhang A simple treatment approach has been performed to achieve enhanced surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers by incorporation of nano-silicon dioxide (SiO2) in the presence of silane coupling agent during gel-spinning process. The SiO2 -treated UHMWPE (UHMWPE/SiO2) nanocomposite fibers with different nano-SiO2 compositions were characterized with Fourier transform infrared spectra, scanning electron microscopy, and wide-angle X-ray diffraction, and their interfacial adhesion and mechanical properties were also investigated. The nano-SiO2 can be trapped on the surface of the fibers to form rough surface for UHMWPE/SiO2 fibers, and diffused into the inner of fibers to induce the lower crystal sizes and higher crystallinity of polyethylene in UHMWPE/SiO2 fibers. The resulting UHMWPE/SiO2 fibers therefore exhibit a dramatic enhancement in the adhesive properties because of the combination of rougher surface compared with those of UHMWPE fiber and polar groups absorbed on the surface of fibers. The mechanical properties of UHMWPE/SiO2 nanocomposite fibers are enhanced simultaneously because of the influence of nano-SiO2 on the structure of UHMWPE crystalline regions and fibrils. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] | ||||||||||