Nanoindentation properties of compression-moulded ultra-high molecular weight polyethylene

2003 ◽  
Vol 217 (5) ◽  
pp. 357-366 ◽  
Author(s):  
S P Ho ◽  
L Riester ◽  
M Drews ◽  
T Boland ◽  
M LaBerge
Keyword(s):  
Molecular Weight ◽  
Elastic Modulus ◽  
High Molecular Weight ◽  
Mechanical Response ◽  
Total Joint Replacement ◽  
Scanning Calorimetry ◽  
Nanomechanical Properties ◽  
Significant Difference ◽  
Ultra High Molecular Weight ◽  
Penetration Depths

This paper investigates the elastic modulus and hardness of untreated and treated compression-moulded ultra-high molecular weight polyethylene (UHMWPE) tibial inserts of a total knee replacement (TKR) prosthesis. Investigations were carried out at a nanoscale using a Nanoindenter™ at penetration depths of 100, 250 and 500 nm. The nanomechanical properties of surface and subsurface layers of the compression-moulded tibial inserts were studied using the untreated UHMWPE. The nanomechanical properties of intermediate and core layers of the compression-moulded tibial insert were studied using the cryoultrasectioned and etched UHMWPE treated samples. The cryoultrasectioning temperature (-150°C) of the samples was below the glass transition temperature, Tg(-122± 2°C), of UHMWPE. The measurement of the mechanical response of crystalline regions within the nanostructure of UHMWPE was accomplished by removing the amorphous regions using a time-varying permanganic-etching technique. The percentage crystallinity of UHMWPE was measured using differential scanning calorimetry (DSC) and the Tg of UHMWPE was determined by dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) was used to assess the effect of surface preparation on the samples average surface roughness, Ra. In this study, it was demonstrated that the untreated UHMWPE samples had a significantly lower ( p<0.0001) elastic modulus and hardness relative to treated UHMWPE cryoultrasectioned and etched samples at all penetration depths. No significant difference ( p > 0.05) in elastic modulus and hardness between the cryoultrasectioned and etched samples was observed. These results suggest that the surface nanomechanical response of an UHMWPE insert in a total joint replacement (TJR) prosthesis is significantly lower compared with the bulk of the material. Additionally, it was concluded that the nanomechanical response of material with higher percentage crystallinity (67 per cent) was predominantly determined by the crystalline regions within the semi-crystalline UHMWPE nanostructure.

High Molecular Weight Polyethylene Nanospheres: Synthesis Physical and Mechanical Properties

2008 ◽  
Vol 8 (6) ◽  
pp. 3123-3135 ◽  
Author(s):  
Pradip Paik ◽  
Kamal K. Kar
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Particle Size ◽  
Electron Microscope ◽  
Elastic Modulus ◽  
High Molecular Weight ◽  
Melting Temperature ◽  
Ion Beam ◽  
Atomic Scale ◽  
Scanning Calorimetry

The high molecular weight (MW) polyethylene (PE) particles of particle size varied from macro to micron to nanometer were synthesized by Grignard reagent. The microscopy analysis (scanning electron microscope, SEM; transmission electron microscope, TEM; and atomic force microscope, AFM) shows the spherical shape of PE particles. The effects of particle size, varies from macro to nanometer scale on crystal structure, crystallinity (χc), glass transition temperature (Tg), melting temperature (Tm), surface roughness and mechanical properties were studied. Differential scanning calorimetry (DSC) experiments show that the nanoparticles of PE are highly crystalline (χc ≈ 72%). The crystal length of PE nanoparticles is found to be approximately 14 Å. Although the Gibbs-Thomson equation is explained the depression of melting temperature (ΔTm) by 5 °C, the impervious results of Tg are still not fully understood. The low roughness value (2 Å) proves the presence of "atomic-scale-chain" folding at the surface of PE nanoparticles. A novel protocol is developed, and the elastic modulus of individual nanospherical PE particles is computed from 'force-distance' mapping curves of AFM. Hemispherical tungsten (W) tip was fabricated from focused ion beam and used as an indenter to measure the mechanical properties. It is found that the nano sized PE particles have higher elastic modulus (E = 1.2–1.4 GPa) compared to the bulk or macro sized PE (E = 0.6–0.7 GPa). The results corroborate the robustness of our experiments, since, the analogous results for macro sized particles match well with the literature.

Ultra-high Molecular Weight Polyethylene /Graphite Nanocomposites Prepared by High-energy Cryomilling.

2013 ◽  
Vol 1453 ◽  
Author(s):  
Sofía Vazquez-Rodriguez ◽  
Gloria E. Rodríguez-Vázquez ◽  
Selene Sepulveda-Guzman ◽  
Martín E. Reyes-Melo ◽  
Aaron Morelos-Gomez ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Mechanical Performance ◽  
Thermal Characterization ◽  
High Energy ◽  
Graphite Nanoplatelets ◽  
Scanning Calorimetry ◽  
Ultra High Molecular Weight ◽  
Graphite Nanocomposites

ABSTRACTUltra-high molecular weight polyethylene/graphite nanocomposites were prepared by high-energy cryogenic milling followed by syntering. Microstructure changes shows that graphite was reduced to graphite nanoplatelets by high-energy cryomilling and partial exfoliation of graphite to few layered graphene nanoplatelets occurred in a small extent. The resulting nanocomposites revealed high electrical conductivity and good mechanical performance. Thermal characterization of the nanocomposites was also carried out by differential scanning calorimetry.

scholarly journals High-density polyethylene crystals with double melting peaks induced by ultra-high-molecular-weight polyethylene fibre

2018 ◽  
Vol 5 (7) ◽  
pp. 180394 ◽  
Author(s):  
Weijun Miao ◽  
Hao Zhu ◽  
Tianchen Duan ◽  
Hongbing Chen ◽  
Feng Wu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
High Density Polyethylene ◽  
Fibre Composite ◽  
Crystal Form ◽  
High Density ◽  
Scanning Calorimetry ◽  
Orthorhombic Crystal ◽  
Fibre Composites ◽  
Ultra High Molecular Weight

High-density polyethylene (HDPE)/ultra-high-molecular-weight polyethylene (UHMWPE) fibre composites were prepared via solution crystallization to investigate the components of epitaxial crystal growth on a highly oriented substrate. Scanning electron microscopy morphologies of HDPE crystals on UHMWPE fibres revealed that the edge-on ribbon pattern crystals that were formed initially on UHMWPE fibres converted afterwards to a sheet shape as crystallization progressed. Wide-angle X-ray diffraction confirmed that the polymer chain oriented along the fibre axis and the orthorhombic crystal form of HDPE remained unchanged in HDPE/UHMWPE fibre composite systems. The thermal behaviour of the fibre composites measured by differential scanning calorimetry showed double melting peaks, the nature of which, as disclosed by partial melting experiments, is ascribed to bilayer components existing in the induced crystals: the inner layer is composed of more regularly folded chain crystals induced by UHMWPE fibres, and the outer layer formed on the inner one with a thinner and lower ordered crystal structure.

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