scholarly journals Parameterization of an interfacial force field for accurate representation of peptide adsorption free energy on high-density polyethylene

2015 ◽  
Vol 10 (2) ◽  
pp. 021002 ◽  
Author(s):  
Tigran M. Abramyan ◽  
James A. Snyder ◽  
Jeremy A. Yancey ◽  
Aby A. Thyparambil ◽  
Yang Wei ◽  
...  
Keyword(s):  
Free Energy ◽  
Force Field ◽  
High Density Polyethylene ◽  
High Density ◽  
Accurate Representation ◽  
Adsorption Free Energy ◽  
Peptide Adsorption ◽  
Interfacial Force

scholarly journals The Influence of Deformation under Tension on Some Mechanical and Tribological Properties of High-Density Polyethylene

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1429 ◽  
Author(s):  
Maciej Kujawa ◽  
Piotr Kowalewski ◽  
Wojciech Wieleba
Keyword(s):  
Free Energy ◽  
Surface Free Energy ◽  
Polymeric Material ◽  
Tribological Properties ◽  
High Density Polyethylene ◽  
High Density ◽  
Polymer Materials ◽  
Surface Appearance ◽  
Wear Process ◽  
Mechanical And Tribological Properties

Polymer materials are increasingly being used for sliding machine elements due to their numerous advantages. They are used even where they are deformed and in such a state that they interact frictionally, e.g., in machine hydraulics or lip seals. Few publications deal with the influence of deformation, which is the effect of, e.g., assembly on tribological properties of polymeric material. This deformation can reach up to ε ≈ 20% and is achieved without increasing the temperature of the polymer material. The paper presents the results of investigations in which high-density polyethylene (PE-HD) was maintained in deformation by means of a special grip (holder). The wear of the sample was significantly higher than that of the undeformed sample. This effect persisted even after partial relaxation of the stress in the sample after 24 h. Additional investigations were carried out to explain the obtained results. There were the microscopic observations of the surface after friction, measurements of microhardness, and surface free energy. Changes in the value of surface free energy and a significant decrease in microhardness with deformation under tension were observed. Deformed materials have a different surface appearance after friction and a different size and form of wear products. It was indicated that it is probable that the cohesion of the material will decrease and that the character of the wear process will change as a result of tension. Deformation under tension without heating of polymeric material (PE-HD), e.g., as a result of assembly, has been qualified as a threat to be taken into account when designing and analysing polymeric sliding elements.

Composition and Surface Topography Effects on Apatite-Forming Ability of Ceramic-Polymer Composites

2003 ◽  
Vol 774 ◽  
Author(s):  
Susan M. Rea ◽  
Serena M. Best ◽  
William Bonfield
Keyword(s):  
Surface Topography ◽  
High Density Polyethylene ◽  
High Density ◽  
Apatite Layer ◽  
Biologically Active ◽  
Human Blood Plasma ◽  
Apatite Formation ◽  
Polyethylene Matrix ◽  
Composite Surface ◽  
X Ray

AbstractHAPEXTM (40 vol% hydroxyapatite in a high-density polyethylene matrix) and AWPEX (40 vol% apatite-wollastonite glass ceramic in a high density polyethylene matrix) are composites designed to provide bioactivity and to match the mechanical properties of human cortical bone. HAPEXTM has had clinical success in middle ear and orbital implants, and there is great potential for further orthopaedic applications of these materials. However, more detailed in vitro investigations must be performed to better understand the biological interactions of the composites and so the bioactivity of each material was assessed in this study. Specifically, the effects of controlled surface topography and ceramic filler composition on apatite layer formation in acellular simulated body fluid (SBF) with ion concentration similar to those of human blood plasma were examined. Samples were prepared as 1 cm × 1 cm × 1 mm tiles with polished, roughened, or parallel-grooved surface finishes, and were incubated in 20 ml of SBF at 36.5 °C for 1, 3, 7, or 14 days. The formation of a biologically active apatite layer on the composite surface after immersion was demonstrated by thin-film x-ray diffraction (TF-XRD), environmental scanning electron microscopy (ESEM) imaging and energy dispersive x-ray (EDX) analysis. Variations in sample weight and solution pH over the period of incubation were also recorded. Significant differences were found between the two materials tested, with greater bioactivity in AWPEX than HAPEXTM overall. Results also indicate that within each material the surface topography is highly important, with rougher samples correlated to earlier apatite formation.

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