scholarly journals Characterisation of UHMWPE Polymer Powder for Laser Sintering

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3496 ◽  
Author(s):  
Yas Khalil ◽  
Neil Hopkinson ◽  
Adam Kowalski ◽  
John Patrick Anthony Fairclough
Keyword(s):  
Flow Characteristics ◽  
Laser Sintering ◽  
Polymer Chains ◽  
Low Friction ◽  
Artificial Joints ◽  
Suitable Material ◽  
Powder Properties ◽  
Sintering Behaviour ◽  
Ultra High Molecular Weight ◽  
Very High

Ultra-high molecular weight polyethylene (UHMWPE) is a thermoplastic semicrystalline polymer that has outstanding mechanical properties, low friction coefficient, excellent wear resistance, and is highly resistant to corrosive chemicals. UHMWPE is found in many applications including artificial joints and filtration. However, UHMWPE parts cannot be produced easily by traditional techniques, such as injection moulding and extrusion because of its very high melt viscosity owing to the extremely long polymer chains. Few attempts were made to process UHMWPE by additive manufacturing, particularly laser sintering. This is due to the lack of understanding of the powder properties of UHMWPE. Therefore, the aim of the powder characterisation process in this study is to gain a better understanding of the material requirements and provide a detailed insight on whether UHMWPE is a suitable material for laser sintering. The characterisation process includes powder morphological and flow characteristics, thermal behaviour and stability, and crystallinity of UHMWPE. The study reveals that the sintering behaviour of polymers is controlled by the morphology of the particles in addition to the viscous flow of UHMWPE. There are still difficulties of processing UHMWPE due to highly agglomerated structure of smaller particles with the presence of fibrils in the UHMWPE particles.

scholarly journals Roles of polymer brushes in biological applications

2021 ◽  
Vol 2 (1) ◽  
pp. 12-23
Author(s):  
Ajinkya Raut ◽  
◽  
Peter Renner ◽  
Rick Wang ◽  
Serge Kazadi ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Polymer Brushes ◽  
Selective Adsorption ◽  
Polymer Chains ◽  
Biological Applications ◽  
Low Friction ◽  
Binding Properties ◽  
Artificial Joints ◽  
Adhesion Protein ◽  
Functionalized Surfaces

Polymer brushes are macromolecular structures with polymer chains tethered to a surface resembling a brush. They have shown variety of uses in biological applications. Because of the nature of crafted polymers, the functionalized surfaces exhibit unique functions such as low friction, altered adhesion, protein binding and selective adsorption. Functionalization can be controlled by changing parameters such as grafting densities, chemical configurations, shapes and thickness. In this review, a particular emphasis has been provided for studies related to biological applications of polymer brushes based on their ultra-low friction, hydrophilic elongated surfaces, and binding properties. It provides useful information for researches and labs working on finding better solutions for drug delivery, arthritis, artificial joints, antibiofouling coatings and protein immobilization and purification.

Highly sinter-active nanocrystalline RE2O3 (RE = Gd, Eu, Dy) by a combustion process, and role of oxidant-to-fuel ratio in preparing their different crystallographic modifications

2007 ◽  
Vol 22 (3) ◽  
pp. 587-594 ◽  
Author(s):  
V. Bedekar ◽  
S.V. Chavan ◽  
A.K. Tyagi
Keyword(s):  
Combustion Process ◽  
Sintering Behavior ◽  
Stoichiometric Ratio ◽  
Monoclinic Modification ◽  
Fuel Ratio ◽  
Metal Nitrates ◽  
Powder Properties ◽  
Very High ◽  
Scanning Electron

Highly sinter-active powders of RE2O3 [rare earth (RE) = Gd, Eu, Dy] have been prepared using the corresponding metal nitrates as the oxidants, and glycine and citric acid as the fuels. Two different oxidant-to-fuel ratios, namely stoichiometric ratio and fuel-deficient ratio were used to explore the possibility of preparing different crystallographic modifications. By a careful control of oxidant-to-fuel ratio, nanocrystalline Eu2O3 and Gd2O3 could be prepared in cubic (C-type) as well as monoclinic (B-type) modifications. However, the high-temperature monoclinic modification could not be obtained for Dy2O3 due to a very high C-to-B-type phase transition temperature. The crystallite size, surface area, and sintering behavior were also studied for powders prepared using different oxidant-to-fuel ratios, and the results showed a remarkable correlation between different fuel contents and powder properties. Some of these powders resulted in pellets of nearly theoretical density. The sintered microstructure was studied by scanning electron microscopy.

Recommendations with Respect to the Improvement of Lubricating Qualities of Synovial Fluid in Artificial Joints

1993 ◽  
Vol 207 (2) ◽  
pp. 111-114 ◽  
Author(s):  
N S Gavrjushenko
Keyword(s):  
Synovial Fluid ◽  
Short Description ◽  
Plate Model ◽  
Red Bone Marrow ◽  
Artificial Joints ◽  
Hip Endoprosthesis ◽  
New Approach ◽  
Red Marrow ◽  
Ultra High Molecular Weight ◽  
Lubricating Properties

This paper gives a short description of the lubricating properties of yellow and red bone marrow taken from a femur of a cadaver. The experiments have been conducted on a ‘ball-on-plate’ model. The balls were made from steel 100 CR6 (German) and the plates were made from the same steel and ultra-high molecular weight polyethylene (UHMWPE, German ‘Herulen’). The friction coefficients under loads of 50 and 300 N were determined with different combinations of friction components. It has been found that the lubricating properties of yellow and red marrow have advantages over synovial fluid. In the light of these results the author develops a new approach to the design of a new hip endoprosthesis.

scholarly journals Selective laser sintering of copper filled polyamide 12: Characterization of powder properties and process behavior

2018 ◽  
Vol 40 (5) ◽  
pp. 1801-1809 ◽  
Author(s):  
Lydia Lanzl ◽  
Katrin Wudy ◽  
Sandra Greiner ◽  
Dietmar Drummer
Keyword(s):  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Polyamide 12 ◽  
Process Behavior ◽  
Powder Properties

A Comparison of (100) Hg1−x Cdx Te and Hg1−x ZnxTe Grown By Molecular Beam Epitaxy

1987 ◽  
Vol 102 ◽  
Author(s):  
R. D. Feldman ◽  
R. F. Austin ◽  
P. M. Bridenbaugh
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Near Infrared ◽  
Wave Length ◽  
High Electron ◽  
Mbe Growth ◽  
Suitable Material ◽  
Zn Content ◽  
Length Range ◽  
Very High

ABSTRACTFilms of HgCdTe with x < 0.6 and of HgZnTe with x < 0.26 have been grown by molecular beam epitaxy (MBE). Very high electron mobilities have been achieved for both materials in the small bandgap region. Hall mobilities at 77K reach 4.8 × 105 cm2 /V-s for Hg0 87 Zn0.13 Te, and 3.1 × 105 cm2/V-s for Hg0.87 Zn0.13 Te. HgCdTe growth was easily extended to the 1.5 – 3 μm wave length range. Attempts to extend HgZnTe to these bandgaps were unsuccessful due to defects that are induced by surface roughness in high Zn-content films. These results suggest that HgCdTe is the more suitable material for MBE growth for near infrared applications.

Effects of the properties of bulk solids on the relative performance of polyethylene and stainless steel wall lining materials in mass flow hoppers and other applications

2000 ◽  
Vol 214 (1) ◽  
pp. 53-62 ◽  
Author(s):  
M S A Bradley ◽  
M Bingley ◽  
R J Farnish ◽  
A N Pittman ◽  
G Lee
Keyword(s):  
Stainless Steel ◽  
Mass Flow ◽  
Wall Friction ◽  
Friction Test ◽  
Low Friction ◽  
Flow Discharge ◽  
Flow Problems ◽  
Bulk Solids ◽  
Bulk Solid ◽  
Ultra High Molecular Weight

Reducing the friction between the walls of storage vessels and the bulk solids that they contain is widely known to be beneficial in obtaining more satisfactory flow patterns in such vessels, and to reduce flow problems. In particular, the advantages of low friction in promoting a mass flow discharge pattern are well understood; means of obtaining data to design a hopper for mass flow are also well established. In recent years a number of polyethylene materials have come on to the market, intended for use in lining silos and claimed by their manufacturers to offer low wall friction in comparison with other materials. In this paper, one particular commercial grade of ultra-high molecular weight polyethylene (UHMWPE) material has been tested alongside a commonly used type and finish of ferritic stainless steel. The wall friction has been measured for both materials, with a variety of bulk solid materials and conditions, and the hopper half-angles needed for mass flow computed for each combination. The results show that the UHMWPE material does not always offer a lower friction than the stainless steel; in some cases it offers much lower friction and hence much greater scope for obtaining mass flow discharge. However, in other cases it gives significantly higher friction and is a bad choice for promoting flow. The principal conclusion is that, under certain circumstances, UHMWPE offers substantial advantages over other wall materials. However, this advantage is by no means universal and, if it is to be considered for employment in a hopper design, then a wall friction test should be undertaken. This test should use a sample of the bulk solid to be handled against both the UHMWPE material and other possible materials.

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