Ultra High Molecular Weight Polyethylene

This study involves the failure analysis of an ultra high molecular polyethylene (UHMWPE) tibial insert from Apollo® Total Knee System, which was removed after 10. years of service from 70. years old female patient. The tibial insert was investigated by using a stereoscope, scanning electron microscope (SEM), infinite focus microscope (IFM) and energy disperse spectroscopy (EDS) to characterize the morphology and composition of the bearing surface. Differential scanning calorimetry (DSC) and Fourier transform spectroscopy (FTIR) were employed to characterize the degradation and crystallinity of the component. Gel-permeation chromatography (GPC) was used to measure the polyethylene tibial insert molecular weight. Results showed that the failure of total knee replacement (TKR) was associated with high grade wear and oxidation degradation. Surface delamination, scratch marks, pitting, folding, and embedded third body particles were observed on the retrieved UHMWPE tibial surface. Pit depth as large as 60 μm was measured on the surface. The damage features observed on the UHMWPE tibial insert suggested degradation is due to fatigue related wear and is oxidation-induced. Overall results show that the UHMWPE tibial insert which was retrieved from a patient who is active and but not overweight underwent degradation of material properties and high grade wear during 10. years of service.

http://www.sciencedirect.com/science/article/pii/S1350630711000999

This context aims to investigate and give scrutiny report on flexural strengthening of RC beams with the help of ultrahigh molecular weight polyethylene. The experimental phase of this study is to explore the flexure behavior of RC beams by contrasting control RC beams with retrofitted RC beams. Here UHMW PE was used as a retrofitting material. It is one type of geosynthetic. UHMW PE (Ultra High Molecular Weight Polyethylene) is an extremely tough plastic with high abrasion and wear resistance. The versatility of polyethylene has made it a popular plastic for countless industrial applications that require durability, low friction, and chemical resistance. UHMW PE sheet were bounded externally using EPOXY and hardener. RC beams were made weak in flexure and then retrofitted to detect the flexure action considered. Two sets of beams were considered Set-1 consisting of three control samples with 100%,70%and 40% of flexural reinforcement. Set-2 consists three samples with 100%,70%and 40% flexural reinforcement and retrofitted with UHMW PE. The results showed that the retrofitting samples had more capacity to carry load than those of control samples. Thus, retrofitting is a feasible solution to overcome the stresses in the structure. This study also involves ultimate carrying load capacity, failure mode and pattern of cracks of the beam are also investigated.

There are described nanocomposites based on ultra high molecular weight polyethylene and graphite nanoplates prepared by in-situ polymerization method. It is carried out a comprehensive study of electric properties of these composites, including direct current (dc) and alternating current (ac) properties. There is explored dependence of the conductivity and dielectric permeability on filler concentration, temperature, deformation and frequency of electric field. These relationships are compared with those for composites based on other carbon fillers including both nanoscale (carbon nanotubes, carbon black) and micron-sized (graphite, schungite) fillers. More specific electrical properties of investigated materials such as lower percolation threshold and higher dielectric permittivity compared to those for composites based on other carbon fillers are attributed to the plate-like shape of graphite nanoplates. These materials are distinguished also by their high electrical stability against temperature and deformation. Therefore, it makes graphite nanoplates the most preferable conductive filler for some practical applications. Some possible application areas for UHMWPE/graphite nanoplates nanocomposites will be also discussed.