Papers by Keyword: UHMWPE

Abstract: The following research is aimed at understanding the influence of Zirconia-Toughened Alumina (ZTA) and Silicon Nitride (Si₃N₄) on Ultra-High Molecular Weight Polyethylene (UHMWPE) acetabular liners. Bioceramic femoral heads were systematically tested against UHMWPE in controlled environment according to static/load-free coupling in hydrothermal environment, pin-on-ball wear testing, and hip-simulator wear testing. In addition, a retrieved ZTA femoral head has been analyzed and results have been compared to the simulations. Experimental results from X-ray photoelectron (XPS), cathodoluminescence (CL), Raman and Fourier-Transformed Infrared spectroscopy suggest that, despite conventional notions imply that bioceramics are inert, the surface chemistry of bioceramics was relevant to the oxidation rate of polyethylene liners. Non-biointertness could either be advantageous or disadvantageous toward polyethylene oxidation. The main reason resides in the peculiar chemical interactions between polyethylene and different ceramics, and, more specifically, depends on the direction of oxygen flow at the interface between the ceramic and the polymer. ZTA femoral heads were found to release a non-negligible amount of oxygen moieties from their surfaces, thus accelerating oxidative degradation of polyethylene. Conversely, Si₃N₄ ceramics exerted a protective role towards the polyethylene liner by scavenging oxygen from the tribolayer. The results of this work provide new insights into the interaction between bioceramics and polymers, which should also be considered when designing the next generation artificial hip joints with significantly elongated lifetimes.

Abstract: With the increasing demand of biomaterials, numerous studies have been developed seeking to improve its properties through new obtaining and manufacturing processes. This work aimed to aggregate antimicrobial property to a biocomposite constituted of a matrix of ultra-high molecular weight polyethylene (UHMWPEE) and hydroxyapatite, by the incorporation of zinc oxide nanoparticles. The samples were prepared based on a standard composition containing 95.0 wt% of UHMWPEE and 5.0 wt% of hydroxyapatite (blank). Three compositions were evaluated ranging the amount of zinc oxide nanoparticles incorporated in the standard sample. It was observed that the increase of zinc oxide concentration aggregate a good antibacterial property in the samples tested without cause significant changes in the mechanical properties of the composites.

Abstract: This research investigated the influence of silicon dioxide (SiO₂) with particle size of 5 micron on microstructure, mechanical properties and wear resistance of UHMWPE polymeric composite materials under dry sliding friction that was tested by Block–on–ring technique according to ASTM G77. Bulk UHMWPE composite specimen was reinforced with SiO₂ particles by weight fraction of 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4 and 5 wt.%. Specimen was performed by hot compression process with the compression forming conditions at the temperature of 202°C, pressure of 9.7 MPa and exposure time of 77 minutes. It was found that, SiO₂ particle fraction in the range of not exceed than 0.5 wt.% did not affect to change microstructure of the specimen, which its microstructure did not significantly different from the initial UHMWPE specimen due to SiO₂ particles were dispersed uniformly in the UHMWPE matrix. Its microstructure appeared in a spherulitic structure pattern. However, the increasing of SiO₂ more than 0.5 wt.% affect to changed microstructure due to the SiO₂ particles separated from the matrix and accumulated on the UHMWPE matrix. For the case of mechanical and wear resistance properties, the increasing of SiO₂ particle of 0.5-1 wt.% affect to increased various mechanical properties to have a highest value and lowest wear rate as compared with initial UHMWPE up to 1.7 times. After that, the increasing of SiO₂ particle affect to mechanical properties and wear resistance were decreased, except for the hardness that continuously increased according to the increasing of SiO₂.

Abstract: This study focused on the mixing methods used in the manufacture of ultra-high molecular weight polyethylene (UHMWPE) reinforced by multi-walled carbon nanotubes (MWCNTs) and how these methods enhance the wear performance of the composite. Two mixing methods, ball milling and ultra-sonication, were used in this study, and the most effective forms of these mixing methods were analysed to allow an effective comparison. The performance of the mixing methods was evaluated through a comparison of wear volume loss, coefficient of friction, and hardness. The optimal power and mixing time for sonication in this study was determined and composites with 0.5% CNTs w/w concentration were conformed. It was evidenced that the mixing process influence the mechanical and wear performance of UHMWPE / MWCNTs composites and ultrasonication was identified as an effective mixing method that improves significantly the wear performance of the composite.

Abstract: We developed a retainer with a new kind of design. This retainer has pockets with angles which we think could improve wear durability. We used ultra high molecular weight polyethylene (UHMWPE) because it is a tough thermoplastic polymer with self-lubrication ability. We performed rolling contact fatigue tests and found that wear durability was improved compared with the standard bearings.

Abstract: In our previous work, we designed a new joint system for humanoid sized robot. This system consists of a servomotor, a harmonic drive and a link unit. This link unit includes three components; polymer bushes, a metal cam plate and a metal camshaft. However elastic deformation of all-polymer bushes can cause a large backlash in the system. In the present work, a new bush was developed and its fatigue behavior was investigated.

Abstract: The reduced wear rate of hip-joint bearing components is the main issues in biotribology researches for the biomedical implants. Ultra-high molecular weight polyethylene (UHMWPE) is extensively used as a bearing material because of having its great properties of friction and wear. Surface texturing can be selected as a method of enhancing tribology properties of engineering surfaces. In this present study, surface texturing examination was performed by 3D finite element method under influence of normal load. Stress distribution of UHMWPE surface under the influence of texturing with the variation in diameter cavities and separation was investigated. The result showed that the surface texturing provided the higher stress distribution of the lower separation in the cylindrical cavities.

Abstract: The effects of Modified NanoSiO₂ Agents on the morphology and performance of ultra-high-molecular weight polyethylene (UHMWPE) microporous membranes via thermally induced phase separation were investigated in this work. The NanoSiO₂ was surface modified by silane coupling agent KH570 (KH570-NanoSiO₂). Differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD) were performed to obtain crystallization of UHMWPE/white oil/ KH570-NanoSiO₂ doped system. The morphology and performance of the prepared UHMWPE microporous membranes were characterized with scanning electron microscopy (SEM) and microfiltration experiments. The results showed that the morphology of UHMWPE membrane could be disturbed by KH570-NanoSiO₂. Porosity and the rejection of Bovine serum albumin (BSA) of the blend membrane increased with increasing concentration of Modified NanoSiO₂, while the water flux slightly decreased.

Abstract: The wear of polymeric bearing material in contact with metallic biomedical implant has often been the main cause of long-term clinical failure of such implants. Very few studies seem to have been undertaken to investigate the wear behaviour of Ultra-High-Molecular-Weight-Propylene (UHMWPE) bearing material in contact with titanium alloy implant material under various loading conditions. This research paper presents an investigation on the wear properties of UHMWPE under dry and wet sliding conditions at different loading conditions. In this study, the well-known pin-on-disk equipment was used to carry out the sliding wear test. The titanium pin was made by Electron Beam Melting (EBM) technology and machined to rub on the UHMWPE disk. The aim is to understand the wear characteristics of UHMWPE in relation to Ti6Al4V alloy under various loading and lubricating conditions. Results include volume loss and wear rate analysis.

Abstract: Stainless steel AISI 316L (SS316L) and ultra-high molecular weight polyethylene (UHMWPE) are widely used materials for artificial hip joint components. The SS316L material is typically used for the acetabular cup, femoral head and the stem, while the UHMWPE material is used for the acetabular liner in an artificial hip joint. The aim of this work is to study the biocompatibility of SS316L and UHMWPE materials by implanting and installing these materials in the tissues of rabbits. The tissues around the implants were examined after eight weeks of the installment. Results showed that the reaction of the rabbit tissues around the implants was positive. It was concluded that the SS316L and the UHMWPE materials are biocompatible and the applications of these materials for implants seems conceivable.