Papers by Keyword: UHMWPE

Abstract: A study was conducted on gamma-ray modified nanoHydroxyapatite (HAp)/Ultra High Molecular Weight Polyethylene (UHMWPE) composite as orthopedic implant material. This study aims to characterize the effect of gamma radiation on the physical, chemical, and mechanical properties of UHMWPE/HAp composites so that they can be used as orthopedic implant materials. The composite film was irradiated with gamma rays at a dose variation of 0 kGy, 15 kGy, and 30 kGy and a dose rate of 8 kGy/hour. Composites before and after radiation were tested for physical, chemical and mechanical properties. Physical properties test includes surface microstructure analysis; chemical properties test includes phase and functional group analysis; mechanical properties test, including hardness, tensile strength, and elongation at break. The results obtained are gamma radiation from IRKA changes the chemical properties of composites in terms of crosslinking and the number of radicals, as well as mechanical properties in terms of hardness, tensile strength, and elongation at break with different changes from the initial state before radiation. The best mechanical properties were obtained at 25% HAp composition in a dose of 30 kGy with a hardness (shore A) of 97.17; tensile strength of 18.15 MPa; and elongation at break of 17.85%, so that the UHWMPE/HAp composite has potential as an orthopedic implant material following the Ultimate Tensile Strength (UTS) of cancellous bone ranging from 10-20 MPa.

Abstract: Ultra-high Molecular Weight Polyethylene (UHMWPE) is a highly versatile polymer known for its exceptional mechanical properties, however, its limited life as an implant material for Total Joint Replacement (TJR) necessitates surface modification to extend its lifespan. This study aims to enhance the surface properties of UHMWPE through application of ceramic coatings. Magnetron sputtering method was used to deposit thin film of white Titania (TiO₂) on the material’s surface. To evaluate the surface characteristics, such as surface roughness, uniformity and structure, coated and uncoated samples were analyzed through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD). The material performance in relation to biological context was investigated through Contact Angle measurement. A comparative analysis of coated and uncoated samples was then performed. The coated samples showed better wettability compared to uncoated sample. This fact highlights the hydrophilic nature of film. The results of the coated UHMWPE suggest that this surface modification technique could significantly extend the lifespan of UHMWPE implants in TJR, potentially addressing the current limitations associated with their longevity.

Abstract: Fused filament fabrication (FFF) has nowadays become a popular 3-dimensional (3D) printing technique for the fabrication of polymeric components with customized and complex-shape design, including biomedical implants. However, the use of this technique is often constrained by the limited number of polymeric materials that can be printed to form the final product. Despite excellent wear resistance and widely used as the acetabular component of a joint prosthesis, ultra-high molecular weight polyethylene (UHMWPE) is among such the rarely-found filament material in the market. In this research, preliminary work to fabricate UHMWPE filament for the FFF processing is carried out by using extrusion. The influences of extrusion temperature, addition of polyethylene glycol (PEG), and rotational speed of the extruder’s screw on the physical, chemical, and mechanical properties of the extruded UHMWPE filament were determined. The result demonstrated no change in the chemical compositions of the filament due to the processing parameters applied, as noted from the FTIR spectra. The result of the tensile test showed that the highest tensile strength of UHMWPE filaments could reach 23.5 MPa.

Abstract: Wear is a problem for metal on polymer (MOP) hip implants to perform lifetime endurance. Polymer excessive volumetric loss leads to implant failures. Attempts to solve this problem are usually initiated with tribological tests. The method is time-consuming because the sliding speed is low. There is a faster way to use a computational method to gather wear data. This research aims to investigate the numerical convergence of predicted wear volume with the finite element method (FEM). The model is a commercially pure titanium (cp Ti) and ultra-high molecular weight polyethylene (UHMWPE) MOP hip implant. A dynamic Paul physiological load was applied to the model. Volumetric loss of the polymer was calculated with a wear equation involved nonlinear contact load and contact area. The inputs of calculation are wear factor and the computational contact mechanic performed by FEM. The wear factor was obtained by performing biotribological experiments with a multidirectional pin on disc tribotest. Predicted wear volume was validated with hip simulator experimental data from the literature. Convergences were found at the mesh density of 1.38 elements/mm³. An acceptable numerical error was obtained in the model with 1 mm element size for femoral head and 0.3 mm for acetabular cup. This model was then used for the investigation of load increment effects. The result is that load increment variations do not affect wear volume and contact mechanic numerical outputs. The calculated stresses are below the UHMWPE yield stress limit. In this elastic region, the effects of strain rate caused by load increment are negligible.

Abstract: In order to study the effect of UHMWPE fiber laminate on effective protection area of ceramic composite target, a dynamic analysis software ANSYS/LS-DYNA was used to calculate the effective protection area of ceramic/aluminum/aluminum composite target and ceramic/UHMWPE/aluminum/ aluminum composite target, both of whose areal density were 139.5kg/m², against 14.5mm armor piercing projectile at the speed of 1000m/s. The result showed that UHMWPE fiber laminates will increase the effective protection area by 64.4% for ceramic composite targets under the same areal density.

Abstract: The UHMWPE acetabular cups are the most popular joints for joint prostheses after Charnley introduced UHMWPE for the acetabular component in 1962. It has been demonstrated that polyethylene wear remains the main source of particles in the THR and therefore requires particular attention. The paper presents a series of theoretical and practical aspects regarding the wear of acetabular cups (made of UHMWPE) from the total hip prosthesis component. At the same time, the other tribological phenomena that occur in these MoP (metal on polyethylene) combinations are treated, such as lubrication and friction. Total Hip Replacement & Hip Resurfacing A hip replacement involves replacing the hip joint with a mechanical bearing system which is comprised of a femoral component and an acetabular component. During a hip replacement the acetabulum is reamed and the acetabular component is fitted into the cavity and the femoral component can either be placed over a reamed femoral head, in a procedure referred to as hip resurfacing, or positioned inside the femoral shaft during a total hip replacement [1]. Fig. 1. Total Hip Replacement (a) and Hip Resurfacing Replacement (b) [2].

Abstract: The paper presents a series of aspects regarding the design, manufacturing (through Rapid Prototyping) and FEA analysis of an intervertebral disk made from UHMWPE. In the first part are presented the most used model existing on the market. The CAD model and Finite Element Analysis (FEA) of the intervertebral disc (IVD) were made using the SolidWorks program. As a material, UHMWPE has been preferred due to good mechanical and biocompatibility characteristics.

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.