Ultra-high Molecular Weight Polyethylene Composites Research Articles

Ultra-high molecular weight polyethylene bioactive composites with carbonated hydroxyapatite

To develop an orthopedic material for bone substitution, the substitute material must mimic living tissue from an anatomical and physiological point of view. The high wear and impact resistance besides the low friction coefficient, make ultra-high molecular weight polyethylene (UHMWPE) a suitable material to be used in orthopedic applications. However, UHMWPE is a bioinert material, not providing a proper interaction with the bone tissue surrounding to the implant. One way to mitigate this issue is improving UHMWPE bioactivity. This can be done by adding bioactive fillers in the polymeric matrix. In this work, UHMWPE composites were prepared by twin-screw extrusion. The fillers used were carbonated hydroxyapatite (CHA) and hybrids formed by precipitating CHA in collagens (hydrolyzed and type II). The results show that the fillers used caused a slight reduction in UHMWPE crystallinity degree, while both crystallization and melting temperatures remained almost unchanged. Dynamic-mechanical thermal analysis indicated a weak adhesion between filler and polymeric matrix, which is good from the biological point of view since the bioactive filler surface will be available to apatite deposition. The obtained materials exhibited good mechanical properties and in vitro bioactivity assay showed that all of the prepared materials are bioactive.

Features of the Charge State of UHMWPE + α-SiO2 Nanocomposites

This paper presents the results into the study of electret properties of composite materials based on ultrahigh molecular weight polyethylene (UHMWPE) and nano-dispersed amorphous silica filler α-SiO2 (aerosil) depending on the volume content of silicon dioxide and the absorbed dose D γ-irradiation at room temperature using the method of thermally stimulated depolarization (TSD). It was found that introducing up to 5% of spherical nanoparticles of amorphous α-SiO2 silicon dioxide with a diameter of 20 nm in UHMWPE first increases and then reduces the electret characteristics of the composites. UHMWPE + 1% α-SiO2 has the maximum value of the electret potential difference and the stability of the electret state. It was shown that preliminary γ-irradiation affects the electret properties of the studied composite material, which is associated with its increased electrical conductivity and a high charge relaxation rate. The observed increase in the initial surface charge density σel of UHMWPE compositions is associated with the presence of energy traps of injected charge carriers. Based on the analyzing the spectra of TSD, it was shown that the thermal stability of electrets from the UHMWPE composite + 1% α-SiO2 is improved. The nature of the TSD current of pre-γ-irradiated films once again proves that, after γ-irradiation, the injected charges from the corona zone mainly accumulate in the near-surface layers of the irradiated samples. The results of TSD suggest that the relaxation of the electret state in the materials under study occurs due to the bulk conductivity.

Tribological and physical performance of micro bearing concept for diluted epoxy filled with UHMWPE composite

Short fillers have been widely used as reinforcing agents due to their successful effects on composite materials. However, studies for short fillers were mainly focusing on even dispersion of fillers in the composite system. As for the application related to bearing, the fillers needed to be deposited on the surface to improve the physical and tribological properties. Therefore, in this study, the fundamental of micro bearing concept was imparted by relating to the rheological study of polymer. These relations can be supported by the theory of particulate fillers in suspensions according to Modified Mooney-Einstein’s Theory of Viscosity. The Ultra High Molecular Weight Polyethylene (UHMWPE) fillers, which possess high wear resistance, were fabricated with epoxy resin. The mixture was prepared by diluting with acetone solvent and varying the filler loadings percentage for 1%, 3%, 5%, 7%, and 10%, accordingly. Based on the results observed, there were increment up to 41.7% for viscosity value. For the wear test, the results showed decrease in the wear rate up to 72.0%. For the hardness test, the results indicate increment in the hardness value up to 94% compared to UHMWPE alone. For the density test, the results showed decrease in the density value up to 3.8%.

Preparation and characterization of ultrahigh molecular weight polyethylene composites with high content of multiwall carbon nanotubes

AbstractIn order to obtain the ultrahigh molecular weight polyethylene (UHMWPE) composites with high conductivity and mechanical property, an effective route of solution mixing and followed by hot‐pressing was investigated for UHMWPE composites with high content of multiwall carbon nanotubes (MWCNTs). The effect of MWCNT contents on the crystallization and melting behavior, crystal structure, electrical conductivity, and mechanical properties of MWCNT/UHMWPE composites was characterized by differential scanning calorimetry, four‐probe measurement configuration, X‐ray diffraction, and universal testing machine, respectively. The effect of MWCNTs on crystallization temperatures of UHMWPE is discussed by the heterogeneous nucleation of MWCNTs and the restriction of the macromolecular chain motion of UHMWPE by MWCNTs. The electrical conductivity of UHMWPE is significantly increased with increasing of MWCNT contents and the UHMWPE composite with the conductivity of 5649 S m−1 can be obtained at the MWCNT content of 60 wt%. The influence of MWCNTs on tensile strength and modulus of UHMWPE composites is explained by the reinforce effect of MWCNTs and the lower content of UHMWPE not enough to support the structure of composites.

Fretting Wear Behavior of Cu/Ultra-High Molecular Weight Polyethylene Nanocomposites Under Different Strokes

Ultrahigh molecular weight polyethylene (UHMWPE) composites reinforced with various contents of nanometer sized particles of Cu were prepared by a hot pressing technique. The fretting wear behavior of UHMWPE and the Cu/UHMWPE nanocomposites were evaluated on an oscillating reciprocating friction and wear tester. The study focused on the effect of the Cu nanoparticle contents and the fretting strokes on the fretting wear behavior of the composites. The results showed that both the strokes and the contents of Cu nanoparticles had an influence on the tribological properties of the composites. The friction coefficients and wear rates first decreased and then increased with the increasing of Cu nanoparticles contents. The content corresponding to the lowest friction coefficient was 1.5%. When the amounts of Cu nanoparticle ranged from 0.5% to 1%, the composites showed the lowest wear rates. In general, the higher number of strokes corresponded to the lower wear rates, which were attributed to alleviated abrasion. More importantly, thin and uniform transfer films were formed on the worn surfaces of the steel balls after sliding against the 1% Cu/UHMWPE nanocomposites. Consequently, the wear rate was decreased. It was inferred that the inclusion of Cu nanoparticles is beneficial for improving the wear resistance of the composites.

Computer-Aided Design of the Composition of Extrudable Polymer–Polymer UHMWPE Composites with Specified Antifriction and Mechanical Properties

An algorithm for computer design (calculated determination of the composition) of a multicomponent antifriction material is proposed. First, the minimum initial set of composite characteristics is determined experimentally for a number of controlling parameters from tribological and mechanical tests. The subsequent computer-aided design of the material in the form of constructing the corresponding response surfaces in the space of states makes it possible to identify the range of variation of the controlling parameters to provide the specified operational and technological characteristics. This approach is illustrated by the computer-aided design of the material composition (feedstock) in the form of an extrudable polymer composite based on ultra-high molecular weight polyethylene (UHMWPE) for applications in additive technologies. An optimal formulation is proposed for the UHMWPE + n wt % HDPE-g-SMA + n wt % PP ternary mixture that has tribological and mechanical properties at the level of unfilled UHMWPE and, at the same time, the melt flow index required for 3D printing by the fused deposition modeling method.

Microwave-assisted composite fabrication of nano-hydroxyapatite reinforced ultra-high molecular weight polyethylene composite

Fabrication of composite using microwave energy is a rapid and emerging manufacturing route. This paper deals to address fabrication challenges during fabrication of nano-hydroxyapatite (HA) reinforced ultra-high molecular weight polyethylene (UHMWPE) composite by utilization of microwave energy. In the proposed fabrication technique, composite constituents were taken as UHMWPE and nano-HA powders with average particle size of 100 μm and 100 nm, respectively. In this work, the weight fraction of nano-HA was 10%, 15% and 20%. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was done to confirm the dispersion of nano-HA (reinforcement) in UHMWPE (matrix). Mechanical behaviour of the fabricated composite was studied in terms of uniaxial tensile loading, flexural loading and Shore D hardness test. The thermal degradation of UHMWPE/nano-HA composite was studied using differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). With addition of 20% wt% of nano-HA fillers, the comparative percentage increase in Young’s modulus, ultimate tensile strength, flexural strength and hardness of UHMWPE/nano-HA composite were 70.65%, 35.52%, 42.84% and 39.24%, respectively

Mulberry-like carbon spheres decorated with UiO-66-NH2 for enhancing the mechanical and tribological performances of UHMWPE composites

Abstract Preparing nanoparticles with hierarchical structure is a promising approach to improve the interfacial adhesion between additives and polymer matrix. Herein, we exploited hydrothermal carbon spheres (HCSs) decorated with amino-functionalized UiO-66 (UiO-HCSs) to enhance the mechanical and tribological properties of ultra-high molecular weight polyethylene (UHMWPE) composites. Experimental analyses of the morphologies and chemical structure indicate the successful growth of Zr-based metal-organic frameworks (MOFs) on the surfaces of HCSs. The comprehensive studies reveal the beneficial effects of mulberry-like UiO-HCSs nanoparticles on the interfacial properties. The transfer of Zr-based materials onto the steel counterpart also contributes to decrease the wear rate of UHMWPE composites. Furthermore, the present work may pave a route for applying MOFs to tribology.

Design of the ultrahigh molecular weight polyethylene composites with multiple nanoparticles: An artificial intelligence approach

This study proposes a suitable composite material for acetabular cup replacements in hip joint that involves ultrahigh molecular weight polyethylene, a clinically proven material, as the matrix. To design new ultrahigh molecular weight polyethylene composites with multiple reinforcements for the improvement in mechanical and tribological performance, artificial neural network and genetic algorithm, the two artificial intelligence techniques, are employed. Published reports on the use of ultrahigh molecular weight polyethylene reinforced with multi-walled carbon nanotube and graphene are used as database to develop two artificial neural network models for Young's modulus and tensile strength. The optimum solutions are obtained using genetic algorithm, where the artificial neural network models are used as the objective functions. Two different composites, derived from the optimum solutions, are made reinforcing both multi-walled carbon nanotube and graphene. Tensile and wear tests show significant enhancement in the properties. The structures of the composites are also characterized, and wear mechanisms are discussed.

Selective electromagnetic interference shielding performance and superior mechanical strength of conductive polymer composites with oriented segregated conductive networks

Manipulation of the conductive network is essential for the electromagnetic interference (EMI) shielding performance of conductive polymer composites, which have broad application prospects to address the concerns of electromagnetic pollution emitted by modern electronics. In this work, the oriented segregated structure was achieved in carbon nanotube (CNT)/ultrahigh molecular weight polyethylene (UHMWPE) composites via solid-phase stretching and the orientation of segregated network was controlled by adopting different draw ratios. Benefiting from the unique oriented segregated structure, the composites delivered prominent EMI shielding performance with intriguing frequency selectivity, which did not occur in conventional segregated composites. Moreover, remarkable mechanical reinforcement was obtained in the oriented segregated composites, which was attributed to the interfacial crystallization along segregated pathways and the formation of highly oriented lamellae. At a draw ratio of 6, the oriented segregated composite with 2 wt% CNTs showed the maximum EMI shielding effectiveness of 33.5 dB and tensile strength of 216.1 MPa, which surpassed the conventional segregated composite by 69.2% and 455.5%, respectively. This effort demonstrates a simple, feasible, and effective approach for the design and fabrication of mechanically robust, bandwidth-selective EMI shielding composites.

Structure, as well as the Tribological and Mechanical Properties, of Extrudable Polymer-Polymeriс UHMWPE Composites for 3D Printing

In order to develop dispensable materials for additive manufacturing technologies, the structural and functional analysis of antifrictional polymer-polymer blends based on ultrahigh-molecular weight polyethylene (UHMWPE) are performed. The problem of the optimal selection of polymer plasticizers from the commercially available thermoplastic is solved in order to improve the extrudability of UHMWPE. It is shown that the effective plasticizing filler for UHMWPE from the standpoint of maintaining its tribological and mechanical characteristics and providing the required melt flow index is a double mixture of 10 wt % HDPE-g-SMA + 10 wt % PP. Using the developed materials will make it possible to manufacture parts of a complex shape for tribojoints, including endoprostheses, by the 3D printing method.

Material Selection And Development Of Ankle Foot Orthotic Device

Abstract People with disease like stroke, spinal cord injury have disabilities in the lower limb and results abnormal walking. Weakness of plantar and dorsiflexion muscles at ankle is a major factor of neuromuscular disorder. Hence it necessitates invention of supportive device for the treatment of ankle impairments. This paper provides design concepts of ankle foot orthotic (AFO) based on selected material and analysis of motion of normal human GAIT with motion analyzing system to develop suitable AFOs. In this research paper material like Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), Nylon 6/6, Polypropylene, 13% Kevlar Fiber reinforced ultra-high molecular weight polyethylene (UHMWPE) composite are selected for development of AFO. Based on finite element analysis, Kevlar Fiber Reinforced UHMWPE based composite material is selected as best material for fabrication of AFO. Proper selection of material for manufacturing of AFO leads to greater increase in popularity to patients during walking providing better and compatible ankle foot orthotic device for patient specific.

Preparation and thermal property of ultrahigh molecular weight polyethylene composites filled by calcium carbonate modified with long chain

Ultrahigh molecular weight polyethylene (UHMWPE) is an excellent property polymer, but its poor processability due to high melt viscosity limits the more wide-ranging application. To improve the processability of UHMWPE composites filled by calcium carbonate (CaCO3), a novel method is reported to modify CaCO3. PE wax coated on the surface of CaCO3 (PEW@CaCO3) can be prepared by acrylic acid–modified CaCO3 (AA-CaCO3) and PE wax. The crystallization and melting behavior of UHMWPE and its composites filled by CaCO3, AA-CaCO3, and PEW@CaCO3 was compared by differential scanning calorimetry. The processability of UHMWPE composites was characterized by torque rheometer. The effect of CaCO3, AA-CaCO3, and PEW@CaCO3 on the crystallization and processability of UHMWPE was discussed.

Simultaneously enhanced mechanical properties and thermal properties of ultrahigh‐molecular‐weight polyethylene with polydopamine‐coated α‐alumina platelets

AbstractPolydopamine (PDA) was employed to modify micrometric Al2O3 platelets to improve the interfacial compatibility between α‐Al2O3 powder and ultrahigh‐molecular‐weight polyethylene (UHMWPE). The structure of PDA‐coated Al2O3 and UHMWPE composites was investigated via Fourier transform infrared spectroscopy, scanning electron microscopy and X‐ray photoelectron spectroscopy. The thermal stability and mechanical performance of the samples were also evaluated. It is clear that UHMWPE/PDA‐Al2O3 composites exhibit better mechanical properties, higher thermal stability and higher thermal conductivity than UHMWPE/Al2O3 composites, owing to the good dispersion of Al2O3 powder in the UHMWPE matrix and the strong interfacial force between the macromolecules and the inorganic filler caused by the presence of PDA. The tensile strength and the tensile elongation at break of UHMWPE/PDA‐Al2O3 composite with 1 wt% PDA‐Al2O3 are 62.508 MPa and 462%, which are 1.96 and 1.98 times higher than those of pure UHMWPE, respectively. The thermal conductivity of UHMWPE/PDA‐Al2O3 composite increases from 0.38 to 0.52 W m−1 K−1 with an increase in the dosage of PDA‐Al2O3 to 20 wt%. The results show that the prepared PDA‐coated Al2O3 powder can simultaneously enhance the mechanical properties and thermal conductivity of UHMWPE. © 2018 Society of Chemical Industry

Assessment of Delamination in Tensylon� UHMWPE Composites by Laser-induced Shock

Ultra-High Molecular Weight Polyethylene (UHMWPE) composites are the result of recent developments in material research for ballistic protection due to their ability to absorb the kinetic energy of the bullet by various mechanisms of dissipation, among which an important one is delamination. In order to study this mechanism independently, the laser induced shock wave testing procedure has been used on thin Tensylon� laminate samples. Laser-induced shock represents a modern approach that can be used for assessing the interlaminar bond strength between two plies of a composite material, in dynamic conditions, at high strain rates representative for a ballistic impact. Through this technique, a delamination failure stress threshold can be determined. In the present work, the laser induced shock technique was applied on the commercial UHMWPE material called Tensylon�. The delamination threshold of this material was determined by using the Novikov approach, and, compared to the literature, the results match the values determined by other means of measurement.

Highly Anisotropic, Thermally Conductive, and Mechanically Strong Polymer Composites with Nacre-like Structure for Thermal Management Applications

The conventional approach to improve the thermal conductivity (TC) of polymers by blindly adding inorganic fillers suffers from the limited TC enhancement (<3.0 W/mK) with isotropic TC and poor mechanical performance. Here, highly anisotropic, thermally conductive, and mechanically strong boron nitride (BN)/ultrahigh molecular weight polyethylene composites are prepared via a facile solid-phase extrusion (SPE) technology. The in-plane TC approaches 12.42 W/mK at the BN loading of 50 vol %, which is 242% higher than that of the high-pressure compressed counterpart (3.63 W/mK). The anisotropic index of TC reaches as high as ∼1000%, allowing the heat transfer more readily along in-plane direction than through-plane direction as revealed by infrared imaging results. We attribute the increased TC to the unique nacre-like structure induced by the flow-assisted alignment. BN platelets are highly oriented to form connected thermal conductive pathways for phonon transport along the basal plane. The interfacial the...

The Influence of SBF on Surface Properties of Irradiated GO/UHMWPE Nanocomposites

In this study, the irradiated ultra-high molecular weight polyethylene (UHMWPE) components doping with graphene oxide (GO) were immersed in simulated body fluid (SBF) environment at 37°C for 6 months, and their surface properties were studied by ball indentation, scratch, and wetting tests. The results show that both the irradiation cross-linking treatment and the addition of 0.5 wt % GO can increase the indentation hardness and scratching coefficient of the surface of UHMWPE composites, and wettability of it becomes better. After soaking in SBF, the ball indentation and scratch coefficient of irradiated GO/UHMWPE nanocomposites decreased by 12.4 and 10.0%, respectively. Which may due to a swelling action and the oxidative degradation occurred on the surface of GO/UHMWPE nanocomposites. However, irradiation cross-linking and filling with GO can prevent the macromolecules from penetrating into UHMWPE base material and materials, thereby reducing the rate of swelling and oxidative degradation.

Segregated conductive CNTs/HDPE/UHMWPE composites fabricated by plunger type injection molding

The advantages of segregated conductive polymer composites are greatly hampered owing to its limited preparation technology, which seriously relies on hot compression with low efficiency. The plunger type injection molding (PTIM) is employed to fabricate segregated carbon nanotubes (CNTs)/high density polyethylene (HDPE)/ultra-high molecular weight polyethylene (UHMWPE) composites in this paper, which lowers the production cycle by 45%, compared with the conventional hot compression. The morphology and conductive properties are investigated in detail. Graceful segregated conductive network and a very low percolation threshold (0.45 vol%) of the polymer composites have both been achieved. The present processing technique with short production cycle provides a fancy idea to realize segregated conductive polymer composite in mass production.

Deep penetration of ultra-high molecular weight polyethylene composites by a sharp-tipped punch

The penetration of unidirectional (UD) and [0o/90o] cross-ply ultra-high molecular weight polyethylene fibre composites by sharp-tipped cylindrical punches has been investigated. While the measured penetration pressure for both composite types increased with decreasing punch diameter, the pressure was significantly higher for the cross-ply composites and increased with decreasing ply thickness. A combination of optical microscopy and X-ray tomography revealed that in both composites, the sharp-tipped punch penetrated without fibre fracture by the formation of mode-I cracks along the fibre directions, followed by the wedging open of the crack by the advancing punch. In the cross-ply composites, delamination between adjacent 0o and 90o plies also occurred to accommodate the incompatible deformation between plies containing orthogonal mode-I cracks. Micromechanical models for the steady-state penetration pressure were developed for both composites. To account for material anisotropy as well as the large shear strains and fibre rotations, the deformation of the composites was modelled via a pressure-dependent crystal plasticity framework. Intra and inter-ply fracture were accounted for via mode-I and delamination toughnesses respectively. These models account for the competition between deformation and fracture of the plies and accurately predict the measured steady-state penetration pressures over the wide range of punch diameters and ply thicknesses investigated here. Design maps for the penetration resistance of cross-ply composites were constructed using these models and subsequently used to infer composite designs that maximise the penetration resistance for a user prescribed value of fibre strength.

Effect of consolidation pressure on the impact behavior of UHMWPE composites

Abstract For the first time, the influence of the manufacturing process on the dynamic performance of ultra-high molecular weight polyethylene (UHMWPE, Dyneema® HB26) composites is investigated. The material is significantly influenced by the hot-pressing parameters temperature and pressure. The ballistic resistance and shock wave behavior was characterized for the UHMWPE composite consolidated with three different pressures. In the case of UHMWPE composites, higher consolidation pressures result in a better ballistic performance. The shock wave behavior converges to high-density polyethylene (HDPE). Based on these observations, an analytical approach is proposed describing the equation of state as a function of consolidation pressure.