Ultra-high Molecular Polyethylene Research Articles

Wear resistance of composite materials based on ultra-high molecular polyethylene with combined filling

Polymer composite materials (PCM) of antifriction duty with self-lubricating properties are used for the manufacture of various parts in friction units of machines and mechanisms. PCM can partially replace parts made of metals and alloys, increasing the reliability and service life of the equipment when the use of oils or external lubricants is limited or prohibited. The goal of the study is the effect of fillers (sulfenamide, sulfur, magnesium and zinc oxides) on the tribological parameters of polymer composite materials based on ultra-high molecular weight polyethylene (UHMWPE). Samples were prepared by hot pressing at a temperature of 175°C and a pressure of 10 MPa. Composites with filler concentrations 0.5 and 1 wt.% were considered (for sulfenamide, sulfenamide with sulfur, and combinations of 0.5 and 1 wt.% sulfenamide with sulfur and zinc oxide or magnesium oxide). It is shown that the introduction of sulfenamide leads to an increase in the wear resistance by six times, and the introduction of a combination of fillers of 0.5 wt.% sulfenamide, sulfur, and magnesium oxide — by 1.5 times. The friction surfaces of composites were studied using methods of scanning electron microscopy and IR-spectrometry. The formation of an oriented ordered structure in the form of clusters of wear products was revealed on the friction surfaces of composites filled with sulfenamide. In the case of combined filling, secondary structures were found on the friction surface, which visually differ from the UHMWPE friction surface. The appearance of peaks in IR spectra corresponding to oxygen-containing groups (–C=O, –COOX) was observed on the friction surface of composites with combined filling. It is shown that IR spectra of composites with mono- and binary fillers have peaks of less intensity due to the formation of secondary structures. The introduction of sulfenamide into UHMWPE, together with zinc and magnesium oxides, promotes the crosslinking of polymer macromolecules in the friction zone due to frictional heating, shear loads, and the action of a counterbody. The developed materials can be used as parts of friction units for cars and transport equipment that can withstand harsh operating conditions in a sharply continental climate.

Investigation of the Friction Properties of a New Artificial Imitation Cartilage Material: PHEMA/Glycerol Gel.

The absence of artificial articular cartilage could cause the failure of artificial joints due to excessive material wear. There has been limited research on alternative materials for articular cartilage in joint prostheses, with few reducing the friction coefficient of artificial cartilage prostheses to the range of the natural cartilage friction coefficient (0.001-0.03). This work aimed to obtain and characterize mechanically and tribologically a new gel for potential application in articular replacement. Therefore, poly(hydroxyethyl methacrylate) (PHEMA)/glycerol synthetic gel was developed as a new type of artificial joint cartilage with a low friction coefficient, especially in calf serum. This glycerol material was developed via mixing HEMA and glycerin at a mass ratio of 1:1. The mechanical properties were studied, and it was found that the hardness of the synthetic gel was close to that of natural cartilage. The tribological performance of the synthetic gel was investigated using a reciprocating ball-on-plate rig. The ball samples were made of a cobalt-chromium-molybdenum (Co-Cr-Mo) alloy, and the plates were synthetic glycerol gel and two additional materials for comparison, which were ultra-high molecular polyethylene (UHMWPE) and 316L stainless steel. It was found that synthetic gel exhibited the lowest friction coefficient in both calf serum (0.018) and deionized water (0.039) compared to the other two conventional materials for knee prostheses. The surface roughness of the gel was found to be 4-5 μm through morphological analysis of wear. This newly proposed material provided a possible solution as a type of cartilage composite coating with hardness and tribological performance close to the nature of use in wear couples with artificial joints.

К ВОПРОСУ СОВЕРШЕНСТВОВАНИЯ ПОСЕВА ЗЕРНОВЫХ КУЛЬТУР В УСЛОВИЯХ АРИДИЗАЦИИ КЛИМАТА

The working bodies of the seeders experience significant loads, leading to wear of the working surfaces (WP) and violation of the sowing technology, which necessitate reseeding on more than 10% of the area when sowing grain in dried soil. The sowing itself is delayed due to sticking of the working bodies during precipitation during the sowing period. Promising is the use of coulters, in which (RP) they have both wear resistance and the ability to reduce soil stickiness when sowing grain crops. It is proposed to use overlays made of ultrahigh molecular polyethylene (UHMWPE) on the RP of standard disc coulters (SDS), converting them into upgraded disc coulters (MDS). The research determined the parameters and method of fastening the lining from the SVPME to the RP disk. Field tests have confirmed that fixing the lining to the disk with rivets in the amount of 24 pieces ensures the reliability of the MDS, which fulfill the requirements of sowing in the studied modes. There was a decrease in the adhesion of soils during the operation of the MDS by 1.6...2.9 times relative to the SDS. On all types of soils, the traction resistance of MDS at a sowing depth of 0.06 m varies within 60...80 N, which is 1.23...1.55 times less than that of SDS. The wear rate of the MDS working surfaces made of UHMWPE RE-500 is more than 3 times less than that of 65G steel, which makes it possible to increase their resource by 1.5-2.4 times in comparison with SDS. Grain seeders equipped with MDS allow to extend the periods of trouble-free operation both in arid conditions and at high soil humidity, providing the specified agrotechnical requirements for sowing technology in various climatic conditions.

Investigation of Compression and Hardness for UHMWPE Bio-composites as Internal Bone Plate Fixation

Bone plates are essential for bone fracture healing because they modify the biomechanical microenvironment at the fracture site to provide the necessary mechanical fixation for fracture fragments. This paper addresses the use of composite bone plates in healing long-bone fractures such as transverse fractures of the femur. However, stress shielding in the bone due to metal plates can be reduced by designing implants with Bio-composites that involve Ultra high molecular polyethylene reinforced (UHMWPE) with Nano hydroxyapatite (n-HA) and Nano titanium dioxide (n-TiO2) particles at different weight fraction (0,1.5,2.5,3.5and 4. 5%) and 5% of carbon and Kevlar fibers. FRIT spectrum was used to identify the incorporation between the matrix and Nano particles, and the shifting in main peaks confirmed the good cross-linking within the composite structure. The specimens thus prepared were subjected to a compression test, hardness test, and density. The results indicated that UHMWPE+4.5%n-HA+CF hybrid biocomposite has the highest compressive strength and hardness properties. In contrast, UHMWPE+4.5%TiO2+CF has the highest density, which increased with increasing percentages of weight fraction of Nano-particles, where the compression strength 53 MPa, hardness property ranges 65.6 shore D, and density 1.09 (g/cm3). According to the current study's findings, it is possible to create bio-composites as internal fixation device with improved performance by placing different fiber reinforcements.

Electret-thermal analysis of dielectric objects

The development of methodological tools for studying the most possible range of the objects of dielectric nature is an urgent task. We present the results of studying dielectric objects by the method of electret-thermal analysis (ETA). Electrophysical changes in dielectric objects were studied taking into account polarization effects and electret state. The ETA data of ultrahigh molecular polyethylene, polyvinyl alcohol, human blood, synovial fluid, starch-containing polymer biodegradable compositions, chitosan, and vegetable oils are presented. Analysis of the spectra of thermally stimulated currents obtained during tests revealed that ETA method is characterized by high information content regarding various dielectric objects.Thermally stimulated current response makes it possible to identify and interpret phase phenomena occurring upon heating of the objects, including those accompanied by electrophysical processes of transfer and relaxation of the electret charge. The results obtained can be used to improve the methodology for analyzing electrophysical changes in dielectric objects.

On the characterization of viscoelastic behaviours of ultra-high molecular polyethylene composite with 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid

On the characterization of viscoelastic behaviours of ultra-high molecular polyethylene composite with 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid

Finite element analysis of tibio‐femoral contact mechanics of a customised knee spacer

With one-third of patients having osteoarthritis predominantly in one compartment of the knee, unicompartmental knee spacers have been introduced as a less invasive alternative to total knee replacement. However, patients with the knee spacer implanted were seen to have persistent pain, resulting in high revision rates. A static finite element model of the knee and its interaction with a knee spacer implant at full extension and 90° flexion was used to investigate the tibio-femoral contact mechanics of the knee joint after a knee spacer surgery. Three different knee spacer designs (contoured, flat and C-shaped) were modelled and prescribed with cobalt-chrome, ultra-high molecular polyethylene and polyurethane material properties. The results suggested that a softer spacer is generally preferred as this helps in the conformity of knee spacer to the condyle, effectively distributing the load subjected to the implant. Flat spacers that result in high stresses resulting from lower contact areas should be avoided.

ИССЛЕДОВАНИЕ ПОЛИМЕРНЫХ МАТЕРИАЛОВ, МОДИФИЦИРОВАННЫХ С ИСПОЛЬЗОВАНИЕМ КАРБИДА БОРА В4С, ДЛЯ РАДИАЦИОННОЙ ЗАЩИТЫ

Novel material Tivarobor, an ultra-high-molecular polyethylene (UHMP) containing B4C nanoparticles, was tested for the ability to attenuate neutrons and ϒ-quants. Attenuations of orthogonal prompt neutrons and ϒ-quants established based on ambient dose measurements were compared with calculations. Digital radiography detector (DRD) was used for regular electron beam targeting at a DRD water phantom. Good agreement of attenuations was confirmed on two accelerators. The authors discuss the composite materials technology and Tivarobor applicability in radiation therapy and onboard manned spacecrafts.

Friction Behavior of 3D-printed Polymeric Materials Used in Sliding Systems

Recently, 3D-printed polymeric materials have been successfully replacing the usual ones especially used in sliding systems like couplings. Among the polymeric materials, Acrylonitrile Butadiene Styrene (ABS) and Poly Lactic Acid (PLA) can be the competitive materials in such application after 3D-printing. In this study, 3D printing was used to produce samples from ABS and PLA via fused deposition modelling (FDM) technology. Then friction behavior of 3D-printed samples was investigated depending on printing orientation of the samples. Ultra High Molecular Polyethylene Weight (UHMWPE), as a well-known industrial polymer, was also used for comparing the friction behavior of 3D-printed ABS and PLA polymers. Friction tests were conducted using a pin-on-plate type tribometer according to ASTM G133 under different applied loads and sliding speeds at room temperature. It was found that printing orientation of all ABS and PLA samples has a considerable effect on their friction behavior. Transverse direction (T.D) of the 3D-printed samples shows higher coefficient of friction (COF) values than the longitudinal direction under all applied loads and sliding speeds. On the other hand, COF values obtained in both 3D-printed samples increase as the load and speed increase regardless of the printing direction. When both 3D-printed materials are compared, PLA samples exhibit lower COF values than ABS samples in both printing directions and under all loads and speeds. However, the UHMWPE sample produced with traditional method shows much lower COF values and stable change in friction behavior under all conditions compared to 3D-printed PLA and ABS samples.

Investigation on Dynamic Characteristic of Geared Rotor System Composed of Ultrahigh Molecular Polyethylene Gear and Metal Gear

A geared rotor system model consisting of UPE gears and steel gears for medium speed, medium load and long servo time is proposed. The solid models of steel-steel, steel-UPE and UPE-UPE gear systems were established. The dynamic models of steel-UPE gear system and UPE-UPE gear system were reconstructed by using the theoretical mechanical model of UPE. The time-varying meshing stiffness of three gear systems is analyzed. The vibration responses of three gear systems are studied by STFT method. The dynamic loads of three gear systems under different loads and rotational speeds are researched in detail, and the changing rules of dynamic loads of three gear systems under different loads and rotational speeds are revealed. At last, the first ten modes of three gear systems are calculated and the results are discussed. At the same time, the modal results are used to verify the correctness of the research on vibration response and dynamic load of three gear systems.

Primary complex total hip replacement in 13 months old neglected Pelvi-acetabular fracture

Old pelvi-acetabular fracture are very difficult to operate in terms of achievement of anatomical reduction. Although two staged procedures are still treatment of choice(first stage acetabular osteosynthesis then THR if complication occurs) but neglected cases(more than 3 weeks old untreated fractures)can also treated by total hip replacement. Our case is A 35 years old patient sustained railway traffic accident. He had crush injury left lower limb severe abdominal and chest trauma, bilateral sacroiliac join disruption, iliac wing fracture left side and pelvi-acetabular fracture right side.at that time patient was treated at other hospital where above knee amputation of left lower limb done, abdominal and chest injury managed but pelvi-acetabular fracture was treated conservatively. After 1 year patient presented to us with pain and restriction of movement of right hip and inability to sit also. we performed primary complex total hip replacement using multi-hole acetabular cup and un-cemented femoral stem with metal on ultra high molecular polyethylene bearing and bone graft. results are satisfactory with fair range of motion at hip and modfied harris hip score. So primary complex total hip replacement is viable option for old pelvi-acetabular fracture cases where anatomical and biological reduction of fracture is not possible.

Tribological and Mechanical Properties of UHMWPE Polymer Composite filled with TiO2 and Al2O3 Particles used as TKR Implant

This study focused on the development of a polyethylene biomaterial for replacement of the joints like knee joints, etc. Through forming aluminum oxide and titanium oxide particles into ultra-high molecular polyethylene, commonly known as high modulus polyethylene, this substance has strengthened its mechanical and wear properties. The composite is made using the injection molding machine by reinforcement materials like bio-inert aluminum oxide (Al2O3) and titanium di oxide (TiO2) with UHMWPE. Mechanical properties like Tensile, Bending, impact strength and hardness and wear rate of the synthesized polymer composite is tested according to ASTM standards.C3 composite shows enhancement in mechanical and tribological properties, only decrease in the impact strength is seen comparing to other two compositions. So C3 composite can be used as implant.

The impact of non-vacuum electron beam treatment on the structure and properties of ultra-high molecular weight polyethylene

The results of work on the impact of electron beam treatment on the structure, mechanical properties, microhardness, and thermal stability of ultra-high molecular polyethylene (PE-UHMW) are presented in this work. Electron beam processing was carried out on an industrial impulse accelerator ILU-10. The samples were irradiated with electrons with energies of 2.5 MeV, 3.5 MeV and 4.5 MeV, and the radiation dose varied from 2MGy to 9 MGy. It was determined by the method of differential scanning calorimetry that the melting temperature of the PE-UHMW polymer practically does not change for all samples, regardless of the radiation dose. After electron beam treatment, the morphology of the surfaces of the PE-UHMW polymer is significantly improved, spherulites are formed at the micro level, which indicate the displacement of polymer molecules under the influence of irradiation. It was revealed that during electron beam treatment oxidation occurs as a result of chemical reactions of the polyethylene chain with oxygen O2. Significant changes in the mechanical properties of the PE-UHMW polymer were not observed after electron beam treatment. However, a significant decrease in the elongation from 300 % to 10 % as a result of radiation aging was observed after electron beam treatment.The hardness of the PE-UHMW polymer varies slightly in the studied mode of electron beam processing.

Development of a Wear-Resistant Extrudable Composite Material Based on an Ultrahigh-Molecular Polyethylene with Predetermined Properties

The necessary composition and content of fillers of a multicomponent extrudable composition based on an ultrahigh-molecular polyethylene (UHMPE) with specified mechanical and tribotechnical characteristics are determined. For the purpose of effective and operational development of extrudable composites based on an UHMPE, a minimum amount of experimental data and an algorithm for determining the governing parameters (formulations) is used, which give the needed (restrictive) values for the effective characteristics of multicomponent polymer-polymer compositions. This allows one to secure the tribological, mechanical and technological properties required. The limited amount of experimental data for the relation between the effective properties and the formulation required is supplemented by values calculated using the Lagrange interpolation polynomial. The relations obtained are represented as surfaces and the corresponding level lines. The imposition of level lines allows one to determine the area that meets the requirements specified and to find the formulation necessary for it. On the basis of this algorithm, the optimum formulation of a three-component mixture consisting of an UHMPE, a high-density polyethylene grafted with maleic anhydride, and a polypropylene having tribomechanical properties at the level of an UHMPE, but with a melt flow-behavior index suitable for 3D printing by fused deposition modeling, is determined. According to the formulation found, samples were made and tested, and they completely satisfied the properties prescribed.

Development and research of tillage operating device with polymeric materials

Polymeric materials are advised to be used in the construction of operating devices for energy-saving soil cultivation. Purpose of work is to develop the design of new operating devices with polymer materials. Development of the design of new operating devices with polymeric materials is carried out by replacing part of the metal parts with ultra-high molecular polyethylene of low density. New operating devices carry out several technological operations in one pass. The design of the new operating device contains a rack with a chisel for deep tillage. The front of the rack is equipped with removable plowshare blades. Clod crusher with a possibility of movement and thrust plate are located at the chisel. In the upper part of the rack the ripper for surface tillage is mounted with the possibility of replacing. Ultra-high molecular polyethylene of low-density was installed on the chisel and clod crusher of the tillage operating device, the thrust plate and the ripper for surface tillage are made entirely of polymeric material. Decrease to 18.28% of draught resistance of the operating device with polymeric materials was established.

Electron irradiation resistance of the composite material structure based on ultra-high molecular polyethylene and boron carbide

Effect of electron irradiation on the structural state of a composite material based on ultrahigh molecular weight polyethylene (UHMWPE) and boron carbide particles (B4C) which is a precursor for functional radiation protection materials has been investigated. Composite powder materials were synthesized from industrially available components by the method of mechanochemical activation under conditions of intense shock-shear deformations. Specimens in the form of 2 mm thick composite powder’s pressed plates were irradiated with 2 MeV electrons in air. Studies of changes in the structural and morphological characteristics of the composite samples were carried out by means of scanning electron microscopy, X-ray diffraction, FTIR spectroscopy and differential scanning calorimetry. Effects of electron irradiation on the structure of the composite as a whole and its components were analysed. The analysis of the obtained data showed the resistance of the composite material with respect to the electron irradiation fluence up to 8·1014 cm–2.

INVESTIGATION OF PHYSICO-MECHANICAL AND RHEOLOGICAL CHARACTERISTICS OF NANOCOMPOSITES OF ULTRAHIGH-MOLECULAR POLYETHYLENE

The paper presents the results of a comparative study of the physicomechanical and rheological characteristics of nanocomposites of ultrahigh-molecular-weight polyethylene, grade GUR 4120 (Ticona) with nanocrystalline silica with a dispersity of 20 nm (0.05% - 0.2%), nano scale aluminum oxide of the mark “Nafen” 10 ... 20 nm (0.1%) and carbon nanotubes Tuballmatrixbeta (0.1%). It was established that the introduction of silicon dioxide in the optimal concentration of 0.1 ... 0.15% contributes to an increase in the tensile strength by 44%, and the final modulus of elasticity by 46%. The limit of forced elasticity and the initial modulus of elasticity are more influenced by carbon nanotubes (an increase of 23%). However, the results in this case are characterized by a significant scatter of values. Nanofibres of the Nafen brand provide growth of strength by 22%, final elastic modulus by 28.6%. The dependence of the complex viscosity of composites at a temperature of 180 °C on the angular velocity is described by the Ostwald de Ville power equation. The introduction of nanoscale modifiers leads to an increase in the consistency coefficient of ultrahigh molecular weight polyethylene by 3.9 ... 6.6 times, with the flow index increasing only by 1.02 ... 1.28 times. It is shown that the use of optimal (0.1 ... 0.15%) concentrations of nanocrystalline silicon dioxide, aluminum oxide nanofibers and carbon nanotubes combined with ultrahigh-molecular polyethylene by mechanochemical activation in a planetary ball mill, significantly improves physical and mechanical characteristics of the latter. In this case, a more effective modifier is nanocrystalline silicon dioxide. The significant effect of ultra-low concentrations of nanoscale modifiers is apparently due to the formation of a spatial network of physical bonds in the composite volume, which persists even at a temperature of 180 ° C, as evidenced by the results of rheological tests.

PREPARATION OF BLENDING COMPOSITIONS BASED ON SECONDARY POLYPROPYLENE WITH CONTROLLED PHYSICO-MECHANICAL PROPERTIES

It was investigated the effect of the method of obtaining polymer composites based on the blend of polymers over a wide range of their ratios on the rheological and physical-mechanical properties. The composites were prepared (using pressing or pressure die casting) on the basis of secondary polypropylene (PP) and the following polymers: 1) ultra high molecular polyethylene (UHMPE); 2) ethylene propylene diene monomer (EPDM); 3) secondary low pressure polyethylene (LPPE). Pressing was carried out on an automatic hydraulic press "AutoMH-NE" (Carver, the USA) at 210°C and endurance under pressure of 7000 kgfs within 3 min. Injection molding was performed using a Babyplast automatic molding machine of the horizontal type with an injection volume of up to 15 cm3. In both cases, the compositions also went through a stage of the preliminary mixture at the laboratory station (plastograf) of "PlastographEC" (Brabender, Germany) within 15 min at a load of 200 N. Estimation of rheological properties of the polymer composition melts was performed using a Haake Mars III rheometer. The deformation-strength properties were studied according to the State Standard GOST 11262-80 with a tensile testing machine "Shimadzu AGS-X". Using the data of relative rheometry, it is determined for all the systems studied (blends PP with UHMPE, EPDM, and LPPE) that variation of the maximum torque with composite composition is non-additive. This seems to be due to the occurring phase reversal. The present fact finds its support when performing rheological investigations using absolute rheometry. It is shown that variations in the phase structure of composites occurring in the phase reversal area lead to the corresponding changes in the deformation-strength properties of composites.

Evaluation of operation indicators of the working units of transporting devices made of polymeric materials

In this paper we presents the results of production tests of a new transporting devices type made of with using new polymeric materials based on ultrahigh-molecular polyethylene (UHMWPE). It is possible to improve the operational properties of technological cleaning lines for grain seeds and improve the quality of grain cleaning.

Thermooxidative Destruction of Solvent During Production of High-Strength Fibers of Ultrahigh-Molecular Polyethylene (UHMPE) by Gel-Formation Method

Changes in the chemical composition of the solvent (Vaseline oil) as a result of its thermooxidative destruction were detected and investigated by UV and IR spectroscopy. It was found that an absorption band at ~270 nm, corresponding to the chromophoric C=O and C=C groups, appears in the electronic spectrum and increases in intensity during thermal destruction of Vaseline oil while absorption bands at 1720 and 1740 cm-1, due to the appearance of terminal acid and aldehyde groups respectively, appear in the IR spectrum. The kinetics of the accumulation of chromophoric groups in relation to the experimental temperature was investigated, and a correlation was established between the intensity of the color of the solvent and the concentration of chromophoric groups.