Molecular Weight Polyethylene Composites Research Articles

Impact response of Shear Thickening Fluid (STF) treated ultra high molecular weight poly ethylene composites – study of the effect of STF treatment method

Shear thickening fluids (STFs) are a special class of field responsive non-Newtonian fluids which exhibit transition from low viscosity to high viscosity state when these are subjected to shear deformation, particularly when the shear rate exceeds a critical value termed as the critical shear rate (CSR). Due to this unique characteristic of STFs, these are generally used for vibration mitigation or shock absorbance such as in vibration dampeners, hip protection pads, in protective gear for athletes etc. From the last two decades, STFs have found application in the field of ballistics, particularly in the development of special class of STF-intercalated armours called Liquid Body Armours (LBAs). These new age armours are lighter in weight and more flexible as compared to conventional heavy armours, which, infact seriously affect the mobility and agility of the soldier, especially in combat situations. Although, exhaustive studies are available which show the improvement in impact resistance of STF-treated high performance fabrics, but there are limited studies which explore the efficacy of STF treatment method. In this study, an attempt is made to understand this aspect. The low velocity impact studies were conducted on drop tower machine, while high velocity impact studies were accomplished on in-house designed and fabricated Split Hopkinson Pressure Bar (SHPB) experimental set-up. It was observed that when STF was kept in liquid form between layers of ballistic fabrics, the composite exhibited reduced performance, whereas, STF-treated ballisic composites exhibited enhanced impact toughness at high strain rates in SHPB testing.

Friction and wear characteristics of ultrahigh molecular weight polyethylene (UHMWPE) composites containing glass fibers and carbon fibers under dry and water-lubricated conditions

The effects of introducing glass fiber (GF) and/or carbon fiber (CF) filler materials on the friction and wear characteristics of ultra-high molecular weight polyethylene (UHMWPE)-based composites were investigated. The composites were evaluated against GCr15 steel under dry and water-lubricated conditions. The goal was to develop an improved material for water-lubricated journal bearings. The friction coefficients of UHMWPE composites were obtained using a pin-on-disc tribometer using sliding speeds ranging from 0.2 to 1.0m/s, contact pressures from 1.0 to 5.0MPa, and two counterface roughness values (Ra=0.1 and 0.3μm). The samples were lubricated by dropping distilled water onto the sliding surface. To evaluate the wear mechanisms, the morphologies of the worn surfaces were examined by scanning electron microscopy and laser 3D micro-imaging profile measurements. In addition, the elemental distribution and content in the transfer film on the GF/UHMWPE composite surface were measured using an energy-dispersive X-ray spectrometer. The results show that glass fibers could effectively reduce the wear rate of composites. In addition, a hybrid filling of glass and carbon fibers could significantly reduce the friction coefficient under water lubrication and dry conditions.

Synthesis and Tribological Performance Study of Ultrahigh Molecular Weight Polyethylene Composites Reinforced with Graphene Oxide

In order to improve the hardness and tribological properties of ultrahigh molecular weight polyethylene (UHM-WPE), UHMWPE composites reinforced with graphene oxide (GO) nanosheets by ball milling is presented in this article. The results show that the content of 20 wt% GO composite exhibits the lowest friction coefficient and the best wear resistance among all specimens under distilled water lubrication conditions. The mechanism of GO content on tribological properties of the composites under dry conditions and distilled water were investigated. Super low friction coefficient value and the best wear resistance under distilled water is attributed to water provides passivation of interacting dangling bonds on the sliding surface of GO. This study provides a new path to synthesize the high wear resistance and mechanical performance GO/UHMWPE composite materials under water condition and may have huge potential applications in many related fields, such as biomedical and marine engineering.

The addition of acid treated carbon nanotube on the interfacial adhesion of carbon fiber reinforced UHMWPE composite

Carbon fiber reinforced Ultra High Molecular Weight Polyethylene (CF/UHMWPE) composites have been filled with acid treated carbon nanotube to enhance the adhesion. According to the modification, the interlaminar shear strength (ILSS) of composites has been greatly improved. Dynamic wetting method, XPS and SEM are used to examine the microscopic properties of resultant composites. The enhanced ILSS is attributed to the CNT interlock, which improves the wetting between carbon fibers and resins. Copyright © 2017 John Wiley & Sons, Ltd.

Stick-slip behaviours of water lubrication polymer materials under low speed conditions

This study investigated the different stick-slip behaviours of ultra high molecular weight polyethylene (UHMWPE), synthetic rubber (SR) and fiber resin composite (FRC) polymer materials with ZCuSn10Zn2 plates under water-lubricated conditions on an UMT-3 tribo-tester. The stick-slip phenomena of the polymers at the starting processes were significant and led to different frictional noise emissions. With better hydrophilicity and viscoelasticity, fiber resin composite resulted in the smallest frictional noise. A better hydrophobicity and worse self-lubricating property resulted in the largest stick-slip phenomenon and frictional noise of synthetic rubber. Thus the results disclosed the relationship between the lubrication property of the polymers and their frictional noise performance, and could be of help for the selection of high performance water lubrication materials.

Study of dynamic compressive behaviour of aramid and ultrahigh molecular weight polyethylene composites using Split Hopkinson Pressure Bar

In this paper, high strain rate compression properties of aramid and ultrahigh molecular weight polyethylene composites in the out-of-plane direction are tested at room temperature on a Split Hopkinson Pressure Bar apparatus. Tests were conducted on composites reinforced with woven or Uni-Directional (UD) fabrics made from aramid or ultrahigh molecular weight polyethylene as well as on composites reinforced with hybrid reinforcement. The strain rate is varied in the tests by changing the projectile shooting pressure. Four different pressures 2, 4, 6 and 8 bar were selected to change the strain rate. Stress–strain and energy absorption behaviour of eight type of samples were noted. Hybrid samples showed better performance in the energy absorption compared with other samples.

Development of electrically conductive nano bamboo charcoal/ultra-high molecular weight polyethylene composites with a segregated network

Electrically conductive nano bamboo charcoal (NBC)/ultra-high molecular weight polyethylene (UHMWPE) composites with a segregated structure were prepared by the high-speed mechanical mixing and hot-pressing method. Instead of uniform dispersion in polymer matrix, NBC distributed along specific paths and formed a segregated conductive network, which resulted in a low electrical percolation threshold (2.0 vol%) of the composites. The composite with 7 vol% NBC possessed a conductivity of 1.1 × 10−2 S/cm, which is adequate for many electrical applications. With the incorporation of NBC, the tensile strength of the segregated composites first increased by 10% with 3 wt% NBC content as compared with neat UHMWPE and then decreased with increasing filler content. Moreover, the thermal stability of NBC/UHMWPE composites was also improved as the loading of NBC increased.

Electrical and electromagnetic interference shielding characteristics of GNP/UHMWPE composites

Conductive polymer composites (CPC) are attractive materials for a wide range of applications because of their weight, corrosion resistivity, design flexibility and low cost. In the present work, the electrical and electromagnetic interference (EMI) shielding characteristics of graphene nanoplatelets (GNP)/ultrahigh molecular weight polyethylene (UHMWPE) composites filled with up to 40 wt% GNP were investigated. In addition, the intrinsic conductivity of the GNP network was estimated based on the statistical power law and the rule of mixtures for randomly oriented filler particles in insulating matrix. Due to the formation of a segregated conductive network at the external surface of UHMWPE powder, an electrical percolation threshold of between 2 and 3 wt% GNP was obtained. At GNP loading of 15 wt%, the composite exhibited an EMI shielding effectiveness of 33 dB, corresponding to 99.95% blocking of the EMI.

Preparation, tribological properties and biocompatibility of fluorinated graphene/ultrahigh molecular weight polyethylene composite materials

Fluorinated graphene (FG)/ultra-high molecular weight polyethylene (UHMWPE) composites were successfully prepared by ultrasonic dispersion and liquid thermoforming method. The mechanical and tribological properties of pure UHMWPE and FG/UHMWPE composites were investigated using micro-hardness tester and high-speed reciprocating friction tester. The results showed that: adding FG could not only increase the micro-hardness of the composites, but also decrease the wear volume of the composite significantly. The friction coefficients of the composites were also reduced with the increasing of FG content. In addition, the MC3T3-E1 cells adhered and grew well on the surface of the FG/UHMWPE composites as observed by SEM and fluorescence microscope, indicating the addition of FG did not affect the morphology and activity of the cells. The FG/UHMWPE composites exhibited excellent mechanical properties, tribological properties and biocompatibility, which could be used as the potential artificial joint replacement material.

Synthesis and tribological behavior of novel UHMWPE‐Ti3SiC2 composites

This article reports the synthesis and tribological behavior of Ti3SiC2‐UHMWPE (Ultra High Molecular Weight Polyethylene) composites for the first time. The compositions were designed by adding 5, 20, and 35 vol% Ti3SiC2 particulates in the UHMWPE matrix. The microstructure evaluation by SEM (Scanning Electron Microscopy) showed that the Ti3SiC2 particles are well dispersed in the green body, but after hot pressing, the Ti3SiC2 particulates segregated to the phase boundaries in Ti3SiC2‐UHMWPE composites with 20 vol% or higher concentration of particulates. The addition of Ti3SiC2 particulates enhanced the UYS (ultimate yield strength) and hardness of the composites. Tribological studies were performed by tab‐on‐disc method by testing samples either against alumina or self. Against alumina, mean friction coefficient (µmean) remained constant ∼0.20 for all the compositions, whereas, during self‐mating, the µmean decreased from ∼0.54 in UHMWPE to ∼0.15 in 35 vol% Ti3SiC2‐UHMWPE. Comparatively, the specific wear rate (WR) increased steadily during testing against alumina, whereas during self testing, the WR decreased by three order of magnitude. POLYM. COMPOS., 39:254–262, 2018. © 2016 Society of Plastics Engineers

Applications of Fiber Reinforced Polymer Composites

Fueled by the need to surpass the limitations of conventional materials, recent years have seen a large increase in engineering applications of advanced fiber reinforced polymer (FRP) composite materials in many major industries, such as aerospace and defense, automotive, construction, marine, and oil and gas. FRP composites are very attractive for these applications due to their highly favorable material properties, including high strength-to-weight and stiffness-to-weight ratios, and corrosion resistance. Studies conducted to date have demonstrated the numerous advantages offered by FRP composites in various engineering applications. However, there are still a number of technical and implementation issues that need to be resolved prior to broader uptake of the application of FRP composites by some engineering communities such as civil construction. This special issue is aimed at disseminating the most recent advances and developments in this exciting field. A total of 17 paperswere submitted to the special issue and after a rigorous peer-review process six of themwere accepted to appear in the issue as original research articles. These six papers deal with a range of topics on the structural behavior of composite members/structures and mechanical properties and development of composite materials. The studies on the former investigate the dynamic behavior of composite FRP bridge systems and flexural behavior of previously damaged steel beams repaired with FRP. The studies on the latter are concerned with the development of ecoefficient engineered cementitious composites, mechanical properties of carbon fiber composites obtained using different molding techniques, and properties of high-density and ultra-high molecular weight polyethylene and heat-treated bamboo fiber composites. We hope that some of the most recent advances on the development and applications of FRP composites that have been disseminated in this special issue will be of interest to readers and contribute toward the advancement of research in the field.

Studies on Mechanical Properties of UHMWPE Composites filled with Al2O3/PEEK Particles

In this present work, Ultra-high molecular weight polyethylene composites reinforced individually and combined with different loadings of Al2O3 (900 grit) and PEEK particles were prepared using hot compression molding. The effects of Al2O3 and PEEK particles on the mechanical properties of the UHMWPE composites were studied as per ASTM standards. The results revealed that the addition of Al2O3 and PEEK to the UHMWPE matrix reduced tensile strength and elongation at break, whereas the Young's modulus of the composites was increased. The composites reinforced with 3vol. % Al2O3 and 9vol. % PEEK had better flexural properties and greater impact strength when compared to other composites reinforced with different volume percentages of Al2O3 and PEEK. The hardness of the UHMWPE composites was proportionately increased with the increase of filler content. The morphologies of the fracture surface of the Al2O3/PEEK/UHMWPE composites were analyzed by means of field emission scanning electron microscope. The results indicated poor interfacial bonding between Al2O3/PEEK and UHMWPE.

Strontium-doped calcium polyphosphate/ultrahigh molecular weight polyethylene composites: A new class of artificial joint components with enhanced biological efficacy to aseptic loosening

To enhance implant stability and prolong the service life of artificial joint component, a new approach was proposed to improve the wear resistance of artificial joint component and endow artificial joint component with the biological efficacy of resistance to aseptic loosening. Strontium calcium polyphosphate (SCPP) were interfused in ultrahigh molecular weight polyethylene (UHMWPE) by a combination of liquid nitrogen ball-milling and flat-panel curing process to prepare the SCPP/UHMWPE composites. The micro-structure, mechanical characterization, tribological characterization and bioactivities of various SCPP/UHMWPE composites were investigated. The results suggested that this method could statistically improve the wear resistance of UHMWPE resulting from a good SCPP particle dispersion. Moreover, it is also observed that the SCPP/UHMWPE composites-wear particles could promote the production of OPG by osteoblasts and decrease the production of RANKL by osteoblasts, and then increase the OPG/RANKL ratio. This indicated that the SCPP/UHMWPE composites had potential efficacy to prevent and treat aseptic loosening. Above all, the SCPP/UHMWPE composites with a suitable SCPP content would be the promising materials for fabricating artificial joint component with ability to resist aseptic loosening.

Combined effect of fibers and PTFE nanoparticles on improving the fretting wear resistance of UHMWPE-matrix composites

Ultra-high molecular weight polyethylene composites reinforced with carbon fibers (CF) and polytetrafluoroethylene (PTFE) were prepared. The effects of fillers on the microstructure and fretting wear behavior of composites were investigated. The results of X-ray diffraction and scanning electron microscopy measurements indicated that the microstructure of composites were greatly changed, and the distinct interface between fillers and matrix had been formed with the incorporation of CF and PTFE. In addition, results also showed that the simultaneously filled with CF and PTFE at a proper weight fraction contributed to dramatically improving the friction reducing and wear resistance of ultra-high molecular weight polyethylene. It can be found that there exists synergism between fillers. Copyright (c) 2015 John Wiley & Sons, Ltd.

The influences of several carbon additions on the fretting wear behaviors of UHMWPE composites

Ultra-high molecular weight polyethylene (UHMWPE) composites filled with several carbon materials including carbon fiber (CF), graphite (Gr), graphite fluoride (CFx), multi-walled carbon nanotube (MCNTs) and graphene oxide (GO) were prepared. Fretting wear behaviors of the composites were evaluated using a ball-on-plate test machine. Their thermal and mechanical properties were also studied. Results showed that the wear resistance of these composites increased orderly: UHMWPE<UPE–10%Gr<UPE–1%MCNTs<UPE–10%CF<UPE–1%GO<UPE–10%CFx. Abrasive and adhesive wear were dominated wear mechanism during the process of fretting test. Besides, the structure–function relationship of microstructures, mechanical properties and tribological performances were detailedly discussed.

Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

ABSTRACTThis is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42869.

Analysis of the shock response of UHMWPE composites using the inverse planar plate impact test and the shock reverberation technique

Ultra-high molecular-weight polyethylene (UHMWPE) composites are commonly used in ballistic protection systems. In order to understand the behavior under shock conditions, dynamic material properties were recently measured by inverse planar plate impact tests providing US–uP-data for particle velocities from 170 m/s up to 900 m/s. In this paper the previously known data range is extended at both ends. On the one hand, inverse flyer plate tests were performed at impact velocities less than 200 m/s in order to assess potential effects of porosity. On the other hand, the mechanical response under extremely high pressures was determined using the shock reverberation technique.For low shock pressures no effect of porosity was identified. For high shock pressures, the available data range was extended by a factor of 3. For the whole range of velocities and pressures, the slope of the US–uP relationship indicates a slight concave curvature.

Highly thermally conductive POSS-g-SiCp/UHMWPE composites with excellent dielectric properties and thermal stabilities

Polyhedral oligomeric silsesquioxane grafting thermally conductive silicon carbide particle (POSS-g-SiCp) fillers, are performed to fabricate highly thermally conductive ultra high molecular weight polyethylene (UHMWPE) composites combining with optimal dielectric properties and excellent thermal stabilities, via mechanical ball milling followed by hot-pressing method. The POSS-g-SiCp/UHMWPE composite with 40wt% POSS-g-SiCp exhibits relative higher thermal conductivity, lower dielectric constant and more excellent thermal stability, the corresponding thermally conductive coefficient of 1.135W/mK, the dielectric constant of 3.22, and the 5wt% thermal weight loss temperature of 423°C, which holds potential for packaging and thermal management in microelectronic devices. Agari’s semi-empirical model fitting reveals POSS-g-SiCp fillers have strong ability to form continuous thermally conductive networks.

Three kinds of charcoal powder reinforced ultra-high molecular weight polyethylene composites with excellent mechanical and electrical properties

Abstract Highly filled charcoal powder reinforced ultra-high molecular weight polyethylene (UHMWPE) composites with tunable electrical conductivity and good mechanical properties were prepared using extrusion and hot-compression techniques. Three kinds of charcoal carbonized under various temperatures were used in this study. The scanning electron microscopy showed that charcoal powder was dispersed uniformly in the UHMWPE matrix and strong interfacial interaction was achieved. The tensile test results showed that with the incorporation of charcoal powder, the tensile strength increased by 325%, 262% and 203% respectively compared to neat UHMWPE. Furthermore, the composites containing 70 wt.% charcoal powder (above 700 °C) exhibited good electrical conductivity, which is adequate for many electrical applications. It was obvious that the storage modulus of all the composites increased remarkably with the incorporation of charcoal powder, E′ reached 30.2, 26.8 and 25.9 GPa for samples PC1100/UHMWPE, AC1100/UHMWPE and BC1100/UHMWPE at − 150 °C respectively.

The compressive response of ultra-high molecular weight polyethylene fibres and composites

Measurements are reported for the compressive response of ultra-high molecular weight polyethylene (UHMWPE) fibres and laminated composites loaded along the fibre direction. The compressive strength of the fibres was measured by both recoil tests and knot (or bend) tests. The strength of the fibres is governed by micro-kinking of the fibrils within the fibres. The recoil tests suggest that this kinking occurs at a compressive stress of approximately 340MPa. Consistent with observations of other fibres such as Kevlar and carbon fibres, the compressive strength inferred from bending tests is approximately a factor of two higher than that from a direct compression test, such as the recoil test. The in-plane compressive response of laminated UHMWPE composites was measured using notched specimens. Two grades of composites with shear strengths of about 1.5 and 0.5MPa were investigated and found to have compressive strengths of about 12MPa and 3MPa, respectively. Thus, unlike Kevlar composites, the composite compressive strength is not governed by the compressive strength of the fibres but by the micro-buckling of the composite plies. Detailed experimental measurements are reported for the kink-band width, fibre rotation within the band and its subsequent broadening after lock-up due to fibre rotation. These are shown to be adequately modelled by traditional kinking theory while a net section stress analysis models the propagation of the micro-buckle with sufficient fidelity.