High Molecular Weight Polyethylene Composites Research Articles

Improved processability for ultra‐high molecular weight polyethylene/polyolefin elastomer composites: Effect of ethylenevinyl acetate copolymer

AbstractPolyolefin elastomer (POE) films can be used as a matrix for ultra‐high molecular weight polyethylene (UHMWPE) fiber‐reinforced composites via a hot‐melt process. However, the low melting temperature of UHMWPE limits composite processing. Therefore, this study aimed to create a film by blending POE with ethylene vinyl acetate (EVA) to reduce the film's processing temperature. Morphological analysis revealed that due to limited compatibility, EVA appeared as droplets within the immiscible POE matrix. T‐Peel tests demonstrated increased self‐adhesion in both the POE/EVA films and the fiber‐reinforced composites with higher EVA content. However, the mechanical properties of POE/EVA films, including tensile properties and shore hardness, were reduced due to EVA having lower inherent properties. UHMWPE fiber‐reinforced composites were fabricated from these films. In composites, optimal tensile and flexural properties were observed at lower EVA content. Scanning electron microscopy analysis suggests that the POE/EVA films are sufficiently infiltrated at 10–20 wt% EVA content. As EVA content increased, the drop weight impact test indicated a reduction in the maximum impact load and an increase in impact energy, attributed to improved adhesion and a broader distribution of impact load across the interface.Highlights Polyolefin elastomer/ultra‐high molecular weight polyethylene composites' properties were studied with varying ethylene vinyl acetate (EVA) additive content. Add EVA to improve film impregnation when forming composites Increase in impregnation affects increase in properties of composites. Characterization shows that the optimal EVA content is 10–20 wt%.

High Speed Impact Testing of UHMWPE Composite Using Orthogonal Arrays

BackgroundUltra high molecular weight polyethylene composites are fiber based composites used in armor applications. While some characterization has been conducted experimentally, this study varies multiple parameters simultaneously to investigate material response under a wide range of conditions.ObjectiveThis work focuses on characterizing the response of Dyneema® HB26 hard laminate composites under high-speed impacts to examine the influence of plate diameter, clamping pressure, and plate spacing on target performance. Additionally, micro Computer Tomography scans are used to nondestructively evaluate the damage evolution in the targets.MethodsThese scan results are used in concert with more traditional armor performance metrics to evaluate the effect of various parameters using the method of orthogonal array analysis. This technique allows for multiple variables to be investigated in the same test series, saving time and budget while still providing quality results across a range of variables and variable values.ResultsWe conclude that of the parameters investigated, the plate spacing parameter has the largest effect on performance, followed by the plate diameter. Bolt torque was found to not have a significant impact on results, indicating that an edge clamping pressure is not critical to material response. Additionally, by examining the high resolution scans, we can quantify the damage with an effective damage angle and that this angle is a good predictor of performance. ConclusionFinally a damage theory involving the effective bending strength of the plates is discussed as an explanation for all of the results observed in this test series.

Preparation and characterization of activated carbon/ultra‐high molecular weight polyethylene composites

AbstractThis research uses physical mixing and twin‐screw extrusion process to prepare biomass activated carbon (BAC)/ultra‐high molecular weight polyethylene (UHMWPE) composite materials. The mechanical properties, micro‐morphology, and thermodynamic properties of the composite materials were explored. The experimental results show that the tensile strength of 65% activated carbon added to the composite material has changed from 22.93 to 97.65 MPa, which is an increase of 325.86%. According to the Scanning electron microscope (SEM) image, a schematic diagram of the internal combination of the composite material is made, the concept of a three‐dimensional network interpenetrating three‐dimensional structure is proposed, and the mechanism of tensile properties enhancement is explained. Obviously, as the carbon content increases, the storage modulus (E′) also increases, and the loss factor (tan δ) and glass transition temperature (Tg) also change. The ability of composite materials to resist pyrolysis has also been enhanced. The above results indicate that BAC as a filler of composite materials can improve various performances.

Damping evaluation of a ballistic foam: from tests to simulations

The perpetual evolution of soldiers light weight armors include now high technology ceramic, composite and polymeric in ballistic vest that are optimized by simulations. Knowledge of individual material response in the strain, strain rate regime closed to the threat stays mandatory and thus collecting parameters to fit material models guarantees reliable numerical investigations. Since 2015, THIOT INGENIERIE Shock Physics Laboratory has been selected by the French Defence procurement agency DGA-Land Systems to perform materials characterization in three main families of ballistic materials [1-2]. A coupled approach between laboratory experiments and numerical simulations has shown its relevance with ceramic and an Ultra High Molecular Weight PolyEthylene composite (UHMWPE). This paper presents succinctly the last part of those experimental investigations on a polymeric foam that is implemented on the soldier’s chest [3]. The material behavior under dynamic loading has been first evaluated using Split Hokinson Pressure Bars (SHPB) up to 5000s-1. Ballistic tests have been performed in a second time using Digital Image Correlation (DIC) with ultrahigh speed cameras at the back of the target plate to evaluate the damping behavior. Numerical simulations are under progress and the first results are promising.

Role of nano-fillers on tribological behaviour of ultra high molecular weight polyethylene composites

An investigation has been made of the dry slithering wear and two-body abrasive wear (2-BAW) performance of ultra high molecular weight polyethylene (UHMWPE) loaded up with carbon nanotubes (CNTs) and copper nanoparticles (n-Cu). Tribological tests were carried out utilizing a pin-on-disc test rig employing EN32 steel and SiC emery paper as counterparts against UHMWPE composite glued to a circular pin, under different test circumstances. Scanning electron microscopy (SEM) was expended to dissect the morphologies of chosen worn surfaces. The configurations of friction coefficient (µ), weight reduction and explicit wear rate (Ks) were assessed in adhesive wear-mode and the Ks in the event of multi-pass 2-BAW mode under various dissociate/masses. It has been demonstrated that inclusion of exceptionally little extents (0.1 and 0.5 wt%) of nano-fillers has resulted in significant improvement in the slithering wear performance. Moreover, 1-D filler (CNTs) diminished the contact surface, advanced the exchange of UHMWPE and diminished the interlocking and furrowing of the composite from the steel partner, which added to the reduction of both Ks and µ. UHMWPE loaded up with 0.5 wt% CNTs has outpaced the material system in the study group in tribological properties. Abrasive wear assessment revealed that the UHMWPE composites demonstrated diminished Ks with expanding abrading distance and coarseness of SiC emery paper. Further, UHMWPE/CNTs demonstrated good resistance to abrasion wear in contrast with unfilled UHMWPE and n-Cu filled UHMWPE composites.

Mechanical and Electrical Characterization of Two Carbon/Ultra High Molecular Weight Polyethylene Composites Created Via Equal Channel Angular Processing

Ultra-high-molecular-weight-polyethylene (UHMWPE) has the greatest impact strength of any thermoplastic and has a variety of both industrial and biomedical applications. Equal channel angular processing (ECAP) is a fabrication method for UHMWPE that introduces shear into the polymer matrix by deforming the polymer through an angular channel, with the goal of enhancing mechanical properties. Both nanographite (NG) and carbon black (CB) attract interest as potential carbon additives for use in creating UHMWPE conductive polymer composites (CPC), but they have not yet been extensively tested in conjunction with ECAP. This study presents a systematic evaluation of the mechanical and electrical properties of 1.0 wt % CB/UHMWPE and NG/UHMWPE composites created using ECAP. These samples are compared against pure UHMWPE ECAP controls as well as compression molded (CM) composite samples. Results indicate that both NG and CB carbon additives successfully create CPCs with a corresponding decrease in mechanical properties. ECAP results in comparatively high mechanical and conductive properties when compared with compression molding. Electrical conductivity is shown to be inversely correlated with tensile strain in a repeatable manner, and microstructural theory is discussed. This work suggests a method to produce flexible, conductive UHMWPE composites that vary consistently and predictably with applied strain, which could have a variety of biomedical and industrial applications.

Mechanical, electrical, and thermal properties of highly filled bamboo charcoal/ultra‐high molecular weight polyethylene composites

Highly filled bamboo charcoal (BC)/ultra‐high molecular weight polyethylene (UHMWPE) composites were prepared using extrusion and hot‐compression molding methods. The addition of BC remarkably improved the tensile properties of UHMWPE composites. When the BC content reached 70 wt%, the tensile strength and Young's modulus rose from 28.0 and 326.6 MPa for the neat UHMWPE to 128.9 and 2,027.7 MPa, increasing by 360 and 520%, respectively. The incorporation of BC also significantly improved the creep resistance, especially at high temperature. The creep strains of the composites with 60, 70 and 80 wt% were reduced by 70.1, 78.3, and 85.2% compared to the neat UHMWPE at 80°C, respectively. To understand the mechanism, the Burger's model was employed to illustrate the influence of BC on the creep performance of the polymer composites. The addition of BC also increased the electrical conductivity of the composites: the composite with 80 wt% BC had a conductivity of 0.53 S/cm. Moreover, the thermal stability of BC/UHMWPE composites improved apparently with the increased charcoal loading. POLYM. COMPOS., 39:E1858–E1866, 2018. © 2018 Society of Plastics Engineers

Size effect of charcoal particles on the properties of bamboo charcoal/ultra‐high molecular weight polyethylene composites

ABSTRACTThis study was aimed at examining the size effect of charcoal particles on the properties of bamboo charcoal (BC)/ultra‐high molecular weight polyethylene (UHMWPE) composites. Four types of BC with various particle sizes were mixed with UHMWPE using a twin‐screw extruder. It was found that the melting temperature and crystallinity of the composites were slightly decreased with the addition of BC. The incorporation of BC remarkably improved the tensile properties and creep resistance of UHMWPE, and the particle size of BC strongly affected the properties of BC/UHMWPE composites. The BC with lowest particle size exhibited best reinforcement, where the tensile strength and Young's modulus were increased by 385% and 517% compared with neat UHMWPE. The composites with 70 wt % BC possessed conductivities of 16.8, 14.1, 13.5, and 10.9 S/m. The storage modulus and glass transition temperature of the composites also increased with the addition of BC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45530.

Effects of carbon nanotube aspect ratio on strengthening and tribological behavior of ultra high molecular weight polyethylene composite

Carbon-based nanomaterials are great choice as reinforcement to Ultra-High Molecular-Weight Polyethylene (UHMWPE), with potential use in orthopedics. While high in-plane-stiffness and strength of these nanomaterials help in toughening, their weaker out-of-plane integrity offers lubrication. Present study investigates effect of aspect ratio of carbon nanotubes (CNT) on toughening and solid-lubrication efficiency of UHMWPE-matrix. A nominal 0.05–0.1wt.% of CNT addition increases hardness and elastic modulus of UHMWPE by 3–45% and 8–42%, respectively. Higher aspect ratio (HAR) CNTs are found more effective in improving hardness and modulus of UHMWPE. Wear rate and friction-coefficient also increase by 530% and 220%, respectively, while reinforced with HAR CNTs. Thermal analysis shows slight increase in crystallinity and stability of composite. HAR CNTs improve interfacial bonding with matrix, due to their morphological similarity to polymer chains, as compared to low aspect ratio CNT. Aspect ratio of CNTs significantly dominates strengthening and tribological behavior of UHMWPE.

The effect of target thickness on the ballistic performance of ultra high molecular weight polyethylene composite

The ballistic performance of thick ultra-high molecular weight polyethylene (UHMW-PE) composite was experimentally determined for panel thicknesses ranging from 9 mm to 100 mm against 12.7 mm and 20 mm calibre fragment simulating projectiles (FSPs). Thin panels (∼<10 mm thick) were observed to undergo large deflection and bulging, failing predominantly in fibre tension. With increased thickness the panels demonstrated a two-stage penetration process: shear plugging during the initial penetration followed by the formation of a transition plane and bulging of a separated rear panel. The transition plane between the two penetration stages was found to vary with impact velocity and target thickness. These variables are inter-related in ballistic limit testing as thicker targets are tested at higher velocities. An analytical model was developed to describe the two-stages of perforation, based on energy and momentum conservation. The shear plugging stage is characterised in terms of work required to produce a shear plug in the target material, while the bulging and membrane tension phase is based on momentum and classical yarn theory. The model was found to provide very good agreement with the experimental results for thick targets that displayed the two-stage penetration process. For thin targets, which did not show the initial shear plugging phase, analytical models for membranes were demonstrated as suitable.

Carbon fiber reinforced highly filled charcoal powder/ultra high molecular weight polyethylene composites

Effects of wood charcoal powder and carbon fiber (CF) on morphologies, tensile properties and dynamic mechanical properties of ultra high molecular weight polyethylene (UHMWPE) composites prepared by the twin-screw extrusion method were studied. Scanning electron microscopy was used to investigate the surface of initial charcoal power as well as interfaces in the UHMWPE, filled with high-modulus carbon fibers. The results showed that wood charcoal could have strong interfacial interaction with UHMWPE and good dispersion of carbon fiber was achieved. The tensile strength and Young׳s modulus significantly increased up to 123.0MPa and 2551.1MPa respectively. It is obvious that while increasing charcoal and carbon fiber concentration resulted in increased storage modulus, the E׳ reached 25.1GPa for the sample 30UHMWPE-70charcoal/8CF at −150°C. Furthermore, the composites show lower tanδ values than those of the neat UHMWPE in the glass-transition temperature (Tg) and melting temperature (Tm).

Nanotribological behavior of graphene nanoplatelet reinforced ultra high molecular weight polyethylene composites

Nano-scratch behavior of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with graphene nanoplatelet (GNP) in varying composition of 0, 0.1, 0.5 and 1wt% is reported. Hot pressed composite structures are characterized for their tribological behavior in scratch mode using a normal load of 100–300μN. Increasing GNP content from 0.1 to 1wt% results in lowering of the coefficient of friction due to easy shear of graphene nanoplatelets. Graphene reinforcement also increases the wear resistance by more than four times, which is a combined effect of lubrication as well as toughening offered by GNPs.

Ballistic impact simulation of an armour-piercing projectile on hybrid ceramic/fiber reinforced composite armours

This paper presents a ballistic impact simulation of an armour-piercing projectile in hybrid ceramic/fiber reinforced composite armour. The armour is composed by an alumina plate and an ultra high molecular weight polyethylene composite. In order to model the armour behavior three different constitutive models were formulated and implemented into ABAQUS/Explicit finite element code. Comparisons between numerical predictions and experimental results in terms of damage shape/extent and V50 are also presented and discussed in the paper.

Preparation and characteristics of nano-B4C/PVA particles and ultra high molecular weight polyethylene composites

In-situ mechanical process for preparation of the polyvinyl alcohol (PVA) coated nano-B4C powder was investigated by using a high-energy ball mill. The produced PVA coat on the surface of nano-B4C particles was observed by x-ray diffraction (XRD) and confirmed by TEM images. The average particle size of the produced nano-B4C/PVA particles was in the range of several tens to hundreds of nanometers depending on the milling conditions. The polymer composites were fabricated by hot pressing ultra high molecular weight polyethylene (UHMWPE) powder mixed with nano-B4C/PAV and micro-B4C powders, respectively. Nano-B4C/PVA dispersed UHMWPE shows slightly lower crystallinity and stiffness than micro-B4C dispersed UHMWPE based on differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) evaluations.

Synergy effect of hybrid fillers on the positive temperature coefficient behavior of polypropylene/ultra‐high molecular weight polyethylene composites

AbstractHybrid nanocomposites of polypropylene/ultra‐high molecular weight polyethylene (PP/UHMWPE, 70/30) with various amounts of carbon black (CB) and carboxylated multiwalled carbon nanotubes (c‐MWNTs) were prepared by the solution mixing and melt blending techniques. The effects of the mixture of CB and c‐MWNTs on the positive‐temperature‐coefficient (PTC) behavior and the negative‐temperature‐coefficient (NTC) behavior, as well as the room temperature resistivity, were studied. The transmission electron microscopy (TEM) images showed that the CB particles were aggregated at the interface, between PP and UHMWPE. This selective localization of the CB particles at the interface along with the formation of continuous conducting media leads to the formation of additional conducting networks, resulting in a percolation threshold at a low CB content. A synergy effect of the hybrid conducting fillers of CB and c‐MWNTs on the PTC behavior of the hybrid blends was also observed. The room temperature resistivity was reduced significantly by the incorporation of the c‐MWNTs into the PP/UHMWPE/CB composite. The intensity and repeatability of the PTC effect in the nanocomposites were improved and the NTC effect weakened by incorporating a small amount (0.5 wt %) of c‐MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Biotribological behavior of ultra high molecular weight polyethylene composites containing bovine bone hydroxyapatite

Abstract Wear particles of ultrahigh molecular weight polyethylene (UHMWPE) are the main cause of long-term failure of total joint replacements. Therefore, increasing its wear resistance or bioactivity will be very useful in order to obtain high quality artificial joints. In our study, UHMWPE composites filled with the bovine bone hydroxyapatite (BHA) were prepared by the method of compression moulding. A ball-on-disc wear test was carried out with a Universal Micro-Tribometer to investigate the friction and wear behavior of a Si3N4 ceramic ball, cross-sliding against the UHMWPE/BHA composites with human plasma lubrication. At the same time, the profiles of the worn grooves on the UHMWPE/BHA surface were scanned. The experimental results indicate that the addition of BHA to UHMWPE had a significant effect on the biotribological behavior of UHMWPE cross-sliding against the Si3N4 ceramic ball. The addition of BHA powder enhanced the hardness and modulus of elasticity of these composites and decreased the friction coefficients and wear rates under conditions of human plasma lubrication. When the added amount of BHA powders was up to 20%∼30%, UHMWPE/BHA composites demonstrated the designed performance of the mechanical properties and biotribological behavior.

Synthesis and characterization of multiwalled carbon nanotube reinforced ultra high molecular weight polyethylene composite by electrostatic spraying technique

In the present work, multiwalled carbon nanotube (MWNT) reinforced UHMWPE composite films were prepared by electrostatic spraying followed by consolidation. X-ray diffraction and differential scanning calorimetry studies showed a decrease in the crystallinity of UHMWPE due to the nature of the fabrication process as well as addition of MWNT. Tensile test showed an 82% increase in the Young’s modulus, decrease in stress to failure from 14.3 to 12.4 MPa and strain to failure from 3.9% to 1.4% due to 5% addition of MWNT. Raman spectra showed the presence of compressive stresses in the nanotubes. Fracture surface showed presence of pullout like phenomena in the MWNT reinforced film. � 2007 Elsevier Ltd. All rights reserved.

Post failure analysis of 0 degrees /90 degrees ultra high molecular weight polyethylene composite after ballistic testing

The ballistic performance of a 0 degrees /90 degrees ultra high molecular weight polyethylene (UHMWPE) composite was investigated. Two areal densities were considered: one for fragmentation protection and one for high velocity bullet protection. The role of microscopy in the post-failure analysis of the UHMWPE was explored. Stereo, optical and environmental scanning electron microscopy were utilized and attempts were made to correlate the results obtained with other characterization techniques available. These included high speed photography, visual inspection and ultrasonic inspection. Visual inspection revealed the gross effects of ballistic testing. These primarily included deformation and delamination of the composite plate. The result obtained corresponded with the predicted impact event and, for high velocity bullet impact, corresponded well to the images obtained using high speed photography. Optical, stereo and electron microscopy allowed for fibre and matrix characterization. Fibre displacement and pull-out were also observed on impact and exit faces.