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Ultrahigh molecular weight polyethylene (UHMWPE) belongs to an emerging class of high-performance specialty polymers with a unique set of properties and applications. The field has ...witnessed many scientific and technological advances in recent years. However, synthesis of UHMWPE is not a trivial exercise and presents several challenges. This review addresses these fundamental challenges and provides an overview of recent developments in the field of UHMWPE. The nature of catalysts, reaction conditions that favor its formation, their physical properties, methods of processing them into products, and their applications are discussed. Recent developments in formation of UHMWPE in a disentangled state by use of appropriate catalysts and reaction conditions are also discussed. This has elicited considerable interest as a means of enabling melt processing of UHMWPE. This review provides a comprehensive source of information and understanding of the multifaceted aspects of UHMWPE with specific reference to chemistry, catalysis, processes for manufacturing, and an analysis of catalyst structure-polymer property relationships.
Friction and wear behavior of ultra-high molecular weight polyethylene (UHMWPE) sliding against TiAl6V4 alloy, against AISI316L austenitic stainless steel and against Al2O3 ceramic under dry and ...lubricated conditions was investigated. Tests were conducted by using a reciprocating pin-on-flat tribometer with several applied normal loads. Lubricated sliding tests were carried out with a fluid containing a large amount of sodium hyaluronate. The worn surfaces of the UHMWPE were examined with a 3D confocal microscopy. The tribological performances of pairs UHMWPE/AISI316L, UHMWPE/TiAl6V4 and UHMWPE/Al2O3 were also investigated for the purpose of comparison. The results were interpreted on the basis of the evolution of the friction coefficient and worn surfaces in order to understand the acting wear mechanisms.
•Experimental analysis of tribological behavior of UHMWPE against TIAL6V4 Alloy.•Experimental analysis of tribological UHMWPE behavior against AISI316L.•Experimental analysis of tribological behavior of UHMWPE against AL2O3 ceramic.•We used a reciprocating bio-tribometer in dry and lubricated conditions (Hyalgan®).•The friction coefficient and the wear were measured.
To tackle the challenge for materials in the fields such as deep space exploration with flexibility, light weight, high strength, and highly efficient neutron shielding properties, a novel ...organic-inorganic composites has been developed in this study. Based on ultrahigh molecular weight polyethylene (UHMWPE) fibers self-reinforcing linear low-density polyethylene (LLDPE) matrix method and hierarchical scattering and absorption strategy, a flexibly and light-weight multilayer structure has been designed with alternating gadolinium oxide (Gd2O3)/LLDPE layers and UHMWPE fiber layers by stacking hot-pressing to augment the mechanical properties and neutron shielding efficiency of the composites. Moreover, PE, including UHMWPE fibers and LLDPE matrix, and Gd2O3 has been utilized as neutron shielding element to enhance its neutron scattering and absorption capability via an abundance of hydrogen atoms and Gd element. The neutron shielding performance of the multilayer Gd2O3/UHMWPE/LLDPE composite, with a low density of ca. 1 g/cm3, has been verified by neutron shielding test and a simulation method of equivalent Gd areal density (EGdAD). As a result, an ca. 90.0% neutron shielding efficiency can be achieved with only 2 mm thickness of the composites (with 20 wt% Gd2O3), and an EGdAD value of 0.0489 g/cm3 is required to achieve 99% shielding efficiency. Moreover, the composites have a significant improvement in the tensile strength and modulus, with an average increase of 1000% (15.86 MPa–179.95 MPa) and 1238% (230.53 MPa–2787.55 MPa) compared to the Gd2O3/LLDPE composites, respectively. The comprehensive performance of our developed multilayer Gd2O3/UHMWPE/LLDPE composites is superior to previously reported results in the literatures. Therefore, it has great application prospect in the various fields like aerospace.
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Ultrahigh molecular weight polyethylene (UHMWPE) is widely used in industrial, military, and civilian applications owing to its excellent properties. However, the high entanglement degree of UHMWPE ...melt leads to great difficulties in diffusion and crystallization, which causes poor interfacial strength and mechanical properties of pre-melted UHMWPE, restricting its high-quality processing and high-value recycling. To this end, we propose a rapid interface stitching technology with a pulsed vibration force driving free volume homogenization and chain segment orientation. For the first time, pulse vibration molding (PVM) is applied for the hot-pressing of pre-melted UHMWPE, successfully realizing the interface stitching and product strengthening. Compared with those of the convention molding (CM) samples at 180 °C, the interfacial adhesive fracture toughness of the adhesive samples processed using PVM is increased by 105.9 % and the work of tension of the recycled samples processed using PVM is also increased by 49.09 %, respectively. The fracture strength of the PVM recycled samples at 180 °C reaches 91.77 % of that of the pure samples and the yield strength is also higher, which significantly enhances the recycling of UHMWPE. The characterization results of the interfacial molecular chain entanglement and crystallization show that PVM strengthens the molecular chain diffusion and induces crystallization by promoting the orientation of chain segments, especially at the interface. Consequently, we believe that the proposed technology can play a significant role in the UHMWPE processing methods that involve surface healing.
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•A rapid interface stitching technology with a pulsed vibration force driving free volume homogenization and chain segment orientation was proposed.•The processing-structure-properties relationships of pre-melted UHMWPE at different processing conditions were established.•The response law of the interfacial entanglement and crystal structure is proposed.•The interfacial strengthening and the high-value recycling of UHMWPE are realized at a low time cost.
Two series of UHMWPE composites were developed using boron carbide (B4C) particles in different amounts and sizes. Micro-series contained micro B4C particles (2–5 μm) in various wt% (0, 2, 4, 6, 8 ...and 10) while nano-series contained nano-particles (NPs) of size 70–90 nm in 0, 2 and 3%. Abrasive wear studies against silicon carbide (SiC) paper in a single pass condition were conducted under varying loads and speeds. Inclusion of B4C particles proved beneficial to enhance the wear resistance and optimum amounts of filler for micro and nano-series were ≈ 6–8% and 3% respectively. Scratch hardness showed fairly good linearity with the wear resistance. SEM studies confirmed that inclusion of hard fillers mainly reduced the severity of micro-cutting mechanism and hence wear.
Ultra-high-molecular-weight polyethylene (UHMWPE) has been extensively utilized in various tribological systems due to its high wear resistance, low friction coefficient, anti-corrosion behavior and ...eco-friendly properties. However, the demand from the market requires further improvements to withstand the harsh conditions in the applications. For this reason, different kinds of fillers have been included in the UHMWPE matrix to produce composite materials possessing advanced properties especially against wear. Although several investigations have been carried out to develop the tribological behavior of UHMWPE based composites by using various fillers, there has been a little attention on the effect of manufacturing parameters such as molding pressure. Furthermore, polymeric fillers in the polymeric matrices have not been studied extensively as such in polymer based composites with hard fillers. For this reason, the tribological properties of the UHMWPE based composites were investigated by using different polymeric fillers such as polytetrafluoroethylene (PTFE) particles and aramid fibers in this study. The filler loadings were varied in the composites to investigate their effects on the tribological behavior. Moreover, molding pressure was changed from 100 to 300 bar in the compression molding process of the UHMWPE specimens to investigate the influence of manufacturing conditions. The tribological tests were conducted in a ball-on-disk apparatus against a tungsten carbide ball and from the results, increase in the molding pressure leads to a consolidation in the microstructures and thereby enhancing the wear performance of the specimens. Furthermore, both fillers contribute to the wear resistance of the UHMWPE matrix however, by exhibiting different mechanisms in the sliding process.
Ultra-high molecular weight polyethylene (UHMWPE) is prone to deformation and wear under harsh conditions of dry friction with high contact stress, and failing friction parts. In this work, ...CZrP/UHMWPE composites with different organic-modified α-zirconium phosphate (CZrP) contents were prepared. The tribological properties of the GCr15/composites friction pair under dry friction conditions were studied by ball-on-disk tribology experiments, and the wear mechanism was analyzed. The results show that when the content of CZrP is 5 wt%, the friction coefficient and wear loss of CZrP/UHMWPE composites are the smallest, which are about 30% and 58% lower than those of pure UHMWPE. In the process of dry sliding friction and wear, CZrP will gradually accumulate on the friction surface of the composite material, and a protective layer with certain strength and lubricity will be formed through the unique interlayer sliding effect of CZrP. The hydrogen bonding between the molecular chains of the surface coupling agent and the physical entanglement with the molecular chains of UHMWPE make the accumulated CZrP not easy to be worn and peeled off. This work aims to provide an effective strategy to improve the tribological properties of UHMWPE under severe conditions with high contact stress.
•CZrP effectively improved the tribological properties of UHMWPE.•CZrP forms a protective film on the friction surface during the friction process.•A higher load and shear force can be tolerated by the CZrP interlayer sliding.•The friction and wear mechanism of CZrP/UHMWPE composites was revealed.
A lightweight composite armor system composed of boron carbide (B4C) ceramic panels, carbon-fiber interlayer, and ultra-high molecular weight polyethylene (UHMWPE) backplate has been widely used. ...This study aims to explore the effect of different constraint conditions on the ballistic resistance of lightweight composite armor. Thus, ballistic experiments of 12.7 mm armor-piercing incendiary (API) projectiles impacting armor targets under different constraint conditions are designed, and numerical simulations are performed to simulate the structural impact response of composite armor. A satisfied consistency is revealed by comparing the numerical results and the ballistic experimental results. Besides, the numerical simulation method is used to research the influence of the distance between the impact point and the constraint conditions on the ballistic performance of the composite armor. The results demonstrate that the ballistic performance of the composite armor is better if the impact point is farther from the constraint conditions as this can enhance the flexibility of composite armor. In conclusion, the flexibility of the constraint conditions is positively correlated with the ballistic performance of B4C/C/UHMWPE composite armor. This conclusion provides a guideline for the design and application of composite armor.
•Fabric structure induced role of STF in modulating the impact resistance has been established.•Impact resistance of firm fabrics, having higher interlacements, deteriorates after STF ...impregnation.•STF impregnated firm fabrics sustain the impacting force for lower duration due to stress concentration.•Enhancement of yarn pull-out force cannot be a true indicator of improved impact resistance.
The structural parameters of woven fabrics play a crucial role in determining its impact resistance performance. Conventionally, treatment with shear thickening fluid (STF) has been found to increase the impact energy absorption capacity of fabrics. However, the findings of the current study present a new perspective, and suggest that the effect of STF treatment is favorable based on the structural integrity of woven fabrics. Plain woven fabrics with different fabric sett (threads per inch) were produced using ultra-high molecular weight polyethylene (UHMWPE) yarns of 400 denier and 1350 denier linear density. These fabrics were then treated with STF (65% w/w) made from silica particles (100 nm) dispersed in polyethylene glycol i.e. PEG (200 Mw) and subsequently evaluated for yarn pull-out force and impact energy absorption. The increased yarn pull-out force, at all levels of yarn linear density and fabric sett, implies that STF treatment considerably increases the inter-yarn friction. However, increased yarn to yarn friction is not necessarily beneficial in terms of impact energy absorption and rather becomes detrimental for fabrics made from finer yarns (400 denier) beyond a particular fabric sett.
