Ultra-high Molecular Weight Polyethylene Research Articles

Comparison of Suture Types and Techniques in Achilles Tendon Repair: An Ex Vivo Biomechanical Animal Experiment.

The ideal suture technique and type in tendon repair remain unclear. This biomechanical study aimed to assess the biomechanical characteristics of three techniques-modified Kessler (mKE), modified Krackow (mKR), and modified tension Bunnell (mtBU)-in sheep Achilles tendon tear repair using three suture types-polypropylene, polyester, and ultra-high-molecular-weight polyethylene (UHMWPE)-which are also compared. Sixty-three Achilles tendons harvested from sheep were transversely hacked as a replacement for rupture in a standardized measure and repaired using mKE, mKR, and mtBU techniques with No. 2 polypropylene, polyester, and UHMWPE sutures. Biomechanical parameters, such as Young's modulus, ultimate strength, and strength to the 5-mm gap, were recorded for statistical analysis. The mtBU technique with UHMWPE use resulted in increased ultimate strength, strength to 5-mm gap, Young's modulus, and quantity of specimens with low clinical failure modes compared with the other techniques with other suture materials. Furthermore, mtBU has the lowest thickness at the repair side of the tendons. This approach showed tendon failure during maximal traction testing, whereas the mKE and mKR techniques had polyethylene and polyester suture failures. The UHMWPE suture was significantly superior to the other sutures in each technique in terms of strength and durability. The mtBU technique using UHMWPE suture showed better biomechanical results, implying that this repair might be more appropriate to obtain early mobilization after tendon ruptures.

Effect of Zirconia and Graphene Nanoparticles Loading on Thermo-Mechanical Performance of Hybrid Polymer Nanocomposite

This study demonstrates the development of a unique hybrid thermoplastic composite using reduced Graphene oxide (rGO) content and Zirconia (ZrO2) nanoparticles into the Ultra-High Molecular Weight Polyethylene (UHMWPE) biomaterials for continuous loading conditions. Specimens with different loadings of rGO (0 to 1.5 wt.%) and ZrO2 (5 to 10 wt.%) were fabricated using liquid phase ultrasonication followed by the hot press moulding method. The samples were analyzed using Thermogravimetric Analysis (TGA), Impact (Izod) testing, and Dynamic Mechanical Analysis (DMA). The developed material feasibility was assessed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses. The findings revealed that the 1 wt.% rGO/5 wt.% ZrO2/UHMWPE sample improved the storage modulus by 66.15%, and the Impact absorbed energy by 11.33% compared to the pristine UHMWPE. The proposed nanocomposite could be endorsed for artificial joints, prostheses, and other Artificial Bio-Bearing (ABB) applications.

One-Pot Construction of Articular Cartilage-Like Hydrogel Coating for Durable Aqueous Lubrication.

Articular cartilage has an appropriate multilayer structure and superior tribological properties and provides a structural paradigm for design of lubricating materials. However, mimicking articular cartilage traits on prosthetic materials with durable lubrication remains a huge challenge. Herein, an ingenious three-in-one strategy is developed for constructing an articular cartilage-like bilayerhydrogel coating on the surface of ultra-high molecular weight polyethylene (BH-UPE), which makes full use of conceptions of interfacial interlinking, high-entanglement crosslinking, and interface-modulated polymerization. The hydrogel coating is tightly interlinked with UPE substrate through hydrogel-UPE interchain entanglement and bonding. The hydrogel chains are highly entangled with each other to form a dense tough layer with negligible hysteresis for load-bearing by reducing the amounts of crosslinker and hydrophilic initiator to p.p.m. levels.Meanwhile, the polymerization of monomers in the top surface region is suppressed via interface-modulated polymerization, thus introducing a poroussurface for effective aqueous lubrication. As a result, BH-UPE exhibits an ultralow friction coefficient of 0.0048 during 10000 cycles under a load of 0.9MPa, demonstrating great potential as an advanced bearing material for disc prosthesis. This work may provide a new way to build stable bilayer coatings and have important implications for development of biological lubricating materials.

Structural Evolution of High-Entanglement Ultrahigh Molecular Weight Polyethylene Films with Reserved Shish Crystals during the Hot Stretching Process

Structural Evolution of High-Entanglement Ultrahigh Molecular Weight Polyethylene Films with Reserved Shish Crystals during the Hot Stretching Process

Temperature and strain rate effects on ultra‐high‐molecular‐weight‐polyethylene compression: An experimental and modeling approach

AbstractThis study aims to predict the compression behavior of ultra‐high molecular weight polyethylene (UHMWPE) at various temperatures (25, 40, and 55°C) and strain rates (~10−4/s and ~10−2/s) using a single set of three‐network (TN) viscoplastic model parameters. The TN model is made up of three parallel networks: networks A and B use nonlinear springs and dashpots to control the responses of the crystalline phase and confined amorphous phases, respectively, while network C captures the macromolecular amorphous networks using a single nonlinear spring. A single set of TN model parameters captures the yield and post‐yield hardening responses of the stress–strain curves at experimental temperatures and strain rates. When these TN model calibrated parameters are used as material property in a commercial finite element tool to simulate UHMWPE compression, the predicted and simulated results match well, showing the model's fidelity. Additionally, the model predicts experiments conducted at 40 and 70°C with loading rates of ~10−3/s and ~10−2/s, respectively. The study also correlates the deformations of UHMWPE's crystalline structure and macromolecular amorphous networks with its global stress versus strain response by extracting stresses from individual networks of the TN model at different strain rates and temperatures.Highlights UHMWPE's mechanical behavior predicted by a single set of TN model parameters TN model predicts mechanical response at various strain rates and temperatures. TN model explains microstructural crystalline and amorphous phase deformations.

Anterior Cruciate Ligament Reconstruction Using Hamstring Graft with and without Suture Augmentation: A Randomized Trial

Background: The anterior cruciate ligament (ACL) is a vital knee joint stabilizer with rising injury rates. Anatomic ACL reconstruction (ACLR) aims to restore the ACL to its original dimensions, collagen orientation, and insertion sites, but complete restoration may not be possible. Suture augmentation (SA) involves the use of autologous hamstring tendons with a braided ultrahigh molecular weight polyester or polyethylene (UHMWPE) suture or suture tape to act as a secondary stabilizer until complete integration. This study aimed to compare the outcomes of ACLR using hamstring grafts with and without SA.
 Methods: This trial was conducted at a tertiary-level health care center, with 50 patients divided randomly into two groups: 25 patients for standard ACLR (group A) and 25 patients for ACLR with SA (group B). Participants provided informed consent. Baseline clinical characteristics including range of motion (ROM), pain [Numeric Pain Rating Scale (NPRS)], and functional outcomes [Lysholm and International Knee Documentation Committee (IKDC) scores] were collected.
 Results: The mean age was 25.5 years, with 96% male and 4% female participants. A statistically significant improvement was found in both groups in ROM, NPRS scores, and functional outcomes at 1 and 6 months. There was no significant difference in both groups regarding the IKDC score. Lysholm’s score showed a remarkable improvement in both groups.
 Conclusion: SA could be an effective technique for ACLR, with comparable outcomes to standard ACLR.

Low-velocity impact responses of UHMWPE fiber/epoxy laminates with plasma treatment and polypyrrole grafting

The physical–chemical method with plasma treatment and polypyrrole grafting was used to improve the low velocity impact resistance of the ultra-high molecular weight polyethylene (UHMWPE) fiber/epoxy laminates. The experimental impact force–time curves and impact force-central displacement curves were recorded. The microscopic void distribution of impact region was quantitatively counted by high-resolution X-ray micro-computed tomography (μCT). Then the residual compressive strengths for the laminates after low velocity impact were explored. Experimental results showed that the impact resistance and residual strength of the laminates treated by the combined plasma treatment and polypyrrole grafting were significantly improved by comparing with the plasma treatment alone, and the void fraction also reduced remarkably. In addition, the impact resistance with single physical plasma treatment method was more affected by the mixture ratio of nitrogen and oxygen.

The Isothermal Melting Kinetics of Ultra-High Molecular Weight Polyethylene Crystals.

The isothermal melting behaviors of ultra-high molecular weight polyethylene (UHMWPE) with different entangled states (i.e., nascent and melt-crystallized samples) are studied. For two kinds of UHMWPE samples, the result shows that the relative content of survived crystals (Xs) exponentially decreases with time and reaches a constant value. It is suggested that such a melting behavior is related to the observed nonlinear growth of crystals induced by the kinetically rejected entanglements accumulated at the growth front. Additionally, the exponential decay of Xs with time provides a characteristic melting time (τ) for the melting process. Compared to the melt-crystallized UHMWPE, the τ value of nascent UHMWPE is generally longer even in a higher temperature range, which is mainly because the former has a larger entanglement density difference. Furthermore, these observations demonstrate that UHMWPEs with different entangled states have an analogous melting mechanism since they exhibit a similar melting activation energy (≈1300kJ mol-1).

Study on the resistance of UHMWPE laminates against oblique penetration of projectiles

AbstractTo solve the problem of the wall panel of high‐performance shelters protecting against the oblique penetration of projectiles, ballistic experiments were carried out with ultra‐high molecular weight polyethylene (UHMWPE) laminates subjected to normal penetration by high‐velocity projectiles, and the deformation and failure characteristics of UHMWPE laminates were analyzed. The numerical model of the resistance of UHMWPE laminates against penetration of projectiles was established by using the finite element program LS‐DYNA. The validity of the numerical model was verified by the experimental results of damage morphology and the depth of depression of the target plate and the deformation of the warhead. On this basis, the ricochet angle and failure mode of the UHMWPE target plate against projectile penetration were studied numerically, and the impact of the angle of incidence on the residual kinetic energy and normal penetration displacement of the bullet, as well as the damage morphology of the UHMWPE target plate, was revealed by using simulation. The results showed that the ricochet angle of the bullet obliquely penetrating into the UHMWPE target plate was in the range of 45° to 50°; at the initial stage of projectile penetration, the shear fracture failure of the fiber layer mainly occurred at the striking face of the UHMWPE target plate. Under the impact of the warhead deformation, with the reduction of the residual velocity of the bullet, the failure mode gradually changed to the tensile and interlaminar cohesion failure of the fiber layer near the back face; When the angle of incidence was greater than the ricochet angle, the residual kinetic energy of the projectile increased slowly with the increase of the angle of incidence of the bullet and then went up approximately linearly; the normal displacement of the bullet obliquely penetrating into the UHMWPE target plate decreased slowly after reaching the peak, and the peak value of the normal penetration displacement decreased gradually with the increase of the angle of incidence, and the time to peak of the displacement shortened gradually. The damage area of the bulge on the back surface of the UHMWPE target plate after penetration decreased gradually with the increase of the angle of incidence. The research results can provide a theoretical reference for the application of UHMWPE laminates in the design of military bulletproof shelters and armor.

Ultra‐high molecular weight polyethylene micro‐ribbon fibers gel spun using orange terpenes

AbstractToxic, hazardous petrochemical solvents are commonly used for industrial‐scale ultra‐high molecular weight polyethylene (UHMWPE) fiber production, but orange terpenes, a byproduct of orange fruit production, present a bio‐derived, sustainable alternative. In this work, fine UHMWPE fibers were spun using orange terpenes as the spin solvent, hot‐drawn at a draw ratio of 5:1, investigated for their morphology, microstructure, and thermal and mechanical properties. The resulting fibers exhibited a flat, micro‐ribbon cross‐section, which is highly desirable for achieving high fiber volume fractions in UHMWPE‐fiber reinforced composites. After drawing, the fibers possessed 4× greater breaking tenacity than any previously published studies on UHMWPE fibers spun using orange terpenes with a tenacity of 8.6 cN/dtex and tensile modulus of 229.2 cN/dtex. Microstructural analysis via differential scanning calorimetry and X‐ray diffraction revealed that the hot drawing process significantly increased molecular orientation, but crystallinity decreased due to crystallite melting during drawing. Therefore, the mechanical properties of these fibers may be significantly improved with optimization of the fiber drawing process. This work establishes the strong potential of orange terpenes as an environmentally‐friendly alternative solvent for UHMWPE gel spinning and sets a foundation for future parametric optimization of the spinning and drawing of these fibers.Highlights Micro‐ribbon ultra‐high molecular weight polyethylene fibers were prepared using bio‐solvent orange terpenes. Flat profile enables tight packing, aspect ratio maintained after drawing. Drawn fibers were 4× stronger than any previous work with orange terpenes. Near‐melt drawing reduced crystallinity, improved molecular alignment.

Classification of Progressive Wear on a Multi-Directional Pin-on-Disc Tribometer Simulating Conditions in Human Joints-UHMWPE against CoCrMo Using Acoustic Emission and Machine Learning

Human joint prostheses experience wear failure due to the complex interactions between Ultra-High-Molecular-Weight Polyethylene (UHMWPE) and Cobalt-Chromium-Molybdenum (CoCrMo). This study uses the wear classification to investigate the gradual and progressive abrasive wear mechanisms in UHMWPE. Pin-on-disc tests were conducted under simulated in vivo conditions, monitoring wear using Acoustic Emission (AE). Two Machine Learning (ML) frameworks were employed for wear classification: manual feature extraction with ML classifiers and a contrastive learning-based Convolutional Neural Network (CNN) with ML classifiers. The CNN-based feature extraction approach achieved superior classification performance (94% to 96%) compared to manual feature extraction (81% to 89%). The ML techniques enable accurate wear classification, aiding in understanding surface states and early failure detection. Real-time monitoring using AE sensors shows promise for interventions and improving prosthetic joint design.

Insights into synergic antioxidant effects for vitamin E and sugar alcohol stabilized ultrahigh molecular weight polyethylene composites for artificial joints

Oxidation resistance is strongly necessary for the use of crosslinked ultrahigh molecular weight polyethylene (UHMWPE) in artificial joints. The hybrid antioxidant strategy emerged as a promising alternative to the single rival that relies on vitamin E (VE). The goal of this study was to investigate the universality of the antioxidant synergy between VE and sugar alcohol (SA). Three types of SA, including D-sorbitol, maltitol and erythritol, were employed to cooperate with VE. Compared to the use of VE alone, these hybrid antioxidants generally enabled the corresponding UHMWPE composites with prolonged oxidation induction time (OIT) and increased crosslink density. The correlation between OIT and crosslink density of VE/SA-stabilized UHMWPE composites showed low attenuation. The applicability of the hybrid antioxidants to protect UHMWPE against oxidation was further demonstrated using the in vitro clinically relevant accelerated aging. Among the used SA, D-sorbitol exhibited the strongest ability to enhance the synergetic efficiency. The possible mechanism was revealed from the following aspects: the number of secondary hydroxyls per molecular mass and the molecular polarity determined via polarity parameter calculation. These findings provide significant insights for fabricating UHMWPE bearing materials with superior comprehensive performance and extended service longevity.

Homogeneous Non-Metallocene Group 4 Metals Ligated with [N,N] Bidentate Ligand(s) for Olefin Polymerization.

The development of catalysts has significantly advanced the progress of polyolefin materials. In particular, group 4 (Ti, Zr, Hf) non-metallocene catalysts ligated with [N,N] bidentate ligand(s) have garnered increasing attention in the field of olefin polymerization due to their structurally stability and exceptional polymerization behaviors. Ligands containing nitrogen donors are diverse and at the core of many highly active catalysts. They mainly include amidine, guanidinato, diamine, and various N-heterocyclic ligands, which can be used to obtain a series of new polyolefin materials, such as ultrahigh molecular weight polyethylene (UHWMPE), olefin copolymers (ethylene/norbornene and ethylene/α-olefin) with high incorporations, and high isotactic or syndiotactic polypropylene after coordination with group 4 metals and activation by cocatalysts. Herein, we focus on the advancements and applications of this field over the past two decades, and introduce the catalyst precursors with [N,N] ligand(s), involving the effects of ligand structure, cocatalyst selection, and polymerization conditions on the catalytic activity and polymer properties.

A universal strategy for rapid and scalable surface modification of ultra high molecular weight polyethylene fiber

The high performance UHMWPE fiber usually demonstrates extremely poor surface adhesion with resin matrix. Therefore, improving the interfacial adhesion property becomes one of the toughest challenges faced by UHMWPE fibers. In this study, a simple and universal surface welding strategy is promoted to effectively modifying UHMWPE fiber with improved surface adhesion in a short time. The surface welding manufacturing approach is realized by the controllable Joule heating generated from the high contact resistance and rapid thermal response of the conductive nano-material layer coated on UHMWPE surface, which can locally melt the UHMWPE fiber surface and weld the nano materials on UHMWE with a strong and robust mechanical bonding. Since the whole welding process is simple and lasts only for a few seconds, it can be easily applied to the current industrial UHMWPE fiber and fabric manufacturing, enabling a continuous, fast, efficiency and scalable roll-to-roll UHMWPE surface modification process.

The Development and Performance of Knitted Cool Fabric Based on Ultra-High Molecular Weight Polyethylene

In order to withstand high-temperature environments, ultra-high molecular weight polyethylene (UHMWPE) fibers with cooling properties are being increasingly used in personal thermal management textiles during the summer. However, there is relatively little research on its combination with knitting. In this paper, we combine UHMWPE fiber and knitting structure to investigate the impact of varying UHMWPE fiber content and different knitting structures on the heat and humidity comfort as well as the cooling properties of fabrics. For this purpose, five kinds of different proportions of UHMWPE and polyamide yarn preparation, as well as five kinds of knitted tissue structures based on woven tissue were designed to weave 25 knitted fabrics. The air permeability, moisture permeability, moisture absorption and humidity conduction, thermal property, and contact cool feeling property of the fabrics were tested. Then, orthogonal analysis and correlation analysis were used to statistically evaluate the properties of the fabrics statistically. The results show that as the UHMWPE content increases, the air permeability, heat conductivity, and contact cool feeling property of the fabrics improve. The moisture permeability, moisture absorption and humidity conductivity of fabrics containing UHMWPE are superior to those containing only polyamide. The air permeability, moisture permeability, and thermal conductivity of the fabrics formed by the tuck plating organization are superior to those of the flat needle plating and float wire plating organization. The fabric formed by 2 separate 2 float wire organization has the best moisture absorption, humidity conduction, contact cool feeling property.

Study on the Effect of the Molding Process and Service Temperature on the Mechanical Properties and Low‐Velocity Impact Performance of the Ultra‐High Molecular Weight Polyethylene Fiber Laminates

The ultra‐high molecular weight polyethylene (UHMWPE) fiber laminates were prepared by hot pressing at temperatures ranging from 120 to 140 °C and pressures of 15 and 25 MPa. Mechanical test results demonstrated that increasing the molding temperature improved the interlaminar shear strength, in‐plane shear strength, and bending strength of the laminates. Additionally, the in‐plane tensile properties of the laminate were influenced by both the positive effect of increased bond strength and the negative effect of reduced fiber strength. The mechanical properties of the laminate showed improvements at −50 °C but decreased at 70 °C. Low‐velocity impact tests revealed that higher molding temperature and pressure enhanced the dynamic bending stiffness and peak force while reducing the bulge in the laminate's back. Remarkably different low‐velocity impact performance was observed in the laminate at −50 and 70 °C compared to room temperature.

The penetration resistance behavior and corresponding size effects of ultra-high molecular weight polyethylene composite laminates

Focusing on the energy absorption characteristics of ultra-high molecular weight polyethylene (UHMWPE) fiber laminated panels, this study conducts ballistic tests and numerical simulations using 6 mm spherical projectiles to impact the UHMWPE laminated panels. The residual velocity characteristics, energy absorption patterns, and failure modes of the UHMWPE laminated panels under steel ball impacts were analyzed. The results show that the residual velocity of the steel ball increases with the increase of the incident velocity. In the velocity range near the ballistic limit velocity, the residual velocity of the steel ball increases sharply. When the incident velocity exceeds 340 m/s, the increase in residual velocity gradually slows down, tending towards a straight line. When the steel ball velocity is less than 330 m/s, the energy absorption of the UHMWPE laminated panels exhibits linear growth with increasing velocity, with a maximum energy absorption of 47.3 J. In the 327–340 m/s velocity range, the energy absorption of the laminated panels drops sharply from 47 J to around 30 J. In the 340 m/s–600 m/s velocity range, the decline in energy absorption gradually becomes more moderate, decreasing to around 20 J. Beyond 500 m/s, the energy absorbed by the UHMWPE laminated panels stabilizes with increasing velocity, and the fiber tensile failure is the main form of energy absorption of UHMWPE composite laminates under ballistic impact. The failure process of UHMWPE laminated panels presents a multi-stage failure mode, including fiber shear failure, tensile failure, and delamination. As the projectile’s incident velocity increases, the damage mechanism of the UHMWPE laminated panels transitions from tensile-dominated to shear plugging-dominated. Through similarity theory analysis, under certain conditions, the ballistic limit velocity and the dimensionless parameter of unit energy absorption for the UHMWPE laminated panels satisfy geometric similarity.

The Influences of Chemical Modifications on the Structural, Mechanical, Tribological and Adhesive Properties of Oriented UHMWPE Films

Preparing a friction pair “polymer-metal” using improved polymeric composites is contemplated a complicated task due to the inert surface of the polymer. Gluing polymer composites with improved mechanical and tribological properties on metals and saving their unique properties at the same time is considered the best way to prepare slide bearing products based on polymer/metal. In this work, ultraviolet initiation is used after a process of mixed acid pre-treatment. The surface of highly oriented films based on ultra-high molecular weight polyethylene (UHMWPE)/graphene nanoplatelets (GNP) is grafted with nanocellulose. The grafting treatment is analyzed using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and contact angle measurements. Mechanical T-peel tests showed that the peel strength for the treated UHMWPE films increased by three times, up to 1.9 kg/cm, in comparison to the untreated films. The tensile strength of the treated UHMWPE films decreased by about 6% to 788 MPa. Tribological tests showed that the values of both friction coefficient and wear intensity of the treated UHMWPE films were increased insignificantly, which were 0.172 and 15.43 µm/m·m2, respectively. The prepared adhesive tape based on UHMWPE films, which can withstand a weight of up to 6 kg per 1 cm2 of the bonded surface, has a low coefficient of friction, high wear resistance, and high strength, and is considered a promising material for preparing slide bearing products.

Detailed Morphology and Electron Transport in Reduced Graphene Oxide Filled Polymer Composites with a Segregated Structure

Polymer composites of a segregated network structure are dielectric polymer granules coated with electrically conductive nanoparticles at a low content, the quantity of the junctions between the granules determines the composites' mechanical properties, and the percolation network formed by the nanoparticles determines the electrical conductivity. Here, the morphology and electron‐transport properties in reduced graphene oxide (rGO)‐filled composites with a segregated structure based on polyvinyl chloride (PVC), poly(vinylidene fluoride‐co‐tetrafluoroethylene) (P(VDF‐TFE)), and ultrahigh‐molecular‐weight polyethylene (UHMWPE) are studied. Optical and electron microscopies study of the microtome‐formed cross sections have shown the morphology to be dependent on the polymer—the thinnest rGO layers are in UHMWPE‐based composites, the thicker rGO layers are in PVC‐ and P(VDF‐TFE)‐based ones. The electrical conduction of the composites and the rGO‐paper occurs through the same hopping conduction mechanisms within the wide temperature range, which allows to use the composites in applications where pure rGO is considered. Owing to thicker rGO layers open to the environment, PVC‐ and P(VDF‐TFE)‐based composites are more attractive, rather than the UHMWPE ones, in applications where layered materials are needed, for example, in lithium‐ion batteries or supercapacitors. The UHMWPE‐based composites look more promising as electrically conductive materials when mechanical strength is important.

Numerical study on hydrodynamic behaviors of and flow field around UHMWPE plane nets

The hydrodynamic behaviors of and flow field around the net made by ultra-high molecular weight polyethylene (UHMWPE) were seldom investigated previously. Therefore, a three-dimensional numerical model for the UHMWPE plane net is established herein based on the porous media model, and the unknown Darcy-Forchheimer coefficients are attained by fitting the experimental data of physical model with the minimum error function method. Then, the flow field characteristics around the UHMWPE plane net are investigated and it is noted that the flow velocity reduction along the horizontal centerline of net decreases with the increase in velocity, while larger attack angle and solidity both result in a larger flow velocity reduction. And, the effects of nets spacing and number on the velocity distribution and flow field properties in and around multi-layer nets are revealed. Finally, the empirical formulas for calculating the drag and lift coefficients of the UHMWPE plane net are proposed by considering as the function of solidity, Reynolds number and attack angle.