Ultra-High Molecular Weight Polyethylene Tape Applied for Distal Humeral Condyle Fracture around Total Elbow Arthroplasty in Patients with Rheumatoid Arthritis: Report of Two Cases

Managing fractures of distal humerus in patients with rheumatoid arthritis (RA) is technically challenging. Total elbow arthroplasty (TEA) is one of the treatment options for these fractures. While elbow motion is largely regained by TEA, comminuted condyle fragments are often ignored. Although numerous approaches for repair of condylar fragments around TEA are described, any universal fixation strategy for these fractures has not been established. This report describes, for the first time, application of an ultra-high molecular weight polyethylene (UHMWPE) tape for the treatment of distal humerus fracture in 2 patients with rheumatic elbow arthropathy. The post-operative clinical courses were good. Radiographs showed bony union of the condylar fragments without loosening in two cases. Because of its flat configuration, softness, and flexibility, UHMWPE tape is a promising material for stabilizing fracture of the distal humerus associated with TEA.

Temperature Effect on the Conformation Transition of Ultra-high Molecular Weight Polyethylene/Polypropylene Blends Undergoing Continuous Volume Extensional Flow:A Mesoscopic Simulation

Due to the multiformity and complexity of chain conformation under external flow and the challenge of systematically investigating the transient conformation and dynamic evolution process of polymer chains at the molecular level by means of present experimental techniques,a universal description of both chain conformation and dynamics with respect to continuous volume extensional flow(CVEF)is still absent.Taking into account the temperature effect,we performed dissipative particle dynamics(DPD)simulations with the particles corresponding to the repeat units of polymers over a wide temperature range and analyzed the correlation with the conformational properties of ultra-high molecular weight polyethylene/polypropylene(UHMWPE/PP)blend in response to the CVEF.With time evolution,the polymer chains become highly oriented parallel to the flow direction instead of the initial random coiling and self-aggregation.It is found that a high temperature is necessary for more substantial compactness to take place than low temperature.The low-k plateau and low-k peak in structure factor S(k)curves suggest a low degree of conformational diversity and a high degree of chain stretching.It is also concluded that the intra-molecular C-C bond interaction is the main driving force for the dynamics process of the chain conformations undergoing CVEF,where the motion of the alkyl chains is seriously restricted owing to the increase in bond interaction potential,resulting in a reduction of the difference in diffusion rates among alkyl chains.

Cyclic Pulsating Pressure Enhanced Segregating Structuration of Ultra-High Molecular Weight Polyethylene/Graphene Composites as High-performance Light-Weight EMI Shields

Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring structure for higher EM resonances.Herein,we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration(CPP-SS),which can reinforce these two factors simultaneously.The structural information was supplied by optical microscopy(OM)and scanning electron microscopy(SEM),both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene(UHMWPE)/graphene composites.Then,the result showed that CPP-SS can significantly improve theσof samples.Ultimately,advanced specific EMI shielding efficiency of 31.1 d B/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%.Meanwhile,it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed.This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPPSS,and to bring us a simple and efficient approach for fabricating high-performance,strong and light-weight polymeric EMI shields.

PREPARATION AND CHARACTERIZATION OF ULTRA-HIGH MOLECULAR WEIGHT POLY(ETHYLENE TEREPHTHALATE)(PET)FIBER

This paper reports the spinning and drawing behavior of Ultra-high Molecular Weight polyethylene Terephthalate) (UHMW-PET) fibers. The as-spun fibers were produced by dry-jet wet spinning of a 15%-17% solution in 50:50(v:v) trifluroroacetic acid and dichloromethane. Both molecular weight and polymer solution concentration have marked effect on the drawability of the as-spun-fibers. The maximum extension drawing ratio (EDRmax) of as-spun fiber increases with increasing molecular weight, whereas optimal concentration to achieve the EDRmax of as-spun fibers decreases with increasing molecular weight. Drawing speed and temperature during the first step have remarkable effect on the drawability of these fiber during the second step. Relatively lower drawing temperature and drawing speed (19 ℃ , 60 mm/min) during the first drawing step was beneficial to mechanical properties of ultimate fibers. At the range of 210 ℃ to 230 ℃, the draw ratio (DR) during the second step increases with increasing temperature.

Progressive Failure Analysis of Quasi-isotropic Self-reinforced Polyethylene Composites by Comparing Unsupervised and Supervised Classifications of Acoustic Emission Data

Unsupervised and supervised pattern recognition( PR)techniques are used to classify the acoustic emission( AE) data originating from the quasi-isotropic self-reinforced polyethylene composites,in order to identify the various mechanisms in the multiangle-ply thermoplastic composites. Ultra-high molecular weight polyethylene / low density polyethylene( UHMWPE / LDPE)composites were made and tested under quasi-static tensile load. The failure process was monitored by the AE technique. The collected AE signals were classified by unsupervised and supervised PR techniques, respectively. AE signals were clustered with unsupervised PR scheme automatically and mathematically. While in the supervised PR scheme,the labeled AE data from simple lay-up UHMWPE / LDPE laminates were utilized as the reference data.Comparison was drawn according to the analytical results. Fracture surfaces of the UHMWPE / LDPE specimens were observed by a scanning electron microscope( SEM) for some physical support. By combining both classification results with the observation results,correlations were established between the AE signal classes and their originating damage modes. The comparison between the two classifying schemes showed a good agreement in the main damage modes and their failure process. It indicates both PR techniques are powerful for the complicated thermoplastic composites. Supervised PR scheme can lead to a more precise classification in that a suitable reference data set is input.

Micro-Macro Scale Relationship in Creep Deformation of Ultra High Molecular Weight Polyethylene

Macroscopic and microscale creep deformations of UHMWPE were investigated by using in situ SAXS.A methodology for the measurement of the local creep deformation of inter-lamellar amorphous phase has been proposed.The local strain of inter-lamellar amorphous phase(£a)and macroscopic strain(£macro)were evaluated and they were compared to study the relati on ship betwee n macroscopic and microscale creep deformation of UHMWPE.Both of them exhibit two deformation regions against creep time.The entanglements show a strong impact on both the macroscopic and local inter-lamellar amorphous phase creep behavior and they can be well correlated to the molecular weight between two entanglements estimated from strain-hardening modulus.Compared to the macroscopic creep deformation,local inter-lamellar amorphous layers have a smaller creep deformation.From the local creep measurement,the apparent modulus of inter-lamellar amorphous phase can also be estimated(200<Ma<500 MPa).These values are much higher than the Young's modulus of bulk amorphous PE,which can be well explained by the confinement of the lamellar stacks and the enhancement of the amorphous phase with the relatively high concentration of entanglements.This study provides a useful means and quantitative data for achieving the scale transition between the micro and the macro structural levels for the study of viscos-elastic deformation.

Ballistic Penetration Damage of Hybrid Thermoplastic Composites Reinforced with Kevlar and UHMWPE Fabrics

Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybrid composites with thermoplastic polyurethane(PU)matrix.The hybrid composites were penetrated by fragment-simulating projectiles(FSPs)using an air gun impact system.The effects of stacking sequences on the ballistic performance of hybrid composites were analyzed.Two types of specific energy absorption(the energy absorption per unit area density and the energy absorption per unit thickness)were investigated.It was found that the main damage modes of PU hybrid composites were fiber breakage,matrix damage,fiber pullout and interlayer delamination.The instantaneous deformation could not be used as a reference index for evaluating the ballistic performance of the target plate.The energy absorption process of the PU hybrid composites showed a nonlinear pattern.The hybrid structure affected the specific energy absorption of the materials.

Dissolving of Ultra‑high Molecular Weight Polyethylene Assisted Through Supercritical Carbon Dioxide to Enhance the Mechanical Properties of Fibers

The molecular weight of ultra-high molecular weight polyethylene(UHMWPE)fbers is severely decreased compared with raw materials due to high temperature and strong shearing in the dissolving process.In this study,we reported a novel method to assist the dissolving of UHMWPE in parafn oil without severe degradation in order to improve the tensile strength of resultant fbers.UHMWPE fbers with relatively high molecular weight and more excellent disentanglement efect were prepared by gel-spinning with UHMWPE suspension treated with supercritical carbon dioxide(SC-CO_(2)).The dynamic thermomechanical,mechanical and crystalline properties of UHMWPE extracted fbers and drawn fbers were researched comprehensively.UHMWPE extracted fbers obtained after SC-CO_(2) treatment display a higher molecular weight.More importantly,it is clear that the disentanglement of UHMWPE gel fbers gained by processing SC-CO_(2) has been signifcantly promoted compared with that without SC-CO_(2) treatment from dynamic thermomechanical and rheological results,which could also be demonstrated from the cross-sectional morphology of UHMWPE extracted fbers.Furthermore,the tensile strength of UHMWPE fbers prepared through SC-CO_(2) treating is able to attain 30.11 cN/dtex,increased by 10.3%in comparison to UHMWPE fbers gained without assistance of SC-CO_(2).Beyond that,the thermal behavior and crystallization performance of UHMWPE extracted fbers and drawn fbers acquired by way of SC-CO_(2) treatment have also been enhanced.

Optimization of the Production Process of Flash-Spinning UHMWPE Superfine Fiber by Response Surface Methodology

In this paper, statistical optimization method was used to optimize the flash-spinning process conditions. Ultra-high molecular weight polyethylene （UHMWPE） superfine fiber was fabricated by flash-spinning method using UHMWPE as the fiberforming polymer, 1, 2-dichloroethane as the main solvent. The important parameters of the flash-spinning were filtered by Plackett-Burman experimental design based on the single factor experiments. After determining the best regions of the fiber properties, the optimum level of the important parameters were determined by Box-Behnken design. The results of the design showed that the important parameters influencing on the properties of the flash.spinning fiber were spinning temperature, spinning pressure, and spinning solution concentration. The optimum technical parameters were： spinning temperature 186. 4 ~C, spinning pressure 6. 16 MPa, spinning solution concentration 3.06 %. The highest combination property of the flash-spinning fiber was 86.39 under this condition.

Surface Treatment of UHMWPE Fibers for Adhesion Promotion in Epoxy Polymers

Surface of Ultra-high molecular weight polyethylene （UHMWPE） fiber were treated by chromic acid chemical etching, pyrrole chemical vapour phase deposition and the complex of these two methods, respectively. The change of surface properties and structure of fibers were discussed by Fiour Transform Infrared Spectroscope （FTIR）, Dynamic Mechanical Analysis （DMA） and Scanning Electron Microscope （SEM）. The results show that some new oxygenous groups could be found on surface of UHMWPE fiber after chromic acid chemical etching, which enhanced intemolecular interaction with polypyrrcle. The adhesion of the fiber and resin natrix increased after pyrrole chemical vapour deposition. When chromic acid etching combined with pyrrole chemical vapor deposition, the treated fiber not only has the same properties as original fiber bat also outstanding adhesion to epoxy resin matrix, and its composites have better mechanic properties shear strength）, resulting from intemolecular interaction treated fiber and polypyrrole.

Effect of bombarding energy on ion beam assisted deposited DLC film on UHMWPE

Diamond-like carbon (DLC) films on ultra-high molecular weight polyethylene substrates were prepared at CHn+ ion bombarding energies of 200-1000eV at room temperature using ion beam assisted deposition technique. The wear tests exhibited a high wear resistance for all DLC films. X-ray photoelectron spectfoscopy and Raman spectroscopy analysis indicated that DLC film was amorphous with a characteristic high fracdion of sp3 bonds in the structure of mixed sp:2+ sp3 bonding at an optimal bombardingenergy of 600eV.

Improvement of Toughness of UHMWPE/PP Blends

Ultra-high molecular weight polyethylene (UHMWPE) was blended with polypropylene (PP) in order to ensure good processing. Inorganic rigid particles were also used to toughen UHMWPE/PP blends. CaCO3 and a compound additive containing heat mixed polyethylene glycol 2000 and white diatomite were added to the blends. The crystalline, surface morphology and mechanical properties of the blends were investigated comprehensively. The toughness of the material is effectively improved. By contrast, the compound additive had a better result. When the content of additive was 15%, the elongation at the break increased by 279.2% and the fracture energy increased by 343.8% compared to the original samples.

Out-of-Plane Compressive Behavior for UHMWPE/Polyurethane Composites after Hygrothermal Treatment

Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane(UHMWPE/PU)composites have been studied in this paper.Firstly,the UHMWPE composites were immersed in water at 70℃.The out-ofplane compression test was then performed on the dry/wet state specimens at quasi-static states(0.001-0.01 s^(-1))and high strain rate states(800-2 400 s^(-1)).The split Hopkinson pressure bar(SHPB)was adopted in the dynamic tests and waveform shapers were used to smooth and control the incident pulse.The results show that there are two platforms for the water absorption curve of UHMWPE composites.The absorption of moisture reduces the quasi-static compressive strength of the material while initially increasing,then decreasing the dynamic compressive strength.Matrix plasticization,fiber/matrix interface degradation and void expansion are the main factors affecting the irregular change of static/dynamic compressive strength of UHMWPE composites.

Semi-analytical calculation model for friction of polymers on the example of POM|PE-UHMW and steel|PE-UHMW

In this paper,a semi-analytical calculation model for the coefficient of friction(COF)of single spherical protrusions is presented.It allows the prediction of the deformative friction part(μ_(def))and adhesive friction part(μ_(def))of the friction pairings steel|polyethylene with ultra-high molecular weight(PE-UHMW)and polyoxymethylene(POM)|PE-UHMW.The experimental studies included unlubricated friction tests,which served to determine the total COF(μ_(def)),as well as tests being lubricated with silicone oil,from whichμ_(def)is obtained.Based on the verification tests,it could be shown that both states of lubrication result in the same deformation and that the relationship between the rear angle(w)andμ_(def)postulated in the calculation model is valid.Therefore,friction tests with segmented spheres were carried out,which allow a specific variation of thew.It can be concluded that for both pairings theμ_(def)is generally of minor significance(approx.1/3μ_(tot))and the influence of theμ_(adh)predominates(approx.2/3μ_(tot))the friction process.Furthermore themtot decreases with increasing contact pressure especially in the low pressure range and depends on the form of motion(continuous and discontinuous).

Tribological evaluation of thermoplastic polyurethane-based bearing materials under water lubrication:Effect of load,sliding speed,and temperature

Polymers are widely used in bearing applications.In the case of water-lubricated stern tube bearings,thermoplastic polyurethane(TPU)-based composites are used due to their excellent wear resistance,corrosion resistance,and tunable mechanical properties.Their tribological performance,however,depends on operating conditions.In this work,TPU was blended with carbon fiber,graphene platelet,and ultra-high molecular weight polyethylene(UHMWPE).Friction tests of TPU based-composites against copper countersurface were carried out in water to mimic the actual operating conditions of the bearing.Most of the resulting contacts were in the boundary lubrication regime,in which friction was attributed to both contact mechanics of asperities as well as water lubrication.Our results show that the viscoelasticity of TPU has a considerable impact on its tribological performance.Water lubrication at 50°C promotes the softening of polymer surface material during sliding,resulting in higher fluctuation in the coefficient of friction and wear loss.This is attributed to the reduced thermomechanical properties.In addition,Schallamach waviness is observed on worn surface.The tribological properties of TPU are significantly improved by the inclusion of carbon fiber,graphene platelet,and UHMWPE.The formation of graphene transfer-layers and UHMWPE transfer film reduces friction and wear loss,while the inclusion of carbon fiber enhances wear resistance due to improved mechanical properties and load bearing capacity.

Olefin Polymerization Behavior of Titanium(IV) Complexes with Fluorinated and Non-fluorinated Aliphatic Phenoxyimine Ligands

A series of Ti(Ⅳ) dichloride and dialkoxide com plexes with phenoxyimine ligands containing fluorinated and nonfluorinated aliphatic imine fragments have been synthesized.The molecular structures of complexes 1 and 4 were established by single-crystal X-ray diffraction studies.The complexes adopt a distorted octahedral coordination structure around the titanium atom and two oxygen atoms are situated in trans position while two nitrogen atoms and two outgoing ligands(Cl or iPrO) are situated in cis position.Effect of activators(MMAO-12 and combinations Et_nAICl_(3-n)+Bu_(2)Mg) and outgoing ligand(Cl or iPrO) nature on the catalytic activity and properties of the resulting polymers was studied.The Ti complexes,despite the nature of the outgoing ligands(Cl or iPrO) in the presence of Al/Mg activators,was found to display a high ethylene polymerization activity in the range 1600-3830 kg_(polymer)·mol_(Ti)^(-1)·h^(-1)·atm^(-1) with a viscosity average molecular weight(M_v) value in the range 1.1×10~6-7.1×10~6 Dalton(Da).The resulting UHMWPE can be processed by a solventless method into high-strength and high-modulus oriented films.The rheological characteristics of a polymer melt have been studied.The absence of a cross-over point did not allow to compare the values of the molecular weight distribution of polymers obtained on fluorinated and non-fluorinated pre-catalysts,however,the estimation of the entanglement density is in good agreement with the mechanical characteristics of oriented film s.Upon activation with methylalumoxane,the activity of the com plexes decreased very significantly;however,a polymer with a molecular weight of about 12 million Da was obtained.In the process of ethylene/octene-1 copolymerization,fluorine-containing precatalysts showed a clear advantage over non-fluorinated analogues both in activity and in comonomer content.

Properties and evaluation of amidoxime-based UHMWPE fibrous adsorbent for extraction of uranium from seawater

An amidoxime-based ultra-high molecular weight polyethylene （UHMWPE） fibrous adsorbent was successfully prepared by T-irradiation-induced graft copolymerization of acrylonitrile （AN） and acrylic acid （AA）, followed by amidoximation. The grafting of AN and AA on the UHMWPE fiber and the amidoximation of the grafted fiber were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The mechanical property of the original and modified UHMWPE fibers was compared by single-filament strength test. The adsorption property of the UHMWPE fibrous adsorbent was evaluated by adsorption test in uranyl nitrate solution and seawater. The surface of the modified UHMWPE fibers was covered by the grafting layer and became rough. The tensile strength of the amidoxime-based UHMWPE fibrous adsorbent was influenced by the absorbed dose and hydrochloric acid elution, but was independent of the grafting yield and amidoximation. The uranium adsorption amount of the amidoxime-based UHMWPE fibrous adsorbent after immersing in seawater for 42 days was 2.3 mg-U/g.

Trichlorozirconium η~2-Hydrazonides： Synthesis, Characterization and Their Catalytic Behavior toward Ethylene Polymerization

The trichlorozirconium η~2-hydrazonides（R=H, A; R=CH_3, B） were synthesized through the finely controlled stoichiometrical reactions of anhydrous zirconium tetrachloride with the lithium salt of either 1-（furan-2-ylmethylene）-2-phenylhydrazonide or 1-（furan-2-ylethylidene）-2-phenyl hydrazonide in the solvent tetrahydrofuran（THF）, respectively. These complexes were highly sensitive to air and moisture due to solely using less bulky ligand of hydrazonides. The molecular structures of the title complexes, determined by means of single crystal X-ray diffraction, were found to be the distorted pentagonal bipyramid geometry around zirconium atom, with three chlorides and the hydrazonato ligand acting as the η~2-coordination mode as well as two incorporated THF molecules. Upon activation with either methylaluminoxane（MAO） or modified methylaluminoxane（MMAO）, both complexes A and B exhibited catalytic activities toward ethylene polymerization, producing polyethylenes with ultra-high molecular weights.