Neat Ultra-high Molecular Weight Polyethylene Research Articles

Flexural strength and impact properties of UHMWPE bio-composite as bone plate fixation

ABSTRACT Ultra-high molecular weight polyethylene (UHMWPE) is utilised for several purposes, including as a biomedical material for artificial joint replacement. This study looks at the effects of adding nanosized hydroxyapatite (HAP), nanosized titanium dioxide (TiO2), carbon fibre (CF), and Kevlar fibre (KF) to bone plate fixation in the femur bone prosthesis. Because of the ease with which they could be processed, their low cost, remarkable mechanical properties, good cell interaction, different amounts of n-HAP and n-TiO2 (1.5, 2.5, 3.5, and 4.5 wt%), and a fixed amount of CF and KF (5 wt%) were dispersed in UHMWPE-based biocomposites. The UHMWPE/n-HAP and UHMWPE/n-TiO2 particulate biocomposites were prepared by using the dispersing technique followed by hot pressing moulding, then mechanical testing was performed, including flexural, maximum shear stress, and impact tests. Scanning electron microscopy (SEM) is used to observe reinforcement and matrix fractures. Biocomposites with n-HA/Carbon fibre hybrid biocomposites showed better results concerning specific mechanical strength, as well as flexural strength, max. shear and impact energy. The composites show an increase in flexural strength, flexural modulus, impact strength, and max. shear stress by 44%, 32.49%, 120.7%, and 182.6% respectively concerning neat UHMWPE. This review focuses on the benefits of UHMWPE particulate biocomposites in a variety of weight proportions and hybrid biocomposites, which have not yet been tested as a superior alternative for the creation of bone plate fixation.

Algal extracts – The appropriate stabilizers for radiation processed UHMWPE

The present paper presents the stabilization effects of commercially available algal extracts of Chlorella vulgaris, Spirulina platensis and Ascophyllum nodosum added in UHMWPE matrices at the concentration of 2 wt%. The chemiluminescence assay reveals the high efficiency of active antioxidant components in γ-radiated materials after their exposure at 25 and 100 kGy in respect with pristine polymer. The main kinetic parameters depicting the progress of degradation, as well as the stabilization efficiency: onset oxidation temperature, oxidation induction time and oxidation rate are taken into consideration for the evaluation of protective activities. While the unirradiated neat ultra-high molecular weight polyethylene (UHMWPE) is degraded four times faster than the stabilized samples, all the modified polymer samples keep their exceptional oxidation resistance after the γ-exposure even at 100 kGy. The application of technological dose of 100 kGy maintains constantly oxidation endurance even at high operation temperature exceeding 200 °C. The extension of antioxidant features over the large dose range recommends the tested algal extracts safety usage compounds for the protection of various classes of polymer applied working in several conditions such as UV exposure during food handling, γ-sterilization, outdoor corrosion protection and insulation, sealing products for the security of fluid loops as functional units in nuclear power plants. The reported antioxidant evidences for the stability improvement of UHMWPE may be generally applied for all polymer formulations based on the oxidation protectors provided by nature.

Investigation of mechanical properties of UHMWPE composites reinforced with HAP+TiO2 fabricated by solvent dispersing technique

This work seeks to contribute to solving the problems of inadequate artificial joint design from the mechanical perspective in total joint replacement (TJR) surgery. Ultra-high molecular weight polyethylene (UHMWPE)/hydroxyapatite (HAP) + titanium dioxide (TiO2) hybrid composites were fabricated and tested for use as artificial cartilages in the total joint prosthesis. Different amounts of TiO2 (1–10 wt%) and fixed amount of HAP (20 wt%) were dispersed in UHMWPE-based nanocomposites due to obtaining a material easy to be processed, inexpensive, with remarkable mechanical properties, and good cells interaction. The UHMWPE/HAP + TiO2 composites were prepared by using the solvent dispersing technique and twin-screw mixer, followed by hot compression molding, then mechanical testing was performed. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) are used to study the effect of the additives and the dispersion quality of the composites. The solvent dispersing technique shows better dispersion of the additives in the polymer matrix. The composites show an increase in Young's modulus, hardness, and flexural strength, by 71%, 33%, and 95% respectively concerning neat UHMWPE. The composite contains 3 wt% TiO2 showing the best enhancement percentage.

Study on the effects of soluble POSS on chain disentanglement in UHMWPE polymerization

Polyhedral oligomeric silsesquioxanes (POSS) was added in ultrahigh molecular weight polyethylene (UHMWPE) to intercalate the molecular network and produce chain disentanglement. To avoid agglomeration, the POSS/UHMWPE composites were prepared by in-situ polymerization. In particular, POSS used in this experiment is soluble in the polymerization process, so it can be dispersed in the form of nm-scale in UHMWPE. The reduced melt viscosity and the increased molecular weight between entanglement (Me) revealed that the addition of POSS can induce the disentanglement of UHMWPE and the optimal content is 0.2 wt%. The isothermal and nonisothermal crystallization behavior of nanocomposites were studied by a differential scanning calorimetry (DSC). The crystallization rate and the crystallinity of UHMWPE increased with the addition of POSS, indicating that POSS could act as a nucleating agent in UHMWPE. The annealing study was carried out by a Flash DSC and two melting peaks were observed. The data was analyzed by Arrhenius equation and the POSS/UHMWPE was found to have a lower melting activation energy than neat UHMWPE, proving the disentanglement effect of POSS on UHMWPE.

Fabrication of Kevlar®-reinforced ultra-high molecular weight polyethylene composite through microwave-assisted compression molding for body armor applications

Kevlar®-reinforced composites are used in high energy absorption applications. In the present work, Kevlar®-reinforced ultra-high molecular weight polyethylene composites were fabricated through microwave-assisted compression molding. The microwave-assisted compression molding parameters were optimized through trial and error method. Analysis of mechanical behavior of composites was accessed through uniaxial tensile testing, flexural testing, impact testing, and nano-indentation. The fractured specimens were observed using scanning electron microscopy. An increment of 92.2% was observed in the ultimate tensile strength of the ultra-high molecular weight polyethylene/Kevlar® composite compared to neat ultra-high molecular weight polyethylene. Flexural properties, impact energy absorption rate, and hardness property of the composite were increased by 27.1%, 91.6%, and 4.77%, respectively, compared to pure ultra-high molecular weight polyethylene. Enhanced mechanical properties may be attributed to unique microwave heating phenomena during microwave-assisted compression molding.

SiO2‐covered graphene oxide nanohybrids for in situ preparation of UHMWPE/GO(SiO2) nanocomposites with superior mechanical and tribological properties

ABSTRACTThe modified Hummer technique was used in the preparation of graphene oxide (GO) nanosheets, and then SiO2 decorated GO [GO(SiO2)] nanosheets were synthesized via the sol–gel method. Then, ultrahigh‐molecular‐weight polyethylene (UHMWPE) nanocomposites loaded with 0.5, 1, 1.5, and 2 wt % of GO(SiO2) were prepared using magnesium ethoxide/GO(SiO2)‐supported Ziegler–Natta catalysts via the in situ polymerization. Morphological study of the prepared polymer powders was assessed using field‐emission scanning electron microscopy, which showed that GO(SiO2) nanohybrids have been uniformly dispersed and distributed into the UHMWPE matrix. Also, the neat UHMWPE and its nanocomposites were evaluated with different analyses, including viscosity‐average molecular weight measurement, differential scanning calorimetry, thermogravimetric analysis, tensile test, scratch hardness, and pin‐on‐disk test. The characterization of the UHMWPE nanocomposites indicated that many characterizations, including the mechanical, thermal, and tribological properties of UHMWPE, were significantly improved by incorporation of these new nanosheets in spite of the molecular weight reduction of the polymeric matrix and the improved flowability and processability of the produced nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47796.

Studies on the Wear Characteristics of Ultra High Molecular Weight Polyethylene (UHMWPE) Polymer Nanocomposites containing Nano Zinc Oxide

Results of wear characteristics of Ultra High Molecular Weight Polyethylene (UHMWPE) Polymer Nanocomposites reinforced with micron zinc oxide and Nano zinc oxide are presented. Produced Nano ZnO had flower moprphology (typical flower petal has a length of ∼ 200 nm). Wear rates were acquired using a fabricated wear tester, with applied normal load of 20N, and 40N in rotation and reciprocation modes in dry conditions for 4 hours. In rotation mode neat specific wear rate of UHMWPE being 2.8 x 10-5 g/Nm for test duration of 2 hours and decreased thereafter to 1.9x10-5 g/Nm till the end of 4 hours of test duration with applied normal load of 20N. UHMWPE-5% micron ZnO showed highest specific wear rate in both rotation and reciprocation modes. UHMWPE-10% Nano ZnO exhibited intermediate specific wear rate in both rotation and reciprocation modes. UHMWPE-5% NanoZnO possessed lowest wear rate, and smooth worn-out surfaces were observed for UHMWPE-Nano ZnO composites. There has been a 3 fold increase in Ra and Rq values of worn out neat UHMWPE, 1.5 fold increase for micron ZnO composites. However, Ra and Rq values of UHMWPE-10% Nano ZnO composites are decreased. 3D surface images were complementing the test results obtained in this preliminary investigation.

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.

Photodegradation of UHMWPE Filled with Iron Ore Fine

Ultra high molecular weight polyethylene (UHMWPE) is one of the most important engineering materials owing to outstanding properties like impact strength and abrasion resistance. However, the relatively low Young´s modulus restricts some application and the use of fillers may be a suitable way to overcome this. The fillers can influence the photo stabilization of the compound, as it occurs to other polymers. Neat UHMWPE and its composites with 1 and 10% of iron ore fine were exposed to ultraviolet radiation for up to 33 days and then tested for mechanical properties. The stress-strain behaviour changed with degradation, with an evident necking and strain hardening region that was not observed before exposure, due to a reduction in entanglements density. From the tensile results, the filler may have a protection action against UV, particularly when a loading of 10% was present. Complementary analyses were performed, including X-ray diffraction, DSC and SEM.

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.

In vitro evaluation of UHMWPE/zirconia composite using human peripheral blood mononuclear cells

The objective of the present study was to investigate in vitro biocompatibility of ultra high molecular weight polyethylene (UHMWPE)/zirconia-polymerized composite (PC) using human peripheral blood mononuclear cells (PBMCs). This study was undertaken to compare the levels of free radical generations for neat UHMWPE and PC through irradiation sterilization, and their response to PBMCs viability. Electron spin resonance (ESR) studies showed that γ-ray irradiation of the samples generated free radicals; the extent was inversely related to zirconia content, and the free radicals strongly influenced cell viability. DNA fragmentation and DAPI staining assays revealed that cell death was associated with the induction of apoptosis. Flow cytometry also showed that cell death was largely dependent upon both early and late apoptosis, and, importantly, oxidized PC (ox-PC) exhibited a significantly lower rate for late apoptosis compared to that of oxidized UHMWPE (ox-UHMWPE). Open image in new window

An in-situ X-ray scattering study during uniaxial stretching of ionic liquid/ultra-high molecular weight polyethylene blends

An ionic liquid (IL) 1-docosanyl-3-methylimidazolium bromide was incorporated into ultra-high molecular weight polyethylene (UHMWPE) and formed IL/UHMWPE blends by solution mixing. The structure evolution of these blends during uniaxial stretching was followed by in-situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. During deformation at room temperature, deformation-induced phase transformation from orthorhombic to monoclinic phase was observed in both IL/UHMWPE blends and neat UHMWPE. The elongation-to-break ratios of IL/UHMWPE blends were found to increase by 2–3 times compared with that of pure UHMWPE, while the tensile strength remained about the same. In contrast, during deformation at high temperature (120 °C), no phase transformation was observed. However, the blend samples showed much better toughness, higher crystal orientation and higher tilting extent of lamellar structure at high strains.

Gelation mechanism of ultra-high-molecular-weight polyethylene (UHMWPE) chains in dispersion solutions containing multiwall carbon nanotubes (MWNTs) analyzed in terms of liquid-liquid phase separation

Abstract Gelation mechanisms of ultra-high-molecular-weight polyethylene (UHMWPE) in dispersion solutions containing multiwall carbon nanotubes (MWNTs) were investigated in terms of liquid-liquid phase separation mechanisms. When an incident beam of He-Ne gas laser was directed to the dispersion solution quenched to a desired temperature, the logarithm of scattered intensity increased linearly with elapsing time and tended to deviate from this linear relationship. The two different increasing behaviors of the scattered intensity were termed as initial and latter stages, respectively, of the phase separation. The linear increase in logarithmic light-scattered intensity was analyzed within the framework of the linear theory of spinodal decomposition in terms of the viewpoint that the quenched solution becomes thermodynamically unstable and tends to incur phase separation to resolve the unstable state. The growth rate of the concentration fluctuation of neat UHMWPE solution (without MWNTs) calculated from the slope of linear increase was faster than that of the dispersion solution. In spite of the rapid growth rate, however, the gelation time of the dispersion solution was much shorter than that of the neat UHMWPE solution and the gelation and quasi-spinodal temperatures were slightly higher. These phenomena were in contradiction with the result of the concentration fluctuation. This contradiction was thought to be due to the fact that diffused UHMWPE chains in the dispersion solution were gelled easily on the MWNT surface rather than the gelation by self-coagulation.

Sliding wear performance of HD-PE reinforced by continuous UHMWPE fibres

This paper deals with the wear and creep resistance of a new composite material consisting of high density polyethylene (HD-PE) reinforced by continuous ultra high molecular weight polyethylene (UHMWPE) fibres. Unidirectional PE/PE laminates with fibre contents between 0%and 50% by volume were produced via hot pressing of HD-PE powder impregnated UHMWPE fibres. Flat specimens were tested in a ball-on-prism tribometer with polished steel balls. The penetration of the steel balls into the composite specimen was measured continuously. Creep deformation and material removal by wear were separated. The results were compared with the neat UHMWPE (good wear resistance but poor creep resistance and mechanical properties) and HD-PE (better creep resistance but poor wear resistance). The composites were found to combine the good wear resistance of UHMWPE with a superior creep resistance and mechanical properties. Further work is needed to improve the homogeneity of the composites in order to reduce the scatter of the wear results.