Ultra-high Molecular Weight Polyethylene Nanocomposites Research Articles

Optimization through combined compromise solution and weight determination through SHANNON-ENTROPY for multi criteria decision making in tribological testing of ultrahigh molecular weight polyethylene nano-composite in SBF environment and compression testing with it’s invitro analysis

Aluminium oxide and graphene reinforced with ultrahigh molecular weight polyethylene (UHMWPE) composites offer significant potential for prosthetic and implant applications due to their unique combination of properties. In this article, a series of aluminium oxide and graphene reinforced with ultrahigh molecular weight polyethylene (UHMWPE) composites were successfully fabricated through compression moulding. The average hardness of all the composites was observed to be higher than the UHMWPE (6.1 Hv). Composite U-15A-5 G was found to be the hardest with hardness of 10.5 Hv owing to strong bond between Al2O3 and UHMWPE. The compression strength of the U-15A-5 G material was about 81.936 MPa, which is 40.9% better than the pure UHMWPE. The compression modulus was about 330 MPa which is 22.2% higher than neat UHMWPE. Composite samples were tribo tested under simulated body fluid (SBF) lubricating environment. Using combined entropy-COCOSO method it was found that 50 mm/s speed, 200N load and 5% graphene are the optimum tribological parameters. with Cof of 0.04 and wear rate of 4.8745*10−4 mm3/Nm. Microstructure analysis indicated that long-range structured lamellar structures and microfibers were created between the crystals with the assistance of graphene layers. Apatite layer was also found on the sample. The apatite layer included phosphate and carbonate ions, which is good for in vitro bioactivity on polymeric films. This composite is a good candidate for prosthetics and implant components.

Reviewing dental materials: Progresses for oral health and restoration

The field of density has made great progress in the modern era, especially in the aspects of developing a variety of novel materials that are used to repair teeth. Compared to traditional c, novel dental restorative materials are devoted to combining practicality and aesthetics, which are under the full consideration of the demands of patients. The emphasis of this review lies in the comparison of different novel dental restorative materials by providing their principles, benefits, disadvantages, and applications. The main advanced materials in this area that are chosen to be researched in this review are Ultra-High Molecular Weight Polyethylene Nanocomposites, Zirconia-based Composites, Activa Bioactive Restorative, Hydroxyapatite Restoration Materials, Bioprinting Materials, as well as Biomimetic and Tooth Surface Regeneration Materials. Researchers need to innovate in dental restorative materials with continuous pursuit. As these novel materials rapidly develop and are taken actions into application, they have a positive influence on dentistry. Our work involving studies of novel dental restorative materials provides patients with more practical and aesthetic therapy suggestions.

Analysis of interfacial characteristics in polymer nanocomposites via visual particle recognition methodology and micromechanical predictive models

This study examines the morphological features of nano-zeolite nanoparticles incorporated into ultra-high molecular weight polyethylene nanocomposites, known for their excellent biocompatibility and significant potential in structural biomedical applications. The analyses involved qualitative assessments and a statistical approach based on visual particle recognition technique. Scanning electron microscopy was adopted for morphological assessments of impact-fractured surfaces. The scanning electron microscopy observations unveiled the improved dispersion of nanoparticles within the polymer matrix following nano-zeolite incorporation. In the quantitative approach, the nanoparticles size and distribution were systematically determined through tailored histograms, utilizing the customized particle recognition strategy applied to images. This analysis yielded average particle sizes for each composite, further used for calculating the effective elastic moduli of nanocomposites by employing a two-fold micromechanics-based homogenization technique, accounting for interfacial effects. The computation of average particle size based on visual measurements substantially improved the accuracy regarding the quantitative analysis of interphase effects on macroscopic properties, marking a departure from the conventional practice of conducting such calculations by relying on unrealistic particle sizes based on their as-received values before compounding with the polymer.

Chemically expanded graphite-based ultra-high molecular weight polyethylene nanocomposites with enhanced mechanical properties

Chemically expanded graphite (CEG) has recently been identified as promising reinforcement for polymer composites with the ability for commercial up-scaling. In this work, silane and polydopamine functionalized CEG were successfully synthesized and employed to prepare ultra-high molecular weight polyethylene (UHMWPE) nanocomposites with an enhanced interfacial compatibility. Characterisation of the functionalized CEG indicated a significant oxygen reduction, which gave rise to a restoration of the graphitic structure. The polydopamine functionalized CEG showed an enhanced exfoliation and dispersion in organic solvents and the polymer matrix with respect to the non-modified CEG. The silane functionalized CEG provided a higher affinity towards the matrix with polymer chains covering the CEG sheets on the fracture surfaces. The addition of functionalized CEG enhanced the mechanical properties of the UHMWPE matrix with an increase in micro-hardness of up to 25% and storage modulus of up to 58%. Furthermore, the hydrophobicity of the composites was significantly enhanced with an increase in water contact angle from 98.6° for the pure polymer to 119° for 5 wt% silane functionalized CEG. Preliminary wear experiments indicated the potential of the composites for tribological applications with a decrease in wear rate of up to 99% under water lubricated conditions.

TRIBOLOGICAL CHARACTERISTICS OF ANTIFRICTION COMPOSITES OF POLYAMIDE AND ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

Analysis of current trends in improving the designs of tribo-couplings of agricultural machinery has shown that the use of polyamide 6 as an antifriction material is limited by its low moisture resistance, which leads to a significant deterioration in its elastic-strength and tribological characteristics during moisture saturation. The paper shows the possibility of using ultra-high molecular weight polyethylene as its analogue, which allows increasing the durability of tribo- couplings of hydraulic systems of agricultural machinery. (Research purpose) The research purpose is in to study the processes of friction and wear of polyamide PA 6 composites and ultra-high molecular weight polyethylene nanocomposites with obtaining dependencies linking tribological characteristics (friction coefficient and wear intensity) with operational factors (temperature, sliding speed and contact pressure). (Materials and methods). Polyamide PA 6 of the 210/310 brand was used in the work; composite of the UPA 6-15A brand, consisting of 85 percent polyamide PA 6 and 15 percent fibrous carbon filler; ultrahigh molecular weight polyethylene of the GUR 4120 brand; Tuballmatrixbeta concentrate of activated carbon nanotubes; hydrophobic nanocrystalline silicon dioxide with a dispersion of 20 nanometers, Nafen grade aluminum oxide nanofiber with a dispersion of 10- 20 nanometers. Samples were made to study the elastic-strength and tribological characteristics of composites by thermal pressing on a Gibitre hydraulic press. Samples were tested on the UAI-7000 M bursting machine and the Haake MARS III rheometer. (Results and discussion) The values of the intensity of linear wear and the dependence of the friction coefficients of composites on the sliding speed, contact pressure and temperature of industrial oil I-20A were determined for the conditions of dry friction and friction with lubrication. (Conclusions) The research results have shown that the use of ultrahigh molecular weight polyethylene and nanocomposites based on it as commercial antifriction materials of tribo- couplings is promising and requires further study.

Wear resistance of graphene reinforced ultra-high molecular weight polyethylene nanocomposites prepared by octa-screw extrusion process

Ultra-high molecular weight polyethylene (UHMWPE) is one of the well-established bio-materials for artificial prostheses. In order to improve its wear resistance, graphene incorporated UHMWPE nanocomposites are synthesized by octa-screw extrusion process. The exceptional compounding ability of the process is confirmed by uniform graphene dispersion in the matrix. An 18% improvement in yield strength, superior anti-wear property, 67% increase in crystallinity, and 4% increase in the decomposition temperature as compared to pure UHMWPE is measured. The nanocomposites are also more hydrophilic and show absence of cytotoxicity. The UHMWPE/graphene nanocomposites prepared by octa-screw extrusion are a potential candidate for joint replacement applications.

Ultra-high molecular weight polyethylene nanocomposites reinforced with novel surface chemically modified sonic-exfoliated graphene

A sequence of chemical modifications was performed on natural graphite flakes from initial oxidation, producing graphene oxide (GO), followed by thermally-reduced graphene expansion (GE) to a final sonic exfoliation forming nanoparticles (GES). Employing Raman spectroscopy, it is found that the graphite ID/IG intensity ratio of 0.86 was substantially decreased to 0.54 for GES, indicating a smaller number of more ordered graphene sheet layers. The crystalline index (CI) obtained by X-ray diffraction of the final sonic-exfoliated GES (48%) is improved in comparison to the expanded GE (31%), suggesting better-organized sheets. Scanning electron microscopy shows GES with decreasing stacking of almost transparent layers due to increased spacing between graphene sheets. Nanocomposites fabricated with 0.05, 0.1, 1.0, 3.0, and 5.0 wt.% GES incorporated into ultra-high molecular weight polyethylene, lubricated with mineral oil (UHMWPE/OM), disclosed superior CI and higher temperatures for the onset and maximum rate of thermal degradation. Dynamic mechanical analysis reveals improved viscoelastic stiffness from 1 up to 3 wt.% of GES incorporation, indicating that this novel graphene-based GES acts as reinforcement for UHMWPE/OM nanocomposites. In particular, the 3 wt.% GES nanocomposites with the best thermal and mechanical performance as well as enhanced processability might be considered a practical option for replacing structural applied common UHMWPE.

Mechanical and thermal properties of vitamin E-doped UHMWPE reinforced with hydroxyapatite

ABSTRACT The unique biocompatible and wear resistant nature of ultrahigh molecular weight polyethylene (UHMWPE) makes it a suitable material for load bearing applications in total joint replacements (TJR). However, oxidation induced wear is a common cause limiting the life span of implants. Hence, Vitamin-E, a common antioxidant, is added to prevent the wear loss due to oxidation of UHMWPE. In addition, Hydroxyapatite does improve the toughening mechanisms occurring in the polymer matrices. Hence, in this study, a novel hydroxyapatite (HA) nanoparticles reinforced Vitamin-E doped UHMWPE nanocomposites (UHMWPE-E/HA) were developed here in this work. The HA concentration was varied between 0.5 - 3 wt.% and optimum wt% is reported. The mechanical and thermal properties were investigated thoroughly using an array of characterizations. Particularly, a considerable improvement in fracture toughness (KIC) was obtained. Detailed examination of fractured surfaces was performed to understand the effect of HA reinforcement on fracture toughness of UHMWPE-E/HA nanocomposites.

Studying the surface of UHMWPE films modified with graphene nanoplatelets using a Raman mapping method

This article discusses the nature of the distribution of intact polyaniline-functionalized graphene nanoplatelets (GNPs) in the surface layer of nanomodified films of ultra-high molecular weight polyethylene (UHMWPE) using a Raman mapping method. On the Raman maps, D, G, and 2D peaks can be observed for the 0.1 wt.% GNPs content in the UHMWPE. In the surface layer of the films containing 1.0 wt.% GNPs, these signals are not detected, thereby indicating the displacement of the nanomodifier into the polymer bulk. In contrast, the polyaniline-functionalized GNPs tend to migrate to the surface of the UHMWPE nanocomposite film and evenly distribute in the surface layer as the concentration increases from 0.1 to 2.0 wt.%.

UHMWPE-MWCNT-nHA based hybrid trilayer nanobiocomposite: Processing approach, physical properties, stem/bone cell functionality, and blood compatibility.

The development of polymeric nanocomposites for biomedical applications remains a major challenge in terms of tailored addition of nanoparticles to realize the simultaneous enhancement of fracture resistance and cell/blood compatibility. To address this, the present work has been planned to determine whether small addition of surface functionalized multiwalled-carbon-nanotube, MWCNT (<1.5 wt%) and egg-shell derived nanosized hydroxyapatite, nHA (<10 wt%) to ultrahigh-molecular-weight-polyethylene (UHMWPE) can significantly improve the physical properties as well as biocompatibility. The difference in mouse osteoblast and human mesenchymal stem cell (hMSc) proliferation has been validated using both the monolithic composite and a trilayered composite with two different UHMWPE nanocomposites on either face with pure polymer at the middle. The combination of rheology and micro-CT with fractography reveals the homogeneous dispersion of nanofillers, leading to mechanical property enhancement. The quantitative analysis of cell viability and cell spreading by immunocytochemistry method, using vinculin and vimentin expression, establish significant cytocompatibility with hMSc and osteoblast cells onto the trilayer hybrid nanobiocomposite substrates. The hemocompatibility of the investigated composites under the controlled flow of rabbit blood in a microfluidic device reveals the signature of reduced thrombogenesis with reduction of platelet activation on UHMWPE nanocomposite w.r.t. unreinforced UHMWPE. An attempt has been made to discuss the blood compatibility results in the backdrop of the bovine serum albumin adsorption kinetics. Summarizing, the present study establishes that the twin requirement of mechanical property and cyto/hemo-compatibility can be potentially realized in developing trilayer composites in UHMWPE-nHA-MWCNT system.

Probing the Influence of γ-Sterilization on the Oxidation, Crystallization, Sliding Wear Resistance, and Cytocompatibility of Chemically Modified Graphene-Oxide-Reinforced HDPE/UHMWPE Nanocomposites and Wear Debris.

Osteolysis and aseptic loosening due to wear at the articulating interfaces of prosthetic joints are considered to be the key concerns for implant failure in load-bearing orthopedic applications. In an effort to reduce the wear and processing difficulties of ultrahigh-molecular-weight polyethylene (UHMWPE), our research group recently developed high-density polyethylene (HDPE)/UHMWPE nanocomposites with chemically modified graphene oxide (mGO). Considering the importance of sterilization, this work explores the influence of γ-ray dosage of 25 kGy on the clinically relevant performance-limiting properties of these newly developed hybrid nanocomposites in vitro. Importantly, this work also probes into the cytotoxic effects of the wear debris of different compositions and sizes on MC3T3 murine osteoblasts and human mesenchymal stem cells (hMSCs). In particular, γ-ray-sterilized 1 wt % mGO-reinforced HDPE/UHMWPE nanocomposites exhibit an improvement in the oxidation index (16%), free energy of immersion (-12.1 mN/m), surface polarity (5.0%), and hardness (42%). Consequently, such enhancements result in better tribological properties, especially coefficient of friction (+13%) and wear resistance, when compared with UHMWPE. A spectrum of analyses using transmission electron microscopy (TEM) and in vitro cytocompatibility assessment demonstrate that phagocytosable (0.5-4.5 μm) sterilized 1 mGO wear particles, when present in culture media at 5 mg/mL concentration, induce neither significant reduction in MC3T3 murine osteoblast and hMSC growth nor cell morphology phenotype, during 24, 48, and 72 h of incubation. Taken together, this study suggests that γ-ray-sterilized HDPE/UHMWPE/mGO nanocomposites can be utilized as promising articulating surfaces for total joint replacements.

Multi-length scale wear damage mechanisms of ultra-high molecular weight polyethylene nanocomposites

Ultra-high molecular weight polyethylene (UHMWPE) is reinforced with 1–3 wt % sliver (Ag) nanoparticles and zinc oxide (ZnO) micro-rods, and tensile strength as well as wear resistance of the samples is evaluated. Tensile strength was observed to increase with Ag and ZnO reinforcement up to 18% for 1 wt % ZnO and 1 wt % Ag, but in case of 3 wt % ZnO and 3 wt % Ag + 3 wt % ZnO, it decreases marginally by 4% when compared with neat polymer. The sliding wear rate for 1 wt % Ag + 1 wt % ZnO and 3 wt % Ag + 3 wt % ZnO decreases from 9.54 × 10−5 mm3 (neat polymer) to 7.49 × 10−5 mm3 and 5.65 × 10−5mm3, respectively, showing the synergistic effect of Ag and ZnO reinforcement. In scratch testing, minimum damage is obtained in 1 wt % ZnO reinforced polymer. On one hand, where micro-scratch damage is resisted by harder ZnO, whereas on the other hand, pin on disc wear (repeated surface damage) is protected by softer Ag tribolayer. The improved tensile strength (up to 9.7%) and wear resistance with synergistic addition of Ag and ZnO (both 1 wt %) opens a window in the development of bearing surface biomaterials providing improved longevity and durability, thus, may reduce the chances of revision surgery.

UHMWPE Hybrid Nanocomposites for Improved Tribological Performance Under Dry and Water-Lubricated Sliding Conditions

To tap the full potential of polymers to be used as tribo-materials under water lubrication, it is very important to improve their resistance to water uptake on the one hand and improve their strength and load bearing capacity on the other so that their performance under these conditions is not deteriorated. Hence, a unique approach of fabricating a hybrid polymer nanocomposite reinforced with nanoclay for improving the resistance to water uptake and carbon nanotubes (CNTs) to improve the mechanical/tribological properties is undertaken. Ultrahigh molecular weight polyethylene (UHMWPE) hybrid nanocomposites were fabricated via ball milling followed by hot pressing method. Functionalized multi-wall CNTs and C15A organoclay were used as nanofillers in UHMWPE matrix. Hybrid nanocomposites were developed with CNT loadings of 0.5, 1.5 and 3.0 wt% while keeping C15A organoclay content fixed at an optimized value of 1.5 wt%. Initially, the hybrid nanocomposites were optimized under dry sliding conditions whereby a loading of 1.5 wt% of CNTs and 1.5 wt% C15A organoclay resulted in the maximum reduction in the specific wear rate by about 64% as compared to pristine UHMWPE. Later, tribological performance of the optimized hybrid nanocomposite was compared with pristine UHMWPE and its UHMWPE nanocomposites under water-lubricated conditions sliding against a 440C stainless steel ball for 150,000 cycles. The specific wear rate showed a reduction by ~46% for the 1.5 wt% CNTs hybrid nanocomposites as compared to pristine UHMWPE under water lubrication. The improved resistance to wear was attributed to the uniform dispersion of both the nanofillers, namely CNTs and C15A organoclay which effectively increased the load bearing capacity of UHMWPE. Moreover, the excellent barrier properties of the platelet-like structure of C15A clay which presented a torturous path for the diffusion of the water molecule in UHMWPE reduced the softening of the surface layer leading to better resistance to wear under water lubrication.

Evaluation of Tribological Properties of Organoclay Reinforced UHMWPE Nanocomposites

The current study is aimed to investigate the tribological properties of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with organoclay Cloisite (C15A). Nanocomposites are prepared using a high energy ball milling process followed by hot pressing. Three different loadings of 0.5 wt.%, 1.5 wt.%, and 3 wt.% of C15A, respectively, are used as reinforcement. Results from the ball-on-disk wear tests showed that nanocomposites reinforced with 1.5 wt.% of C15A exhibited best wear resistance and lower coefficient of friction (COF), with C15A reducing the wear rate by 41% and the COF by 38%, when compared to the pristine UHMWPE. These improvements are attributed to the uniform dispersion of the nanosized clay platelets preventing large-scale material removal and formation of a thin tenacious, continuous transfer film on the counterface for C15A organoclay composites. X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical profilometry are used to characterize the morphology of the nanocomposites and the wear tracks. SEM images of worn surfaces indicated more abrasive wear for the case of pristine UHMWPE as compared to organoclay composites.

Effect of multi-walled carbon nanotubes reinforcement and gamma irradiation on viscoelastic properties of ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) has been used as a surface for acetabular in total joint replacements for the past 60 years. However, the performance of the implant is influenced by the increase in temperature because of the articulating motion and the contact asperities, which affects its longevity. The viscoelastic properties of multi-walled carbon nanotubes (MWCNTs) reinforced UHMWPE nanocomposites with respect to temperature and irradiation dose are not reported so far. Hence, an attempt was made to study the viscoelastic properties of UHMWPE by varying concentration of MWCNTs and intensity of irradiation dose. The test samples were subjected to sinusoidal loading in the temperature range of 30–80°C. Ultra-high molecular weight polyethylene nanocomposites were prepared at different concentrations of MWCNTs such as 0.5, 1.0, 1.5 and 2 wt-% using compression moulding process and the nanocomposites were subjected to 60Co gamma irradiation up to 100 kGy dose. The viscoelastic characteristics of UHMWPE, such as storage modulus, loss moduls and damping factor of the irradiated nanocomposites, were studied in detail. It was observed that the storage modulus of the pure UHMWPE was increased by 139% with the addition of 2 wt-% MWCNTs; however, it was found to be reduced by 83% with 100 kGy irradiation doses. The damping factor and loss modulus of the nanocomposites were reduced by 27.3 and 71.6% with 2 wt-% of MWCNTs concentration, but both were increased with 100 kGy irradiation dose by 74.7 and 69% compared to virgin UHMWPE. It is concluded that the storage modulus reduced with the increase in temperature and also irradiation dose, which may lead to higher static deformation of material. However, the presence of MWCNTs would minimise the deformation and pave way for the better functionality of the material.

Erratum to: Investigating the Effect of Water Uptake on the Tribological Properties of Organoclay Reinforced UHMWPE Nanocomposites

Ultra-high molecular weight polyethylene (UHMWPE) nanocomposites reinforced with different loadings (0.5, 1.5 and 3 wt%) of C15A organoclay are fabricated. Water uptake tests at an elevated temperature of 70 °C are performed to evaluate the effect of different loadings of nanoclay on the water absorption by the nanocomposites. It is observed that the water uptake by the nanocomposites reduced with an increase in the concentration of the nanoclay. A 21 % reduction in the water uptake is observed for the UHMWPE nanocomposites reinforced with 1.5 and 3 wt% of C15A, respectively, as compared to pristine UHMWPE. This reduction is attributed to the improvement in the barrier properties of the nanocomposites with the addition of nanoclays. Wear tests are also conducted before and after water uptake to investigate the effect of water absorption on the tribological properties. Organoclay composites showed enhanced performance as compared to pristine UHMWPE even after water absorption. This improvement is attributed to the reduced water absorption of organoclay composites leading to less softening and plasticization of the polymer, resulting in better wear resistance. However, among the different loadings of nanoclays, it is observed that the 1.5 wt% of C15A reinforcement showed the best tribological performance even after water uptake with 41 % reduction in the wear rate and a 20 % reduction in the coefficient of friction when compared to pristine UHMWPE.

Tensile and biocompatibility properties of synthesized nano-hydroxyapatite reinforced ultrahigh molecular weight polyethylene nanocomposite

Ultrahigh molecular weight polyethylene–based nanocomposites reinforced with nano-sized hydroxyapatite particles were fabricated using internal mixer and compression molding with different weight percent of the nano-hydroxyapatite. In this study, first, hydroxyapatite nanoparticles were synthesized by sol–gel. Then, the mechanical and biological properties of nanocomposites were studied by tensile test and proliferation and cell adhesion assays using MG-63 osteoblast cells, respectively. Results of the tensile test showed that incorporation of 50 wt% nano-hydroxyapatite led to a 345.64% and 57.58% increase in Young's modulus and yield strength (compared to the pure ultrahigh molecular weight polyethylene), respectively. The effect of the nano-hydroxyapatite powders on the MG-63 osteoblast cells behavior was compared to those of a composite (positive control) and a negative control samples. Scanning electron microscopy micrographs revealed that cell–biomaterial interaction was carried out on the surface of the nanocomposites with normal phenotypic shape. Results of MTT assay exhibited that all samples are biocompatible.

Nanomechanical and tribological behavior of hydroxyapatite reinforced ultrahigh molecular weight polyethylene nanocomposites for biomedical applications

ABSTRACTA hydroxyapatite (HA) particulate reinforced ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite is fabricated by internal mixer at 180°C and using of paraffin oil as a processing aid to overcome the high viscosity of melted UHMWPE. The reinforcing effects of nano‐HA are investigated on nanomechanical properties of HA/UHMWPE nanocomposites by nanoindentation and nanoscratching methods. Results show that the nanocomposite with 50 wt % nano‐HA exhibits a Young's modulus and hardness of 362.5% and 200% higher, and a friction coefficient of 38.86% lower than that of pure UHMWPE, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42052.

Influence of Polyhedral Oligomeric Silsesquioxane Structure on the Disentangled State of Ultrahigh Molecular Weight Polyethylene Nanocomposites during Ethylene in Situ Polymerization

Three kinds of polyhedral oligomeric silsesquioxane (methyl-POSS, cyclohexyl-POSS, and phenyl-POSS) were chosen to adsorb [3-tert-Bu-2-O-C6H3CH═N(C6F5)]2TiCl2 catalyst (FI catalyst) in order to synthesize ultrahigh molecular weight polyethylene (UHMWPE)/POSS nanocomposites according ethylene in situ polymerization. It was shown that the characteristic of “living’’ polymerization of the FI catalyst would be maintained when alkyl-POSS was incorporated. However, the presence of alkyl-POSS could decay the catalyst activity. The incorporation of alkyl-POSS led to an increase of the crystallinity and the lamellar thickness of nascent UHMWPE, as observed by differential scanning calorimetry. This indicated that the alkyl-POSS would be used as a nucleating agent during the chain growth procedure. Interestingly, all the nanocomposites exhibited low starting storage modulus values which was a reflection of disentangled structure in the nascent UHMWPE nanocomposites. However, polymer chains were prior to entanglemen...

The Thermal and Mechanical Properties of Ultra-High Molecular Polyethylene/Montmorillonite Clay (UHMWPE/MMT) Nanocomposites Using Gel and Pressure-Induced Flow Process (PIF)

This paper examines hybrid organic-inorganic polymer nanocomposites incorporating organically modified montmorillonite (MMT) and ultra-high molecular weight polyethylene (UHMWPE). UHMWPE/MMT hybrid nanocomposites were prepared using gel and pressure-induced flow (PIF) processing methods at a gel concentration of 8 wt.% UHMWPE with various organoclay contents (0, 5, 10, 15, and 20 pphr). The interlayer properties of the nanocomposites were studied by X-ray diffraction (XRD) transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal and mechanical interfacial properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and the use of a universal test machine (UTM). XRD and TWM indicated that the nanocomposites were formed upon dispersion of MMT in the polymer matrix. From the DSC, TGA and DMA results, we found that the thermal stability of the UHMWPE nanocomposites increased as the MMT content increased. The nanocomposites showed higher tensile strengths than those of pure UHMWPE gel sheet. These findings indicate that the interfacial and mechanical properties were improved by the addition of MMT and PIF processing.