Thermal and mechanical properties of ultrahigh molecular weight polyethylene/high-density polyethylene/polyethylene glycol blends.

Blends of ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) provide adequate mechanical properties for biomedical application. In this study, the mechanical and thermal properties of UHMWPE/HDPE blends with the addition of polyethylene glycol (PEG) prepared via single-screw extruder nanomixer were investigated. The UHMWPE/HDPE blends exhibit a gradual increase in strength, modulus, and impact strength over pure polymers, suggesting synergism in the polymer blends. The elastic and flexural modulus was increased at the expense of tensile, flexural, and impact strength for the blends containing PEG. The degradation temperature of UHMWPE was improved with the incorporation of HDPE due to good thermal stability of HDPE. HDPE improved the dispersibility of PEG in matrix, consequently reduced the surface area available for the kinetic effects, and reduced the degradation temperature. The morphology analysis confirmed the miscibility between UHMWPE and HDPE and the changes in polymer structure with the presence of PEG modify the thermal behavior of the blends. The mechanical properties of the blends that are underlying values for the design of implant material show the potential used as biomedical devices

Surfactant-assisted hydrothemial synthesis of fluoridated hydroxyapatite nanorods

Fluoridated Hydroxyapatite (FHA) nanorods were synthesized using Apricot Tree Gum (ATG) as a novel surfactant and then compared with Ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Sodium Dodecyl Sulfate (SDS) as conventional surfactant agents under hydrothermal condition (70 degrees C and 1 atm). The effects of pH values and various types of surfactants on the formation of the FHA nanorods, crystalline phase, and chemical compositions were investigated using Field Emission Scanning Electron Microscopy (FESEM) equipped by Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The findings indicated application of the presented ATG as surfactant is able to produce the hexagonal nanorods of FHA along their c-axis direction. Moreover, it is illustrated that diameter and length of nanorods which is obtained by ATG surfactant are bigger than EDTA and SDS. In addition, it is demonstrated that pH values can play a major role on formation of hexagonal FHA nanorods. The increase of pH transformed the shape of synthesized FHA from particles to rods. Ultimately, based on the similarity of synthesized FHA nanorods to the shape, structure, and composition of enamel; it is suggested for its potential to be used for dental applications

Finite element analysis of external fixator for treating femur fracture: analysis on stainless steel and titanium as material of external fixator

An external fixator device is a medical implant used to keep fractured bones stabilized and in alignment. It consists of pins which are placed into the bone, extending outside the surface of the skin, and attached to a rigid external rod to keep it in place. The aim of this study is to investigate the most suitable material used for the external fixator. Firstly, the 3D model of two unilateral uniplanar external fixator with the properties of titanium and stainless steel were constructed at Solidworks software with all the other parameters set to constant. Meanwhile, CT images of the lower limb were used to reconstruct a 3D model of the femur fracture at Mimics Medical software. Positioning and meshing of both the external fixator and the femur done at 3- Matics Medical and export as Patran for simulation at Marc Mentat software. 375 N load was applied at the most proximal femur to simulate stance phase of a gait cycle. From the findings, external fixator by using stainless steel as material properties have lower maximum von Mises Stress (18.40 MPa) at the femur and (103.69 MPa) at the fixator compared to the titanium (32.38 MPa) at the femur and (182.93 MPa) at the fixator. The result shows a difference of 75% of maximum von Mises Stress at the femur and the external fixator. Configuration by using stainless steel displaced 1.15 mm at the femur and 1.01 mm at the fixator which almost double value of displacement for titanium material for both femur (2.35 mm) and external fixator (2.11 mm). In conclusion, stainless steel external fixators provide better stability when compared to titanium external fixators

Synthesis and kinetic study of (Mo,W)Si ²-WSi ² nanocomposite by mechanical alloying

In this study, nanocomposite of (Mo,W)Si2–WSi2 was synthesized via mechanical alloying (MA) and heat treatment. The phase transformation of the powders after various milling durations and annealing was investigated by X-ray diffraction (XRD) and differential thermal analysis (DTA). Microstructural evolutions were characterized by scanning electron microscopy and transmission electron microscopy (TEM). Increasing the milling time to 80 h caused the formation of (Mo, W, Si) solid solution, t-(Mo,W)Si2, h-WSi2 phase, and a trace amount of unreacted raw material. However the post-annealing at 1000 °C caused the complete formation of (Mo,W)Si2–WSi2 nanocomposite. The values of the grain growth exponent of t-(Mo,W)Si2 phase for the powders milled for 40 and 80 h were 0.3 and 0.8, respectively, at 1000 °C. The grain growth activation energy of t-(Mo,W)Si2 phase for the 80 h milled powders (97.19 KJ/mol) was lower than that for the 40 h sample (120.83 KJ/mol). The crystallite size of t-(Mo,W)Si2 decreased to 32 nm (40 h) and 24 nm (80 h) with increasing milling time. However, the crystallite size of the milled samples increased to 60 and 87 nm after annealing at 1000 °C for 90 min. The DTA results of the as-milled specimens showed two exothermic peaks at around 600 and 900 °C relating to the formation of t-(Mo,W)Si2 and h-WSi2, respectively. The formation activation energy of t-(Mo,W)Si2 was higher (144.58 KJ/mol) for the 80 h milled sample compared to the 40 h milled sample (131.61 KJ/mol). The microhardness of (Mo,W)Si2–WSi2 nanocomposite increased with increasing milling time to 1020 Hv but decreased with escalating annealing temperature to 726 Hv

Effect of carburization process on adhesion strength of Ti carbide layer on titanium alloy substrate

Titanium alloys are commonly used in biomedical application in hard tissues replacement especially for knee and hip implants. Surface modifications are required prior to diamond coating process for improving tribological and wear properties of the titanium alloy. In this study, experiments were carried out to investigate the effects of different carburizing times on the adhesion strength of carbide layer formed on the Ti-6Al-7Nb. Prior to carburization process, all samples were treated to remove residual stress and oxide scales by annealing and pickling processes respectively. Hard wood charcoal powder was used as a medium. The carburizing process was carried out for 6, 12 and 24 hours at 950 °C under normal atmospheric condition. Surface morphology, carbide layer thickness and adhesion strength were evaluated using SEM, XRD, 3D Surface Profilometer and Blast Wear Tester (BWT). It is found that a mixture of oxide and carbide layers formed on the substrate and the thickness of these layers increases with carburizing time. It is also revealed that the 24 hr carburizing time provides the strongest adhesion strength among the three and TiC as the dominant layer

A novel poly(xylitol-co-ledodecanedioate)/hydroxyapatite composite with shape-memory behaviour

A novel shape-memory polymer, poly(xylitol-co-dodecanedioate) (PXDD) was developed and the effect of hydroxyapatite (HA) in PXDD/HA composites on the chemical interactions, shape-memory and crystallization behaviours was studied. FIR confirmed the formation of PXDD and also showed that the chemical structure did not change with the addition of HA. DSC and XRD revealed that the degree of crystallinity (X-c) of PXDD/HA composites improved in parallel to increasing HA content. The permanent shape is recovered with a precision of almost 100% as soon as the recovery temperature (T-rec=48 degrees C) is reached. The findings of the study showed that PXDD/HA composites have great potential as shape-memory implant in minimal invasive surgeries. (C) 2014 Elsevier B.V. All rights reserved