Dose and Dose-rate Dependence of Polyethylene Irradiation with Electron Beams “in Air” (original) (raw)
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Mechanical performance of electron-beam-irradiated UHMWPE in vacuum and in air
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009
Ultrahigh molecular weight polyethylene (UHMWPE) was modified by a 5-MeV energy electron beam at different temperatures before, during, and after irradiation, both in air and in high vacuum. Wear resistance, hardness, and tensile strength of irradiated polyethylene were compared with those of untreated one. Physical analyses (like infrared spectroscopy and calorimetric analysis) were carried out to investigate about the changes in the material induced by irradiation. Experimental results suggested that structural changes (double bonds, crosslinks, and oxidized species formation) occur in the polymer depending on the environmental conditions of the irradiation. Mechanical behavior is related to the structural modifications. A temperature of 1108C before, during, and after the in vacuum irradiation of UHMWPE produces a high amount of crosslinks and improves polymeric tensile and wear resistance, compared to that of the untreated material. '
Surface and Coatings Technology, 2014
In this work the influence of two different irradiation techniques on the degree of crystallinity and nanomechanical properties of a medical grade UHMWPE is compared. One technique, widely used in the production of components for total joint replacement, is comprised by γ-irradiation followed by a thermal treatment above the melting temperature of UHMWPE and thus modifies the material's bulk. The other one, an alternative modification technique that affects only the near surface layers of UHMWPE, is swift heavy ion (SHI) irradiation. The effect of two types of ion beams (nitrogen and lithium) with different energies (33 and 47 MeV) and fluences (10 11 to 10 13 ions/cm 2) is investigated. Changes in degree of crystallinity are investigated by DSC and Raman spectroscopy while the nanomechanical propertieselastic modulus and hardnessare evaluated by nanoindentation tests. The γ-irradiated and remelted sample exhibits lower degree of crystallinity than the pristine material due to the hindered recrystallization process of the crosslinked chains. Concomitantly, this sample shows a reduction in hardness and elastic modulus of the bulk. On the other hand, SHI-irradiated samples display a large increase in degree of crystallinity and surface mechanical parameters with respect to pristine UHMWPE. The modification is confined to the ion target depth. The layer affected by the ion beam shows constant mechanical properties that appeared to be slightly influenced by the fluence in the studied range (around the optimum). Despite the changes induced by both techniques are completely different, they are able to enhance the wear performance of UHMWPE due to the beneficial change in elastic to plastic properties. Among SHI-irradiated samples, the N-ion (33 MeV and 1 × 10 12 ions/cm 2) exhibits the better combination of nanomechanical properties.
Electron-Beam-Induced Modifications in High-Density Polyethylene
Brazilian Journal of Physics, 2011
Post-irradiation studies have been carried out to elucidate the effects of electron beam irradiation on the structural, optical, dielectric, and thermal properties of high-density polyethylene (HDPE) films. The experimental results showed that both the optical band gap and activation energy of HDPE films decreases with an increase in the doses of electron radiation. The electrical measurements showed that dielectric constant and the ac conductivity of HDPE increases with an increase in the dose of electron radiation. The thermal analysis carried out using DSC and TGA revealed that the melting temperature, degree of crystallinity, and thermal stability of the HDPE films increased, obviously, due to the predominant cross-linking reaction following high doses of electron irradiation.
On the morphology of some irradiated ultra high molecular weight polyethylenes
Polymer Degradation and Stability, 2009
The morphology of various grades of ultra high molecular weight polyethylene (UHMWPE), prepared for use in orthopaedic implants, has been examined using differential scanning calorimetry (DSC), wide and small angle X-ray diffraction (WAX and SAX) and Raman spectroscopy. Preparation included gamma irradiation at various dose rates and mechanical annealing, and post-irradiation changes were of particular interest. The experimental results are interpreted in terms of previous proposals that UHMWPE is best considered as a three phase material, fully amorphous, all-trans amorphous and fully crystalline. The all-trans amorphous material is thought to be interfacial. The phase analysis shows that the age related increase in crystallinity occurs through conversion of all-trans material to fully crystalline, and there is little change in the total amorphous content of the polymers. SAX patterns show a change in the sharpness of the main diffraction peak and the emergence of a second diffraction peak at a higher q value, and this is considered to arise from crystallisation of all-trans amorphous material. Increasing the irradiation dose rate has a similar effect on the crystallography as does ageing the material. Mechanically annealed polymer also shows a similar trend towards a bimodal crystal population, accompanied by a reduction in interfacial material.
Surface and Coatings Technology, 2008
The damage processes induced by swift heavy ions (SHI), can be very different to those induced by classical low ionising particles. This is due to the high electronic stopping power of SHI. Ultra high molecular weight polyethylene (UHMWPE) was irradiated with 6.77 MeV helium and 12.5 MeV carbon beams and fluences ranging from 10 11 to 10 13 cm − 2 and 2 × 10 10 to 5 × 10 13 cm − 2 , respectively. Structural changes at the polymer near surface region were studied by means of infrared spectroscopy measurements and wear resistance tests. With FTIR spectroscopy we studied the changes in crystallinity, double bond C_C, trans-vynilene and graphite formation and the evolution of methylene group as a function of fluence. The experiments have determined that exists an optimum ion fluence value, that depends on the ion mass and energy, at which the wear resistance increases of about 85% respect to the unirradiated polymer. For helium this value is 2 × 10 12 cm − 2 and for carbon 4 × 10 11 cm − 2 . At these fluence values no sign of graphite was found by FTIR studies. Using a Monte Carlo simulation program we determined that the surface area affected by the track core of the incoming ions was less than 19 and 35% for helium and carbon respectively.
Effect of Gamma Irradiation on the Structural and Properties of High Density Polyethylene ( HDPE )
2015
This study presents an experimental analysis of the effect of dose parameter during gamma irradiation of commercial highdensity polyethylene (HDPE) samples. The effect of different doses of γ-irradiation on the physical and mechanical properties of HDPE with different thickness (1 mm and 2 mm) was studied. The effect of γ-irradiation on HDPE led to remarkable changes in the physical and mechanical properties of the samples due to chain scission, oxygen effects and crosslinking activities. The experimental results show the mechanical properties reduce as radiation dose increase, also, it was found that HDPE with thickness (1 mm) is more susceptible than HDPE with thickness (2 mm) according to the influence of radiation.
The alterations in high density polyethylene properties with gamma irradiation
Radiation Physics and Chemistry, 2017
In the present investigation, high density polyethylene (HDPE) polymer has been used to study the alterations in its properties under gamma-irradiation. Physico-chemical properties have been investigated with different spectroscopy techniques, Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), biocompatibility properties, as well as, mechanical properties change. The FT-IR analysis shows the formation of new band at 1716 cm-1 that is attributed to the oxidation of irradiated polymer chains, which is due to the formation of carbonyl groups (C=O). XRD patterns show that a decrease in the crystallite size and increase in the Full Width at Half Maximum (FWHM). This means that the crystallinity of irradiated samples is decreased with increase in gamma dose. The contact angle measurements show an increase in the surface free energy as the gamma irradiation increases. The measurements of mechanical properties of irradiated HDPE samples were discussed.
Radiation Physics and Chemistry, 2009
Electron irradiation effects in HDPE have been studied using positron annihilation lifetime spectroscopy. In the four-component analysis of a spectrum, two long-lived states are ascribed to ortho-positronium (o-Ps) annihilation in the crystalline phase and in the amorphous phase. The study of the o-Ps parameters highlights the different behaviour of the two phases. From the o-Ps lifetime in the crystalline phase, it is shown that the effect of irradiation is larger at 250 kGy. Thermal analysis (DSC) reveals two different melting temperatures and also an increase in the fusion enthalpy, at 250 kGy. This phenomenon induced by an electron beam is erased by thermal treatment: fusion and re-crystallisation. However, before and after thermal treatment no changes are observed in the crystallite size and in the crystalline rate using wide-angle X-ray scattering.