The Experts below are selected from a list of 73350 Experts worldwide ranked by ideXlab platform
Kazuhiko Ishihara - One of the best experts on this subject based on the ideXlab platform.
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups.
Masayuki Kyomoto - One of the best experts on this subject based on the ideXlab platform.
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups.
Diganta Bhusan Das - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of hysteretic Dynamic effect in capillary pressure saturation relationship for two phase flow in porous media
Aiche Journal, 2013Co-Authors: Mahsanam Mirzaei, Diganta Bhusan DasAbstract:Well-defined laboratory experiments have been carried out to investigate hysteretic Dynamic effect in capillary pressure–saturation relationships for two-phase flow in homogeneous and heterogeneous (layered) porous media. Conceptually, the dependence of the capillary pressure curves on the rate of change of saturation (dSw/dt) is defined as the Dynamic effect in capillary pressure relationship, which is indicated by a Dynamic Coefficient, τ (Pa s) and it determines the rate at which two-phase flow equilibrium is reached, i.e., dSw/dt = 0 where Sw and t are the water saturation and time, respectively. The dependences of τ on various fluid and porous materials properties have been studied in the context of drainage; but, there is limited study for imbibition and the hysteresis of τ−Sw relationships. As such, the emphasis in this article is on reporting τ−Sw curves for imbibition while also demonstrating the hysteresis in the τ−Sw relationships by comparing τ−Sw curves for drainage (previously reported) and imbibition (this study) in carefully designed laboratory experiments. Homogeneous sand samples composed of either fine (small particle size and lower permeability) or coarse (larger particle size and higher permeability) sand have been used for these experiments. Furthermore, a layered domain made of a find sand layer sandwiched between two coarse sand layers is used as a model of heterogeneous domain. The results of the study confirm that the τ−Sw relationships are hysteretic in nature and, as such, the speed to flow equilibrium should vary depending on whether drainage or imbibition takes place. At a particular water saturation, the magnitudes of the Dynamic Coefficient (τ) are found to be generally higher for imbibition, which imply that the speed to flow equilibrium at the same saturation will be slower for imbibition.
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Dynamic effects in capillary pressure relationships for two phase flow in porous media experiments and numerical analyses
Aiche Journal, 2012Co-Authors: Diganta Bhusan Das, Mahsanam MirzaeiAbstract:Well defined experiments and numerical analyses are conducted to determine the importance of Dynamic effect in capillary pressure relationships for two-phase flow in porous media. Dynamic and quasi-static capillary pressure-saturation (P c -Sw) and, qSw/qt-t curves are determined. These are then used to determine the Dynamic effects, indicated by a Dynamic Coefficient (� ) in the porous domains which establishes the speed at which flow equilibrium (qSw/qt ¼ 0) is reached. s is found to be a nonlinear function of saturation which also depends on the medium permeability. Locally determined s seems to increase as the distance of the measurement point from the fluid inlet into the domain increases. However, the functional dependence s-Sw follows similar trends at different locations within the domain. We argue that saturation weighted average of local s-Sw curves can be defined as an effective s-Sw curve for the whole domain which follows an exponential trend too. V V C 2012 American Institute of Chemical Engineers AIChE J, 58: 3891–3903, 2012
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Dynamic effects on capillary pressure saturation relationships for two phase porous flow implications of temperature
Aiche Journal, 2012Co-Authors: Navraj Hanspal, Diganta Bhusan DasAbstract:Work carried out in the last decade or so suggests that the simulators for multiphase flow in porous media should include an additional term, namely a Dynamic Coefficient, as a measure of the Dynamic effect associated with capillary pressure. In this work, we examine the dependence of the Dynamic Coefficient on temperature by carrying out quasi-static and Dynamic flow simulations for an immiscible perchloroethylene–water system. Simulations have been carried out using a two-phase porous media flow simulator for a range of temperatures between 20 and 80°C. Simulation domains represent 3-D cylindrical setups used by the authors for laboratory-scale investigations of Dynamic effects in two-phase flow. Results are presented for two different porous domains, namely the coarse and fine sands, which are then interpreted by examining the correlations between Dynamic Coefficient(s) and temperature, time period(s) required for attaining irreducible water saturation, and the Dynamic aqueous/nonaqueous phase saturation and capillary pressure plots. The simulations presented here maintain continuity from our previous work and address the uncertainties associated with the dependency of Dynamic Coefficient(s) on temperature, thereby complementing the existing database for the characterization of Dynamic Coefficients and subsequently enabling the users to carry out computationally economical and reliable modeling studies. © 2012 The Authors. AIChE Journal, published by Wiley on behalf of the AIChE. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. AIChE J, 58: 1951–1965, 2012
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Dynamic effects in capillary pressure saturations relationships for two phase flow in 3d porous media implications of micro heterogeneities
Chemical Engineering Science, 2007Co-Authors: Mahsanam Mirzaei, Diganta Bhusan DasAbstract:Abstract The capillary pressure–saturation ( P c – S ) relationships are essential in characterising two-phase flow behaviour in porous media. However, these relationships are not unique and depend on the flow Dynamics, i.e., steady state or Dynamic, among other factors. It has been shown that empirical models describing two-phase flow processes in porous media may be inadequate to account fully for the physics of flow in Dynamic conditions. New capillary pressure relationships have been proposed which include an additional term to account for the dependence of capillary pressure on saturation and time derivative of saturation ( ∂ S / ∂ t ) . This parameter is a capillary damping Coefficient, also known as Dynamic Coefficient ( τ ) , which establishes the speed at which flow equilibrium is reached. The dependence of P c – S relationships on ∂ S / ∂ t is called Dynamic effects . In most laboratory experiments for measuring two-phase flow properties, it is implicitly assumed that the sample is homogeneous. However, this is not the case and micro-heterogeneities with their distinct multiphase flow properties may exist within the domain. They affect the Dynamics of the multiple fluid phases and saturation distributions in the domain. These issues have been studied individually but the combination of Dynamic effects and micro-scale heterogeneities on the P c – S relationships has not been quantified accurately, particularly in 3D domains. Consequently, there are significant uncertainties on the reported values of τ in the literature. In this work, we have carried out a numerical study to investigate how the presence of micro-scale heterogeneities affects the Dynamics of dense non-aqueous phase liquid (DNAPL) and water flow in porous domain. The relative significance of the variations in nature, intensity and distribution of micro-scale heterogeneities on Dynamic flow conditions are manifested on P c – S curves which are quantified in terms of the Dynamic Coefficient, τ . There is a complex interplay of various factors (e.g., Dynamic flow conditions, distribution and intensity of micro-heterogeneity, pore size distribution, domain size and geometry and media anisotropy) which affects P c – S curves. However, our results show that as the intensity of heterogeneity increases the Dynamic Coefficient at a given saturation increases, provided all other factors remain the same. The effects of domain shapes (cylindrical vs. rectangle), aspect ratios, dimensionality (2D vs. 3D), permeability anisotropy on τ are also analysed in order to generalise their effects as far as possible. We envisage that our simulations will minimise some of the inconsistencies on the reported data on τ in the literature.
Mahsanam Mirzaei - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of hysteretic Dynamic effect in capillary pressure saturation relationship for two phase flow in porous media
Aiche Journal, 2013Co-Authors: Mahsanam Mirzaei, Diganta Bhusan DasAbstract:Well-defined laboratory experiments have been carried out to investigate hysteretic Dynamic effect in capillary pressure–saturation relationships for two-phase flow in homogeneous and heterogeneous (layered) porous media. Conceptually, the dependence of the capillary pressure curves on the rate of change of saturation (dSw/dt) is defined as the Dynamic effect in capillary pressure relationship, which is indicated by a Dynamic Coefficient, τ (Pa s) and it determines the rate at which two-phase flow equilibrium is reached, i.e., dSw/dt = 0 where Sw and t are the water saturation and time, respectively. The dependences of τ on various fluid and porous materials properties have been studied in the context of drainage; but, there is limited study for imbibition and the hysteresis of τ−Sw relationships. As such, the emphasis in this article is on reporting τ−Sw curves for imbibition while also demonstrating the hysteresis in the τ−Sw relationships by comparing τ−Sw curves for drainage (previously reported) and imbibition (this study) in carefully designed laboratory experiments. Homogeneous sand samples composed of either fine (small particle size and lower permeability) or coarse (larger particle size and higher permeability) sand have been used for these experiments. Furthermore, a layered domain made of a find sand layer sandwiched between two coarse sand layers is used as a model of heterogeneous domain. The results of the study confirm that the τ−Sw relationships are hysteretic in nature and, as such, the speed to flow equilibrium should vary depending on whether drainage or imbibition takes place. At a particular water saturation, the magnitudes of the Dynamic Coefficient (τ) are found to be generally higher for imbibition, which imply that the speed to flow equilibrium at the same saturation will be slower for imbibition.
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Dynamic effects in capillary pressure relationships for two phase flow in porous media experiments and numerical analyses
Aiche Journal, 2012Co-Authors: Diganta Bhusan Das, Mahsanam MirzaeiAbstract:Well defined experiments and numerical analyses are conducted to determine the importance of Dynamic effect in capillary pressure relationships for two-phase flow in porous media. Dynamic and quasi-static capillary pressure-saturation (P c -Sw) and, qSw/qt-t curves are determined. These are then used to determine the Dynamic effects, indicated by a Dynamic Coefficient (� ) in the porous domains which establishes the speed at which flow equilibrium (qSw/qt ¼ 0) is reached. s is found to be a nonlinear function of saturation which also depends on the medium permeability. Locally determined s seems to increase as the distance of the measurement point from the fluid inlet into the domain increases. However, the functional dependence s-Sw follows similar trends at different locations within the domain. We argue that saturation weighted average of local s-Sw curves can be defined as an effective s-Sw curve for the whole domain which follows an exponential trend too. V V C 2012 American Institute of Chemical Engineers AIChE J, 58: 3891–3903, 2012
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Dynamic effects for two phase flow in porous media fluid property effects
Aiche Journal, 2007Co-Authors: Robert Gauldie, Mahsanam MirzaeiAbstract:Traditional descriptions of multiphase flow in porous media rely on an extension of Darcy's law along with relationships between capillary pressure (Pc), saturation (S), and relative permeability (Kr). New theories have been proposed which suggest that Pc relationships should include a Dynamic Coefficient (τ) (Hassanizadeh and Gray, Water Resour Res. 1993;29:3389–3405) to indicate how “quickly” or “slowly” flow equilibrium is reached. While validity of these theories must be examined, it is also necessary to determine the significance of τ and its range of values. In this article, we analyze the significance of τ depending on fluid properties. We address the ways in which they cause nonuniqueness of Dynamic two-phase flow in porous media and, hence, Dynamic effect. Simulations are conducted for quasi-static and Dynamic flow of perchloroethylene (PCE) in water saturated domains. The data are then fitted to the Dynamic Pc relationships to obtain values of τ. The effects of flow directions and, viscosity and density ratios are discussed. To consider the lumped effects of various fluid properties, τ–S relationships are examined for silicone oils. The results are interpreted by examining the correlation between τ and a mobility Coefficient, m. We discuss a scaling relationship that shows the dependence of τ on fluid and material properties. © 2007 American Institute of Chemical Engineers AIChE J, 2007
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Dynamic effects in capillary pressure saturations relationships for two phase flow in 3d porous media implications of micro heterogeneities
Chemical Engineering Science, 2007Co-Authors: Mahsanam Mirzaei, Diganta Bhusan DasAbstract:Abstract The capillary pressure–saturation ( P c – S ) relationships are essential in characterising two-phase flow behaviour in porous media. However, these relationships are not unique and depend on the flow Dynamics, i.e., steady state or Dynamic, among other factors. It has been shown that empirical models describing two-phase flow processes in porous media may be inadequate to account fully for the physics of flow in Dynamic conditions. New capillary pressure relationships have been proposed which include an additional term to account for the dependence of capillary pressure on saturation and time derivative of saturation ( ∂ S / ∂ t ) . This parameter is a capillary damping Coefficient, also known as Dynamic Coefficient ( τ ) , which establishes the speed at which flow equilibrium is reached. The dependence of P c – S relationships on ∂ S / ∂ t is called Dynamic effects . In most laboratory experiments for measuring two-phase flow properties, it is implicitly assumed that the sample is homogeneous. However, this is not the case and micro-heterogeneities with their distinct multiphase flow properties may exist within the domain. They affect the Dynamics of the multiple fluid phases and saturation distributions in the domain. These issues have been studied individually but the combination of Dynamic effects and micro-scale heterogeneities on the P c – S relationships has not been quantified accurately, particularly in 3D domains. Consequently, there are significant uncertainties on the reported values of τ in the literature. In this work, we have carried out a numerical study to investigate how the presence of micro-scale heterogeneities affects the Dynamics of dense non-aqueous phase liquid (DNAPL) and water flow in porous domain. The relative significance of the variations in nature, intensity and distribution of micro-scale heterogeneities on Dynamic flow conditions are manifested on P c – S curves which are quantified in terms of the Dynamic Coefficient, τ . There is a complex interplay of various factors (e.g., Dynamic flow conditions, distribution and intensity of micro-heterogeneity, pore size distribution, domain size and geometry and media anisotropy) which affects P c – S curves. However, our results show that as the intensity of heterogeneity increases the Dynamic Coefficient at a given saturation increases, provided all other factors remain the same. The effects of domain shapes (cylindrical vs. rectangle), aspect ratios, dimensionality (2D vs. 3D), permeability anisotropy on τ are also analysed in order to generalise their effects as far as possible. We envisage that our simulations will minimise some of the inconsistencies on the reported data on τ in the literature.
Fumiaki Miyaji - One of the best experts on this subject based on the ideXlab platform.
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008
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enhanced wear resistance of orthopaedic bearing due to the cross linking of poly mpc graft chains induced by gamma ray irradiation
Journal of Biomedical Materials Research Part B, 2008Co-Authors: Masayuki Kyomoto, Toru Moro, Fumiaki Miyaji, Tomohiro Konno, Masami Hashimoto, Hiroshi Kawaguchi, Yoshio Takatori, K Nakamura, Kazuhiko IshiharaAbstract:We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The Dynamic Coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups.
