Wear Mechanisms of Untreated and Gamma Irradiated Ultra-High Molecular Weight Polyethylene for Total Joint Replacements

2005 ◽  
Vol 127 (2) ◽  
pp. 273-279 ◽  
Author(s):  
J. Zhou ◽  
K. Komvopoulos
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Wear Mechanisms ◽  
Irradiation Dose ◽  
Cross Link ◽  
Link Density ◽  
Cross Link Density ◽  
Gamma Irradiated ◽  
Ultra High Molecular Weight

Modification of the surface microstructure of ultra-high molecular weight polyethylene (UHMWPE) is essential for improving the wear resistance of orthopedic implants. A common approach is to cross-link the polymer by gamma irradiation. The objective of this study was to examine the tribological behaviors of untreated and gamma irradiated UHMWPE under physiologically relevant contact conditions. Emphasis was placed on the identification of the dominant wear mechanisms in the early stage of polymer wear. The irradiation dose exhibited a strong effect on the tribological properties of UHMWPE sliding against Co–Cr alloy in a bath of bovine serum. Transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM) were used to examine the microstructure and morphology of the worn surfaces. Regularly spaced folds with average spacing depending on the irradiation dose (i.e., cross-link density) formed on the wear tracks. Surface folding was related to plastic flow and the degree of mobility of the crystalline lamellae. SEM and TEM results elucidated the roles of the cross-link density and crystalline lamellae in the wear process. Based on the experimental evidence, a deformation model was obtained that provides explanation for the dependence of surface folding on the cross-link density and lamellae reorientation during sliding.

Wear Mechanisms of Untreated and Gamma Irradiated Ultra-High Molecular Weight Polyethylene for Total Joint Replacements

2004 ◽  
Author(s):  
J. Zhou ◽  
K. Komvopoulos
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Wear Mechanisms ◽  
Irradiation Dose ◽  
Crosslink Density ◽  
Early Stage ◽  
Deformation Model ◽  
Gamma Irradiated ◽  
Ultra High Molecular Weight

Modification of the microstructure of ultra-high molecular weight polyethylene (UHMWPE) is essential for improving the wear resistance of orthopaedic implants. A common approach is to crosslink the polymer by gamma irradiation. The objective of this study was to examine the tribological behaviors of untreated and gamma irradiated UHMWPE under physiologically relevant contact conditions. Emphasis was given on the identification of the dominant wear mechanisms in the early stage of polymer wear. The irradiation dose exhibited as strong effect on the tribological properties of UHMWPE sliding against Co-Cr alloy in a bath of bovine serum. Transmission electron microscopy (TEM) and environmental scanning electron microscopy (ESEM) were used to examine the microstructure and morphology of the worn surfaces. Regularly spaced folds with average spacing depending on the irradiation dose (i.e., crosslink density) formed on the wear tracks. Surface folding was related to plastic flow and the degree of mobility of the crystalline lamellae. SEM and TEM results elucidated the roles of the crosslink density and crystalline lamellae in the wear process. Based on the experimental evidence, a deformation model was obtained that provides explanation for the dependence of surface folding on the crosslink density and lamellae reorientation during sliding.

scholarly journals Dynamical mechanical analysis as an assay of cross-link density of orthopaedic ultra high molecular weight polyethylene

2015 ◽  
Vol 45 ◽  
pp. 174-178 ◽  
Author(s):  
Steven D. Reinitz ◽  
Evan M. Carlson ◽  
Rayna A.C. Levine ◽  
Katherine J. Franklin ◽  
Douglas W. Van Citters
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Mechanical Analysis ◽  
Cross Link ◽  
Dynamical Mechanical Analysis ◽  
Link Density ◽  
Cross Link Density ◽  
Ultra High Molecular Weight

PEG Cross-Linked Alginate Hydrogels with Controlled Mechanical Properties

1998 ◽  
Vol 530 ◽  
Author(s):  
Petra Eiselt ◽  
Jon A. Rowley ◽  
David J. Mooney
Keyword(s):  
Mechanical Properties ◽  
Tissue Engineering ◽  
Molecular Weight ◽  
Elastic Modulus ◽  
Cell Transplantation ◽  
Cross Linking ◽  
Cross Link ◽  
Link Density ◽  
A Cell ◽  
Cross Link Density

AbstractReconstruction of tissues and organs utilizing cell transplantation offers an attractive approach for the treatment of patients suffering from organ failure or loss. Highly porous synthetic materials are often used to mimic the function of the extracellular matrix (ECM) in tissue engineering, and serve as a cell delivery vehicle for the formation of tissues in vivo. Alginate, a linear copolysaccharide composed of D-mannuronic acid (M) and L-guluronic acid (G) units is widely used as a cell transplantation matrix. Alginate is considered to be biocompatible, and hydrogels are formed in the presence of divalent cations such as Ca2+, Ba2+ and Sr2+. However, ionically cross-linked alginate gels continuously lose their mechanical properties over time with uncontrollable degradation behavior. We have modified alginate via covalent coupling of cross-linking molecules to expand and stabilize the mechanical property ranges of these gels. Several diamino PEG molecules of varying molecular weight (200, 400, 1000, 3400) were synthesized utilizing carbodiimide chemistry. Sodium alginate was covalently cross-linked with these cross-linking molecules, and mechanical properties of the resulting hydrogels were determined. The elastic modulus of the cross-linked alginates depended on the molecular weight of the cross-linking molecules, and ranged from 10-110 kPa. The theoretical cross-link density in the hydrogels was also varied from 3 to 47% (relative to the carboxylic groups in the alginate) and the mechanical properties were measured. The elastic modulus increased gradually and reached a maximum at a cross-link density of 15%. In summary, covalently coupled hydrogels can be synthesized which exhibit a wide range of mechanical properties, and these materials may be useful in a number of tissue engineering applications.

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