Four Ultra-High Molecular Weight Polyethylene (UHMWPE) materials were evaluated after various irradiation crosslinking processes to determine the effects of the materials and processes on their properties for orthopaedic applications. The materials and processes included two molecular weight materials (GUR 1020 and GUR 1050), two fabricated forms (ram extruded bar and compression-molded sheet), two irradiation sources (gamma and e-beam) and multiple irradiation doses ranging from 30–120 kGy. Increasing irradiation dose led to increased crosslinking, decreased wear, and decreased toughness. The molecular weight of the starting material and the irradiation source both had effects on the final properties while the fabricated form did not. Wear testing of selected groups indicated that there was a direct correlation with irradiation dose but not with the crosslink density (as calculated from the swell ratio).
Four Ultra-High Molecular Weight Polyethylene (UHMWPE) materials were evaluated after various irradiation crosslinking processes to determine the effects of the materials and processes on their properties for orthopaedic applications. The materials and processes included two molecular weight materials (GUR 1020 and GUR 1050), two fabricated forms (ram extruded bar and compression-molded sheet), two irradiation sources (gamma and e-beam) and multiple irradiation doses ranging from 30–120 kGy. Increasing irradiation dose led to increased crosslinking, decreased wear, and decreased toughness. The molecular weight of the starting material and the irradiation source both had effects on the final properties while the fabricated form did not. Wear testing of selected groups indicated that there was a direct correlation with irradiation dose but not with the crosslink density (as calculated from the swell ratio).
The compression molding process is known to produce UHMWPE components of improved oxidation resistance [1] and quality surface finish. Induction of molecular orientation in non-crosslinked UHMWPE was demonstrated by using a slot drawing process [2]. The objective of this study was to assess the effect of flow ratio on wear and mechanical properties of crosslinked UHMPWE. Pre-irradiated GUR 1020 preforms, corresponding to flow ratios from 1.06 to 1.40, were evaluated in this study. Molecular orientation was shown by Thermal Mechanical Analysis and crossed polarizer microphotographs. Tensile (Type V), double notched Izod and pin on disk wear data were generated. The degree of molecular orientation was correlated with the flow ratio and was reflected by the enhancement of the mechanical properties. Pin on disk wear data show that there was no significant difference in wear resistance between oriented, crosslinked UHMWPE and its machined counterpart.
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