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Influence of the irradiation dose on the properties of crosslinked UHMWPE
Abt, N.
Abstract
The purpose of this study was to investigate the influence of a dose of e-beam irradiation on the mechanical and tribological properties of crosslinked UHMWPE.
Four specimens of UHMWPE (GUR 1050) were irradiated at different dose levels using the WIAM e-beam process. The specimens where heated to a temperature of 125°C and then irradiated with an electron beam at dose levels of 5, 6.5, 8 and 9.5 Mrad. Irradiation was followed by melt annealing (150°C) and slow cooling.
Ultimate tensile strength, yield strength, Charpy impact strength, elongation, crystallinity (DSC) and wear rate (pin on disc) were measured and compared with the untreated material.
In general, the mechanical properties of irradiated UHMWPE decrease with increasing irradiation dose. The loss of mechanical properties is most evident for samples irradiated at doses from 0 to 5 Mrad. Similarly, a reduction of crystallinity was seen.
Increasing the irradiation dose from 5 to 9.5 Mrad results in a negligible loss of mechanical properties (e.g. elongation: ~16%, yield strength: ~12%, impact strength: ~18%, ultimate tensile strength: ~19%). Moreover, crystallinity does not change significantly.
On the other hand, wear resistance is increased with higher irradiation dose. While irradiating with 5 Mrad results in a reduction of the wear rate by 73% compared to the untreated material, a further reduction by 56% can be reached by an increase in the dose from 5 to 9.5 Mrad. In total, a reduction of 88% can be achieved.
This investigation indicates that wear properties of UHMWPE implants could be drastically improved by irradiation at high dose levels (higher than 8 Mrad) if the decrease in mechanical properties can be compensated for appropriately.
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