Oral Ebru, Greenbaum Evan S, Malhi Arnaz S, Harris William H, Muratoglu Orhun K
Department of Orthopaedic Surgery, Massachusetts General Hospital, 55 Fruit Street, GRJ 1206, Boston, MA 02114, USA.
Biomaterials. 2005 Nov;26(33):6657-63. doi: 10.1016/j.biomaterials.2005.04.026.
Adhesive/abrasive wear in ultra-high molecular weight polyethylene (UHMWPE) has been minimized by radiation cross-linking. Irradiation is followed by melting to eliminate residual free radicals and avoid long-term oxidative embrittlement. However, post-irradiation melting reduces the crystallinity of the polymer and hence its strength and fatigue resistance. We proposed an alternative to post-irradiation melting to be the incorporation of the antioxidant alpha-tocopherol into UHMWPE prior to consolidation. alpha-Tocopherol is known to react with oxygen and oxidized lipids, stabilizing them against further oxidative degradation reactions. We blended GUR 1050 UHMWPE resin powder with alpha-tocopherol at 0.1 and 0.3 wt% and consolidated these blends. Then we gamma-irradiated these blends to 100-kGy. We characterized the effect of alpha-tocopherol on the cross-linking efficiency, oxidative stability, wear behavior and mechanical properties of the blends. (I) The cross-link density of virgin, 0.1 and 0.3 wt% alpha-tocopherol blended, 100-kGy irradiated UHMWPEs were 175+/-19, 146+/-4 and 93+/-4 mol/m3, respectively. (II) Maximum oxidation indices for 100-kGy irradiated UHMWPE previously blended with 0, 0.1 and 0.3 wt% alpha-tocopherol that were subjected to accelerated aging at 80 degrees C in air for 5 weeks were 3.32, 0.09, and 0.05, respectively. (III) The pin-on-disc wear rates of 100-kGy irradiated UHMWPE previously blended with 0.1 and 0.3 wt% alpha-tocopherol that were subjected to accelerated aging at 80 degrees C in air for 5 weeks were 2.10+/-0.17 and 5.01+/-0.76 mg/million cycles, respectively. (IV) Both accelerated aged, alpha-tocopherol-blended 100-kGy irradiated UHMWPEs showed higher ultimate tensile strength, higher yield strength, and lower elastic modulus when compared to 100-kGy irradiated, virgin UHMWPE. These results showed that alpha-tocopherol-blended 100-kGy irradiated UHMWPEs were not cross-linked to the same extent as the 100-kGy irradiated, virgin UHMWPE.
通过辐射交联，超高分子量聚乙烯（UHMWPE）中的粘着/磨料磨损已降至最低。辐照后进行熔融以消除残留的自由基并避免长期氧化脆化。然而，辐照后熔融会降低聚合物的结晶度，从而降低其强度和抗疲劳性。我们提出了一种替代辐照后熔融的方法，即在固结前将抗氧化剂α-生育酚掺入UHMWPE中。已知α-生育酚能与氧气和氧化脂质发生反应，使其稳定，防止进一步的氧化降解反应。我们将GUR 1050 UHMWPE树脂粉末与0.1 wt%和0.3 wt%的α-生育酚混合，并将这些混合物固结。然后我们将这些混合物伽马辐照至100 kGy。我们表征了α-生育酚对混合物的交联效率、氧化稳定性、磨损行为和机械性能的影响。（I）未添加α-生育酚、添加0.1 wt%α-生育酚和添加0.3 wt%α-生育酚并经100 kGy辐照的UHMWPE的交联密度分别为175±19、146±4和93±4 mol/m³。（II）预先分别与0、0.1和0.3 wt%α-生育酚混合并在80℃空气中加速老化5周的100 kGy辐照UHMWPE的最大氧化指数分别为3.32、0.09和0.05。（III）预先分别与0.1 wt%和0.3 wt%α-生育酚混合并在80℃空气中加速老化5周的100 kGy辐照UHMWPE的销盘磨损率分别为2.10±0.17和5.01±0.76 mg/百万次循环。（IV）与100 kGy辐照的未添加α-生育酚的UHMWPE相比，两种经加速老化且添加α-生育酚的100 kGy辐照UHMWPE均表现出更高的极限拉伸强度、更高的屈服强度和更低的弹性模量。这些结果表明，添加α-生育酚的100 kGy辐照UHMWPE的交联程度与100 kGy辐照的未添加α-生育酚的UHMWPE不同。
