Nanocomposite UHMWPE

描述（由申请人提供）：在这个SBIR一期项目中，我们的目标是通过形成具有独特的新型双重用途纳米颗粒增强/抗氧化剂的复合材料来改善高交联超高分子量聚乙烯的关键机械性能。超高分子量聚乙烯（UHMWPE）长期以来被广泛应用于关节植入物中，近年来通过交联聚乙烯链进一步提高了其耐磨性。交联最常见的方法是在惰性气氛或电子束照射下伽马射线照射时形成自由基，然后熔化和自由基复合。然而，交联过程也与机械性能的降低有关，包括韧性、疲劳和屈服强度，这导致了关节植入物的一些过早失效。此外，超高分子量聚乙烯的氧化降解是由残余自由基氧化和在空气中的储存引起的。将我们的纳米材料纳入交联UHMWPE提供了两种机制，以改善其材料性能并降低使用交联UHMWPE植入物的故障率。首先，我们的初步数据显示，在约1 wt.%的载荷下，纳米复合材料的韧性有了显著改善，我们假设在疲劳强度和屈服强度方面也有类似的改善。其次，由于纳米材料是一种强大的抗氧化剂，它将减少高交联UHMWPE的残余自由基含量和氧化降解。我们将通过制备不同负载的纳米复合材料，将测试样品置于工业中使用的各种加工条件下，然后评估其结构、机械和摩擦学性能，来验证这些假设。如果新的UHMWPE材料的性能符合我们的假设，那么它的好处将包括更持久的植入物，更不容易失效，在氧化环境中使用寿命更长。公共卫生相关性：关节植入物是类风湿性关节炎、骨关节炎、骨坏死和其他严重破坏性损伤患者的有效治疗方法；仅在美国，每年就有大约50万例关节置换手术。随着预期寿命的延长，患者的寿命往往比植入物更长。因此，需要不断改进材料以延长假体的使用寿命（目前的产品在体内使用寿命为10至15年）。

DESCRIPTION (provided by applicant): In this SBIR Phase I project we aim to improve the key mechanical properties of highly cross-linked ultrahigh molecular weight polyethylene by forming composites with a unique new dual purpose nanoparticulate reinforcement/antioxidant. Ultrahigh molecular weight polyethylene (UHMWPE) has long been widely used in joint implants, and further improvements to its wear resistance have recently been obtained by cross-linking the polyethylene chains. The cross-links are most commonly obtained by radical formation during gamma irradiation in an inert atmosphere or electron beam irradiation, followed by melting and radical recombination. However, the cross-linking process has also been associated with decreases in mechanical properties, including toughness, fatigue and yield strengths, which have led to some premature failures of joint implants. Furthermore, some oxidative degradation of the UHMWPE results from oxidation by residual free radicals and storage in air. Incorporating our nanomaterials into cross-linked UHMWPE provides two mechanisms for improving its materials properties and decreasing the failure rate of implants utilizing cross-linked UHMWPE. First, our preliminary data shows significant improvements in toughness of the nanocomposite at ca. 1 wt.% loading, and we hypothesize that similar improvements in fatigue and yield strengths are also provided. Secondly, since the nanomaterial is a powerful antioxidant, it will reduce the residual radical content and oxidative degradation of highly cross-linked UHMWPE. We will validate these hypotheses by preparing nanocomposites at various loadings of the nanomaterial, subjecting test specimens to various processing conditions used in the industry, and then assessing their structural, mechanical and tribological properties. Should the new UHMWPE materials perform according to our hypotheses, the benefits would include longer-lasting implants that are less prone to failure, with longer lifetimes in oxidative environments. PUBLIC HEALTH RELEVANCE: Joint implants are an effective treatment for those with rheumatoid arthritis, osteoarthritis, osteonecrosis, and other severe destructive injuries; within the U.S. alone, roughly 500,000 joint replacements are performed each year. As life expectancy increases, patients more frequently outlive their implant. Thus, continued improvements in materials that lead to longer lifetimes for the prostheses are required (current products have an in vivo lifetime of 10 to 15 years).