提高超高分子量聚乙烯的耐磨性:交联与结晶

Improving Wear Resistance of Ultrahigh Molecular Weight Polyethylene:Cross-linking versus Crystallinity

耐磨性能是超高分子量聚乙烯(UHMWPE)制品的重要评价指标,其增强机理为在摩擦表面阻止分子链滑移和脱落.改善耐磨性在本质上是形成有效的分子链整体网络.对于人工关节用交联UHMWPE模塑料,辐照改性会残存有自由基,容易造成氧化降解,破坏长期耐久稳定性.发展能够替代辐照交联的新方法,具有重要的现实意义.在本文中,我们选用不同分子量(M_(w))的原料树脂,通过改变结晶热历史实现结晶度(X_(c))大范围调节,以及改变γ辐照剂量调整交联密度(V_(d)).测定了各种样品的体积磨损率,建立X_(c)、V_(d)、M_(w)与磨损率的关系.研究发现,随着X_(c)、V_(d)、M_(w)增加,磨损率线性降低;更为重要的是,对于所有分子量的UHMWPE,通过增加结晶度能够使磨损率降至比传统辐照交联方法更低的水平.利用高结晶度改善耐磨性,由于不会引起活性自由基,从根本上消除了氧化风险,具有明显的优势.研究结果为发展新型的高耐磨人工关节用UHMWPE模塑料提供了一种新思路.

Wear resistance is an important evaluation index of ultra-high molecular weight polyethylene(UHMWPE)products,and its strengthening mechanism is to prevent molecular chain from sliding and falling off on the friction surface.In essence,the improvement of wear resistance is to form an interaction network of molecular chains.For cross-linked UHMWPE molding materials used as artificial joints,radiation modification will induce free radicals,which is easy to cause oxidative degradation and damage the long-term durability.It is of great significance to develop new method that can replace irradiation cross-linking.In this paper,we choose raw resin with different molecular weights(M_(w)),and adjust the crystallinity(X_(c))in a large range by changing the crystallization thermal history,and adjust the cross-linking density(V_(d))by changing theγradiation dose.The volume wear rates of various samples were measured,and the relationships between the wear rates and the values of X_(c),V_(d),M_(w) were established.It is found that the wear rate decreases linearly with the increase of X_(c),V_(d) and M_(w).More importantly,for each M_(w) of UHMWPE,increasing the crystallinity enables wear rate to reduce to a lower level than that of traditional irradiation crosslinking method.The introduction of high crystallinity to improve wear resistance has obvious advantages because it will not cause active free radicals,thus fundamentally eliminating the risk of oxidation.Our study provides a new idea to develop UHMWPE articles with superior wearresistance for artificial joint field.