提高超高分子量聚乙烯的耐磨性：交联与结晶

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...     

Electrical field-driven ripening profiles of colloidal suspensions

Electrorheological(ER) fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason why viscosity changes.Experimentally, the transparent electrodes are used to investigate the column size distribution where an external electric field is applied to a colloidal suspension, i.e., ER fluid is increased. The coarsening profile of ER suspensions is strongly related to electrical field strength, but it is insensitive to particle size. In addition, in a low field range the shear stress corresponding to the mean column diameter is studied and they are found to satisfy a power law. However, this dependence is invalid when the field strength surpasses a threshold value.