Rheology of hydroxyapatite dispersions
Rheology of hydroxyapatite dispersions
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DOI：
10.1111/j.1551-2916.2005.00068.x
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发表时间：
2005-02-01
影响因子：
3.9
通讯作者：
Lapasin, R
中科院分区：
文献类型：
--
作者：
Gardini, D;Galassi, C;Lapasin, R
羟基磷灰石(HA)由于其生物活性和与周围组织的生物相容性，是一种有趣的骨科应用陶瓷材料，特别是用于种植手术和骨再生。即使可以使用不同的成型工艺来获得具有最佳最终性能的多孔陶瓷体，HA水分散体海绵浸渍法尤其适合于获得合适的大孔率来实现骨再生。对于传统的注浆或流延成型，HA悬浮液的流变性必须与工艺条件相适应，并通过分散相的稳定来控制，即通过适当的分散剂用量和分散粉末的精确均质。本文以不同结晶度的羟基磷灰石为原料，制备了不同固形物和分散剂(聚丙烯酸铵)含量的水分散体。羟基磷灰石的比表面积很大，分散相的结构条件对悬浮液的流变性有很大的影响，因此必须特别注意分散剂的选择和分散过程。即使分散剂浓度的微小差异也会在相对较低的固体体积浓度下导致流变性的显著变化。在临界浓度以上，与表观塑性行为相关的粘度降被限制在非常窄的应力范围内，线性粘弹性性质出现了整齐的转变，剪切历史引起的随时间变化的效应对实验表征变得非常重要和关键。
Hydroxyapatite (HA) is an interesting ceramic material for orthopedic applications, in particular for implant operations and bone regeneration, owing to its bioactivity and biocompatibility with the surrounding tissues. Even if different shaping processes can be used in order to obtain porous ceramic bodies with optimal final properties, the sponge impregnation method with aqueous HA dispersions is particularly suitable to achieve an appropriate macroporosity to bone regeneration. As for conventional slip or tape casting, the rheological behavior of HA suspensions must be properly fitted to process conditions and controlled through a satisfactory stabilization of the disperse phase, i.e., through an appropriate dispersant dosage and an accurate homogenization of dispersed powder. In the present work, HA powders with different crystallinity degree were used to prepare aqueous dispersions with different contents of solids and dispersant (ammonium polyacrylate). The specific surface area of HA powders is very high, and then special attention must be dedicated to the dispersant selection and the dispersion process since the rheology of HA suspensions is strongly influenced by the structural conditions of the disperse phase. Even small differences in dispersant concentration can lead to dramatic changes in the rheological properties also at relatively low values of solids volume concentration. Above a critical concentration, the viscosity drop associated with the apparently plastic behavior is confined within a very narrow stress range, a neat transition is observed in the linear viscoelastic properties, and the time-dependent effects induced by the shear history become quite important and crucial for the experimental characterization.