Department of Engineering, University of Leicester, Leicester, UK.
Eur J Pharm Biopharm. 2013 Aug;84(3):642-52. doi: 10.1016/j.ejpb.2013.01.012. Epub 2013 Feb 9.
The flow behaviour of powders during the process of die fill was examined. Gravity and suction fill experiments were carried out using a model shoe-die system. Five grades of microcrystalline cellulose were studied to identify the effect of particle size and density on flow. Flowability was quantified using the concept of critical velocity. Under gravity fill, the critical velocity was one order of magnitude higher for powders with large particle size compared to smaller particles. Under suction fill conditions, the critical velocity increased significantly compared to gravity fill, showed no consistent relationship with particle size, and the powders performed more similar to one another. Using high speed video, the gravity and suction fill mechanisms were discussed in the context of air flow and pressure build-up. The effect of shoe velocity, suction velocity and height of the powder in the shoe was explored in more detail. It was shown that one can identify individual contributions from material properties and process parameters to the flow behaviour during die fill; however, the flow performance depends on the inter-relationships between powder characteristics and process parameters. The die fill mechanisms described can be used to assist the optimisation of powder formulation and process design.
研究了粉末在模腔填充过程中的流动行为。使用模型鞋模系统进行了重力填充和抽吸填充实验。研究了五种微晶纤维素，以确定粒径和密度对流动的影响。使用临界速度的概念来量化可流动性。在重力填充下，粒径较大的粉末的临界速度比粒径较小的粉末高一个数量级。在抽吸填充条件下，临界速度与重力填充相比显著增加，与粒径没有一致的关系，并且粉末彼此之间的表现更为相似。使用高速摄像机，根据气流和压力建立讨论了重力和抽吸填充机制。更详细地探讨了鞋速度、抽吸速度和鞋内粉末高度的影响。结果表明，可以确定材料特性和工艺参数对模腔填充过程中流动行为的单独贡献；然而，流动性能取决于粉末特性和工艺参数之间的相互关系。所描述的模腔填充机制可用于辅助粉末配方和工艺设计的优化。
