School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK.
Int J Pharm. 2010 May 31;391(1-2):90-7. doi: 10.1016/j.ijpharm.2010.02.022. Epub 2010 Feb 20.
The compression behaviour of powders during roller compaction is dominated by a number of factors, such as process conditions (roll speed, roll gap, feeding mechanisms and feeding speed) and powder properties (particle size, shape, moisture content). The moisture content affects the powder properties, such as the flowability and cohesion, but it is not clear how the moisture content will influence the powder compression behaviour during roller compaction. In this study, the effect of moisture contents on roller compaction behaviour of microcrystalline cellulose (MCC, Avicel PH102) was investigated experimentally. MCC samples of different moisture contents were prepared by mixing as-received MCC powder with different amount of water that was sprayed onto the powder bed being agitated in a rotary mixer. The flowability of these samples were evaluated in terms of the poured angle of repose and flow functions. The moist powders were then compacted using the instrumented roller compactor developed at the University of Birmingham. The flow and compression behaviour during roller compaction and the properties of produced ribbons were examined. It has been found that, as the moisture content increases, the flowability of moist MCC powders decreases and the powder becomes more cohesive. As a consequence of non-uniform flow of powder into the compaction zone induced by the friction between powder and side cheek plates, all produced ribbons have a higher density in the middle and lower densities at the edges. For the ribbons made of powders with high moisture contents, different hydration states across the ribbon width were also identified from SEM images. Moreover, it was interesting to find that these ribbons were split into two halves. This is attributed to the reduction in the mechanical strength of moist powder compacts with high moisture contents produced at high compression pressures.
粉末在辊压过程中的压缩行为受多种因素的影响，例如工艺条件（辊速、辊隙、给料机构和给料速度）和粉末特性（粒径、形状、水分含量）。水分含量会影响粉末的特性，例如流动性和内聚性，但目前尚不清楚水分含量会如何影响辊压过程中粉末的压缩行为。本研究通过实验研究了水分含量对微晶纤维素（MCC，Avicel PH102）辊压行为的影响。通过将不同量的水喷洒到在旋转混合器中搅拌的粉末床上，来制备具有不同水分含量的 MCC 样品。通过休止角和流动函数来评估这些样品的流动性。然后，使用伯明翰大学开发的仪器化辊式压片机对这些湿粉末进行压缩。考察了辊压过程中的流动和压缩行为以及所制得的带状物的性质。研究发现，随着水分含量的增加，湿 MCC 粉末的流动性降低，粉末的粘性增加。由于粉末与侧板之间的摩擦导致粉末不均匀地流入压实区，因此所有制得的带状物在中间的密度较高，而在边缘的密度较低。对于水分含量较高的粉末制得的带状物，还可以从 SEM 图像中识别出带状物宽度上不同的水合状态。此外，有趣的是发现这些带状物被分成了两半。这归因于在高压缩压力下制得的高水分含量的湿粉末压块的机械强度降低。
