Rippie E G, Danielson D W
J Pharm Sci. 1981 May;70(5):476-82. doi: 10.1002/jps.2600700503.
The processes of nonequilibrium generation and decay of axial and radial stresses within tablet compacts were analyzed in terms of three-dimensional linear viscoelastic theory. A rotary tablet press was instrumented to measure punch and die wall stresses during the compression and postcompression periods. Following compression, tablets were permitted to remain at the compression site within the die, and the die wall stress was followed. Microcrystalline cellulose, spray-processed lactose, and sulfacetamide are known to have different compression characteristics and were found to differ significantly in their viscoelastic parameters. Compacts assumed their final viscoelastic state prior to the time of punch separation. Theory permits separation of material behavior into dilation and distortion components. Dilation, thought to be dependent on voids, was elastic in all cases. Distortion effects could be described well by a Kelvin solid model. Results indicate that viscoelastic properties are functions of compression conditions and may be useful in adjusting compression conditions to avoid problems such as capping.
根据三维线性粘弹性理论，分析了片剂压坯内轴向和径向应力的非平衡产生和衰减过程。对旋转式压片机进行了仪器化处理，以测量压缩和压缩后阶段的冲头和模壁应力。压缩后，允许片剂留在模具内的压缩位置，并跟踪模壁应力。已知微晶纤维素、喷雾干燥乳糖和磺胺醋酰具有不同的压缩特性，并且发现它们的粘弹性参数有显著差异。压坯在冲头分离之前就达到了其最终的粘弹性状态。理论允许将材料行为分为膨胀和畸变分量。膨胀被认为取决于孔隙，在所有情况下都是弹性的。畸变效应可以用开尔文固体模型很好地描述。结果表明，粘弹性性能是压缩条件的函数，可能有助于调整压缩条件以避免诸如裂片等问题。
