Wet massing is commonly performed during the wet granulation process after the addition of a liquid binder. Torque values were measured using a Mixer Torque Rheometer (MTR) by the method of multiple additions of water and variable mixing time. The main objective of this work is to link water diffusion coefficients and penetration time in pharmaceutical powders to torque profiles generated in an MTR. The diffusion coefficients were calculated by fitting the experimental data to an exponential decay function and by minimizing the Root Mean Square Error between the fitted curve and the solution of Fick’s 2nd law. Water penetration times were measured and calculated using experimental drop penetration and Washburn methods, respectively. The main research hypothesis is that the temporal change in torque profiles after each water addition step is related to the mass diffusion coefficients and water penetration time in the powder of varying degrees of water content. The results show that for the microcrystalline cellulose (MCC) powders at varying granulating fluid levels, capillary diffusion seems to be more adequate to explain the rheological behavior observed compared with the Fickian diffusion model.

湿法制粒通常在湿法制粒过程中在添加液体粘合剂后进行。使用混合器扭矩流变仪（MTR）通过多次添加水和可变混合时间的方法来测量扭矩值。这项工作的主要目的是将药物粉末中的水扩散系数和渗透时间与MTR中产生的扭矩曲线联系起来。通过将实验数据拟合到指数衰减函数并通过最小化拟合曲线与菲克第二定律解之间的均方根误差来计算扩散系数。分别使用实验性滴入渗透法和Washburn方法测量和计算水渗透时间。主要研究假设是，每个加水步骤后扭矩曲线的时间变化与含水量不同的粉末中的质量扩散系数和水渗透时间有关。结果表明，对于不同造粒液水平的微晶纤维素（MCC）粉末，与Fickian扩散模型相比，毛细管扩散似乎更能解释所观察到的流变行为。