(473c) Powder Characterization Using an Annular Ring Shear Cell Under Temperature and Humidity Control

Powders exhibit various levels of complexity; hence determining their physical and chemical properties and categorizing them can help with powder handling and processing. Powder characterization plays a critical role in various industries, including pharmaceuticals and catalyst manufacturing. It helps to classify powders depending on their flow and bulk properties, such as flowability, compressibility, bulk density, etc. These categories, in turn, help identify surrogates, selection of process parameters, and any pre-treatments the powder must undergo before processing. Various methods and equipment have been designed for powder characterization. Recently an air-bearing rheometer equipped with a convection temperature device (CTD), a humidity generator and a powder shear cell was developed to characterize effects of intrinsic and extrinsic factors on powder flowability The above-mentioned system can perform shear tests with robustness and accuracy. The instrument is especially advantageous due to its sensitivity and ability to produce data at very low torque levels. Effects of temperature and humidity can be systematically studied with such a system. This allows us to predict powder behavior in systems with variable temperature/humidity conditions during processing. This
rheometer uses an annular ring geometry to measure the shear properties. The shear stress is calculated based on the torque measured by the rheometer head to which the shear cell geometry is connected. The rheometer with a dedicated software is able to control the system temperature, humidity and apply normal force and strains consistent with shear cell testing. A 2-factor 3-level design of experiments (DoE) was performed to investigate the effect of temperature and humidity on three powders (Do we need to mention what these powders are). The highest temperature was selected to be below the melting point of the powder. A model was constructed for predicting cohesion values within the range of temperature and humidity that was investigated.