(231e) Temperature Gradient Induced Caking of Pharmaceutical Grade Salt

Temperature gradients caused by either packaging the product too hot or imposed during transport cause moisture movement in packaged powders which can lead to caking. A mathematical model of this induced moisture movement in powders was developed by [2] in order to be able to predict when caking would occur when given sized temperature gradients were imposed. To use the model for pharmaceutical grade salt (NaCl) a moisture sorption isotherm for below saturation (75%) relative humidity RH conditions was required. This was measured and an equation fitted. The model was then applied to a one dimensional heat transfer set up and confirmed by experiment. The level of caking was measured by a blow test and the conditions needed to create significant caking established. The model was then used to generate graphs showing the water activity required for given expected temperature gradient conditions.