Caking of amorphous powders — Material aspects, modelling and applications

Caking of powders and bulk granules and adhesion of powders on equipment surfaces is a serious problem in the food, chemical and pharmaceutical industries. While caking of crystalline particles is tackled only briefly, this publication deals mainly with caking of water-soluble amorphous particles. Caking of amorphous particles starts with stickiness of the powder surface and can result in a collapse of the powder structure. The powder bulk turns from a free flowable powder bulk composed of single particles into a massive block. The material aspects (hygrocapacity, hygrosensitivity and viscosity) of water-soluble amorphous materials and sintering are discussed. The increase of the sinter bridges during caking could be modelled through the known sinter equations and measured by carrying out experiments in a ring shear cell. The calculated sinter bridge diameter could be correlated with the strength of the caked powder bulk measured in a ring shear tester.

Graphical AbstractCaking of amorphous particles starts with stickiness of the powder surface and can result in a collapse of the powder structure. The increase of the sinter bridges during caking could be modelled through the known sinter equations. The calculated sinter bridge diameter could be correlated with the strength of the caked powder bulk measured in a ring shear tester.Figure optionsDownload full-size imageDownload as PowerPoint slide