(64c) Stress Generation in Drying Colloidal Systems: From Film Fracture to Drop Buckling

Understanding why and how cracks nucleate and spread in drying colloidal dispersions is important in describing naturally occurring processes such as cracking of soil and river beds along with many technological process applications such as paints and coatings, electronics, and pharmaceuticals. An equivalent problem is that of rapid drying colloidal drop that is encountered in spray drying applications where the fast drying of particulate drops results in a fascinating array of morphological transitions ranging from perfect spheres through spheres-with-dimples to toroids. In all the above cases, capillary menisci at the air-liquid interface generates stresses in particle packing. When the stress exceeds a critical value, the drying film cracks or the shell of drying drop buckles.

Bill Russel laid the foundation of this field by deriving a nonlinear constitutive relation that accounts for the microstructural details of the packing (Russel and co-workers, Langmuir 1999 and 2008). The talk will discuss the varied applications of the model from predicting cracking in drying colloidal films to conditions for buckling in drying particulate drops.