Salinity induced stiffening of drying particulate film and dynamic warping

Abstract

When the particle dispersion is dried, its constituents consolidate to form a solid particulate film, resulting in a transition from a liquid to a solid phase. The resultant particulate film stores the strain energy, which builds up during its formation and is often released to crack and warp. Here, we investigate the dependence of ionic strength of dispersion on the mechanical property of a resultant dried particulate film in conjunction with their role in warping. We show that the increasing ionic strength results in a faster consolidation of its constituents, increasing interparticle adhesion, thereby changing the particulate film's Young's modulus and limiting the drying induced warping. We explain this phenomenon using a theoretical model, wherein we show that the differential shrinkage during the drying in the particulate film generates the strain gradient, which later results in warping. Furthermore, our calculation shows that the curvature of a warped region is proportional to the strain gradient and is inversely proportional to the particulate film's Young's modulus.