Effect of film thickness and particle size on cracking stresses in drying latex films

The stress at which latex films crack during drying was investigated using beam bending. Two systems were investigated: (i) poly(methyl methacrylate/butyl acrylate) particles cast as thin films to examine the effect of film thickness on cracking film stress and (ii) polystyrene particles dried as drops to investigate the effect of particle size. Results indicated an inverse relationship between film thickness and film stress, whilst film stress was shown to be independent of the original particle size. These outcomes were in good agreement with Tirumkudulu and Russel’s theoretical analysis [M.S. Tirumkudulu and W.B. Russel, Langmuir 21 (2005) 4938], albeit the measured stress values were almost twice the theoretical estimation.

Graphical abstractThe stress at which drying colloidal films crack is found to depend inversely with the film thickness and to be independent of the particle size.Figure optionsDownload full-size imageDownload high-quality image (68 K)Download as PowerPoint slideResearch highlights► Measured stress in drying film using cantilever technique. ► Measured in two different geometries: A film and a drying droplet. ► Stress due to a capillary pressure generated during drying. ► Maximum stress in film before onset of cracking agrees with model of Tirumkudulu and Russel.