Cracking in soft-hard latex blends: theory and experiments.
Volatile organic compounds (VOCs) in the traditional paint and coating formulations are an important health and environmental concern, and current formulations are increasingly moving toward water-based dispersions. However, even within the water-based systems, small quantities of organic solvents are used to promote particle coalescence. One route to achieving this goal has been to use mixtures of soft and hard particles, also known as latex blends. We investigate the drying of colloidal films containing mixtures of silica and acrylic particles. Since both the particles deform only slightly at room temperature, this work investigates the cracking behavior of films containing elastic particles of two different elastic moduli. We extend an existing model for the stress versus strain relation for identical particles in a colloidal film to that containing a mixture of equal-sized hard and soft elastic spheres while accounting for the nonaffine deformation. A transition from soft to rigidlike behavior is observed beyond a critical hard particle volume fraction ratio that matches with published results obtained from computer simulations. The model predictions are validated with extensive experimental data on the critical stress and critical cracking thickness for various ratios of hard and soft particle volume fraction.
Singh
Karnail B
KB
Department of Chemical Engineering, Indian Institute of Technology-Bombay, Mumbai 400076, India.
Deoghare
Girish
G
Tirumkudulu
Mahesh S
MS
D000180:Acrylic Resins / Q000737:chemistry*; D003102:Colloids / Q000737:chemistry; D003198:Computer Simulation; D008567:Membranes, Artificial; D008956:Models, Chemical; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D055549:Volatile Organic Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D003102:Colloids; D008567:Membranes, Artificial; D055549:Volatile Organic Compounds; D014867:Water; D012822:Silicon Dioxide