Model of water evaporation stage during drying of latex coatings

AbstractModel of Water Evaporation Stage during Drying of Latex CoatingsVenkata Ramana GundabalaRichard Allan Cairncross, Ph.DTraditional solvent-based coatings pose several environmental concerns due to high volatility and polluting effects of the solvents. Water-based latex coatings have been identified as a worthy alternative because of the ease of application; however the properties of latex coatings are often inferior to solvent-based coatings due to incomplete film formation. To achieve suitable film properties for most applications, it is necessary for latex particles to aggregate and coalescence into a continuous film during drying. Film formation during drying of latex coatings is occurs in three stages. This thesis presents a particle dynamics model that predicts evolution of particle layers and packing structure during the first stage of drying of latex coatings, which is period of constant evaporation rate. In this model the inertia of particles is negligible and the velocity and trajectory of each particle is determined by balancing the drag force on the particle with interparticle repulsion, surface tension and Brownian forces. DLVO theory was used to predict the screened electrostatic interactions between particles. The Brownian force has random magnitude and direction to simulate random particle motions observed in colloidal systems. Areal density profiles and 3D plots are used to make base case and parametric analysis on evolution of particle layers and packing structure. The parameters used for investigation include electrolyte concentration, drying rate, particle size, magnitude of random force variance, initial volume fraction, and initial particle distribution. FCC and HCP are the most commonly observed packing structures. The results show that use of smaller particle sizes, lower electrolyte concentrations, and slower drying rates produce more highly ordered packing structure.M.S., Chemical Engineering -- Drexel University, 200