THE FILM FORMATION OF ACRYLIC LATEXES - A COMPREHENSIVE MODEL OF FILM COALESCENCE

A comprehensive model of film formation that was proposed in an earlier article by the present authors was evaluated for latexes having a wide range of physical properties. In this model, capillary force and interfacial forces act in tandem to promote film coalescence. The emulsion polymers studied were all based on poly (methyl methacrylate- co-butyl acrylate). The viscoelastic nature of the copolymer was varied by the addition of molecular weight modifiers (CBr4 chain-transfer agent and ethylene glycol dimethacrylate cross-linking monomer) during synthesis. In contrast to the simplifications of the previous analysis, the experimental system was well characterized. The effect of water plasticization was investigated. The surface energetics of the system were studied. Also, drying kinetics were considered. Results showed that the degree of coalescence ranged from complete fusion to superficial fusion. The minimum film temperature was found to increase with increasing polymer rigidity, as is expected. Comparison of the model predictions and experimental observations validated the model. (C) 1994 John Wiley & Sons, Inc.