COALESCENCE MECHANISMS OF POLYMER COLLOIDS .2. COALESCENCE WITH EVAPORATION OF WATER

Mechanisms of coalescence of model latices were studied under standard conditions, i.e., with simultaneous evaporation of water. The model latices had core-shell particles with the same diameters and the same bulk properties but different surface characteristics. Different surface compositions were achieved by varying the amount of methacrylic acid (MAA) in the shell, by neutralizing the MAA to different extents, or by adding various amounts of surfactant to the latices. The limit temperature/relative humidity diagrams for film formation were established for several latices. They were all identical, regardless of the surface characteristics of the particles. Total coalescence times of latices and dense packings of latex particles were measured and compared with the coalescence times of the same packings of particles in water. This led to the conclusion that particle-water interfacial tension has a negligible contribution to the coalescence mechanisms under standard conditions. The mechanisms and their relationship to evaporation of water for various thermal conditions of coalescence are discussed. © 1992.