COALESCENCE MECHANISMS OF POLYMER COLLOIDS .1. COALESCENCE UNDER THE INFLUENCE OF PARTICLE WATER INTERFACIAL-TENSION

Coalescence of dense packings of spheres of model latex particles was studied in water. The model particles had a core-shell structure. The core comprised 90% of the mass of the particle, thus largely determining the mechanical properties. The shell contained 10, 15, or 25 wt% methacrylic acid, resulting in three kinds of particles with different particle-water interfacial tensions. It was shown that coalescence in water under the influence of particle-water interfacial tension was possible even at temperatures below the glass transition temperature. The kinetics of coalescence was closely related to interfacial tension. It was shown that the rate of coalescence decreased when interfacial tension decreased, i.e., when the amount of methacrylic acid increased in the shell or when sodium dodecyl sulfate was adsorbed onto the particles, or when the methacrylic acid was neutralized by sodium hydroxide. It was also established that the activation energy of coalescence was equal to the activation energy of the motions of the macromolecules at the glass transition. © 1992.