The analysis of phenomena and factors having an effect on the sedimentation stability and rheology of water-based dispersions of MMA/BA/MAA copolymer in xylene

This paper presents essentially the results of sedimentation and rheological studies on aqueous dispersed systems of copolymer methyl methacrylate with butyl acrylate and methacrylic acid (MMA/BA/MAA) in a xylene solution. Non-ionic surfactants such as oxyethylenated unsaturated fatty alcohol, lauryl alcohol and oxyethylenated amines were used as well as the thickening agents: polyvinyl alcohol, sodium salt of carboxymethylcellulose (CMC-Na) and water-soluble polyurethane oligomer. The properties of surfactant water solutions were determined with the use of tensiometric and viscometric methods. The structure of the obtained copolymer was analysed by gel chromatography. The sedimentation experiment was a basic test used to determine the stability of aqueous dispersions of the obtained copolymer in xylene. It consisted in determining types of phases occurring in sedimentation equilibrium. The formation of a foamed copolymer phase was the most interesting phenomenon. A rheological test was carried out by using the so-called stable phase and was aimed to define maximum viscosity, pseudoplasticity and activation energy of a viscous flow. Moreover, the reduced viscosity, a limiting viscosity number and the Huggins constant were also determined. The relationships between these quantities were established indicating the dependences, which were the best interpretation describing interactions between particles in the dispersed system. Basing on rheological and sedimentation tests, the most probable mechanisms of stability in systems of this type were determined. The factors reducing their stability and concerned with flocculation and coalescence of particles have been defined.