What should I know about the viscosity of emulsion?
(1) The viscosity of the emulsion is related to the fluidity of the emulsion, which is a property with practical significance. We know that a polyvinyl acetate emulsion with a solid content of about 35% has a viscosity even smaller than his solution with a solid content of about 10%. This is because the emulsion is a colloidal dispersion system, and its viscosity mainly shows It is the viscosity of the dispersion medium (water), and has little to do with the concentration of the dispersed phase (vinyl acetate polymer), and has nothing to do with the molecular weight of the polymer. Calculated according to the spherical particle model of the dispersed phase, when the concentration is below 35% by volume, the viscosity basically does not change. Therefore, the way to increase the viscosity of the emulsion is to add a thickener, which can significantly increase the viscosity of the aqueous phase.
(2) The particle size and distribution of the polymer (dispersion) affect . When the particle size is above 0.5 μm, the effect is not significant; when the particle size is below 0.5 μm, the viscosity of the system increases rapidly as the particle size becomes smaller. Emulsions with a narrower particle size distribution are more viscous than emulsions with a wider particle size distribution .
(3) The pH value will affect the latex viscosity. In general, the higher the pH value, the lower the viscosity; if the polymer molecule contains carboxyl groups, such as acrylic acid, and the original viscosity is low, the alkaline pH value will make the curled molecules in the latex particles stretch At the same time, due to the hydrogen bond, a large number of water molecules enter the stretching layer, and the volume of the mobile phase is reduced , which shows that the viscosity of the system increases macroscopically, and reaches . Continuing to increase the pH value, the viscosity will decrease accordingly.
