Abstract:
Influence of relative factors, such as dimethylol propionic acid content ( w DMPA ), NCO/OH ratio, PA content ( w PA ), pH value and preparing techniche, on the viscosities of aqueous polyurethaneurea acrylic (PUA) dispersions was studied. The results show that the viscosity of PUA dispersion increases with raising the level of DMPA. The effect of NCO/OH ratio and w PA on the viscosity is sophisticated. The viscosity of PUA dispersions fluctuates with varying NCO/OH ratio, but has no pH value dependence in the range of pH value from 7 to 9.6. A mechnism by which the relationship between pH value and viscosity can be explained was presented. The gist of the mechanism is that pH value in the surface layer of disperse phase particle is different from that in the dispersion medium and the reason for this is that the surface layer of particle has the character of buffer solution. The comparison of prepolymer dispersing with inverted core shell method shows that the appearance of dispersion prepared by the former is clearer and the viscosity of that lower than by the later.