聚氨酯-丙烯酸酯水分散液的流变性能

研究了二羟甲基丙酸（DMPA）含量、NCO／OH比、PU／PA比、pH值及制备工艺对水性聚氨酯－丙烯酸酯（PUA）混杂体系粘度的影响。结果表明：DMPA用量增大会使PUA水分散液的粘度增大；NCO／OH比和PU／PA比对粘度的影响比较复杂，PU／PA比在60／40（m/m）左右出现粘度最小值，NCO／OH比的变化则引起PUA水分散液的波动；体系的酸碱度（pH）对PUA水分散液的粘度有一定的“缓冲”作用，即pH值在7.0-9.6范围内粘度不会发生变化，提出了PUA水分散液非均相体系中，分散相粒子表层与分散介质中pH值不同的观点，并认为这判别是由于粒子表层具有缓冲溶液的性质造成的；用预聚物分散法制得的PUA水分散液外观较清澈，其粘度低于核壳反转法制得的分散液。

Rheology of Water-borne Polyurethane-acrylic (PUA) Dispersions

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.