阳离子型聚氨酯-脲水溶液的性质

Properties of Cationic Water-soluble Polyurethane-urea Solution

由聚醚二元醇与甲苯二异氰酸酯 ( TDI)预聚后 ,经二乙烯三胺扩链、冰乙酸中和而制备了阳离子型聚氨酯 -脲 ( PUU)水溶液。 Ubbelohde毛细管粘度计测得 PUU水溶液在不同浓度下的粘度 ,用 Huggins和 Kraemer方程及 Fox和 Flory等效圆球理论计算可知 ,PUU在水溶液中的分子尺寸随相对分子质量的增加而增加 ;加入小分子电解质后 ,PUU分子链尺寸变小 ,说明其构象由舒展变为卷曲 ,有效体积分数变小 ,粘度下降。研究表明 ,分子链中的空间位阻效应是决定聚氨酯 -脲在水溶液中分子尺寸的主要因素 ,水溶液中 PUU分子尺寸与真溶液中溶质分子尺寸 ( 1 0 -10 m～1 0 -9m)相近。水溶性 PUU的流变特性说明 ,不同浓度的水溶性 PUU都为牛顿流体 ,表观粘度不随剪切速率而变 ;水溶性 PUU稀溶液的粘度都相近 ,与乌氏毛细管粘度计法测得的结果也相近 ,且与相对分子质量基本无关 ;随着溶液浓度的增加 ,其粘度也随之增加 ,而水溶性 PUU浓溶液的粘度随相对分子质量的增加而减小。PUU水溶液的牛顿型流变行为也说明该分子链在水中的形态是稳定的 ,不受外界剪切应力的影响。

Water soluble polyurethane ureas(PUU) were synthesized by prepolymerization of poly oxidepropene glycol and toluene diisocyanate, and by chain extending with diethylenetriamine and then neutralized by anhydrous acetic acid. Viscositie s of PUU solutions at different concentrations were measured by Ubbelohde capillary tube viscometer, and the PUU molecular sizes were also calculated by Huggins, Kr aemer equation and Fox, Flory equivalent pellet theory. The results demonstrate that the dimensions of the water solube PUU chain increase with the molecular w eight in water; and the decreasing of the PUU E(containing the polyether diol w i th n=1 911) chain size by addition of sodium acetate reveals that th e chain conformation is changed from the stretch to winding form, and the viscos ity is declined because of decreasing effective volume fraction. The results als o indicate that the PUU chain size in water is determined by the steric hindranc e, and the range of the PUU sizes is close to that of the solute molecules in t rue solution(10 -10 m^10 -9 m). The rheological properties of the PUU at different concentrations reveal that the water solube PUU should belong to New tonia fluid, and the apparent viscosity of PUU is not changed with shear rate, a nd the viscosities of the dilute solution(1%) of PUU are close and similar to th e results of Ubbelohde viscosimeter, and independent on the molecular weight. Wi th the concentration increasing, the PUU viscosity increases, while the viscosit y of the thick PUU decreases by increasing the molecular weight. The Newtonia fl ow behaviour of PUU solutions elucidates that the conformation of the PUU chain is stable in water, and not influenced by shear stress.