羧基在水基聚氨酯分散体粒子中的分布

Distribution of Carboxyl Groups in Aqueous Polyurethane Dispersion Particles

在水基聚氨酯分散体中 ,羧酸型聚氨酯分散体应用最为广泛。它通常采用所谓自乳化工艺合成 ,在聚氨酯分子链中引入亲水基团 ,亲水基团成为其自身分散的分散剂。虽然理论可以推论羧基将分布在分散体粒子表面 ,但目前还没有直接证据。本文采用电导滴定和透射电子显微镜 (TEM)观测证明羧基分布在分散体粒子表面。

Among the aqueous polyurethane dispersions, the anionic polyurethane dispersions have been most frequently used in coating and adhesive industries. Anionic polyurethanes are usually prepared by introducing a pendant acid group, such as dimethylolpropinonic acid (DMPA), into the backbone of the polyurethane prepolymer. The pendant carboxylic acid groups are neutralized with base to form internal salt group-containing prepolymers that can easily be dispersed in water. There arises a question whether the salt groups are located on the surface of the dispersed particles or embedded within the particles. In this study, we use conductometric titration and TEM to study the distribution of carboxyl groups in the dispersion particles and the study shows that the carboxyl groups are all located on the surface of the dispersed particles.