软段含羧基的水性聚氨酯物性研究

合成了单官能团小分子物质封端的软硬段皆含羧基的脂环族水性聚氨酯(PU),研究了反离子种类、固含量、外加小分子盐/酸、pH值对水性PU的粘度、粒径、CMC和电导率的影响,同时,比较了不同软段分子量水性PU分散液pH临界值和CMC的差异.实验结果表明,随固含量升高,PU分散液体系粘度增大,当固含量为30wt%时,粘度比固含量20wt%的体系粘度增大约20倍;随小分子盐NaCl的加入,PU分散液电粘滞效应逐渐消失,电导率呈现先减小后增大的趋势,随NaCl的加入/软段分子量提高,PU分散体系的CMC值减小,钙离子对PU粒子扩散双电层的破坏作用更加明显.随pH值的增大,PU分散液体系粒径减小,电导率则升高,随软段分子量提高,pH临界值增大,PU分散体对外加小分子酸存在缓冲作用.

STUDY ON SOME PROPERTY OF AQUEOUS POLYURETHANE WITH CARBOXYLATED SOFT SEGMENT

An alicyclic aqueous polyurethane (PU) prepolymers with soft segment containing carboxyl was synthesized from isophorone discarnate (IPDI), dimethylol butnoic acid (DMBA), polycaprolactone (PCL) and 2-propanol, followed by neutralization pendant carboxyl by triethylamine (TEA)/KOH. In the article, the effects of the type of counter ions, PU solid content, the pH value, small molecule salt /acid on its stability, viscosity, CMC, particle sizes, conductivity were investigated. In the meanwhile, it was compared that difference and relation of the pH critical value and CMC in PU dispersions with different soft segment molecular weight. The result showed that while PU content was raising its viscosity was enhancing. PU viscosity with 30wt% solid content was higher twenty times than PU viscosity with 20wt% solid content. With the addition of small molecule salt NaCl, electroviscous effect of PU dispersions gradually disappeared and PU conductivity appeared fluctuating. With NaCl addition/molecular weight of soft segment increase, CMC value minished, the calcium ion was more obvious destructive function to the diffuse electrical double layer of PU dispersions. With the increasing of pH value, PU particle sizes gradually decreased but conductivity increasingly rose. With the increasing of molecular weight of soft segment, PU viscosity was going up, pH critical value increased. PU system was of buffer effect on adscititious acid.