脂肪族水性聚氨酯的动态力学行为研究

合成了一系列脂肪族水性聚氨酯 .考察了软段的组成、软段分子量及DMPA用量对产物动态力学性能的影响作用 .实验结果表明 ,软段的化学结构对水性聚氨酯的相态结构影响很大 .聚醚型水性聚氨酯具有较低的软段玻璃化转变温度 (Tgs) .聚醚型产物的微相分离程度高于聚酯型产物 .当采用聚酯和聚醚二元醇为混合软段时 ,Tgs随软段中聚醚含量的提高而逐渐降低 .提高DMPA用量 ,软段玻璃化转变温度Tgs移向低温区 ,硬段玻璃化转变温度Tgh移向高温区 ,说明体系的微相分离程度加大 .当软段分子量较低时 ,产物为半相容结构 ,只有一个主转变峰 ,软段的玻璃化转变以肩峰的形式出现 ;当软段分子量较高时 ,产物的微相分离程度较高 ,可以分别观察到软段及硬段的玻璃化转变 .总之 ,通过改变软段的种类、组成和分子量以及DMPA用量 ,可以大幅度地改变水性聚氨酯的形态结构 .

THE INVESTIGATION ON THE DYNAMIC MECHANICAL PROPERTIES OF WATERBORNE POLYURETHANES

Several aliphatic waterborne polyurethanes were prepared from isophorone diisocyanate(IPDI),dimethylolpropanic acid(DMPA),poly(ethylene adipate) (PEA) and polypropylene glycol(PPG).Dynamic mechanical analysis(DMA) was adopted to study the relationships between morphology and properties of aliphatic waterborne polyurethanes.The results indicated that the interaction between soft and hard segments depended heavily on the structure of soft segments.The carbonyl of polyester-type diols can form hydrogen bonds with hard segments,which lead to a semi-compatible structure,whereas the hydrogen bonding in the polyether-based polyurethanes is formed mainly between the hard segments,which results in higher level microphase separation.The ionic groups incorporated in the hard segments improve the phase separation.As a result,the increase of DMPA amount is related with a lower glass transition temperature(T gs) and a higher T gh.At the meantime,the level of microphase separation increases with the increasing of soft segments length.