Abstract:

A series of polyurethane aqueous dispersions, which were prepared from raw materials of toluene diisocyanate (TDI), polypropylene glycol (PPG), and dimethylol propionic acid (DMPA), were used to study post-chain extension process with ethylene diamine (EDA) as chain extender, including factors of H₂O, temperature of post-chain extension, molar ratio of -NCO/-OH in raw materials, and chain extension ratio. FT-IR results showed that the post-chain extension process of polyurethanes with EDA was affected by H₂O in aqueous dispersion through competitive reactions of H₂O with residual -NCO groups in polyurethane chains. Measurement of molecular weight, particle diameter, and zeta potential of polyurethane dispersions before and after chain extension indicated that chain extension by H₂O resulted in instability of polyurethane dispersions. The influence of H₂O on EDA post-chain extension process was significant at low chain extension ratio, whereas molecular weight of chain-extended polyurethanes was lowered at high chain extension ratio. When chain extension temperature was increased, molecular weight of EDA chain-extended polyurethanes was decreased,but diameters of polyurethane dispersions were increased. With molar ratio of -NCO/-OH in raw materials at 1.20, chain extension temperature at 30℃, and chain extension ratio at 60%, the H₂O impact on post-chain extension of polyurethanes with EDA was reduced effectively.

Key words: polyurethane, dispersion, toluene diisocyanate, water, post-chain extension, chain extension ratio, particle size distribution

摘要：

以甲苯二异氰酸酯（TDI）、聚氧化丙烯二醇和二羟甲基丙酸等为主要原料制备了聚氨酯水分散体，研究了水、扩链温度、原料的-NCO/-OH摩尔比及扩链比对乙二胺（EDA）后扩链TDI型聚氨酯水分散体过程的影响。FT-IR测试表明，分散体中的H₂O可通过与聚氨酯中残留异氰酸酯基团（-NCO）的竞争反应影响EDA的后扩链过程。分子量及粒径与zeta电位测试表明，H₂O扩链导致分散体失稳；低扩链比时，H₂O对EDA的后扩链过程影响明显，但高扩链比时，后扩链聚氨酯的分子量降低；扩链温度升高，经EDA后扩链聚氨酯的分子量降低，而分散体粒径增大。当原料的-NCO/-OH摩尔比为1.20、扩链温度为30℃、扩链比为60%时，可有效降低H₂O对EDA后扩链聚氨酯过程的影响。

关键词: 聚氨酯, 分散体, 甲苯二异氰酸酯, 水, 后扩链, 扩链比, 粒度分布