In-situ studies of structure development during the reactive processing of model flexible polyurethane foam systems using FT-IR spectroscopy, synchrotron SAXS, and rheology
In-situ studies of structure development during the reactive processing of model flexible polyurethane foam systems using FT-IR spectroscopy, synchrotron SAXS, and rheology
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DOI：
10.1021/ma9511208
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发表时间：
1996-04-08
期刊：
影响因子：
5.5
通讯作者：
VanLieshout, HC
中科院分区：
文献类型：
--
作者：
Elwell, MJ;Ryan, AJ;VanLieshout, HC
FT-LR光谱，同步加速器SAXS，和动态流变仪已被用来监测，在原位，结构发展过程中的模型软质聚氨酯泡沫塑料系统的反应性加工。研究了以下组分的组合：（I）二异氰酸酯、聚醚多元醇和水，以及（II）二异氰酸酯、聚醚一元醇和水。采用绝热反应器法和强制绝热时间分辨FT-IR光谱法研究了在快速本体共聚过程中氨基甲酸酯、可溶性尿素和氢键键合的尿素物种的形成。异氰酸酯的衰变与聚合动力学相关，并强调脲硬段序列的微相分离的开始，氢键脲的演变进行了分析。FT-IR光谱表明，微相分离转变（MST）发生在异氰酸酯官能团的临界转化率，并遵循与成核和生长相关的动力学。在快速本体共聚过程中的微相分离的动力学也进行了研究，采用强制绝热，时间分辨同步小角X射线散射实验。观察到微相分离发生在异氰酸酯官能团的临界转化率，并显示遵循与旋节分解相关的动力学。在快速本体共聚过程中进行了强制绝热流变测量。确定了聚氨酯泡沫形成过程中流变发展的四个主要区域。这些是：（I）气泡成核，（II）液体泡沫和微相分离，（III）物理凝胶化，和（TV）泡沫弹性体。模型系统的使用表明，共价交联的存在延迟脲硬段序列长度的微相分离的开始。虽然泡沫稳定性不依赖于在发泡反应的早期形成氨基甲酸酯共价交联，但通过氨基甲酸酯共价交联的微相之间的分子连接性是关于泡沫的长期尺寸稳定性和机械/物理性质的基本要求。
FT-LR spectroscopy, synchrotron SAXS, and dynamic rheometry have been employed to monitor, in-situ, structure development during the reactive processing of model flexible polyurethane foam systems. The following combinations of components were investigated: (I) diisocyanate, polyether polyol, and water and (II) diisocyanate, polyether monol, and water. The formation of urethane, soluble urea, and hydrogen-bonded urea species during the fast bulk copolymerization has been studied using the adiabatic reactor method and forced-adiabatic, time-resolved FT-IR spectroscopy. The decay of isocyanate is correlated with the polymerization kinetics, and the evolution of hydrogen-bended urea is analyzed emphasizing the onset of microphase separation of urea hard segment sequences. FT-IR spectroscopy indicated that the microphase separation transition (MST) occurred at a critical conversion of isocyanate functional groups and followed the kinetics associated with nucleation and growth. The dynamics of microphase separation during the fast bulk copolymerization have also been investigated employing forced-adiabatic, time-resolved synchrotron SAXS experiments. Microphase separation was observed to occur at a critical conversion of isocyanate functional groups and is shown to follow the kinetics associated with spinodal decomposition. Forced-adiabatic rheological measurements have been conducted during the fast bulk copolymerization. Four main regions of rheological development during the formation of polyurethane foam were identified. These were: (I) bubble nucleation, (II) liquid foam and microphase separation, (III) physical gelation, and (TV) foamed elastomer. The use of model systems demonstrated that the presence of covalent cross-links delay the onset of microphase separation of the urea hard segment sequence lengths. Although foam stability is not dependent upon the formation of urethane covalent cross-links in the early part of the foaming reaction, molecular connectivity between the microphases via urethane covalent cross-links is an essential requirement with regard to long-term dimensional stability and the mechanical/physical properties of the foam.