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首页> 外文期刊>Journal of Applied Polymer Science >Linear segmented polyurethanes: I. A kinetics study
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Linear segmented polyurethanes: I. A kinetics study

机译：线性分段聚氨酯：I.动力学研究

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This work investigates the two-step polymerization between methylene diphenyl diisocyanate (MDI), two different poly(tetramethylene oxide) macrodiols, and 1,4-butanediol (BD) as chain extender. At the end of the prepolymerization, the reaction mixture contains MDI in excess and a prepolymer with isocyanate end group. Then, BD and a solvent (tetrahydrofuran) were added to start the finishing stage under nominal stoichiometric equilibrium. The reaction was analyzed by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (H-1-NMR), and size exclusion chromatography. H-1-NMR was employed to follow global concentrations of unreacted isocyanate end groups and internal urethane groups. This information enabled to estimate the following effective rate constants: k(1)=1.07 x 10(-3) Lmol(-1)s(-1) for the prepolymerization; and k(2)=1.94 x 10(-4) Lmol(-1)s(-1) for the finishing stage. These values are subject to errors caused by biases introduced in the recipe, in the measurements, in the reaction conditions, in the quality of reagents, and in the reaction mechanism assumptions. Such errors also explain the dispersion of the published rate constants values. The H-1-NMR measurements also enabled to estimate the evolution (with extent of reaction) of the number-average number of structural units along the prepolymerization and finishing stages; and such estimates reasonably verify Flory's classical expressions. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45747.
机译：该作品研究了二苯基二异氰酸酯（MDI），两种不同的聚（四甲基氧化物）MACRODOORS和1,4-丁二醇（BD）作为链增量剂之间的两步聚合。在预聚合结束时，反应混合物含有多余的MDI和具有异氰酸酯端基的预聚物。然后，加入Bd和溶剂（四氢呋喃）以在标称化学计量平衡下开始精加工阶段。通过傅里叶变换红外光谱，氢核磁共振（H-1-NMR）和尺寸排阻色谱分析反应。使用H-1-NMR以遵循全局浓度的未反应异氰酸酯端基和内氨基甲酸酯基团。该信息能够估计以下有效率常数：K（1）= 1.07×10（-3）Lmol（-1）Lmol（-1）S（-1），用于预聚合;对于精加工阶段，K（2）= 1.94×10（-4）Lmol（-1）S（-1）。这些值受到配方中引入的偏差引起的误差，在测量中，在反应条件下，在试剂的质量和反应机理假设中。此类错误还解释了发布的速率常量值的分散。 H-1-NMR测量还使沿预聚合和整理阶段估计数均线数量的结构单元数量的进化（反应的程度）;此类估计合理地验证了福伦的古典表达。 （c）2017 Wiley期刊，Inc.J.Phill。聚合物。 SCI。 2018,135,45747。

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