红外光谱法测定聚氨酯预聚体中异氰酸酯基含量

Determination of Isocyanate Group in Polyurethane Prepolymer by FT-IR Spectroscopy

建立了密封池红外光谱法测定聚氨酯预聚体中异氰酸酯基含量的方法。首先考察了溶剂和静置时间的影响。以MDI和TDI作标准物时可用分析纯甲苯作溶剂，以IPDI作标准物时可用分析纯甲苯或丙酮作溶剂，在200min内基本稳定。然后绘制了以MDI、TDI和IPDI作标准物和分析纯甲苯作溶剂时的标准曲线。标准曲线线性范围分别为0～11mg（-NC0）／mL、0～7mg（-NC0）／mL和0～12mg（-NCO）／mL，摩尔吸光系数分别为1．20×10^3L·mol-1·cm-1、1.55×10^3L·mol-1·cm-1和1．04×10^3 L·mol^-1·cm^-1，相关系数分别为0．9991、0．9996和0．9997。最后测定了[PDI与聚酯多元醇反应产生的聚氨酯预聚体中-NCO含量，随反应时间增加预聚体中-NCO含量逐渐减少。与化学分析法和可见分光光度法相比，本文建立的红外光谱法更简便、测定时间短、试剂用量少、分析成本低，但所用仪器贵且需有合适的溶剂。

The quantitative determination method of isocyanate（--NCO） group in polyurethane prepolymer has been established by FTIR spectroscopy using sealed liquid cell. Firstly, the influence of solvents and standing time is studied. When MDI or TDI is used as a standard material, the toluene （AR） can be used as a solvent. When IPDI is used as a standard material, the toluene （AR） or acetone （AR） can be used as a solvent. The absorbance keeps when the MDI, TDI and IPDI are used as stable within 200 rain. secondly, standard materials and the toluene（ the standard curves are drawn AR） is used as a solvent. The linear range of standard curve is 0 - 11 mg（-NCO）/mL, 0 -7 mg（--NCO）/mL and 0 - 12 mg （--NCO）/mL separately; the molar absorptivity is 1.20 × 10^3 L·mol-1·cm-1, 1.55 × 10^3 L·mol-1·cm-1 and 1.04× 10^3 L·mol-1·cm-1 respectively; the linear correlation coefficient is 0. 999 1, 0. 999 6 and 0. 999 7. Last but not the least, the content of residual --NCO group in polyurethane prepolymer is determined when IPDI and polyester polyols are used as raw materials. The content of --NCO group in the polyu- rethane prepolymer decreased as the reaction time increased. This analytical method shows many advantages such as simple operation, shorter testing time and less reagent usage, compared with the chemical analysis and spectrophotometrie method, but the expensive equipment and appropriate solvens are needed.