红外研究丁羟二异氰酸酯的固化反应动力学

用红外分光光度计研究了端羟基聚丁二烯(HTPBD)与二异氰酸酯的反应动力学,结果表明,NCO与OH的反应为二级动力学反应,由于位阻效应和共轭效应,MDI比TDI的反应活性大得多,前者的反应速率常数大约是后者的10～20倍。反应速率常数及活化能随NCO的过量而有所变化。在NCO过量体系中。TDI-HTPBD体系中有次级反应发生,由于氢键的作用,次级反应为对于氨基甲酸酯基为二级、NCO为一级的三级反应动力学.由于位阻效应,MDI体系很难发生次级反应。

STUDIES ON CURE REACTION KINETICS OF DIISOCYANATES AND HYDROXYL TERMINATED POLYBUTADIENE BY IR

The cure reaction kinetics of diisocyanates and hydroxyl terminated polybutadiene(HTPBD) have been studied by IR. The results show that the reaction of diisocyanates (MDI and TDI) and HTPBD (OH group) is a second order reaction. The rate constants change slightly with different equivalent ratio of NCO/OH. The active energy of the reaction of TDI and HTPBD is about 40kJ/mol and about 32kJ/mol for the reaction of MDI and HTPBD(OH group).When the convert ratio of NCO group is more than 50%,the concentration of urethane group is large enough to react with NCO group. The results show that the reaction of NCO and urethane group is a third order reaction which is a first order reaction about NCO group and a second order reaction about urethane group. This may be due to the hydrogen bonding between the two groups. The rate constants of the reaction is very smaller than that of the reaction of NCO and OH.