FT-IR法研究PBT粘合剂的固化反应动力学

FT-IR Studies on the Curing Reaction Kinetics of PBT Binder

为明确3,3-双(叠氮甲基)氧丁环-四氢呋喃共聚醚(PBT)粘合剂与常用固化剂的反应过程,利用傅里叶变换红外(FT-IR)光谱法研究了PBT/多异氰酸酯(N100)、PBT/甲苯二异氰酸酯(TDI)和PBT/TDI/N100体系,50～80℃、TPB催化下的固化反应动力学。结果表明:PBT/N100在整个固化过程中遵循二级反应动力学规律,表观活化能63.10 kJ·mol^(-1),指前因子A=1.63×10~7h^(-1)。含有TDI的体系的固化过程均分为两段,但分段机理不同。PBT/TDI体系整个固化反应遵循二级反应动力学规律,但由于TDI上不同位置—NCO活性的差异,以转化率60%为界线分为两个阶段,转化率小于60%为第一阶段,转化率大于60%为第二阶段,相同温度下,第一阶段的反应速率明显高于第二阶段,两阶段的表观活化能分别为54.71 kJ·mol^(-1)和56.50 kJ·mol^(-1),指前因子分别为4.38×10~7h^(-1)和1.24×10~7h^(-1)。PBT/TDI/N100体系反应由于TDI和N100上—NCO活性的差异也分为两个阶段,转化率小于65%主要发生TDI扩链,表现为二级反应动力学,表观活化能为71.17 kJ·mol^(-1),指前因子A=4.58×10~8h^(-1);转化率大于65%主要发生N100交联,反应速率受扩散控制。TDI/N100复配时,指前因子较单一N100体系和单一TDI前后两阶段分别扩大了28,10,37倍,表明固化剂复配后反应活性位点增加。

To clarify the reaction process of 3,3-diazidomethyloxetane（ BAMO）-tetrahydrofuran（ THF） copolymer（ PBT） binder with commonly used curing agents,the curing reaction kinetics at 50-80 ℃ of PBT/polyisocyanate（ N100）,PBT/toluene diisocynate（ TDI） and PBT/TDI/N100 systems under catalyzing of TPB were studied by FT-IR spectroscopy. Results show that the PBT/N100 system follows the second order reaction kinetic law during the whole curing process,its apparent activation energy is 63.10 kJ ·mol-1,and the pre-exponential factor A is 1.63×107h-1. The whole curing process of systems containing TDI is divided into two stages,but their mechanism is different.The PBT/TDI system follows the second order reaction kinetic law during the whole curing process,but is clearly divided into two stages at the conversion ratio of 60%,the conversion ratio of the first stage is less than 60% and the conversion ratio of the second stage is higher than60%,due to differences in the activity of NCO on TDI. The reaction rate of the first stage is faster than that of the second stage at the same temperature. For the first stage,the apparent activation energy is 54.71 kJ ·mol-1,and the pre-exponential factor A is 4.38×107h-1. For the second stage,the apparent activation energy is 56.50 kJ ·mol-1,and the pre-exponential factor A equals 1.24×107h-1. For the PBT/TDI/N100 system,whose curing process is also divided into two stages at the conversion ratio of 65% due to the differences in the activity of —NCO on TDI and N100. During the first stage,the conversion ratio of less than 65% occurs the expansion chain of TDI,and the curing process follows the second order reaction kinetics,the apparent activation energy is 71.17 kJ ·mol-1,and the pre-exponential factor A is 4.58×108h-1,the conversion ratio of —NCO of more than 65% mainly occurs crosslinking reaction of N100,the reaction rate is controlled by diffusion. When TDI and N100 are mixed,the pre-exponential is 28,10,37 times larger than single N100 and the two stages of single TDI,respectively,indicating that the active sites increase after the combination of curing agents.