FT-IR法研究PBT粘合剂的固化反应动力学

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 1.63×10⁷ h^-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 than 60%, 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 4.38×10⁷ h^-1. For the second stage, the apparent activation energy is 56.50 kJ•mol^-1, and the pre-exponential factor A equals 1.24×10⁷ h^-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 4.58×10⁸ h^-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.