Kinetic research on the curing reaction of PBT/BPS via FT-IR measurements

To investigate the reaction process between 3,3′-bis(aminomethyl)oxetane/tetrahydrofuran copolymer(PBT) binder and acetylenic curing agents, this study employed bis-propargyl-succinate (BPS) as the curing agent and tris(iodoacetate) trimethyl propane ester (TMP-N₃) as the cross-linking agent. The curing reaction kinetics of PBT were analyzed using Fourier Transform Infrared Spectroscopy (FT-IR). The curing kinetic model was fitted by the Kamal model and the apparent activation energy (E_a) was calculated by Friedman's isoconversional method. The results indicated that the reactions of both PBT/BPS and PBT/BPS/TMP-N₃ are autocatalytic in nature. It was observed that with an increase in the TMP-N₃ content, the non-catalytic activation energy (E_a1) showed a decreasing trend, while the autocatalytic activation energy (E_a2) initially increased and then decreased. Additionally, as the curing progressed, the apparent activation energy (E_a) demonstrated an initial increase followed by a decrease. Detailed analysis of the curing kinetics at the molecular level shows that this is a combined effect of the viscosity change of the system, the diffusion of reactants, the autocatalytic effect and the interaction between molecular chains. Furthermore, the mechanical properties of elastomers in different systems were examined using a universal testing machine. The results show that as the TMP-N₃ content increases, the mechanical properties of the elastomers initially improve and then decrease. Among these, In the tested samples, sample P-B-N20 shows the best mechanical properties. Compared with the P-B sample, the tensile strength increased by 33.6%, and the breaking elongation increased by 15.4%.