Synthesis, Characterization, and Kinetic Studies of 1,3‐Bis (3‐isocyanato‐4‐methylphenyl)‐1,3‐Diazetidine‐2,4‐Dione for the Application in Composite Propellants

ABSTRACT 1,3‐Bis (3‐isocyanato‐4‐methylphenyl)‐1,3‐diazetidine‐2,4‐dione, a dimeric form of toluene diisocyanate (TDI), was synthesized with dimethyl aminopyridine as a dimerization catalyst in the toluene medium. The white solid compound was purified by recrystallization in hot toluene, and the purity was determined by titrimetry. The compound was further characterized by various spectroscopic and analytical techniques such as Fourier‐transform infrared, 1 H nuclear magnetic resonance (NMR), 13 C NMR, mass spectrometry, differential scanning calorimetry, etc. Hydroxyl‐terminated polybutadiene, a polymeric binder used in composite propellants, was cured with the synthesized 1,3‐bis (3‐isocyanato‐4‐methylphenyl)‐1,3‐diazetidine‐2,4‐dione (TDI dimer), and the curing kinetics of urethane formation were established through viscosity build‐up and residual isocyanate content by volumetric titration. The activation energy and rate constant for the polyurethane formation were determined by the Arrhenius graphical method. Kinetic studies reveal superior pot life during the initial stage of the reaction. Further, water reactivity studies have shown that the TDI dimer is very stable towards moisture as compared to TDI. Thus, the study establishes the use of TDI dimer solid as a better choice of curing agent in specific applications due to the comparatively slower reaction kinetics, stability towards moisture, and non‐volatile nature.