Synthesis and Characterization of Dimeryl Diisocyanate (DDI) using Curtius Rearrangement Method

Dimeryl diisocyanate (DDI), one of the most frequently used isocyanate curing agents for propellant, DDI is used to cure solid propellants based on HTPB. Diisocyanates are used as a curing agent in HTPB-based composite solid propellant systems. In this study, a three-step process for optimizing the effects of numerous parameters in the manufacture of dimeryl diisocyanate (DDI) was used. In the first step, the reaction with ethanol at a temperature of 85 degrees Celsius led to the preparation of the dimer ester compound with a yield of 99%. In the following stage, high temperatures and no solvent are used to combine the produced dimer ester with hydrazine hydrate to create dimer hydrazide. In the third stage, acyl azide is produced using sodium nitrite, and the target product is produced with a 90% yield using a high-temperature Curtius rearrangement. The product obtained by this method does not have the disadvantages of the phosgene method.