Ultrasonically Accelerated Nitration of Hydroxyl-Terminated Polybutadiene: Process Efficiency and Product Characterization

Hydroxyl-terminated polybutadiene (HTPB) is widely studied and the most used prepolymer for the binder system of composite solid propellants. A suitable functionalization of HTPB with energetic groups greatly improves the performance of the propellant. Therefore, the nitration of HTPB plays an essential role in the obtaining of high-energy binders. Among the reported methods, the nitration of HTPB using nitryl iodide (NO2I) was distinguished as the most preferable due to the facilitated synthesis and product purity. However, the thus established synthesis is long and laborious; therefore, in the present work we focus our attention on the improved procedure using ultrasonic conditions. The resulted nitro-HTPB was characterized using FTIR, 1H NMR, GPC, and DSC analyses. Also, based on the recorded IR-spectra a ratiometric analysis for determining the nitration rate was established, which could replace the expensive and time-consuming NMR analysis that was used.