Theoretical, structural, and thermal aspects of nitro-HTPB as a prospective energetic binder–A detailed computational and experimental analysis

Abstract

This study is focused on several key parameters of nitro-HTPB, such as the theoretical prediction of propulsive performance in composite propellants, determination of microstructural changes on the HTPB backbone before and after nitration, detailed analysis of the thermal decomposition mechanism, and kinetic analysis, to understand its potential as an energetic binder. When compared to conventional AP/Al/HTPB/DOA composition, nitro-HTPB-based propellant with AP/Al/NHTPB/TEGDN composition increases density-specific impulse by 40–50 s, depending on the extent to which the HTPB backbone is nitrated. As evidenced by 2D NMR methods such as 1H–13C HSQC and 1H–1H COSY, nitration only happened on alkene segments via dehydro-nitration, keeping the alkene segment in the process and barely changing the HTPB backbone's olefinic proton percentage (38%). The thermal cross-linking process during the first stage of decomposition of NHTPB begins at about 190 ºC and finishes at about 280 ºC, which is about 130 °C lower than that of HTPB, according to an FTIR analysis of TGA residues. Although nitro-HTPB has a shorter shelf life than HTPB, the kinetic analysis showed that it can be stored for extended periods in tightly packed conditions without degrading its performance, primarily because of its low K (reaction factor) value of 109 min−1. These encouraging results open up new avenues for nitro-HTPB's possible applications as an energetic binder and may eventually encourage other propellant researchers to use it in real-world applications. © 2017 Elsevier Inc. All rights reserved.