Ignition study of amine borane/cyanoborane based green hypergolic fuels

Boron based compounds have been looked upon as possible replacements to conventional toxic hypergolic fuels in propellant system. In an attempt to add to the pool of boron based hypergols, a series of new amine borane/cyanoborane zwitterionic compounds were developed. Their hypergolic reactivity, performance parameters and physico-chemical properties were examined, in detail. The unsymmetrical dimethyl hydrazine (UDMH) based zwitterions, UDMH-borane and UDMH-bisborane displayed strikingly lower ignition delay times of 2.2 and 2 ms, respectively and high specific impulse 241 and 245 s, respectively. The pyridinium-cyanoborohydride exhibited high heat of formation (146 kJ/mol) than UDMH. While all the developed compounds exhibited higher density than the UDMH. Chemical stability of UDMH-borane was investigated at different environmental conditions; it was found to be stable for longer duration. Low ignition delay, good thermal and chemical stability, positive heat of formation, high specific impulse, ease of synthesis, and commercially available starting materials are the promising features of these compounds which make them attractive prospects in revolutionizing the area of green hypergolic fuel in liquid as well as hybrid rocket propulsion. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.