Ignition and Extinction of n‐Butyl Nitroxyethylnitramine‐Plasticized Polyethylene Glycol Propellants

Abstract

The ignition and extinction of n‐butyl nitroxyethylnitramine (BuNENA)‐plasticized polyethylene glycol (PEG) propellants were investigated with respect to the concentration of binder and the ratio of plasticizer to polymer (pl/po). A distinctive change in the ignition delay time (tign) of the propellants was found at a low pressure of 0.03 MPa, where tign increases as the binder concentration increases from 24 % to 32 % and decreases when the pl/po ratio reaches from 1 to 6. The kinetic analysis shows that the ignition delay of BuNENA‐PEG propellants is due to a high activation energy of a condensed phase accompanied by the reduction of NO in the gas phase that plays an important role in the formation of luminous flames. Furthermore, the BuNENA‐PEG propellants with a high concentration of binder or a low ratio of pl/po were found to result in a relatively high value of the pressure deflagration limit (PDL) under which steady combustion cannot occur. With regard to combustion stability, it seems that the BuNENA‐PEG propellants producing relatively large amounts of CO and H2 are easy to extinguish and exhibit significant delay in ignition at low pressure.

Inserting urethane into 1,2,3‐triazole click‐cured solid propellant binder to form microphase separation and enhance mechanical and combustible performances

“…[21][22][23] However, the practical application of a triazole-cured binder system is inhibited by unsatisfied mechanical properties. 24,25 Unlike the isocyanates curing system, the rigid triazole rings failed to induce the aggregation of hard segments to form a micro-phase separation structure, 26 due to insufficient intermolecular force. 27,28 Furthermore, the GAP-based triazole-cured binder system suffers from uncontrollable reaction equivalent because the molecular chain contains many CH 2 N 3 side groups, 29 and the preformed rigid triazoles had great spatial occupancy which hindered the formation of nearby triazoles.…”

“…The GAP binder system can further form a triazole‐based network via alkyne‐azide Huisgen cycloaddition, 19,20 which is insensitive to humidity, simpler, and faster than the traditional isocyanates curing system 21–23 . However, the practical application of a triazole‐cured binder system is inhibited by unsatisfied mechanical properties 24,25 . Unlike the isocyanates curing system, the rigid triazole rings failed to induce the aggregation of hard segments to form a micro‐phase separation structure, 26 due to insufficient intermolecular force 27,28 .…”

Quantum Mechanical Investigation on Decomposition Pathways of BuNENA

“…At present, there is no relevant research on the rate constants for the decomposition of alkyl-NENAs that contain both of nitrate ester and nitramine. Recently, an interesting work demonstrated that the NEPE propellants plasticized by BuNENA resulted in a high pressure deflagration limit (PDL) of 2.28 MPa and a long ignition delay time in vacuum [11]. It was surmised that a very slow reaction involving NO, which is produced by the reduction of NO 2 , would play a significant role in ignition delay and combustion characteristics.…”