Notes on the use of the vacuum stability test in the study of initiation reactivity of attractive cyclic nitramines in the C4 matrix Svatopluk Zeman • Ahmed Elbeih • Qi-Long Yan Received: 31 July 2012 / Accepted: 17 September 2012 / Published online: 9 October 2012 Ó Akade ´miai Kiado ´, Budapest, Hungary 2012 Abstract The zero-order reaction rates (specific rate constants) for isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) were measured by means of the Czech vacuum stability test, STABIL. The PBXs are based on 1,3,5-trinitro-1,3,5-triazinane (RDX), b-1,3,5,7- tetranitro-1,3,5,7-tetrazocane (HMX), cis-1,3,4,6-tetra- nitro-octahydroimidazo-[4,5-d] imidazole (BCHMX), and e-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (e-HNIW, e-CL-20) with 9 wt.% of the C4 type matrix, i.e., a matrix containing 25 wt.% of polyisobutylene, 59 wt.% of dioctyl sebacate and 16 wt.% of the oil HM46. Depen- dencies were found between the specific rate constants mentioned and the detonation velocities of the PBXs, and consequently between these constants and the impact of pure explosive fillers, i.e., RDX, b-HMX, e-HNIW, RS- e-HNIW, and BCHMX and, at the same time, the corre- sponding PBXs. The results obtained are compared with those from a recent analogous study of PBXs using an SBR (Formex P1) binder which could increase the PBXs’ reactivity in comparison with C4 matrix. These results also help to dispel a widely held view about HNIW being a relatively sensitive explosive. Keywords Plastic explosives Á Sensitivity Á Nitramines Á Vacuum stability test Introduction Following on from the work described in papers [1–3] we continue here the study of plastic bonded explosives (PBXs) by means of the modified Czechoslovak mano- metric method (vacuum stability test) which was developed mainly for studying the thermal stability of propellants [2–4] and which is generally known under the name of STABIL [1–3]. This study is compatible with a recently published analogous paper about PBXs with a Formex P1 matrix as the binder [1] and is to be considered as a con- tinuation of paper [2]. This study is focused on PBXs with a polyisobutylene binder (PIB), softened by dioctyl sebacate (DOS), i.e., with the C4 matrix, whose active fillers are attractive cyclic nitramines BCHMX (cis-1,3,4,6-tetranitro-octahy- droimidazo-[4,5-d]imidazole), RDX (1,3,5-trinitro-1,3,5- triazinane), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), and e-HNIW (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexa- azaisowurtzitane, e-CL-20) [5–8]. These explosives are treated in this paper from the point of view of their behavior under the STABIL measurement conditions. Outputs are compared with detonation velocities of the PBXs studied, with their impact sensitivities, and with the results of an analogous study of the Formex P1 type explosives [1]. Experimental Preparation of plastic bonded explosives The C4 matrix refers to a non-energetic binder containing 25 wt.% of polyisobutylene, 59 wt.% of dioctyl sebacate (DOS), and 16 wt.% of the oil HM46. Preparation of the S. Zeman (&) Á Q.-L. Yan Faculty of Chemical Technology, Institute of Energetic Materials, University of Pardubice, 532 10 Pardubice, Czech Republic e-mail: svatopluk.zeman@upce.cz A. Elbeih Military Technical College, Kobry Elkobbah, Cairo, Egypt 123 J Therm Anal Calorim (2013) 112:1433–1437 DOI 10.1007/s10973-012-2710-y