Thermochimica Acta 566 (2013) 137–148 Contents lists available at SciVerse ScienceDirect Thermochimica Acta jo ur nal ho me page: www.elsevier.com/locate/tca The effect of molecular structure on thermal stability, decomposition kinetics and reaction models of nitric esters Qi-Long Yan a , Martin Künzel a , Svatopluk Zeman a,∗ , Roman Svoboda b , Monika Bartoˇ sková c a Institute of Energetic Materials, Faculty of Chemical Technology, University of Pardubice, 53210 Pardubice, Czech Republic b Department of Physical Chemistry, Faculty of Chemical Technology, University of Pardubice, 53210 Pardubice, Czech Republic c Department of Environment, Faculty of Chemistry, Brno University of Technology, CZ-612 00, Brno, Czech Republic a r t i c l e i n f o Article history: Received 8 March 2013 Received in revised form 21 May 2013 Accepted 22 May 2013 Available online xxx Keywords: Nitric esters Thermal stability Critical temperature Reaction models Kinetic compensation effect a b s t r a c t In this paper, the thermal stability and decomposition mechanism functions of 10 nitric esters including nitroglycerine (NG), pentaerythritol tetranitrate (PETN), trimethylolethane trinitrate (TMETN), dipen- taerythritol hexanitrate (DiPEHN), trimethylolpropane trinitrate (TMPTN), erythritol tetranitrate (ETN), xylitol pentanitrate (XPN), sorbitol hexanitrate (SHN), mannitol hexanitrate (MHN) and nitroisobutyl- glycerol trinitrate (NIBGT) are determined by means of non-isothermal TG and DSC techniques. It has been found that the mean activation energies for most nitric esters are comparable at constant heating rate (around 145 kJ mol -1 ), indicating that their main decomposition pathways might be the same. The mass loss activation energies of NG, TMETN and TMPTN are less than 100 kJ mol -1 due to partial evap- oration. Based on the critical temperature of thermal decomposition, the order of molecular stability for involved nitric esters is found to be MHN < XPN < TMPTN < SHN < NIBGT < ETN < PETN < DiPEHN. The introduction of function groups to the tertiary carbon is in favor of increasing thermal stability due to increase of symmetry and rigidity of the molecule. The decomposition kinetics was described in terms of the Johnson-Mehl-Avrami and ˇ Sesták-Berggren models. Two types of kinetic behavior were observed and most nitrate esters followed typical decomposition kinetics close to the first order reaction. However, cer- tain materials showed complex behavior caused by overlapping of more mechanisms/processes, which were represented either by simultaneous evaporation and decomposition or by different decomposition mechanisms originating from varying morphology and structure of the samples. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Nitric esters have been used as plasticizers or energetic fillers in detonators, propellants and explosives for mining, artillery, and engineering since hundreds years ago [1,2]. In the past decades, considerable interest in nitric esters has been expressed by not only the specialists but also the amateurs and terrorists due to require- ments of little synthetic expertise and availability of cheap raw materials from the shops [3]. There has been growth in use of those nitric esters such as erythritol tetranitrate (ETN), most of which are so-called “homemade” explosives (HME). On the one hand, a num- ber of polynitroesters, including nitrocellulose (NC), nitroglycerin (NG), the nitroester of pentaerythritol (PETN), trimethanolethane trinitrate (TMETN), and bis(2-nitroxyethyl)nitramine (DINA) are ∗ Corresponding author. Tel.: +420 466038503; fax: +420 466038024. E-mail addresses: terry.well@163.com (Q.-L. Yan), svatopluk.zeman@upce.cz, svatopluk.zeman@quick.cz (S. Zeman). powerful explosives used mainly for military purposes due to greater compatibility and higher performance than other nitric esters [4–7]. In particular, with regard to spark detonators, PETN can be used to avoid the need for primary explosives due to its lower electric spark initiation energy (10–60 mJ). On the other hand, some nitric esters could be used as drugs in medical treatment. In fact, nitroester drugs have been shown to relax the smooth muscle of blood vessels, and hence were widely accepted for the treatment of angina pectoris [8]. Because of growing practical demands on nitric esters, more and more investigations are carried out with regard to their synthe- sis and physiochemical properties. On the purpose of utilization as energetic ingredients, recent studies have been concentrated mainly on their detailed thermal decomposition mechanisms, com- bustion and detonation performances [9–11]. For instance, density function theory (DFT) has been employed to study the geometric and electronic structures of trinitrate esters including NG, TMETN, butanetriol trinitrate (BTTN), and trimethylolpropane trinitrate (TMPTN) at the B3LYP/6-31G* level [12]. It has been found that 0040-6031/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tca.2013.05.032