Thermo-analytical study of glycidyl azide polymer and its effect on different cyclic nitramines

Abstract

In this work, glycidyl azide polymer (GAP) has been prepared and studied. In addition, a series of different plastic bonded explosive (PBXs) based on GAP were prepared using five cyclic nitramines, namely. 1,3,5-trinitro-1,3,5-triazinane (RDX) and β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (β-HMX), cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), RS-ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (RS-ε-CL-20) and 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurtzitane (TEX). The thermal behavior and decomposition kinetics have been investigated by means of the nonisothermal TG and DSC techniques and the decomposition kinetics were obtained by the isoconversional methods (Kissinger and modified Kissinger-Akahira-Sunose (KAS) methods). It was indicated that GAP has a significant effect on the activation energy distribution for the thermal decomposition of cyclic nitramines and it motivates the initial autocatalysis effect of RDX and CL-20. The mean activation energies of the thermal decomposition were reduced comparing with the individual nitramines, and their values are 187.7, 191.6, 110.7, 118.5, 283.8, 146.1, and 171.6 kJ.mol-1 for BCHMX/GAP, CL-20/GAP, RDX/GAP, HMX/GAP peak 1, HMX/GAP peak 2, TEX/GAP and GAP respectively. The GAP admixture changes an inversely proportional linear relationship between the mentioned energies and longest lengths of the N-N bonds in nitramine molecules into a directly proportional one for the nitramines in the GAP-PBXs due to the possibility of the GAP complex formation with the studied nitramines. The results show that BCHMX/GAP has a good thermal stability reached the same level of TEX/GAP while the thermal stability of RDX/GAP considered the lowest value of all the studied PBXs.