PREIGNITION DYNAMICS OF RDX-BASED ENERGETIC MATERIALS UNDER CO2-LASERHEATING

The preignition dynamics of a series of RDX-based energetic materials were investigated experimentally using a high-power CO2 laser ignition system. The materials tested were three formulations of RDX mixed wit h GAP binder and the energetic plasticizers TMETN or BTTN. All ignitio n tests were conducted at one atmosphere with varied amounts of ambien t oxygen. The delay time based upon the onset of light emission (t(LE) ) decreased monotonically with the increase of incident laser energy f lux (q''). In general, the slope of the t(LE) versus q'' log-log plot became less steep as the oxygen concentration in the ambient gas was i ncreased. This effect was more pronounced for the samples containing e nergetic plasticizers. For most test conditions, the initial appearanc e of luminous emission occurred in the gas phase above the sample surf ace; this implies that gas-phase reactions play an important role in t he initial phase of laser-induced ignition of RDX-based energetic mate rials. Chemical analysis of gaseous products generated from the pyroly sis and ignition processes was conducted using a gas chromatograph and a GC/MSD (mass selective detector). Five different gas-phase zones we re observed during the ignition interval: a primary reaction zone clos e to the sample surface, the first preparation zone, a secondary react ion zone, the second preparation zone, and the final luminous flame zo ne. Gas analysis showed that the products of the secondary reaction zo ne were NO, N2O, C2N2, and HCN. These intermediate species were consum ed in the final flame when the luminous flame was present.