Laser-Induced Dissociation of an Energetic Polymer:  A Spectroscopic Study of the Gaseous Products

Abstract

Previous studies of GAP (glycidyl azido polymer) laser-induced decomposition (Propellants, Explosives, Pyrotechnics 1996, 21, 258), revealed that the shock wave produced from a diluted polymer is more energetic than from the neat polymer. In this paper, direct measurement of the energy disposal into molecular products is reported using spectroscopic methods. Chemiluminescence probes electronically excited species, and laser-induced fluorescence, ground-state radicals. It is found that the initial velocity and internal energy content of small diatomic molecules is larger in some diluted polymers than in the neat one. This finding is in line with a simple model based on the assumption of a self-sustained reaction following initial laser excitation.

Influence of exothermic chemical reactions on laser-induced shock waves

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15] However, a few studies found that a laser ablated energetic polymer (glycidyl azide polymer [GAP]) produced a faster shock wave than nonenergetic polymers. [16][17][18][19] The increased shock wave velocity was attributed to the higher decomposition enthalpy of GAP; the pulsed laser initiated a self-sustaining exothermic reaction resulting in rapid formation of gaseous products. More recently, Roy et al 20 measured spatially and temporally resolved temperatures behind an expanding laser-induced shock wave to demonstrate differences in energy release between reacting aluminum nanoparticle formulations.…”

Determination of propellant products by time resolved and spatial distribution LIPS combined with high-speed schlieren imaging

“…1,2 Besides, the composition of energetic materials can be better adjusted to improve the detonation performance by determining the compositions of the detonation products. Since the reaction time of the internal components of energetic materials during detonation is very fast, 1,3,4 it is difficult to detect the detonation products of energetic materials, and in particular the timing sequence of the products, using the conventional measurement method. The conventional methods 5 of detecting detonation products mainly include mass spectrometry (MS), 6,7 laser induced plasma spectroscopy (LIPS), 8 Fourier transform infrared spectroscopy (FTIR), 9 ultraviolet-visible (UV-vis) spectroscopy, 10 laser-induced uorescence (LIF) 3,11,12 and multiple methods combined.…”

“…Since the reaction time of the internal components of energetic materials during detonation is very fast, 1,3,4 it is difficult to detect the detonation products of energetic materials, and in particular the timing sequence of the products, using the conventional measurement method. The conventional methods 5 of detecting detonation products mainly include mass spectrometry (MS), 6,7 laser induced plasma spectroscopy (LIPS), 8 Fourier transform infrared spectroscopy (FTIR), 9 ultraviolet-visible (UV-vis) spectroscopy, 10 laser-induced uorescence (LIF) 3,11,12 and multiple methods combined. 13,14 Generally, multiple methods are usually utilized jointly to detect more products, since a single detection method can only determine some specic products.…”

“…They found the emission spectra of the plumes for PET and polyimide are characterized by strong CN and C 2 emission molecule bands, and the emission is related to the formation of the shock wave. L. Belau et al 3 used the real time method of chemiluminescence and laser-induced fluorescence (LIF) to probe the formation of gaseous products in the UV laser ablation of GAP. These methods can measure the appearance time of some molecules, such as CN, OH, C 2 , CH and NH.…”