Small‐Scale Detonation of Industrial Urea‐Hydrogen Peroxide (UHP)

Abstract

The adduct of Urea and Hydrogen Peroxide (UHP), also called Carbamide Peroxide, is industrially produced as a solid source of hydrogen peroxide for bleaching, disinfection, and oxidation reactions. As a chemical combination of fuel and oxidiser, UHP has explosive potential but it is unclear whether it could sustain a detonation at small scale. In the configuration we tested, we succeeded in recording self‐sustained detonation at relatively small scale under heavy confinement, measuring a maximum experimental velocity of detonation of 3860 m/s at an optimum 1.1 g/cm3 loading density. UHP can sustain a detonation, even at the 100 g scale, but this is strongly dependant on booster size, confinement material, loading density, charge length and diameter. According to our performance assessment, pure UHP exhibits the behaviour of a non‐ideal tertiary explosive. Maximum calculated detonation pressures are below 10 GPa, the order of magnitude for commercial blasting explosives. Small‐scale results are consistent with literature values from large‐scale experiments, although literature on the matter is quite limited. The proposed experimental method can be used to quantify the detonability and performance of other industrial materials that may have energetic properties, or small samples of homemade explosive compositions, avoiding time‐consuming, expensive and potentially hazardous large‐scale experiments.

Detonation performance of urea‐hydrogen peroxide (UHP)**

“…Complementary lab campaign results are available in Table 2, while theoretical calculations from Explo5 are presented in Table 3. As expected, VoD and indent depth measurements are in excellent agreement with previous measurements [6]. For our reference TNT charges pressed at 1.61 g/cm 3 , we recorded a detonation velocity of 6.90 km/s, a value in very good agreement with the 6.91 km/s predicted from LASL explosive properties data [28] and very close to the theoretical maximum 6.95 km/ s at 1.64 g/cm 3 [7].…”

“…previous work demonstrated UHP detonability at small scale under heavy confinement, providing an initial labscale characterisation of detonation performance parameters, including velocity of detonation (VoD) records consistent with literature values from large-scale experiments [6]. UHP charges non-ideality was further studied by VoD dependence on charge diameter and confinement [7], a behaviour typically observed for charge diameters in the 10 cm range with explosives detonating at a lower regime, such as ANFO explosives, and particularly emphasised by recent research at small-scale [8,9].…”

“…slightly compacted by vibration to achieve more uniform loading and homogeneity. The VoD setup [6] was duplicated (Figure 2) and included a total of 16 optical fibre probes, divided in two rows of 8 probes, with 7.5 mm between probes, and the first probe of each row located 90 mm (3×ID) from the booster charge. The setup was also slightly adapted in an attempt to capture improved signals by reducing the thickness of confinement material between the optical probes and the energetic material under investigation, while avoiding any early triggering from the light preceding the detonation wave due to translucency of the explosive.…”

“…A 1D Euler multi‐material model was used, representing a spherical geometry. For UHP, the JWL parameters previously calculated with Explo5 [6] were fed into Autodyn. Models from Autodyn's standard library were used for C4 and water.…”

“…The standard enthalpy of formation of UHP was calculated from calorimetric measurements and we used the thermodynamic code Explo5 (V6.06.02) to determine UHP ideal detonation parameters. Following our previous work [6], the theoretically based equation of state (EoS) molecular fluid EXP-6 was selected to calculate UHP VoD and detonation pressure (P det ), together with its Jones-Wilkins-Lee (JWL) coefficients, required for further modelling of our experimental firing setups in Ansys Autodyn V14.0. For comparison purposes, we also calculated VoD and P det , using the Modified Becker-Kistiakowski-Wilson (M-BKW) EoS, as this equation of state is known to lead to a better accuracy when dealing with explosives showing a high dipolar molecules content in the detonation products and a low detonation temperature [18].…”