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

Abstract

Carbamide Peroxide, an adduct of Urea and Hydrogen Peroxide, is commonly used in the cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. However, it exhibits explosive properties and can be easily manufactured from readily available household chemicals, making it a potential emerging threat. We carried out a detailed performance assessment, combining experiments, thermochemical calculations and numerical simulations and highlighted a good level of agreement between experimental data from lab, field and underwater firings. A maximum detonation velocity of 3.65 km/s was recorded for unconfined 25 kg UHP charges at 0.85 g/cm 3 (200 mm charge diameter). We determined in these conditions an infinite diameter detonation velocity of 3.94 km/s. These results are also consistent with previous results obtained at small scale under heavy confinement. Airblast measurements highlighted an average 40 % TNT equivalence for impulse and 55 % for peak overpressure at short distance, which are in good agreement with the 57 % (Power Index) calculated from Explo5, while 50 % for bubble energy (explosive power) and 20 % for shock pressure (brisance) were obtained from underwater experiments. The use of different experimental approaches has proven useful to characterise the performances parameters of a non-ideal explosive for risk assessment purposes. K E Y W O R D Sdetonation, non ideal explosive, performance, urea hydrogen peroxide | INTRODUCTIONCarbamide Peroxide or Urea Hydrogen Peroxide (UHP) is commonly used in the dental, cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. This adduct can also be easily manufactured from readily available household chemicals. Like other oxidisers such as ammonium perchlorate [1] or ammonium nitrate [2], UHP exhibits explosive properties [3,4] and could represent a potential emerging threat. Determining UHP detonation performance parameters is hence important for safety purposes.Because there is a need to predict large-scale explosive behaviour from small-scale experiments [5], our

Urea‐Hydrogen Peroxide (UHP): Comparative study on the experimental detonation pressure of a non‐ideal explosive

“…In this study, we selected a charge diameter of 120 mm, a trade-off between the impact of the diameter on the performance characterisation and the practical charge size. In this charge diameter (PVC casing, 2.5 mm thick), we previously recorded an average VoD of 3.520 km/s for unconfined UHP, about 90 % of the VoD extrapolated at infinite charge diameter from our experimental data [6]. We fired 10 cylindrical charges (two shots for each acceptor) containing approximately 5 kg UHP (L = 5xD, ρ = 0.87 g/cm 3 , 60.8% TMD) and initiated by a bespoke moulded conical 350 g C4 booster (Figure 2, top left) and a standard N°8 military detonator.…”

“…As the polytropic exponent describes the rate of pressure release along the detonation isentrope [31], the difference between experimental and calculated Γ value from Explo5 suggests that the predicted isentrope shape, especially in the low pressure region, using the ideal model does not adequately model the detonation product expansion. This limited accuracy could be explained by the low detonation temperature (1500 K) and the specific detonation products of UHP, particularly a rather high water content (triatomic polar molecule), when compared to conventional CHNO explosives, such as TNT [6]. Improvement of the modelling of non-ideal detonation should include kinetics of reaction in the chemical reaction zone and radial expansion of the products [30], which would however considerably increase the complexity of the study.…”

“…Using the standard enthalpy of formation of UHP calculated from calorimetric measurements, thermochemical calculations were carried out with the Explo5 code (V6.06.02) [19]. We initially used the theoretically based equation of state (EoS) molecular fluid EXP-6 [20], which predicted lower detonation pressures and enabled the determination of the Jones-Wilkins-Lee (JWL) coefficients required for the numerical modelling in Ansys Autodyn [5][6]. However, for comparison purposes, we also performed the calculations with the Modified Becker-Kistiakowski-Wilson (M-BKW) EoS, as this equation of state provides greater accuracy for explosives with a low detonation temperature and a high dipolar molecules content in the detonation products [21].…”

“…Matyas investigated UHP sensitivity, thermal properties and detonability at large scale [4], while preliminary work from the authors demonstrated UHP detonability at small scale and highlighted UHP charges non-ideality by Velocity of Detonation (VoD) dependence on charge diameter and confinement. Additionally, UHP relative explosive strength was further assessed from experimental underwater bubble energy and airblast parameters (long distance blast wave) measurements [5][6].…”

“…Examples of standardised tests [7][8] available to assess the relative brisance of explosives include the Hess test, evaluating the compression of a lead cylinder, the Kast's method, using a copper crusher or the plate-denting test [9]. The latter has proven effective to correlate the indentation of a witness plate with the experimentally determined detonation pressure of conventional military explosives but extrapolation to a material such as UHP might be questionable taking into account (major) differences in detonation products composition, particularly water content, and very low detonation temperature [6]. Considering the non-ideal behaviour of UHP, it was decided to quantify the brisance of UHP through its predominant parameter, the detonation pressure (P det ) [8][9], as illustrated in Figure 1.…”