The Role of Pentaerythritol Tetranitrate (PETN) Aging in Determining Detonator Firing Characteristics

Abstract

Pentaerythritol tetranitrate (PETN) is one of the most commonly used explosives for both military and mining applications. PETN is used in EBW (exploding bridge wire) and EFI (exploding foil initiator) detonator devices. Due the widespread usage of PETN, studies focusing on how the explosive changes with age, primarily its function in detonators has received particular interest. Aging studies have identified several factors that affect PETN detonator function over time, most notably the specific surface area of the explosive powder. Though small-scale studies have been performed on specific detonator systems with isolated batches of material, what is missing is a large statistically-significant study focusing on PETN aging characteristics-such as powder coarsening-and their influence on detonator performance. Herein we report the first large statistically viable PETN aging study focusing on four batches of PETN powder from the same stock of PETN using two stabilizers, polysaccharide and TriPEON. PETN was aged both as a free-flowing powder as well as in modified EBW RP-2 detonators, for one month at 75°C. The PETN powder has been analyzed chemically using Fisher specific surface area analysis, SEM imaging and light scattering particle size analysis. Additionally the detonators were tested for performance through voltage-sweep threshold testing and function time measurements. Findings from the study indicate that aging at 75°C for one month significantly changes the specific surface area and particle size of unstabilized PETN, leading to increases in detonator function time, but not detonator threshold values. Powders stabilized with TriPEON displayed less significant increases in function time, while powder stabilized with polysaccharide exhibited no aging effects, despite the high temperature aging.

Sources of Variation in Drop-Weight Impact Sensitivity Testing of the Explosive Pentaerythritol Tetranitrate

“…It was analyzed to contain 17.98% nitrogen, with a surface area of 815 cm 2 /g (Quantasorb). PETN-2 is a recently prepared small batch of fine-grain PETN used in detonators . The scanning electron microscope images of each batch at two magnifications are shown in Figure .…”

“…PETN-2 is a recently prepared small batch of fine-grain PETN used in detonators. 24 The scanning electron microscope images of each batch at two magnifications are shown in Figure 2. PETN-1 has an average particle size of 331.7 μm, while the average particle size for PETN-2 is 26.08 μm.…”

Chemical Evaluation and Performance Characterization of Pentaerythritol Tetranitrate (PETN) under Melt Conditions

“…Although liquid nitrate esters generally exhibit good performance characteristics, to our knowledge, PETN detonability has not been well-established under melt conditions, mostly due to the fact that the melt for PETN is very close to the onset of decomposition. In detonator systems, particle morphology heavily influences detonation characteristics, , so the majority of studies focus on small variations in particle size rather than significant changes due to phase. In order to determine if PETN could detonate in the molten state, it was heated to the melt and tested for performance several times in a commercial detonator configuration.…”

“…The degradation of PETN has been studied extensively, , with detailed investigations on decomposition by acid, metal oxides, , impurities, and radiation − and biological, , explosive, and thermal − insults. The O–NO 2 bond in the nitrate ester of PETN is the weakest in the molecule, and it is generally accepted that this bond is the first to break during both slow decomposition − and fast decomposition found in detonations .…”

“…We also estimate the amount of decomposition relative to sublimation that we measure through gas evolution. As there has been recent interest in the performance of thermally damaged detonators, ,, we also characterize the performance through firing behavior of the molten PETN in commercial detonators. This is a critically important area of study as it influences the handling safety for detonators and other explosive systems which have been thermally compromised and will impact future safety qualifications.…”