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

Abstract

When new explosives are synthesized and developed, handling sensitivity must be measured in a consistent way to dictate safety protocols. Drop-weight impact tests, which represent explosive material sensitivity with the drop height required for a sample to react with 50% probability, are the most common method for understanding and quantifying explosive sensitivity. However, results from impact tests are influenced not only by the explosive material tested but also by the testing conditions and experimental setup. Examples of these testing conditions are the laboratory where the test was performed, the methods for choosing drop height levels and computing sensitivity, and whether grit paper was used to promote the initiation of reactions. We compile a historical data set with over 450 impact test results of the explosive standard pentaerythritol tetranitrate (PETN) from 1959 to 2020. We model the sensitivity of PETN as a function of the test laboratory, the test method, and the use of grit paper and find that all have a significant effect on the measured sensitivity of PETN. We validate the predictions from the fitted model with several new impact tests performed at Los Alamos National Laboratory.

Understanding Explosive Sensitivity with Effective Trigger Linkage Kinetics

“…While drop weight impact tests are performed routinely by most laboratories, they involve sub-shock impacts on small amounts of material in a contrived geometry that real explosives are unlikely to experience. Furthermore, the results can exhibit significant variability that depends on site-to-site and operator-to-operator differences in testing protocols and the properties of the explosive. ,− Nevertheless, sub-shock drop weight impact sensitivity is known to be strongly correlated with small-scale gap test shock sensitivity. , …”

Identifying the Molecular Properties that Drive Explosive Sensitivity in a Series of Nitrate Esters

“…In this system of PETN derivatives, the loss of each nitrate ester functional group led to a decrease in the impact sensitivity of the material (i.e., an increase in H 50 ). Consistent with literature data, 6 Solids are designated as (s), and liquids are designated as (l). b The use of "--" indicates that no data is available.…”

“…The drop-weight impact test is the most widely utilized small-scale test to evaluate explosive safety during the initial design stage. Although there is a high degree of variability in the results of the impact test, in practice, general trends in the sensitivity of energetic materials have emerged from large-scale studies. These include the importance of oxygen balance, heat of explosion, and the type of energetic functional group, all of which can be connected to trigger linkage strength and/or explosive performance. − More recently, our group and others have investigated systematic changes to molecular structure, hydrogen and intermolecular bonding, and physical properties in order to modify explosive sensitivity. − Specifically, we have investigated how changes to the PETN backbone correlate with handling sensitivity. ,, …”

Impact and Friction Sensitivities of PETN: I. Sensitivities of the Pure and Wetted Material

“…An intense study by Marrs et al shows that Fallhammer experiments with PETN are reproducible over decades at the same institute, with some deviation. Furthermore, it becomes clear that PETN is excellently suited to evaluate experiments acoustically [24]. There are some materials (e. g. thallium azide) where it is difficult to detect the actual sensitive character via this method [25].…”