  Citation: Kramarczyk, B.; Pytlik, M.; Mertuszka, P.; Jaszcz, K.; Jarosz, T. Novel Sensitizing Agent Formulation for Bulk Emulsion Explosives with Improved Energetic Parameters. Materials 2022, 15, 900. https:// doi.org/10.3390/ma15030900 Academic Editor: Aleksander B. Vorozhtsov Received: 1 December 2021 Accepted: 18 January 2022 Published: 25 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Novel Sensitizing Agent Formulation for Bulk Emulsion Explosives with Improved Energetic Parameters Bartlomiej Kramarczyk 1,2 , Mateusz Pytlik 3 , Piotr Mertuszka 4 , Katarzyna Jaszcz 2 and Tomasz Jarosz 2, * 1 NITROERG S.A., 1 Alfred Nobel Square, 43-150 Bierun, Poland; b.kramarczyk@nitroerg.pl 2 Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, 44-100 Gliwice, Poland; katarzyna.jaszcz@polsl.pl 3 Conformity Assessment Body, Central Mining Institute, 1 Gwarków Square, 40-166 Katowice, Poland; mpytlik@gig.eu 4 KGHM CUPRUM Ltd. Research & Development Centre, 2-8 Sikorskiego Street, 53-659 Wroclaw, Poland; piotr.mertuszka@kghmcuprum.com * Correspondence: tomasz.jarosz@polsl.pl Abstract: Bulk emulsion explosives, although they are very convenient and safe to use, also have disadvantages, with the main one being the relatively low power in relation to cartridged emulsion explosives or classic nitroesters (e.g., dynamites). Therefore, materials of this type currently have only limited use. In addition, these materials are characterized by the variability of blasting parameters over time from loading into the blasthole, which is closely dependent on the utilised mining method of the mine, which makes it difficult to precisely control the fragmentation. The industry is trying to respond to the demand for bulk emulsion explosives with increased energy and improved parameter stability, but so far it has not been possible to do so in a safe and effective way. Methods of improving blasting parameters mainly rely on additives to oxidant solutions during production, which creates additional risks at the production stage, as it involves handling hot and concentrated ammonium ni- trate solutions, for which there are known cases of uncontrolled decomposition of such solutions, even leading to an explosion. This paper presents a method of improving the thermodynamic parameters and the stability of the sensitization reaction without the need for changes in the oxidant solution. Keywords: emulsion explosive; velocity of detonation; ability to perform mechanical work 1. Introduction Emulsion explosives (EEs) are a fairly recently developed and constantly evolving class of energetic materials [1–3] that feature high safety parameters and excellent per- formance benchmarks, comparable in some cases to the performance of dynamites. EEs are obtained by sensitizing an EE matrix—a water-in-oil emulsion of ammonium nitrate— either physically (e.g., with the use of glass microspheres) or chemically (e.g., through tractions, in which gas is released within the entire volume of the matrix), with the two types of processes being used to produce cartridged and bulk EEs, respectively. Regardless of their form of use, the development of EEs with continuously improving properties is a highly-active and multidisciplinary field that attracts significant scientific interest, focused on various aspects of those materials, be it their rheology [4,5], their energetic properties [6,7] or their safety features [8]. Most of the recent developments in the field focus on introducing a variety of additives into the EE formulations [9,10]. In the case of bulk EEs, which are produced in-situ using special mixing and loading units, the possibility of supplementing the EE with powdered raw materials is very limited. This results from the fact that static mixers, which are widely used in mixing-pumping units, are not suited to mixing solid components, with any larger solid aggregates posing the risk of blocking the mixer, making further loading impossible. Consequently, the sensi- tizing agent must be employed in the form of a liquid, so as to provide lubrication of the loading hose. Materials 2022, 15, 900. https://doi.org/10.3390/ma15030900 https://www.mdpi.com/journal/materials