Chapter 1 - Overview of energetic materials

The Future of Synthesis Chemistry in Energetics

Radio transmission, radar, electric welding, cathodic protection, and electric generators, motors and their connections can create an unsafe environment for certain operations using explosives. Transporting and arming electrically initiated explosive perforating devices in this environment can be hazardous. A premature detonation can occur if correct procedures are not followed. The procedures required to prevent premature detonation often include the interruption of radio and microwave transmission, welding operations and cathodic protection systems. These shutdowns are costly and cause operational and logistical difficulties and may pose new safety problems. This problem is especially acute when operating offshore or in highly congested urban areas. The paper briefly reviews perforating equipment and operations and identifies the potential hazards of transporting and arming explosive devices in the previously described environment. The present safety procedures and equipment are discussed, along with a detailed analysis of the problems and the procedures used to allow limited radio silence. A new method of initiating perforating guns is described that is based on the principle of a foil, subjected to a large electric power burst, slapping a secondary explosive and a safe and arm system that totally eliminates the need for radio silence. Electric welding, cathodic protection and other electric equipment can also be operated without interruption. SECTION 1 - RADIO AND ELECTRIC POWER INSTALLATIONS AFFECTING PERFORATING

Diffraction and transmission of a detonation into a bounding explosive layer

Explosives and propellants are chemical compounds that undergo chemical decomposition reactions at very fast speeds, producing gaseous products and a great deal of heat. In some circumstances a blast wave can be produced. The information provided here gives an introduction to this process covering the theory of detonation and deflagration. Explosives can be divided into three classes: (i) primary explosives, (ii) secondary explosives, and (iii) propellants. The behavior and performance of these three classes of explosives is discussed. Physical and chemical data on primary and secondary explosives are given together with details of new high temperature explosives. Last, future developments in explosives technology are presented with regard to enhancing the performance, insensitive high explosives, and explosives and the environment.

Explosives and propellants are chemical compounds that undergo chemical decomposition reactions at very fast speeds, producing gaseous products, and a great deal of heat. In some circumstances a blast wave can be produced. The information provided here gives an introduction to this process covering the theory of detonation and deflagration. Explosives can be divided into three classes, (1) primary explosives, (2) secondary explosives, and (3) propellants. The behavior and performance of these three classes of explosives is discussed. Physical and chemical data on primary and secondary explosives is given together with details of new high temperature explosives. Lastly future developments in explosives technology are presented with regards to enhancing the performance, insensitive munitions and demilitarization.

Primary explosives, unlike secondary explosives, show a very rapid transition from combustion (or deflagration) to detonation and are considerably sensitive to small stimuli, such as impact, friction, electrostatic discharge, and heat. Primary explosives generate either a large amount of heat or a shockwave, which makes the transfer of the detonation to a less sensitive propellant or secondary explosive possible.1 Primary explosives are key components in detonators and primers, which are the initiating elements to many military items such as small, medium, and large caliber munitions, mortars, artillery, warheads, etc. The two most common military primary explosives are lead azide and lead styphnate. Lead based compounds such as these have well‐established hazards to health and the environment. To overcome these concerns, in common U.S. Army detonators and primers lead azide was replaced with DBX‐1 [copper(I) nitrotetrazolate], recently developed by Pacific Scientific Energetic Materials Company and the U.S. Naval Surface Warfare Center at Indian Head. Further, in order to minimize the dangers to personnel and equipment associated with synthesizing and handling primary explosives, a dedicated, remote‐operated facility for the synthesis and testing of primary explosives has been developed.

The main requirements for primary explosives are sensitivity within useful limits, high initiating efficiency, reasonable fluidity, resistance to dead-pressing, and long-term stability. Useful limits mean that the substance must be sensitive enough to be initiated by an SII but not too sensitive as to be unsafe for handling or transportation. The initiating efficiency, perhaps the most important parameter, determines the ability of a primary explosive to initiate secondary explosives. The reasonable free flowing properties are important for manufacturing where the primary explosives are often loaded volumetrically. Primary explosives must not undergo desensitization when pressed thereby yielding a dead-pressed product. The long-term stability and compatibility with other components, even at elevated temperatures, are essential because primary explosives are often embedded inside more complex ammunition and are not expected to be replaced during their service life. They must also be insensitive to moisture and atmospheric carbon dioxide. Parameters important for secondary explosives such as brisance, strength, detonation velocity, or pressure are of lesser importance to primary explosives although they are of course related to the above properties.

The main focus of this chapter is on the chemical data of primary and secondary explosives. For this 4th edition the data has been up-dated using recent publications and databases. For primary explosives the chemical data on mercury fulminate, lead styphnate, tetrazene, lead and silver azide is presented and for secondary explosives the chemical data is given for nitroglycerine, nitrocellulose, picric acid, tetryl, TNT, nitroguandine, PETN, RDX and HMX, TATB, HNS, NTO, TNAZ, CL-20, FOX-7 and FOX-12, DNAN, LLM-105, DAF, DAAF, ADN, HNF, DNAZ-DN, TATP and HMTD. Chemical data on ammonium nitrate is also included. The classification of explosives is also introduced together with comparisons between primary and secondary explosives, and propellants.

This paper reviews the ballistic properties, stability and vulnerability of gun propellants, gas generators and rocket propellants containing nitroguanidine (NGu), CAS−No [556‐88‐7] as an energetic filler. Nitroguanidine and its formulations burn stable over a broad pressure regime extending from subatmospheric to high pressures (0.1 kPa–400 MPa). Its high nitrogen content (53.83 %) and oxygen balance (Ω=‐30.75 %) effects a high gas pressure in gun propellants combined with low explosion temperature and consequently low signature and reduced erosion. NGu is an effective stabilizer for a broad array of energetic materials encountered in gun and rocket propellants including AP, ADN, HMX, RDX, NGl and also materials with low thermal stability such as NC, HNF, TNAZ and ADN. Finally, the low vulnerability of NGu‐based propellant formulations makes them taylor made to serve insensitive munitions. This review covers 31 NGu‐based rocket and gas generating propellant formulations, 44 gun propellants, five of which contain guanylurea dinitramide, (GuDN, FOX‐12), CAS−No [217464‐38‐5] for comparison, four reference propellants containing neither of the aforementioned ingredients and six combustible cartridge case formulations based on NGu. In addition, the combustion properties of pure NGu, pure GUDN and NGu modified with 17 different catalysts are revised. The review contains 142 references from the public domain.

The scientific community has an urgent need to develop accurate and rapid methods necessary for the solution of national and international problems for the detection and identification of chemical substances, which by anthropogenic uses that are malicious can have an adverse effect on living beings and public - private property in general. These substances of interest can be highly energetic materials such as explosives. A system for detecting explosives (2,4,6-trinitrotoluene (TNT), aliphatic nitrates such as pentaerythritol tetranitrate (PETN), and aliphatic nitramines such as cyclotrimethylentrinitramine (RDX)) based on infrared spectroscopy (IRS) was used to record spectral signals in the middle infrared of highly energetic materials deposited on suitcases of trip, cardboard and wood. Detection of gaseous TATP using IRS by quantum cascade laser (QCL) and 2.4 DNT using TLC-QCL were also carried out. Infrared vibrational spectra of explosives were acquired using quantum cascade laser spectroscopy. Spectral similarities in a multivariate dataset allowed the identification of explosives using two chemometrics algorithms: Principal Component Analysis (PCA) and Partial Least Squares (PLS-DA) Discriminant Analysis. The results show that the infrared vibrational technique used in this study may be useful for the detection of primary and secondary explosives in the types of real world substrates studied.

Hazard initiation in solid rocket and gun propellants and explosives

Professor Dr. Thomas M. Klapötke

Zwitterionic compounds are an emergent class of energetic materials and have gained synthetic interest of many in the recent years. Due to their better packing efficiencies and strong inter/intramolecular electrostatic interactions, they often ensue superior energetic properties than their salt analogues. A systematic review from the perspective of design, synthesis, and physicochemical properties evaluation of the zwitterionic energetic materials is presented. Depending on the parent ring(s) used for the synthesis and the type of moieties bearing positive and negative charges, different classes of energetic materials, such as primary explosives, secondary explosives, heat resistant explosives, oxidizers, etc., may result. The properties of some of the energetic zwitterionic compounds are also compared with analogous energetic salts. This review will encourage readers to explore the possibility of designing new zwitterionic energetic materials.

Safety improvements in the field of energetic materials promoted the development of insensitive gun propellants. A low sensitive gun propellant was prepared by traditional extrusion using nitrocellulose (NC) as a binder, 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) as insensitive solid energetic filler, N‐butyl‐N‐nitramine (Bu‐NENA) as insensitive plasticizer, trimethylolethane trinitrate (TMETN) as co‐plasticizer, and graphite as thermal conductive filler. The density of gun propellants obtained was 1.611 g ⋅ cm−3 which was almost equaled to the theoretical density of 1.615 g ⋅ cm−3. The gun propellants exhibited excellent mechanical properties, especially cryogenic mechanical property, with the impact strength of 12.4 kJ ⋅ m−2 and the compressive strength of 157.1 MPa at −40 °C. The closed bomb test was conducted to investigate the energy and combustion performance. The results showed that the gun propellants had stable and regular combustion properties at a pressure up to 600 MPa. The burning rate pressure index n was about 1, and the impetus f and covolume α were 1045 kJ ⋅ kg−1 and 0.9764 cm3 ⋅ g−1 respectively. The vulnerabilities of the prepared gun propellants were evaluated by bullet impact, fragment impacts, sympathetic detonation, fast cook‐off, and slow cook‐off tests. The results showed that no response that was more severe than burning in test bombs was observed in bullet impact, fast cook‐off, and slow cook‐off tests under the given conditions. Moreover, a partially combustion reaction occurred in the fragment impact test with no obvious burning reaction in the sympathetic detonation test. It demonstrates that the prepared gun propellants possess good low vulnerability characteristics.

This paper describes an experimental study of the initiation of solid explosives, and in particular the effect of artificially introducing transient hot spots of known maximum temperature. This was done by adding small foreign particles (or grit) of known melting-point. The minimum transient hot-spot temperature for the initiation of a number of secondary and primary explosives has been determined in this way. It is shown that the melting-point of the grit is the determining factor , and all the grits which sensitize these explosives to initiation either by friction or impact have melting-points above a threshold value which lies between 400 and 550 ° C. Grit particles of lower melting-point do not sensitize the explosives. The same explosives initiated by the adiabatic compression of air required, for initiation, minimum transient temperatures of the same order as the threshold melting-point values. The results provide strong evidence that the initiation of solids as well as of liquids by friction and impact is thermal in origin and is due to the formation of localized hot spots. There is evidence that in the case of the majority of secondary explosives which melt at comparatively low temperatures, intergranular friction is not able to cause explosion and the hot spots must be formed in some other way. With the primary explosives which explode at temperatures below their melting-points, hot spots formed by intergranular friction can be important.