The influence of migration processes in gunpowder charge on the quality of mortar ammunition Nikola R. Bobić1, Radovan S. Simonović2, Saša Ž. Drmanić3, Stefan Z. Milić3, Jasmina B. Nikolić3, Slaviša D. Stoiljković4, Nebojša S. Terzić5 1Department for Defense Technologies, Ministry of Defense of the Republic of Serbia, Belgrade, Serbia 2Military Technical Institute, Belgrade, Serbia 3Department of Organic Chemistry, Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia 4The Institute for Technical Repair, Kragujevac, Serbia 5Factory „Krušik“, Valjevo, Serbia Abstract The study describes the results of static, physicochemical and ballistic examination of SCIENTIFIC PAPER double-based gunpowder charges, in order to establish the deviations from the demanded quality of mortar ammunition. The examinations were carried out on gunpowder samples UDC 623.451.5:623.5:54 used for laboration of mortar shells 60, 82 and 120 mm caliber and consisted of periodical measurements of the gunpowder mass loss, basic ballistic parameters, and compatibility testing of gunpowder and celluloid containers as well as chemical stability determination. Hem. Ind. 71 (3) 231–240 (2017) The estimation of the gunpowder quality was performed by comparative analysis and the suggestions for more efficient production of it were given. Keywords: mortar shells, gunpowder, nitroglycerine, migration, ballistite, ballistic stability, chemical stability. Available online at the Journal website: http://www.ache.org.rs/HI/ Up-to-date standards for ammunition are rather Terms of production, storage and manipulation of strict, considering the efficiency and the final effect. In ammunition and ammunition elements order to obtain the desired quality and the minimal Ammunition and its elements, such as gunpowder, accident risk, the safe and reliable ammunition for the are produced by the strict technological procedures given time limit should be produced. Due to the variety and with a defined formal quality, for each product, in of the ammunition components, it is necessary to the Defense Industry of Serbia. The applied standards constantly monitor the quality state, during storage precisely define the sort and properties of the material and immediately before use. for ammunition elements and also for packaging. The Every ammunition component (electric, energetic, initial chemical composition and mass portions are electronic, etc.) can harm the projected function of the defined for gunpowders, as well as the demands which round or make it unsafe for further use and keeping. have to be fulfilled in physicochemical and ballistic The energetic components, gunpowder first of all, are investigations. susceptible to change with time and they influence the The ammunition and ammunition elements storage, other components present [1–7]. In order to avoid the manipulation and transport are also defined by rules negative influence it is important to analyze the com- and instructions of the Ministry of Defense and the patibility aspect of used materials with the aim of a Serbian Army, and partly or completely in accordance product, considering the material aging. It is practically with known international standards. impossible to determine the ammunition duration by prediction of the process of components aging, so the Degradation of ballistic characteristics of mortar material quality parameters have to be monitored ammunition often in order estimate the safety and efficiency of The decrease of the muzzle velocity of the labor- ammunition [2]. Determination of the ammunition ated series of ammunition is noticed even in initial components state is performed by various ballistic, polygon testing, if the ammunition was stored for more physic-chemical and statistic examinations. than 6 months [3]. Based on experience and knowledge in the field, it is supposed that the first cause of this is Correspondence: J.B. Nikolić, Department of Organic Chemistry, the loss of ammunition mass induced by the evapor- Faculty of Technology and Metallurgy, University of Belgrade, Bel- ation of nitroglycerine and the degradation of nitro- grade, Serbia. E-mail: [email protected] cellulose [8,9]. Paper received: 19 April, 2016 Nitroglycerine is a strong brisant explosive, color- Paper accepted: 14 July, 2016 less, oily, with high contents of nitrogen (18.5%), very https://doi.org/10.2298/HEMIND160414033B sensitive to impact and heat. It is produced by the 231 N.R. BOBIĆ et al.: QUALITY OF MORTAR AMMUNITION Hem. ind. 71 (3) 231–240 (2017) nitration of glycerin by sulphuric and nitric acid (both • Static examinations of increment charges from 96%), in a ratio 45–50% nitric and 50–55% sulphuric serially produced mines; acid. Combined with nitrocellulose, it is used for the • Laboration of new increment charges for longer production of dibasic gunpowder charges. It forms storage; weak bonds with nitrocellulose, so it is mobile and can • Physicochemical examinations of etalons of gun- easily penetrate to the gunpowder surface. powder charges, gunpowder charges from stored The physical and thermodynamic characteristics of mines and gunpowder charges that have already been nitroglycerin are given in Table 1. stored for 3 and 6 months; • Compatibility examinations for gunpowder and Table 1. Physicochemical properties of nitroglycerin celluloid containers; • Chemical formula C H (NO ) Ballistic examinations of serial ammunition and 3 5 3 3 the ammunition stored in original hermetically closed Molecular mass 227,1 g/mol packages; Density 1,591 g/cm3 • The mortar stand vibration measurements on Solubility Slightly soluble in water, soft and hard surface; soluble in organic solvents • The measurements of pressure gunpowder gas Sensitivity to friction and impact Very high in gunpowder chamber. ° Decomposition temperature 50–60 C The ammunition, gunpowder samples and package Vaporization point 250 °C preparation, as well as other static examination were Detonation point 218 °C carried out in the corresponding industrial plants in the republic of Serbia. The ballistic and vibration examin- The “Krušik” Company (Valjevo, Serbia), which ations were performed in the Technical Test Center, belongs to the group of the Defense Industry of Serbia while the physicochemical examinations were carried is the ammunition manufacturer with long-term expe- out in The Military Technical Institute and the Technical rience and worldly acknowledged results. “Milan Blago- Overhaul Works in Kragujevac, Serbia [3]. jević Industry” (Lucani, Serbia) is also a reliable long- The examinations were carried out on gunpowder -term gunpowder and rocket fuel manufacturer. Their samples given in Table 2 [10–12]. products are laborated into all sorts of conventional For gunpowders A, B and D two samples of each of ammunition throughout the world. different age and of different laborated mass. The usual change of ballistic properties has caused Table 3 displays the chemical composition of each the need for realization of complex testing in order to sample. confirm the assumption or find another reason for All the gunpowder specimens are prepared in cellu- degradation. Based on obtained results, it is necessary loid containers, which represent the primary packaging to take the specific steps to prevent the quality dec- for additional gunpowder charges. rease. Mortar increment propellant container manufac- tured of foamed celluloid, which is composed of 50 to EXPERIMENTAL 84% nitrocellulose, having nitrogen content of from about 10.5 to about 13.5%, and about 15 to about 50% Examination program, sample preparation of camphor. The burn rate of the foamed celluloid can be gunpowder, ammunition and package enhanced by the addition of energetic additives, such The examination program, in accordance with the as energetic plasticizers. The containers are manufac- producer of gunpowder and mortar shells is created by tured from celluloid nitrate sheet with a thickness of The Military Technical Institute of the Ministry of Def- 0.13±0.02mm, totally combustible and leave a negli- ense of the Republic of Serbia. The program contains gible residue. of: Table 2. The examined gunpowder samples Sample label Gunpowder sample properties A B C D A1 A2 B1 B2 D1 D2 Sort NGB-051 EI-021 NGB-021 NGB-261 Caliber of additional charge 60 mm 82 mm 82 mm 120 mm Age, years 25 0 16 0.5 4 5 2 Laboration mass, g 4.70 4.30 14.70 14.50 13.40 76.8 75.8 232 N.R. BOBIĆ et al.: QUALITY OF MORTAR AMMUNITION Hem. ind. 71 (3) 231–240 (2017) Table 3. The initial chemical composition of gunpowder nitroglycerine into celluloid containers, cardboard pack- samples (mass%) aging and the free space inside of it, it is planned to Gunpowder label Component Value follow the mass loss of gunpowder charges placed in: A Nitrocellulose 57.50±2.00 a) original cardboard packaging (serially produced ammunition); Nitroglycerin 40.50±1.50 b) hermetically closed metal boxes (temporary used Centralite 1 1.70±0.20 metal containers designed for gunpowder charge of Vaseline 0.30±0.20 155 mm ammunition); Graphite max 0.20 c) hermetically closed polyvinyl packaging; Volatile species max 0.50 d) hermetically closed metal boxes with free space, Moisture max 0.50 equal in size to original cardboard packaging. B Nitrocellulose max 84.75 For serial ammunition, taken from two different Nitroglycerin 15.00±2.00 warehouses, the mass measurements were performed Diphenylamine 1.20±0.30 for celluloid containers (increment charges), and the Dibutilphtalate max 1.5 determination of mass loss by comparing