Andrzej MARANDA ? Military University of Technology, Warsaw; Barbara GOŁĄBEK, Jacek SUSZKA ? Austin Powder Poland, Łukaszów; Iwona ZAWADZKA-MAŁOTA ? Central Mining Institute, Katowice; Tomasz SAŁACIŃSKI ? Institute of Industrial Organic Chemistry, Warsaw

Abstract:
This paper discuss the results from testing detonation parameters such as: the detonation velocity and detonation capacity of emulsion explosive materials containing  Hydrox S and Hydrox U matrices. The test results for dangerous properties of matrices including classification tests conducted for the eligibility of the dangerous material  for public road transport were presented. It was also indicated that modifications of composite properties of the emulsion explosives were possible by changing the  viscosity of the used matrix.

Please cite as: CHEMIK 2013, 67, 13, 7-12

Introduction

The emulsion explosives have become a predominating blasting agent used in the Polish extractive industry. All leading manufacturers of the mining explosives offer a wide range of this blasting agent having diversified detonation characteristics and formulations. Content, physical and chemical properties of a matrix and density which is conditioned by, among other things, the method of its sensitization, determine the detonation parameters of emulsion explosives. They also influence the explosive properties of constant additives such as ammonium nitrate and aluminium powder. Matrix viscosity can be adjusted by changing its composition and the degree of its homogenization and specifically, the target size of particles in the disperse phase. Adequate mixers may provide matrices of emulsion explosives having extremely small (below 1?m [1]) diameters of micro-drops of the supersaturated solution of oxidisers which provide very high viscosity of the matrix ? a physical and chemical parameter of emulsion explosive matrix which determines the stability of an explosive system. The target viscosity is adjusted depending on emulsion explosive formulation which determines the method of charging blastholes.

The second important element in the production of emulsion explosives is the method of matrix sensitization which also depends on the formulation. Both fundamental methods of sensitization can be applied for packaged explosives: the physical method (using the substances of low density) and the chemical one. However, the bulk emulsion explosives are only sensitized by the chemical method. The method of sensitizing the matrix determines, among other things, the physical stability ? the possible growth in density resulting in the loss of the detonation capacity of the end product.

The measurements of the matrices and emulsion explosive parameters were conducted as part of this paper which can be regarded as the continuation of the wide range of studies on the emulsion explosives performed by a few of these authors, e.g. [2÷7], and were based on these studies. The matrix tests were carried out in regard to requirements for their transport on public roads; whereas detonation velocity and capacity were determined for emulsion explosives produced from these matrices.

Experimental part

Testing properties of emulsion explosive matrices

For these tests, two matrices of emulsion explosives were used. Their compositions were identical (ammonium nitrate (V) ? 64.4%, sodium nitrate (V) ? 14.6 %, organic phase ? 6.0%, water ? 15 %); whereas they had different viscosity. The viscosity of the matrix Hydrox U was 120000 cPa, and of the matrix Hydrox S was 55800 cPa. The full range of tests was conducted to specify their transport classification regarding the requirements for dangerous explosives of class 5.1, UN number 3375. Thermal sensitiveness was determined on the basis of the Koenen Test presented as the test 8(c) in the recommendations approved by the UN [8]. This test consists in determining the destruction of the steel shell that may occur during the decomposition of the test material induced by its heating. An orifice diameter in the orifice plate is a variable value. If the shell deformation is observed in any of three trials, then the test material is found to react at the used diameter of the orifice plate. No ?explosion? result was observed for both Hydrox U and Hydrox S matrices in the conducted tests with the orifice plate of 2 mm diameter. The orifice diameter of 2 mm was found as the limiting one.

The next test ? thermal stability test was determined on the basis of Thermal Stability Test for ANE presented as the test 8(a) in the UN recommendations mentioned above. Assuming that the maximum temperature of the transported and transhipped matrix was 25oC, the tests were performed at a temperature of 50oC fulfilling the requirement of the temperature higher than the maximum temperature by 20oC and increasing the safety margin by another 5oC. The volume of the used Dewar vessel was 500 cm3 and the heat loss of 400 cm3 of water calculated from the equation defined in [8] was 80 ÷ 100 mW (kgK)-1. Hydrox U or Hydrox S matrix in the amount of 0.5 kg was placed in the Dewar vessel and stabilised at the above temperature for 240 hours. After that time, no temperature increase of at least 6oC was observed in any case.

The final test consisted in determining the sensitivity of the tested matrices to the shock wave. The experiment was performed according to ANE Gap Test ? test 8(b) [8]. The detonator made from plastic explosive of 1.60 g/cm3 density was used as a shock wave generator. The photos 1 and 2 illustrate the test results for particular matrices.

The tube fragmentation into large pieces was observed for Hydrox S matrix. The tube fragmentation into small pieces and the slight bent of the witness plate were the effect of the shock wave impact on Hydrox U matrix. The produced effects indicated that the test matrices did not demonstrate the detonation capacity under the experimental conditions.

Testing detonation parameters of emulsion explosives

Detonation velocity and detonation capacity of emulsion explosive materials containing Hydrox S and Hydrox U matrices were determined as part of testing detonation parameters. The velocity of detonation belongs to the basic parameters of explosives. Knowing this value is essential to describe properly the physical effects occurring in the explosive and the surrounding affected by the detonating explosive. It is also one of the parameters which are the basis for determining the application range of the explosive. The method of ionisation probes was used to measure the detonation velocity of tested explosives. During the first phase of tests, the matrices were sensitized by adding 0.6% Expancel 461DET40 microspheres. The explosive specimens were prepared under laboratory conditions. The detonation velocities were measured in 46/50 mm vinidur tubes. The measurements were performed on three courses, each of 40 mm length. The critical diameters of explosive mixtures obtained by the method of conical charges were also determined. The tested emulsion explosive specimens were initiated by mining detonators. The test results are presented in Table 1.

In the next phase of tests, the specimens of matrices were cooled down to -22oC and stabilised for 24 h. Then, they were heated to the ambient temperature and used to prepare the emulsion explosive specimens by adding 0.6% microspheres. The results of test on critical diameters of detonation of emulsion explosives prepared in such a way were the same as for emulsion explosives without cooled matrices.

The final phase of tests included measuring the detonation velocities of emulsion explosives prepared on the mixing and charging equipment PU5001R(3). The trials were performed after about 24 hours from their production. Three types of Hydromite products, whose compositions are presented in Table 2, were tested.

The measurements of detonation velocities were conducted inside the steel tubes with an internal diameter of 35 mm and wall thickness of 2.6 mm. In charges, there were two measurement courses, each of 5 cm length. The explosives were initiated with HC-10 booster using the electric detonator containing 0.6 g of penthrite. The initiation tests on investigated emulsion explosives, which had been conducted earlier, demonstrated that the booster was sufficient to initiate them. The measurement results are presented in Tabele 3.

Discussion of test results

The matrices of emulsion explosives were subjected to standard series of tests and the series also included the measurements of detonation parameters (mainly velocity) of fundamental importance for determining the possibilities and techniques of applying a given blasting agent. Considering the relatively standard composition of matrices, the obtained results of sensitiveness to thermal stimuli were as expected. However, interesting results were achieved while determining the matrix sensitiveness to the shock wave. Hydrox U matrix having higher viscosity demonstrated higher susceptibility to the effect of the shock wave. Within a range of the highest intensity of the shock wave, that is, in the matrix area close to the spacer surface, the exothermic decomposition of this matrix occurred resulting in the tube fragmentation. Such a phenomenon was not observed during the tests using Hydrox S matrix. Such different responses of matrixes are related to their diversified structures. The structure of Hydrox U matrix is more homogeneous, which is caused by the smaller sizes of micro-drops in the supersaturated aqueous solution of oxidisers, and it also determinates lower thickness of the organic phase. The higher degree of fragmentation of both phases of matrix results in forming the more developed surface for a potential reaction between oxidisers and organic components which directly influences the possible initiation.

However, no effect of matrix structures on detonation velocity and critical diameter of detonation of emulsion explosives obtained from these matrices were observed. The test results presented in Table 1 indicate that emulsion explosives sensitized by 0.6% microspheres have very similar detonation parameters. Thus, the adequate sensitization of matrices is vital. It should be emphasized that the tested emulsion explosives had relatively low density (?o) ? lower than the optimum value regarding the relationship D=f(?o). Increasing density of emulsion explosives which reduces the value of ?hot spots? could only demonstrate the impact of matrix structures on detonation parameters. The tests on detonation velocities of Hydromite products prepared in the mixing and charging equipment PU5001R(3) demonstrated that the tested emulsion explosives kept their adequate parameters also after 24 hours of seasoning and transporting within a distance of a few hundred kilometres. The detonation velocities slightly diverge from the values obtained in the tests conducted in Bundesanstalt für Materialforschung und ?prüfung immediately after preparing emulsion explosives.

Summary

The conducted tests, together with the tests performed in Bundensansalt für Materialforschung und -Prüfung [9], were the basis for issuing certificates of public road transport for the tested matrices. Thus, they can be transported in DPPL containers and cisterns to the destination of their application. Using the same composition of matrices, the utility properties and detonation parameters of Hydromite products can be widely adjusted by changing matrix viscosity and adding flammable substances (oil, aluminium powder) and oxidisers (ammonium nitrate). They are characterised by high physical and chemical stability. These products should extend the offer for surface and underground mining.

Literature
1. Maranda A., Gołąbek B., Kasperski J.: Materiały wybuchowe emulsyjne, Wydawnictwa Naukowo-Techniczne, Warszawa 2008.
2. Maranda A., Nowaczewski J., Gołąbek B., Kasperski J.: Badanie właściwości matryc materiałów wybuchowych emulsyjnych. Górnictwo Odkrywkowe, 2001, 43, 5.
3. Maranda, A., Cudziło S., J. Suszka.: Badanie stabilności termicznej matryc materiałów wybuchowych emulsyjnych. Wiadomości Chemiczne, 2008, 59, 11.
4. Papliński A., Maranda A., Paszula J., Gołąbek B., Kasperski J.: Investigation of blast performance of emulsion explosives. Proceedings of the 2003 International Autumn Seminar on Propellants, Explosives and Pyrotechnics (2003 IASPEP) ? Theory and Practice of Energetic Materials vol. 5.
5. Maranda A., Gołąbek B., Kasperski J.: O pewnych właściwościach nowych generacji materiałów wybuchowych emulsyjnych. Prace Naukowe GIG. Mat. Konf. Bezpieczeństwo Robót Strzałowych w Górnictwie, Ustroń, 4-6.10.2006.
6. Maranda A., Cudziło S., Gołąbek, B., Kasperski J.: Work performance of newest generation of emulsion explosives as estimated cylinder test. Proc. 33rd International Annual Conference of ICT, Energetic Materials. Synthesis, Production and Application, Karlsruhe, 25-28 June, 2002.
7. Trzciński W.A., Maranda A., Suszka J.: Badanie zdolności do wykonania pracy materiałów wybuchowych emulsyjnych zawierających chlorek sodu metodą testu cylindrycznego. Prace Naukowe GIG, Górnictwo i Środowisko nr V/2008, Mat. Konf. Bezpieczeństwo Robót Strzałowych w Górnictwie, Ustroń, 8-10.10.2008.
8. Recommendations on the Transport of Dangerous goods. Manual of Tests and Criteria. Fifth revised edition. ST/SG/AC.10/11/Rev 5, United Nations, New York and Geneva 2009.
9. Decyzja BAM (Bundesanstalt für Materialforschung und ?prüfung) nr II.3/0968/09 z dnia 07.04.2009.

Andrzej MARANDA ? (Sc.D., Eng), Professor, graduated from the Faculty of Chemistry at the Warsaw University of Technology in 1971. He is currently working in the Military University of Technology and the Institute of Industrial Organic Chemistry in Warsaw. Research interests: chemistry and technology of explosives, environmental protection. He is the author and a co-author of five monographs, 20 patents and over 500 articles published in science magazines and presented at national and international conferences.
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Barbara GOŁABEK ? Ph.D (Eng.), graduated from the Faculty of Chemistry at the Silesian University of Technology in Gliwice, specialisation in ?Chemistry and Chemical Technology? and ?Chemistry and Industrial Technology of Explosive Materials? and received the degree of Master of Science in chemistry (1981). In 1998, she completed the post-graduate studies in the field of Management and Marketing at the Continuing Education Centre at the University of Economics in Katowice. In November 2006, she received an academic degree of doctor of technical sciences in mining and engineering geology at the Central Mining Institute in Katowice. She has been the President of the Management Board in Austin Powder Polska Sp. z o.o. since 2010. She is a member of German and European Association of Blasting Engineers. She is an author and a co-author of numerous patents on selecting components and technologies for explosives and an author of many publications on introducing a new generation of emulsion explosives, innovative test methods and mixing and charging units applied in the mining industry.
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Jacek SUSZKA ? M.Sc., obtained his Master?s degree at the Faculty of Chemistry at the Silesian University of Technology in Gliwice in 1994. He is an expert in mining explosives. Nowadays, he is the Plant Manager in Austin Powder Polska Sp. z o.o. He is a co-author of many publications on testing and producing emulsion explosives.
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Iwona ZAWADZKA- MAŁOTA ? Ph.D., completed the studies in the field of Chemistry at the Faculty of Mathematics, Physics and Chemistry at the University of Silesia in Katowice in 1985. In 2009, she obtained an academic degree of doctor of technical sciences in mining and engineering geology at the Central Mining Institute [GIG]. She is working in GIG Experimental Mine ?Barbara? holding the post of the Deputy Head of Blasting Safety Department. She is an author and a co-author of 21 publications.
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Tomasz SAŁACIŃSKI ? M.Sc., graduated from the Faculty of Chemistry at the Warsaw University of Technology in 1993. He is currently working at the Institute of Industrial Organic Chemistry. Research interests: properties of dangerous high energy materials.
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