Nghiên cứu ảnh hưởng của một số yếu tố đến các đặc trưng của thuốc nổ nhiệt dẻo PBX trên cơ sở hexogen và pentrit tt tiếng anh

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MINISTRY OF EDUCATION AND TRAINING MINISTRY OF DEFENCE ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY NGUYEN TRUNG TOAN STUDY ON THE EFFECT OF SEVERAL FACTORS ON THE CHARACTERISTICS OF THERMOPLASTIC POLYMERBONDED EXPLOSIVES BASED ON HEXOGEN AND PENTRIT Specialization: Chemical engineering Code: 52 03 01 SUMMARY OF DOCTORAL THESIS IN CHEMISTRY HA NOI - 2019 THE WORK WAS COMPLETED AT ACADEMY OF MILITARY SCIENCE AND TECHNOLOGY Scientific Supervisor: Assoc Prof Dr Phan Duc Nhan Dr Vo Hoang Phuong Reviewer 1: Assoc Prof Dr Tran Van Chung Academy of Military Science and Technology Reviewer 2: Assoc Prof Dr Dam Quang Sang Military Technical Academy Reviewer 3: Dr Dao Thanh Viet General Department of Defence Industry The thesis was defended before the doctoral admission Board of Academy of Military Science and Technology at 8:30 AM, The thesis can be found at: - Library of Academy of Military Science and Technology - Vietnam National Library INTRODUCTION The urgency of the Ph.D thesis Hexogen (RDX) and Pentrit (PETN) are two of the most widely used explosives in military and civilian applications because of its high energetic properties However, RDX and PETN exhibit several notable drawbacks including high sensitivity to mechanical shock, low compressibility, and decomposition when melted In order to overcome these drawbacks, RDX and PETN – based composite explosives were made by three methods: 1combined with an explosive which has low sensitivity to mechanical shock and molding properties such as TNT; 2- phlegmatized explosive; 3combined with a binder system (polymer bonded explosives - PBXs) Compared to other types of composite explosives, thermoplastic PBX has several key advantages Firstly, the binder layer in PBX can absorb impact impulse, reducing the sensitivity of explosives to mechanical shocks In addition, PBXs can be compressed into any special shapes at room temperature with low compression force Last but not least, unused or expired explosive charges based on PBXs can be recycled with the least processing In Vietnam, the demand of thermoplastic PBX explosives for military and civilian purposes is very large, such as in the manufacture of weapons for infantry and tanks, in the manufacture of the explosive charges for the Special Force, etc… Meanwhile, the import of thermoplastic PBXs has not been implemented yet The basic research of thermoplastic PBX explosives based on RDX and PETN will contribute to overcoming the above limitations and clarify the scientific basis for PBX production Therefore, the Ph.D thesis topic "Study on the effect of several factors on the characteristics of thermoplastic polymer-bonded explosives based on hexogen and pentrit" is urgent, with high scientific and practical significance Research objectives of the thesis - Select suitable binder systems for both RDX and PETN and assess the adhesive possibility of explosive with the binder systems; - Determining the law effecting of the content and the composition on the characteristics of PBX explosives, propose suitable components to manufacture thermoplastic PBX explosives with different explosive and binder systems - Determining some kinetic parameters of the thermal decomposition of PBX explosives, thereby predicting the shelf-life of explosive Research scopes of the thesis Study to manufacture and evaluate the effects of several factors such as explosives content, the binder composition, adhesion to the characteristics of thermoplastic PBX based on hexogen and pentrit with the polystyrene (PS) and nitrocellulose (NC)-based binder system at the laboratory scale Experimental methods Method of manufacturing thermoplastic PBXs; methods of evaluating the compatibility of explosives and polymers; methods of assessing the adhesion of explosives and the binders; methods of determining several technical-energy characteristics of thermoplastic PBX (such as ignition temperature, chemical stability, impact sensitivity, compressibility, plasticity, detonation velocity, brisance by Hess and strength of explosive); method of determining kinetic parameters of thermal decomposition process of explosives; method of calculating the shelf-life of explosives The thesis structure The thesis includes the introduction, chapters, conclusions, lists of published articles, and references Specific content as follows: Chapter Overview of PBX explosives: an overview of thermoplastic PBX explosives; evaluating domestic and foreign research situation; interpretation of research issues to be solved by the thesis Chapter Subjects and experimental methods: presenting research objects; chemicals, equipment and experimental methods Chapter Results and discussion: present, evaluate and discuss the research results achieved THESIS CONTENT Chapter OVERVIEW OF THERMOPLASTIC PBX Present an overview of thermoplastic PBX explosives: the appearance and advantages of thermoplastic PBX; components of thermoplastic PBX; energy-technical characteristics; manufacturing methods; domestic and foreign research situation, and the thesis has explained the selection of components of thermoplastic PBX On this basis, the thesis should focus on solving the following main contents: - Study on the component selection of thermoplastic PBX, including assessing the compatibility of explosives with polymers and the adhesion of explosives with the binder systems - Study the law of the effect of explosives content, component of the binders to the technical-energy characteristics of thermoplastic PBX From there, propose the appropriate composition for each PBX system - Study the thermal decomposition characteristics of thermoplastic PBX, determine thermal kinematic parameters, thereby predicting their shelf-life Chapter SUBJECTS AND EXPERIMENTAL METHODS 2.1 Subjects of research Subjects: thermoplastic PBX based on two explosives (e.g RDX and PETN) with several binders (based on polystyrene and nitrocellulose) Research content: manufacturing thermoplastic PBX explosives and assessing the effect of several factors on the characteristics of explosives Besides, the thesis also studies the thermal decomposition process of manufactured explosives, as a basis to predict the shelf-life of thermoplastic PBX explosives 2.2 Chemicals and equipment 2.2.1 Chemicals: RDX (i.e Class-1 with melting temperature ≥ 202.5 ºC) was imported from Korea and PETN (i.e Class-1 with melting temperature ≥ 139.0 ºC) was imported from India Polystyrene (PS) prepared in our laboratory, the average molecular weight of 80,000 u Three types of nitrocellulose, including NC-3, NC-NB and NC-1 with a nitrogen content of 11.96%, 12.20% and 13.39%, respectively, were obtained from a factory in Vietnam Dioctyl phthalate (DOP) from Merk was used as a plasticizer to prepare the binder from PS and NC 2.2.2 Equipment and devices: Equipment for manufacturing PBX explosives by block method; device for determine static contact angle and surface tension CAM-200; Nikon YS-100 optical microscope; plasticity determination device; device for determining compression capability; device for determine the ignition temperature DT-400; device for determine chemical stability Vacuum Stabil tester (VST); device for determine impact sensitivity CAST; differential thermal analysis equipment DSC, TGA; devices for determine energy characteristics (such as device for determining explosion speed FO-2000, devices for determine the brisance by Hess, and equipment for determining the strength of explosive) 2.3 Experimental methods: 2.3.1 Chemical compatibility test Compatibility of explosives and polymers was assessed by VST and DSC thermal analysis methods based on STANAG 4147: - VST method: The volume of gas generated when the mixture of explosives and polymers is heated in vacuum conditions (100 ºC/40 hours) is compared with the volume of gas produced when testing explosives and polymers in the same thing to sue Compatibility is assessed by the difference in the volume of gas produced (VR) due to the interaction between explosives and polymers: 𝑉𝑅 = 𝑀 − (𝐸 + 𝑆), 𝑚𝑙 (2.1) where M is the gas volume released of 5.0 g of mixture; E and S are the gas volumes released of 2.5g of explosives and 2.5g of a polymer, respectively According to STANAG 4147 standard, if VR ≤ ml, two materials are considered compatible, if VR> ml - incompatible - DSC method: Evaluate by a shift in peak temperature on DSC curves with a heating speed of ºC / min: TP = TPS − TPM , ºC (2.2) where TPS and TPM are the temperature of decomposition peaks of the substrate and the mixture, respectively If ΔTP ≤ 4ºC, the system will be compatible; ΔTP> 20 ºC - incompatible; ΔTP from ÷ 20 ºC, another method should be used 2.3.2 Surface parameters calculation The surface tensions of explosives and the binders are calculated based on measuring the static contact angles of standard solvents on the material surface Then, the interfacial tension and the work of adhesion between explosives and the binder are calculated When energetic material and the binder have adhered, the smaller the interfacial tension and the greater the work of adhesion will be, the better the adhesion between them will be 2.3.3 Method of manufacturing thermoplastic PBX - Prepare the original materials; - Prepare the binder systems: Polymer, plasticizer and other additives are quantified, mixed and dissolved in solvent (DOP/PS system uses benzene or toluene, DOP/NC systems use ethyl acetate) The dissolving polymers process is carried out in a stirring mixer - Explosives (e.g RDX and PETN) are added to the above binder solution The mixing process is carried out by stirring, mixing and heating (about 65 ÷ 70 °C) to remove the solvents Then, the mixture was transferred to a water bath, and continue mixing to make sure the mixture is well mixed - the mixture was dried at 90 ÷ 95 ºC for about hours (either at 65 ÷ 70 °C for hours in a vacuum oven) Then, the product was collected and compressed to form a charge 2.3.4 Methods for determining technical-energy characteristics - The plasticity: according to the MIL-STD-650-211 standard: + Using a mold to produce a molded pellet of PBX with a diameter of 50.80 mm, a height of 19.05 mm and a mass of 50 g, and accurately determining the initial height of the PBX pellet (H0, mm); Carefully allow the upper plate of the press to fall until the gage of the press has the same reading as the reading recorded on the gage used to measure the thickness (Figure 2.3); Figure 2.3 The diagram to determine the plasticity of PBX + After 20 minutes, remove the upper steel plate and determine the height of the PBX pellet (H1, mm) The plasticity of PBX is determined as follow: Plasticity = lg H − lg H1 1,3 (2.13) - Compression capability: evaluate the density of PBX explosives at different pressures Compression equipment is a hydraulic compressor with a pressure gauge and cylindrical compression mold (with a diameter of 24.5 mm; PBX mass of 15.0 g) - The ignition temperature was measured by DT-400 (Germany): SP1~190 C, SP2~ 250 C; sample mass of 150 mg and heating rate of C.min−1 - Impact sensitivity studies were carried out using Cast Hammer Impact Test with 10 kg drop hammer according to the TCVN/QS 1837:2017 (powder sample of about 0,05 g; the height of impact, 250 mm) - Chemical stability: The thermal vacuum stability was conducted by the vacuum stability test (VST) using a STABIL apparatus (Czech Republic) following the STANAG 4556-2A standard The sample mass was g Tests were performed at 100 ºC for 48 hours The released gas volume (V) was recorded using a pressure transducer connected to a computer - The brisance by Hess was measured according to the TCVN/QS 6421:1998 (with sample mass, 25 g and 50 g; density, 1.0 g.cm-3) - The strength of explosive was measured by ballistic mortar according to the TCVN/QS 6424:1998 (sample mass, 10g; density, 1.0 g.cm-3) - Detonation velocity: Determined by FO-2000 device, PBX charges are prepared according to the TCVN 6421:1998 standard, charge diameter of 24 mm, charge length of 320 mm, the distance of two sensors is 250 mm 2.3.5 Methods of determining kinetic parameters TG/DTG curves of the samples were established using A NETZSCH STA 409 PC/PG The TG analysis was conducted at various heating rates (e.g 4, 6, 8, and 10 K.min-1) Nitrogen was circulated through the heating chamber at a flow rate of 20 ml.min-1 Based on the results of the TG/DTG curves, applying Kissinger and Ozawa methods to calculate the activation energy Ea and the exponential factor A of the kinetic equation for thermal decomposition reaction 2.3.6 Method of evaluating the shelf-life of PBX explosive The shelf-life of an explosive is defined as a duration (i.e at the temperature of 25 ºC (i.e 298 K)), within which the explosion properties and safety (e.g stability, strength, and sensitivity) of the explosive remain in acceptable ranges In this study, the VST method was used to determine the thermal vacuum stability and hence to estimate shelf-life of the explosives According to the experience of material degradation, especially for brisance explosives, the shelflife of explosive is defined by the length of time for 5% decomposition: t5% = 0, 0513 k298 (2.26) Chapter RESULTS AND DISCUSSION 3.1 Study on the selection of PBX components 3.1.1 Chemical compatibility of explosives and polymers 3.1.1.1 According to VST method: The volume of gas generated by the interaction between explosives and polymers (VR), calculated according to the formula (2.1), is presented in Table 3.1 Table 3.1 The VR values determined by VST method VR, mL Polymer Pentrit Hexogen PS 0.05 0.03 NC-3 0.20 0.13 NC-NB 0.42 0.27 NC-1 1.00 0.90 All VR values are much smaller than the minimum standard values according to STANAG 4147 (5 mL), demonstrate explosives (e.g RDX and PETN) and polymers are compatible with each other Therefore, they can be used to manufacture thermoplastic PBX explosives in subsequent studies 3.1.1.2 According to the DSC method: The difference temperature ( TP ) of the DSC curve of single material compared to the mixture is presented in Table 3.2 and 3.3 Table 3.2 DSC results determine the compatibility of RDX and polymers Materials The exothermic temperature peak, °C ∆TP TPS TPM Single Mixtures RDX RDX/PS 231.2 230.7 0.5 NC-1 RDX/NC-1 202.6 203.9 -1.3 NC-NB RDX/NC-NB 203.5 204.3 -0.8 NC-3 RDX/NC-3 203.7 204.9 -1.2 Where the single system is the component with its exothermic peak temperature lower than another component in the mixture system, and there was not the exothermic peak in the DSC curves of PS Table 3.3 DSC results determine the compatibility of PETN and polymers Materials The exothermic temperature peak, °C ∆TP TPS TPM Single Single PETN PETN/PS 194.5 193.9 0.6 PETN PETN/NC-1 194.5 194.3 0.2 PETN PETN/NC-NB 194.5 194.8 -0.3 PETN PETN/NC-3 194.5 195.0 -0.5 If ∆TP is negative (i.e the mixture has higher temperature decomposition than that of single energetic material), the mixture is compatible If ∆TP is positive, the compatibility of the mixture would be evaluated according to the STANAG 4147 By this standard, RDX and PETN are considered compatible with investigated polymers 3.1.2 Evaluate the interfacial parameters Based on the static contact measurement results of several standard solvents (water, glycerol, ethylene glycol, chloroform), surface tension (γS) of explosive (e.g RDX, PETN) and the binders are calculated (Table 3.6) Table 3.6 Surface tensions of explosives and the binders  S = D + Materials αS βS γD γP RDX 5.90 1.99 34.81 3.96 38.77 PETN 4.92 2.77 24.20 7.67 31.88 DOP/PS (2/1) 5.11 1.94 26.11 3.76 29.88 DOP/PS (1.5/1) 5.22 2.08 27.25 4.32 31.57 DOP/NC (3/1) 5.06 1.44 25.60 2.07 27.67 DOP/NC (2/1) 5.07 1.83 25.70 3.35 29.05 P From the surface tension values, the interfacial tensions, the works of adhesion and the spreading coefficients between energetic materials and the binders are calculated and expressed in Table 3.7 Table 3.7 Interfacial surface parameters of explosives and several binders Interfacial tension, Work of adhesion, Spreading -2 -2 mJ.m mJ.m coefficient The binders RDX PETN RDX PETN RDX PETN DOP/PS (2/1) 0.63 0.73 68.02 61.03 8.27 1.27 DOP/PS (1.5/1) 0.47 0.57 69.87 62.89 6.72 -0.26 DOP/NC (3/1) 1.00 1.79 65.44 57.77 10.08 2.41 DOP/NC (2/1) 0.71 0.90 67.10 60.03 9.00 1.92 When energetic material and the binder have adhered, the smaller the interfacial tension and the greater the work of adhesion will be, the better the adhesion between them will be Besides that, the greater the spreading coefficient will be, the larger the contact area of the binder with an energetic material will be As shown in Table 3.7, the adhesion of RDX to the binder is better than that of PETN In addition, the interfacial tension and the work of adhesion results demonstrated that the adhesion of the binder based on DOP/PS to explosives is better than that the binder based on DOP/NC 12 1.65 1.65 1.60 1.60 1.55 1.50 1.45 DOP/NC - 2/1 1.40 PBX-HN-8001 (NC-1) PBX-HN-8001 (NC-NB) PBX-HN-8501 (NC-1) PBX-HN-8501 (NC-NB) PBX-HN-9001 (NC-1) PBX-HN-9001 (NC-NB) 1.35 1.30 1.25 Density of explosive charge, g.cm-3 Density of explosive charge, g.cm-3 According to the plastic explosive standards used to manufacture US explosive charge such as M5A1 block (plasticity ≤0.03), PBX-HN explosives can be used to make a similar explosive charge However, it is necessary to investigate the compression capability of PBX-HN (Figure 3.8) 1.55 1.50 1.45 DOP/NC - 3/1 1.40 PBX-HN-8002 (NC-1) PBX-HN-8002 (NC-NB) PBX-HN-8502 (NC-1) PBX-HN-8502 (NC-NB) PBX-HN-9002 (NC-1) PBX-HN-9002 (NC-NB) 1.35 1.30 1.25 50 100 150 200 250 Compression pressure, kG.cm-2 300 350 50 100 150 200 250 Compression pressure, kG.cm-2 300 350 Figure 3.8 Relationship between the density of PBX-HN and compression pressure 214 217.0 212 216.5 210 Ignition temperature, C 217.5 o Ignition temperature, oC When the compression pressure increases from 20 ÷ 200 kG.cm-2, the density increases very quickly; when the compression pressure increases from 200 ÷ 320 kG.cm-2, the density increases but is not significant In the compression pressure range, PBX-HN samples using the DOP/NC ratio of 3/1 reached higher density in the initial compression pressure range (from 50 ÷ 100 kG.cm-2), but at higher compression pressures, this density is lower than that of PBX-HN samples using DOP/NC ratio of 2/1 3.2.3 Effect of the content and the composition on the ignition temperature and the chemical stability of PBX-H explosives 3.2.3.1 Ignition temperature Ti (Figure 3.10 and 3.11) 216.0 215.5 215.0 214.5 PBX-HP-80 PBX-HP-85 PBX-HP-90 214.0 213.5 206 204 DOP/NC-1 = 2/1 DOP/NC-NB = 2/1 DOP/NC-3 = 2/1 DOP/NC-1 = 3/1 DOP/NC-NB = 3/1 DOP/NC-3 = 3/1 202 200 198 213.0 1.0 208 1.5 Ratio of DOP/PS 3.10 2.0 80 85 Content of RDX, % 90 3.11 Figure 3.10-3.11 Effect of the RDX content and the DOP/polymer ratio on the ignition temperature of 3.10) PBX-HP and 3.11) PBX-HN 13 a PBX-HP: The ignition temperatures of all PBX-HP samples are lower than that of RDX This can be attributed to the physical interaction between components rendering the systems less thermally stable On the other hand, the thermal decomposition conditions of RDX and PBX are different While the heating process of RDX is considered in isobaric conditions, the heating process of RDX crystals in PBX-HP occurred under isometric conditions Therefore, when the RDX crystals in PBX-HP have been partially decomposed, the generated gas increases the internal pressure In turn, the increased internal gas pressure accelerated the decomposition process of PBX-HP samples b PBX-HN: PBX-HN samples have a much lower temperature than pure RDX Besides the interaction between the components in PBX-HN composition and the differences in thermal decomposition conditions, the most important cause is the presence of NC types (lowest thermal stability) Because of this reason, when the content of RDX increasing (reducing the content of NC), the ignition temperature of PBX-HN explosives tends to increase Ignition temperatures of PBX-HN increased when using NC-1, NC-NB and NC-3 as binders, respectively (PBX-HN using NC-1-based binder has significantly lower Ti), due to the nitrogen content of NC-1 (13.39%) is much higher than NC-NB and NC-3 (12.20% and 11.96%, respectively) 3.2.3.2 Chemical stability of PBX-H (Figure 3.12 and 3.13) 0.34 0.32 0.15 0.14 0.13 0.12 DOP/PS = 2/1 DOP/PS = 1,5/1 DOP/PS = 1/1 0.11 Chemical stability, cm3.g-1 Chemical stability, cm3.g-1 0.16 0.30 0.28 0.26 0.24 DOP/NC-1 = 2/1 DOP/NC-1 = 3/1 DOP/NC-NB = 2/1 DOP/NC-NB = 3/1 DOP/NC-3 = 2/1 DOP/NC-3 = 3/1 0.22 0.20 0.18 0.16 0.10 80 85 Content of RDX, % 3.12 90 80 85 Content of RDX, % 90 3.13 Figure 3.12-3.13 Effect of the RDX content and the DOP/polymer ratio on the chemical stability of 3.12) PBX-HP and 3.13) PBX-HN a PBX-HP samples: PBX-HP samples (RDX content of 80% and 85%) have a higher chemical stability than pure RDX (0.15 mL.g-1), while HPPBX (RDX content of 90%) have similar chemical stability due to two 14 opposite effect factors: Firstly, the physico-chemical interaction between the binder and the explosive makes the stability decrease; secondly, RDX has the lowest chemical stability, deciding to the general chemical stability of PBX-HP Therefore, the chemical stability of PBX-HP samples tends to decrease when the content of RDX increases However, according to STANAG 4556, all of the PBX-HP samples have high chemical stability b PBX-HN: Chemical stability of PBX-HN is lower than that of pure RDX due to the presence of NC When increasing the content of RDX, chemical stability tends to increase On the other hand, the PBX-HN samples using a higher DOP/NC ratio will have higher chemical stability Because the nitrogen content of NC-1 is much higher than that of NCNB and NC-3, so PBX-HN samples (use NC-1 as a binder) have much lower chemical stability Therefore, NC-1 was not selected to manufacture PBXHN in continues studies 3.2.4 Effect of several factors on the impact sensitivity (Table 3.16, 3.17) No Table 3.16 Impact sensitivity of PBX-HP sample Content of RDX, Impact Samples DOP/PS ratio % sensitivity, % PBX-HP-8001 80 2/1 PBX-HP-8501 85 2/1 18 PBX-HP-8503 85 1/1 36 PBX-HP-9001 90 2/1 28 PBX-HP-9002 90 1.5/1 48 A-IX-1 94 25-35 RDX 72 C-4 (USA): 91% RDX, 9% binder 40 C-4 VN 28 Table 3.17 Impact sensitivity of PBX-HN sample Samples Content of RDX, % DOP/NC ratio PBX-HN-8001 PBX-HN-8501 PBX-HN-9001 PBX-HN-9002 RDX 80 85 90 90 100 3/1 3/1 3/1 2/1 - Impact sensitivity, % Type of NC NC-NB NC-3 32 32 36 48 52 72 15 The impact sensitivities of PBX-HP and PBX-HN samples are much lower than that of pure RDX, because: firstly, RDX particles are surrounded by a layer of binder that absorbs and eliminates most of the impact pulse; secondly, the surface of RDX particle dissolved when mixing in a binder solution, eliminating sharp edges and surface defects, resulting in a reduction in the impact sensitivity of the explosive When RDX content increases, the impact sensitivity of PBX-HP and PBX-HN also increases In addition, when the DOP/polymer ratio increases, the impact sensitivity of PBX explosives tends to decrease due to the increasing plasticity of explosives, and DOP/polymer ratio has more influence on impact sensitivity than the content of RDX On the other hand, the impact sensitivity of PBX-HN explosives is higher than that of PBX-HP and A-IX-1 due to the presence of NC 3.2.5 Effect of several factors on the detonation characteristics PBX-HP and PBX-HN samples have much higher energy characteristics than TNT, and belonging to the high explosive group, similar to some high explosive such as C-4, Comp- A, A-IX-1 PBX-HN samples have higher energy characteristics than the HP-PBX samples (with the same RDX content) by the presence of NC (which is the component that provides more energy) in the composition (Table 3.18 and 3.19) Table 3.18 Detonation charcteristics of PBX-HP samples Content Brisance by Hess Strength of Detonation of at 1.0 g.cm-3, [mm] Samples velocity, m.s-1, explosive, RDX, (1.50 g.cm-3) 25g 50g % TNT % PBX-HP-8001 7115 122.6 17.0 24.8 80 PBX-HP-8002 7125 PBX-HP-8501 7298 125.7 18.9 26.2 85 PBX-HP-8502 18.9 26.3 PBX-HP-9001 7400 129.2 19.8 Be destroyed 90 PBX-HP-9002 19.7 Be destroyed TNT 6655 100 15.6 Be destroyed RDX 100 7700 140-150 21.5 Be destroyed C-4 (US) 91 130.0 18.5 Be destroyed C-4 (VN) 91 7363 (1.45) 129.4 18.4 16 Table 3.19 Detonation charcteristics of PBX-HP samples Brisance by Hess Strength of Content Detonation at 1.0 g.cm-3, mm Samples of RDX, velocity, m.s-1, explosive, % (1.50 g.cm-3) 25g 50g % TNT PBX-HN-8001 7280 127.3 25.8 80 PBX-HN-8002 7305 17.2 26.1 PBX-HN-8501 7350 129.7 26.6 85 PBX-HN-8502 7390 27.2 PBX-HN-9001 90 7485 131.5 20.0 Be destroyed Comp-A 91 132.0 A-IX-1 94-95 7420 120-139 ≥15.0 - Discussion: For the purpose of manufacturing PBX-HP and PBX-HN samples with suitable plasticity, good compression capability, low impact sensitivity, high chemical stability and high energy, PBX-HP-9001 sample (90% RDX, 10% DOP/PS with ratio of 2/1) and PBX-HN-9001 sample (90% RDX, 10% DOP/NC with ratio of 3/1, using NC-3 or NC-NB) are appropriate compositions to met the requirements 3.3 Effect of the content and the composition on the characteristics of thermoplastic PBX based on pentrit (PBX-P) 3.3.1 Select the content and the particle size of pentrit Through of the composition of PBX explosives based on PETN explosives in the world such as Semtex-1A, Semtex-10 (Czech Republic), Formex P1 (France), Sprangdeg m/46 (Sweden) and EPX- (Egypt), the content of PETN is in the range of 80 ÷ 85%, some types of PBX have PETN content up to nearly 90% Therefore, the thesis chooses to make PBX explosives based on PETN and PS (PBX-PP) with the content of PETN from 80 to 90% For PBX-P samples based on PETN and NC (PBX-PN), the thesis selected the PETN content from 75 to 85% due to: Firstly, because NC is also a high-energy compound, it also plays contribute to the overall energy of the PBX sample; Second, the ability to completely explode of PETN is better than that of RDX; Third, the adhesion of PETN with the binder is lower than that of RDX The particle size of PETN is chosen similar to the particle size of RDX 17 3.3.2 Effect of the content and the composition on the plasticity and compression capability of PBX-P explosives 3.3.2.1 PBX based on PETN and PS (PBX-PP) - Plasticity (Figure 3.15): Most of PBX-PP samples have high plasticity and easy to shape by hand When the content of PETN increased, the plasticity of PBX-PP samples tends to decrease because of the flexibility of the PBX system is reduced Except for PBX-PP-9003 sample (90% PETN, DOP/PS = 1/1) with low plasticity and PBX-PP-8001 sample (80% PETN, DOP/PS = 2/1) with high plasticity, most of PBX-PP samples meet the plasticity requirements 0.20 DOP/PS = 2/1 DOP/PS = 1.5/1 DOP/PS = 1/1 0.18 0.16 Plasticity 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 80 85 Content of PETN, % 90 Figure 3.15 Effect of the PETN content and the DOP/PS ratio on the plasticity of PBX-PP explosives - Compression capability (Figure 3.16): When the compression pressure increases from 20 ÷ 150 kG.cm-2, the density of the PBX blocks increases rapidly; when the compression pressure increases from 150 ÷ 320 kG.cm-2, the density of PBX blocks increases slowly, reaching the maximum value from 1.52 to 1.62 g.cm-3 (depending on the content of PETN) 1.60 Density of explosive charge, g.cm-3 Density of explosive charge, g.cm-3 1.60 1.55 1.50 1.45 1.40 1.35 1.30 PBX-PP-8001 PBX-PP-8002 PBX-PP-8003 1.25 1.55 1.50 1.45 1.40 PBX-PP-8501 PBX-PP-8502 PBX-PP-8503 PBX-PP-9001 PBX-PP-9002 1.35 1.30 1.25 50 100 150 200 250 300 Compression pressure, kG.cm-2 350 50 100 150 200 250 Compression pressure, kG.cm-2 300 350 Figure 3.16 Relationship between the density of PBX-PP and compression pressure In general, the density of PBX-PP samples is smaller than the PBXHP samples (with the same explosive content and the same DOP/PS ratio), 18 due to the density of PETN (1.770 g.cm3) smaller than the density of RDX (1.816 g.cm3) However, PBX-PP samples have good compression capability (equivalent to PBX-HP samples), much better than TNT 3.3.2.2 PBX based on PETN and NC (PBX-PN) - Plasticity (Figure 3.18): PBX-PN samples have low plasticity and are influenced by the DOP/NC ratio The plasticity of PBX-PN decreases when increasing the content of PETN or reducing the DOP/NC ratio The level reduction of the plasticity of PBX-PN with the DOP/NC ratio of 3/1 (from 0.180 to 0.008) is greater than those with the DOP/NC ratio of 2/1 (from 0.010 to 0.005) 0.020 DOP/NC-NB = 2/1 DOP/NC-3 = 2/1 DOP/NC-NB = 3/1 DOP/NC-3 = 3/1 0.018 0.016 Plasticity 0.014 0.012 0.010 0.008 0.006 0.004 75 80 Content of PETN, % 85 Figure 3.18 Effect of the PETN content and the DOP/NC ratio on the plasticity of PBX-PN explosives - Compression capability (Figure 3.19): Density of explosive charge, g.cm-3 1.60 1.55 1.50 1.45 1.40 PBX-PN-7501 PBX-PN-7502 PBX-PN-8001 PBX-PN-8002 PBX-PN-8501 PBX-PN-8502 1.35 1.30 1.25 50 100 150 200 250 Compression pressure, kG.cm-2 300 350 Figure 3.19 Relationship between the density of PBX-PN and compression pressure The density of PBX-PN samples increases when increasing compression pressure Specifically, the density of PBX-PN samples increased rapidly when the compression pressure increased from 20 ÷ 200 kG.cm-2; when the compression pressure continues to increase from 220 ÷ 350 kG.cm-2, the density of PBX-PN blocks increases not much (to about 1.57 g.cm-3), even if several PBX-PN blocks remain the same density 19 Compared to PBX-HN samples, PBX-PN samples have a significantly lower density (density difference of 0.50 g.cm3), due to: (1) the content of main explosives in the PBX-PN samples are lower and (2) RDX density is higher than that of PETN 3.3.2 Effect of the content and the composition on the ignition temperature and the chemical stability of PBX-P explosives 3.3.2.1 Ignition temperature (Figure 3.20 and Figure 3.21) 184.5 182.0 Ignition temperature, oC Ignition temperature, oC 184.0 183.5 183.0 PBX-PP-80 PBX-PP-85 PBX-PP-90 182.5 181.5 181.0 180.5 DOP/NC-NB = 2/1 DOP/NC-NB = 3/1 DOP/NC-3 = 2/1 DOP/NC-3 = 3/1 180.0 179.5 182.0 1.0 1.5 DOP/PS ratio 3.20 2.0 75 80 Content of PETN, % 85 3.21 Figure 3.20-3.21 Effect of the PETN content and the DOP/polymer ratio on the ignition temperature of 3.20) PBX-PP and 3.21) PBX-PN Ignition temperatures of all PBX-PP and PBX-PN samples are lower than pure PETN (185.7 °C), due to the interaction between explosive components and the difference in thermal decomposition conditions of pure PETN compared to PETN crystals in PBX explosives Besides, with the appearance of NC in the binder composition, ignition temperatures of PBXPN samples are also lower than the PBX-PP samples When PETN content increases, ignition temperatures of PBX-PP and PBX-PN will decrease because PETN has the lowest ignition temperature On the other hand, because NC is poor thermal stability compound, so the PBXPN samples use a low DOP/NC ratio will have lower ignition temperatures 3.3.2.2 Chemical stability (Figure 3.22 and 3.23) The PBX-PP-80 and PBX-PP-85 samples have higher chemical stability than pure PETN; while PBX-PP-90 samples have the same chemical stability as PETN The trend of changing the chemical stability of PBX-PP samples is similar to the PBX-HP explosives (RDX/PS), due to the interaction between components (explosive and polymer) of PBX-PP and the effect of PETN content 20 0.25 0.30 0.29 Chemical stability, ml.g-1 Chemical stability, ml.g-1 0.24 0.23 0.22 0.21 DOP/PS = 2/1 DOP/PS = 1,5/1 DOP/PS = 1/1 0.20 0.19 0.28 0.27 0.26 0.25 0.24 0.23 DOP/NC-NB = 2/1 DOP/NC-NB = 3/1 DOP/NC-3 = 2/1 DOP/NC-3 = 3/1 0.22 0.21 0.20 80 85 Content of PETN, % 3.22 90 75 80 Content of PETN, % 85 3.23 Hình 3.22-3.23 Effect of the PETN content and the DOP/polymer ratio on the chemical stability of 3.22) PBX-PP and 3.23) PBX-PN Most of the PBX-PN samples have slightly lower chemical stability than pure PETN When the PETN content decreases (the content of NC-based binder increases), the chemical stability of the PBX-PN tends to decrease The reasons are due to (1) the interaction between the components and (2) because NC is the compound with the lowest chemical stability According to STANAG 4556, PBX-PP and PBX-PN samples have high chemical stability 3.3.3 Effect of several factors on the impact sensitivity of PBX-P (Table 3.28 and 3.29) No Table 3.28 Impact sensitivity of several PBX-PP samples Content of DOP/PS Impact Sample PETN, % ratio sensitivity, % PBX-PP-8002 80 1.5/1 10 PBX-PP-8003 80 1/1 30 PBX-PP-8501 85 2/1 32 PBX-PP-8503 85 1/1 46 PETN 100 100 The impact sensitivity of PBX-PP samples is much smaller than that of pure PETN, even the impact sensitivity of the PBX-PP-8002 sample is similar to TNT The purpose of sensitivity reduction of the using the binder for the PETN has been achieved by two reasons: the surround binder layer of PETN crystals absorbs and eliminates most of the impact pulse, and the surface defects PETN crystals have been removed when dissolved during fabrication On the other hand, the impact sensitivity of PBX-PP samples depends a lot on the physical state of the binder system 21 Table 3.29 Impact sensitivity of several PBX-PN samples Sample Content of PETN, % DOP/NC ratio Impact sensitivity, % Type of NC NC-NB NC-3 PBX-PN-7501 75 3/1 44 PBX-PN-7502 75 2/1 52 48 PBX-PN-8001 80 3/1 52 52 PBX-PN-8501 85 3/1 68 64 PBX-PN-8502 85 2/1 72 PETN 100 100 The impact sensitivity of PBX-PN samples is much higher than that of PBX-PP samples due to the existence of NC in the composition of explosives However, when compared to the impact sensitivity of pure PETN (100%), the sensitivity reduction effect of the DOP/NC binder is relatively good 3.3.4 Effect of several factors on the detonation characteristics of PBX-P Table 3.30-3.31 Detonation characteristics of PBX-PP and PBX-PN samples Brisance by Strength of Detonation Hess, mm Sample velocity, m.s-1, explosive, -3 (density, g.cm ) % TNT 25g 50g PBX-PP-8001 7100 (1.50) 17.0 23.0 PBX-PP-8002 7129 (1.50) 119.3 16.8 22.6 PBX-PP-8502 7200 (1.50) 124.8 19.0 24.5 PBX-PN-7501 7163 (1.50) 125.7 - 24.5 PBX-PN-8001 PBX-PN-8501 TNT PETN Semtex-10 (85% PETN) Sprangdeg (86% PETN) EPX-1 (86% PETN) 7290 (1.50) 7353 (1.50) 6655 (1.50) 7500 (1.50) 7370 (1.52) 7232 (1.52) 7398 (1.55) 126.2 127.4 100 140 ÷ 150 - 20.1 - 25.0 26.0 15.6 22.0 - PBX-PP and PBX-PN samples have much higher energy characteristics than TNT The PBX-PP-8502 sample has the same energy characteristics as the Semtex-10 sample (Czech Republic) and Sprangdeg m/46 sample (Sweden) The energy characteristic of PBX-PN-8501 sample is slightly higher due to the presence of NC in the composition which increases the 22 energy for the PBX system Thus, it can be confirmed that PBX-PP and PBXPN samples (80 ÷ 85% PETN) belong to the high explosive group Discussion: The PBX-PP samples have high plasticity, can be easily shaped by hand, with the PBX-PP-8501 sample (85% PETN, 15% DOP/PS with a ratio of 2/1) is optimal PBX-PN samples are not too high plasticity, suitable for making an explosive charge by compression method, with PBXPN-8501 sample (85% PETN, 15% DOP/NC with a ratio of 3/1) is optimal 3.4 Evaluate thermal decomposition behaviors and predict shelf-life of thermoplastic PBX 3.4.1 Several thermal decomposition behaviors of thermoplastic PBX Table 3.32-3.33 Composition of PBX-H and PBX-P samples Content of material, % Sample RDX PETN DOP NC-3 NC-NB PBX-HN-80-1 80.0 13.33 6.67 PBX-HN-80-2 80.0 13.33 6.67 PBX-HN-85 85.0 11.25 3.75 PBX-HP-85 85.0 10.00 PBX-PP-8001 80.0 13.33 PBX-PN-8002 80.0 13.33 6.67 PS 5.00 6.67 - Table 3.34-3.37 The kinetic parameters of explosives Kisinger method Ozawa method Sample -1 -1 Ea, kJ.mol logA, Ea, kJ.mol-1 logA, min-1 PBX-HN-80-1 150.72 15.45 151.19 15.50 PBX-HN-80-2 149.37 15.32 149.89 15.38 PBX-HN-85 153.33 15.70 153.70 15.74 PBX-HP-8501 212.35 21.84 209.86 21.58 RDX 206.35 21.23 204.14 21.00 PBX-PP-8001 141.43 15.51 141.87 15.56 PBX-PN-8002 126.54 13.81 127.54 13.92 PETN 132.59 14.50 133.45 14.60 The activation energy values (Ea) of PBX samples used NC-based binder are lower than those of RDX or PETN, and the increase in NC content in the binder composition leads to reduces the value of Ea On the other hand, PBX samples used PS-based binder have a slightly higher Ea than single explosives, due to the low content of main explosives (thermal stability) in PBX explosives is smaller This confirms the effect of the binder system on the thermal stability of the PBX system 23 3.4.3 Predict shelf-life of thermoplastic PBX The prediction of shelf life was carried out through the vacuum stability test (VST) For single RDX and PBX-H samples, VST values are determined at temperatures of 90, 100, 110 and 120 °C For single PETN and PBX-P samples, VST values are determined at temperatures of 80, 90, 100 and 110 °C Based on VST results, the value of k298 is calculated according to the equation (2.26), the shelf-life values of single explosives, PBX-H and PBX-P samples were calculated and presented in Figure 3.28-3.29 PBX-HP-8501 78.3 PBX-PN-8002 PBX-HN-80-2 38.7 41.6 PBX-HN-80-1 56.0 PBX-PP-8001 44.9 48.8 PBX-HN-85 PETN 47.6 70.2 RDX 10 20 30 40 50 60 70 Shelf-life of RDX and PBX-H, years a) 80 90 10 20 30 40 50 60 70 Shelf-life of PETN and PBX-P, years 80 b) Figure 3.28-3.29 The shelf-life of single explosives, PBX-H and PBX-P The influence of the binder was evident over the shelf-life (estimated) of single explosives and thermoplastic PBX explosives While the shelf-life of RDX and PBX-HP samples (about 70 ÷ 80 years), the shelf-life of PBX-HN explosives is smaller (about 40 ÷ 50 years); similar values of explosives PETN is about 48 years, PBX-PP explosives (about 56 years) and PBX-PN explosives (about 38 years) On the other hand, due to the thermal stability of RDX higher than PETN, so the shelf-life of PBX-P explosives is significantly lower than that of PBX-H CONCLUSIONS Single RDX and PETN are well chemical compatible with PS and three types of NC, thereby orienting the use of PS and NC as binders to make thermoplastic PBX explosives In addition, RDX with PS and NCbased binder systems have smaller interfacial tension, greater work of adhesion than those of PETN, so the adhesion of RDX to the binder is better than that of PETN 24 PBX-HP-9001 sample (90% RDX, 10% DOP/PS with ratio of 2/1); PBXPP-8501 (85% PETN, 15% DOP/PS with ratio of 2/1) is optimal composition, have high plasticity, good compression capability, low impact sensitivity, high chemical stability, high energy characteristics, equivalent to some of the famous thermoplastic PBX in the world such as C-4, ΠΒΒ-5A, Semtex-10, EPX-1, PBX samples using NC as a binder suitable to manufacture explosive charge and explosive blocks by compression machine PBX-HN-9001 sample (90% RDX, 10% DOP/NC with ratio of 3/1) and PBX-PN-8501 (85% PETN, 15% DOP/NC with ratio of 3/1) is the optimal composition, have suitable plasticity and compression capability, significantly lower impact sensitivity than single explosives, high energy characteristics, equivalent to many thermoplastic PBX explosives in the world PBX-H samples have higher thermal stability and chemical stability than PBX-P samples The Ea values of PBX-H samples are in the range (150 ÷ 206) kJ.mol-1, much higher than those of PBX-P samples (125 ÷ 141) kJ.mol-1 In addition, while the PS-based binder system is less influential, the NC-based binder system reduces the thermal stability of PBX samples Estimated shelf-life at 25 °C (according to VST testing) of explosives respectively are: RDX and PBX-HP have the highest value (about 70 to 80 years); PBX-HN samples (about 40 to 50 years); PETN and PBX-PP samples (about 49 to 56 years), and PBX-PN samples have the lowest value (about 38 years) New contributions of the thesis: - The thesis has evaluated the chemical compatibility and the adhesion ability of main explosives with binder systems, to select components and manufacture thermoplastic PBX explosives - The thesis has clarified the rule of the effect of explosive content and the composition of the binder system on the characteristics of thermoplastic PBX explosives Based on this basis, propose suitable compositions to manufacture some thermoplastic PBX explosives - The thesis has clarified the thermal decomposition characteristics of thermoplastic PBX explosives based on RDX and PETN, determined thermal kinetic parameters and predicted shelf-life of explosives THE LIST OF PUBLISHED SCIENTIFIC ARTICLES Nguyen Trung Toan, Phan Duc Nhan, Vo Hoang Phuong (2017), “The effects of various factors on the characteristics of polymer-bonded explosives based on pentrit and polystyrene”, Journal of Science and Technique, 186, pp 3-10 Toan Nguyen Trung, Nhan Phan Duc (2017), “Studies on compatibility of high energetic materials with polymers by thermal methods”, The 6th Asian Symposium on Advance Materials (ASAM-6), pp 601-604 Nguyen Trung Toan, Phan Duc Nhan, Vo Hoang Phuong (2018), “The effects of several factors on the characteristics of polymer-bonded explosives based on pentrit and nitrocellulose”, Journal of Analytical Sciences, 23, pp 165-171 Nguyen Trung Toan, Phan Duc Nhan, Vo Hoang Phuong (2018), “Thermal decomposition and shelf-life of PETN and PBX based on PETN using thermal methods”, Journal of Science and Technology, 56(3), pp 303-311 Nguyen Trung Toan, Phan Duc Nhan, Vo Hoang Phuong (2018), “The effects of various factors on the characteristics of polymer-bonded explosives based on hexogen and nitrocellulose”, Journal of Military Science and Technology, 57A, pp 111-117 Nguyen Trung Toan, Phan Duc Nhan, Duong Cong Hung, Vo Hoang Phuong (2018), “Thermal decomposition behavior and shelf-life of polymer-bonded explosives and hexogen - An experimental study”, Vietnam Journal of Chemistry, 56(5), pp 654-659 Trung Toan Nguyen, Duc Nhan Phan, Duy Chinh Nguyen, Van Thom Do, Giang Long Bach (2018), “The chemical compatibility and adhesion of energetic materials and several polymers and binders: An experimental study”, Polymers, 10(12), 1396 (SCOPUS, Q1, IF = 2,935) ... g.cm-3 1.60 1.55 1.50 1.45 1.40 1.35 1.30 PBX- PP-8001 PBX- PP-8002 PBX- PP-8003 1.25 1.55 1.50 1.45 1.40 PBX- PP-8501 PBX- PP-8502 PBX- PP-8503 PBX- PP-9001 PBX- PP-9002 1.35 1.30 1.25 50 100 150 200... single explosives, PBX- H and PBX- P samples were calculated and presented in Figure 3.28-3.29 PBX- HP-8501 78.3 PBX- PN-8002 PBX- HN-80-2 38.7 41.6 PBX- HN-80-1 56.0 PBX- PP-8001 44.9 48.8 PBX- HN-85 PETN... plasticity of PBX- PN explosives - Compression capability (Figure 3.19): Density of explosive charge, g.cm-3 1.60 1.55 1.50 1.45 1.40 PBX- PN-7501 PBX- PN-7502 PBX- PN-8001 PBX- PN-8002 PBX- PN-8501 PBX- PN-8502
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Xem thêm: Nghiên cứu ảnh hưởng của một số yếu tố đến các đặc trưng của thuốc nổ nhiệt dẻo PBX trên cơ sở hexogen và pentrit tt tiếng anh , Nghiên cứu ảnh hưởng của một số yếu tố đến các đặc trưng của thuốc nổ nhiệt dẻo PBX trên cơ sở hexogen và pentrit tt tiếng anh

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