RDX-PBX

Table 9.6 Density, detonation velocity, particle velocity, and pressure at CJ point for various HMX-PBX and RDX-PBX materials.

For military explosives that are deficient in oxygen (negative OB), equil (b) and (c) must be considered and the choice of eqn of state becomes important. Currently the BKW eqn of state (see Vol 4, p D284) is used for most calculations, eg Ref 4. From Mader s calcs (Ref 4) combined with the AHf0,s of Table 1, the heats of detonation of NG, PETN, HMX, RDX, PBX 9404, LX-04, TNT and NM are... 

In general, PBX is used for the warheads of rockets and guns. Thus, the detonation pressure (pj) represented by Eq. (8.7) is a more important parameter than other properties. Since the measurement of the detonation velocity uD is easier and more accurate than the measurement of pj, the performance evaluations are done by uD which is converted to pj by the use of Eq. (8.7). Table 8-3 shows uD and p data, and gives the computed detonation pressure at the CJ point of HMX-PBX and RDX-PBX. 

Table 8-3. Detonation velocity, density, and pressure at the CJ point of HMX-PBX and RDX-PBX.

Both RDX and HMX are substantially desensitized by mixing with TNT to form cyclotols (RDX) and octols (HMX) or by coating with waxes, synthetic polymers, and elastomeric biaders. Most of the RDX made ia the United States is converted to Composition B (60% RDX, 40% TNT, 1 part wax added). Composition A5 (RDX 98.5/stearic acid 1.5) and composition C4 (RDX91/nonexplosive plasticizer) account for the next largest uses. HMX is used as a propellant and ia maximum-performance plastic bonded explosives such as PBX 9401 and PBX N5 and the octols (147—150). 

History. The first attempts to desensitize RDX were reported by Frankel and Carle ton (Refs 1 thru 5) who made use of polymeric materials such as polyurethanes to coat expl crysts by means of emulsion or soln techniques. The first true PB-RDX was developed in 1952 at the Univ of Califs Los Alamos Lab and consisted of RDX coated with polystyrene plasticized with DOP (Refs 6 21). Since then the Lawrence Livermore Lab has evolved a series of PBX formulations, many of which are listed in Tables 3,4 5. These compns are described in Ref 77... 

Plastic-Bonded RDX, Its Preparation By the Slurry Method , Holston Defense Corp, Term, Control No 20-T-16 Series A (PAC 1081) (1953) 8) A.J. Pascazio, The Suitability of a Bare PBX Booster Pellet In The 2.75-Inch HEAT Ml Rocket Head , PATR 2271 (1955) 9) H.W. 

PBX Progress For Quarter Ending 30 June 1958, NOTS 2072, Tech Progress Rept 216 (1958) 1 28) BJ. Zlotuchaet al, Characteristics of Polystyrene-Bonded RDX (PB-RDX) , PATR 2497 (1957) 29) C.W. Falterman et... 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

In general, PBX materials are used for the warheads of rockets and guns. Thus, the detonation pressure pj represented by Eq. (9.7) is the most important parameter above all others. Since the detonation velocity Wj, can be measured more easily and more accurately than pj, performance is evaluated by measuring Wp, which is converted into pj by means of Eq. (9.7). Table 9.6 shows Wj, and p data, along with computed detonation pressures at the CJ point, for various HMX-PBX and RDX-PBXmaterials. 

As shown in Table 9.6, the detonation velocity is highly dependent on the density of the PBX, which, in turn, depends on the mass fraction of HMX or RDX.PB When a mixture of nylon powder and HMX particles is pressed into an explosive of the desired shape, a high-density HMX-PBX is formed. However, during the formulation process, the material is sensitive to pressurization and to mechanical shock. 

This distinction is more in kind than in degree. Small quantities of primary or initiating explosives usually detonate when exposed to flames or high temperatures whiie secondary explosives usually burn or deflagrate under these conditions. However under slightly altered conditions primary explosives can be made to deflagrate and secondary explosives can be made to detonate. Examples of primary explosives are Lead Azide, Mercury Fulminate, DDNP, etc Examples of secondary explosives are PETN, RDX, HMX, Tetryl, TNT, as single HE compns and Comp B, Comp C, PBX 9404, Dynamite ANFO (Ammonium Nitrate/Fuel Oil) as HE mixtures... 

RDX Cyclonite, high explosive used in PBX and other applications. 

Cyclotol 75% RDX + 25% TNT Basically modified Composition with a higher RDX content for better performance. Used as a high VOD castable main explosive and also considered as a substitute for PBX-9404... 

NTO or NTO/RDX or HMX have been reported as fillings to get insensitive munitions (IM) [155]. A comparison of PBXs based on TATB and NTO further confirms the same sensitivity levels while VOD of the NTO-based PBX is slightly higher. 

CL-20 was evaluated in both propellant and explosive formulations. A large number of CL-20-based PBXs are reported in the literature. A comparison of their VOD with that of the corresponding HMX-based formulations reveals a 12-15% higher energy potential of CL-20-based formulations. CL-20 is also a superior alternative to RDX and HMX for application in low-signature rocket propellants. CL-20-based propellants offer burn-rates much higher (-35-110%) than those of HMX-based propellants. The performance of CL-20-based propellants in terms of Isp is found to be higher than those of RDX-based propellants. 

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