PBXs insensitive

PBXs have replaced melt-castable explosives in almost all nuclear weapons. The PBX formulations that have been used include PBX-9010, PBX-9011, PBX-9404, PBX-9501, LX-04, LX-07, LX-09, LX-10, LX-11 and insensitive PBXs used for this purpose are PBX-9502 and LX-17. 

PBX-9502 95% TATB + 5% Kel-F 800 High VOD and insensitive PBX. Prindpal IHE in recent nudear weapons and is likely to replace earlier PBXs... 

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. 

Some years ago, French scientists reported DINGU [Structure (2.40)] as an insensitive explosive but subsequently lost interest in it due to its poor performance (VOD 7580ms"1 and density 1.99 gem"3). It is easy to prepare DINGU (by nitration of the condensation product of glyoxal with urea) at a low cost which makes it very attractive [168]. Based on their studies, Cobum and co-workers called this an IHE. It is of course, somewhat more sensitive than TATB but it is much less sensitive than HMX [169]. The data of Coburn and co-workers are in agreement with the findings of Chinese workers who prepared PBXs of DINGU, TNT and... 

TATB/Kel-F800 (90/10 wt.%) is best in terms of thermal stability coupled with a respectable performance [200]. Similarly, PBXs based on TATB, HMX and Kel-F800 are available, and sensitivity data on TATB/HMX-based PBXs clearly show that insensitivity rapidly decreases with increasing HMX content, even at relatively low levels of HMX. Evidently, some trade-off must be made between VOD and safety [201] (Table 2.5). Further, sensitivity and thermal test data (Table 2.6) also indicate that TATB-based formulations rank as the most insensitive explosive formulations [202]. 

The NTO/TNT formulation is characterized by a lower vulnerability than RDX/ TNT and Composition B. NTO is also used to produce pressed PBXs with thermoplastic binders and cast PBXs with thermosetting binders for IMs. NTO is an explosive with calculated performance near that of RDX but with insensitivity approaching that of TATB. Possible use of NTO is as an alternative to RDX in formulations where a lower sensitivity is desired or as an alternative to TATB where better performance is required without a large increase in sensitivity [123, 152, 153, 215]. The formulations based on NTO/binder (FPC-461, Viton-A, Kel-F800, Estane-5702 and Kraton G) in 95/5 (mass percent concentrations) have also been tested for compatibility and none of the NTO/binder formulations showed evidence of incompatibility. 

A new insensitive, cast-cured PBX called -135, has been developed in order to meet the requirements of US Navy s Insensitive Munitions Advanced Development Programfor High Explosives (IMAD/HE). PBXIH-135 has enhanced internal blast performance, improved non-vulnerability and penetration survivability characteristics compared with PBXN-109. Thermobaric explosives are required to defeat hard and deeply buried structures. PBXIH-135 thermobaric explosive which not only offers effective blast and thermal effects, but is also extremely insensitive to factors responsible for accidental detonation during transit or storage, may also be used for this purpose. 

Sjoberg, P. (1992) Low vulnerability characteristics and processing of cast-cured PBXs for insensitive munitions. Proc. Am. Def. Preparedness Association s Joint International Symp. on Energetic Materials Technology, New Orleans, Lousiana, USA, Oct. 5-7, p. 166. 

In the area of expls, information on plastic-bonded expls incorporating silicones can be found in Vol 8, P60-L to P77-L under PBX also, in this Vol see under RIDE , where a uni-temp silicone grease is used as a constituent of this compn. The patent of Stott et al (Ref 21) claims that by using a silicone resin as a binder-fuel, a compressible expl is produced which is insensitive and heat- and solvent-resistant. Thus, asoln of 9lg of Viton (a DuPont Co fluorelastomer — Ref 39, p 921) in 1000ml of acet and 460ml of a soln of 23g Chemlock ... 

In a recent series of impact tests the plastic deformation rates required to initiate chemical reaction were measured at the reaction site for 10 different explosive materials ranging from the sensitive explosives RDX and HMX to the insensitive explosives PBXN-128 and PBX 9502 [21]. The measured plastic deformation rate ranged from Ay/At =. 7 x lO" s for RDX or HMX to Ay/At > 3 x 10 s PBXN-128 to PBX-9502. Substituting these measured plastic deformation rates into the expression for the calculated plastic deformation rate in the previous paragraph implies that first reaction occurs in the impact tested materials when 10 < T(x,U)pc < 10 . As shown above, T(r, U)pc = 10 predicts the observed plastic strain in RDX crystals just prior to the initiation threshold. 

RDX is a white, crystalline solid with a melting temperature of 204 °C. It attained military importance during World War II since it is more chemically and thermally stable than PETN and has a lower sensitiveness. Pure RDX is very sensitive to initiation by impact and friction and is desensitized by coating the crystals with wax, oils or grease. It can also be compounded with mineral jelly and similar materials to give plastic explosives. Insensitive explosive compositions containing RDX can be achieved by embedding the RDX crystals in a polymeric matrix. This type of composition is known as a polymer bonded explosive (PBX) and is less sensitive to accidental initiation. 

Polymeric materials can be added to secondary explosives to produce polymer bonded explosives (PBXs). The polymers are generally used in conjunction with compatible plasticizers to produce insensitive PBXs. The polymers and plasticizers can be in the nitrated form which will increase the power of the explosive. These nitrated forms are known as energetic polymers and energetic plasticizers. 

Substantial previous work by Pagoria [2] and associates has attempted to discover new insensitive high explosives (IHE) such as LLM-105 that have higher energy densities than 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). TATB is well noted for its thermal stability (m.p. > 370 C) low insensitivity to external stimuli such as drop hammer, spark, and friction and its very low solubility in a wide array of solvents. We compare our results for RX-55-AE-5 to PBX-9502, LX-17 and TATB [3]. PBX 9502 is formulated from 95% TATB and 5% Kel-F 800 and LX-17 is formulated from 92.5% TATB and 7.5% Kel-F 800. 

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