Composite propellants, energetic binder

The third type of propellent explosive, the composite type, is a more recent development, the purpose of which is to provide rocket propellants of increased thrust, compared with the ordinary varieties. Composite propellants are based on an oxidising solid, commonly a perchlorate, together with an organic binder which both acts as fuel and gives adequate mechanical strength to the mixture. The search for even more energetic compositions continues, but because of the military importance of the... 

The energetic nature of the azido group makes its incorporation into energetic polymers and binders very desirable. 3,3-Bis(azidomethyl)oxetane (BAMO) (28) and 3-azidomethyl-3-methyloxetane (AMMO) (33) are energetic monomers which on polymerization result in the energetic polymers poly[BAMO] (32) and Poly[AMMO] (34), respectively, both of which are under evaluation as potential energetic alternatives to HTPB in composite propellant formulations. ... 

Azide polymers such as GAP and BAMO are also used to formulate AP composite propellants in order to give improved specific impulses compared with those of the above-mentioned AP-HTPB propellants. Since azide polymers are energetic materials that burn by themselves, the use of azide polymers as binders of AP particles, with or without aluminum particles, increases the specific impulse compared to those of AP-HTPB propellants. As shown in Fig. 4.15, the maximum of 260 s is obtained at (AP) = 0.80 and is approximately 12 % higher than that of an AP-HTPB propellant because the maximum loading density of AP particles is obtained at about (AP) = 0.86 in the formulation of AP composite propellants. Since the molecular mass of the combustion products. Mg, remains relatively unchanged in the region above (AP) = 0.8, decreases rapidly as (AP) increases. 

The combustion wave of an HMX composite propellant consists of successive re-achon zones the condensed-phase reachon zone, a first-stage reaction zone, a second-stage reaction zone, and the luminous flame zone. The combustion wave structure and temperature distribution for an HMX propellant are shown in Fig. 7.47. In the condensed-phase reaction zone, HMX particles melt together with the polymeric binder HTPE and form an energetic liquid mixture that covers the burning surface of the propellant. In the first-stage reaction zone, a rapid exother-... 

There are a number of inert binders such as polyester, epoxy, polysulfide, polyurethane which have been reported as binders for composite propellants and plastic bonded explosives (PBXs). At present, hydroxy-terminated polybutadiene (HTPB) is regarded as the state-of-the-art workhorse binder for such applications. However, the recent trend is to use energetic binders such as poly [3,3-bis(azidomethyl oxetane)] [poly(BAMO)], poly (3-azidomethyl-3-methyl oxetane) [poly(AMMO)], PNP, GAP diol and triol, nitrated HTPB(NHTPB), poly(NiMMO), poly(GlyN) and nitrated cyclodextrin polymers poly(CDN) for PBXs and composite propellants in order to get better performance. 

By very carefully controlling the reaction of pentaerythritol in nitric acid, PETRJN (Figure 3.29) instead of PETN can be obtained. PETRIN is not a particularly desirable explosive, but because of the hydroxyl group left on the last of the outer carbons, this material has one particularly useful feature. The hydroxyl can be reacted to the acid group in acrylic acid to form a polymerizable material, PETRJN-acrylate. PETRJN-acrylate polymer, a plastic, is used as an energetic binder in some composite rocket propellants. 

Compositions that hold together a charge of finely divided particles and increase the mechanical strength of the resulting propellant grain when it is consolidated under pressure. Binders are usually resins, plastics, or asphaltics, used dry or in solution (-> Energetic Binders). 

Poly-AMMO is synthesized via cationic polymerisation from the monomer 3-azidomethyl-methyl-oxetane (AMMO). The polymerisation reaction is quenched with water to get polymer chains with hydroxyl endgroups which enable to react these pre-polymers later with isocyanate for curing reaction. Poly-AMMO is suggested as - energetic binder component in -< composite propellants and is in the scope of actual research. 

Epichlorohydrin or chloromethyloxirane is manufactured from allyl chloride, and, in 2006, had a merchant price of US 1.66 kg [4]. It is used as a building block in the manufacture of plastics, epoxy resins, phenoxy resins, and other polymers, and as a solvent for cellulose, resins, and paints, and has also found use as an insect fumigant. Epoxy resins (aryl glycidyl ethers) are manufactured successfully in large scale (1.2 x 10 metric tons in 2000) [26] and are widely used in a variety of industrial and commercial applications [27]. These are made by addition reactions of epichlorohydrins or by epoxidation of allyl ethers or esters (Table 1.1). Epichlorohydrin can be reacted with an alkali nitrate to produce glycidyl nitrate, an energetic binder used in explosive and propellant compositions. 

Energetic plasticizers and binders for explosive and propellant compositions... 

Polyurethane energetic block copolymers, (VIII), consisting of toluene diisocyanate, 1,4-butanediol, and dihydroxyl poly(3-azidomethyl-3-methylox-etane) were prepared by Sanderson et al. (3) and used as binders in high-energy compositions, especially rocket propellants. Poly(glycidyl nitrate) urethanes were previously prepared by the authors and are discussed (4). 

Theoretical performance calculations were first made on propellant compositions containing the acetylenic polyurethane binder and ammonium perchlorate as the oxidant. These calculations assumed a shifting equilibrium in the rocket exhaust. The calculations demonstrated two of the principal advantages of the acetylenic binders—namely the increased performance provided by the energetic triple bond and the fact that optimum performance is achieved at relatively low levels of oxidizer. Specific impulse values of 251—253 lbf.-sec./lbm. were calculated at 1000 p.s.i.a. chamber pressure for optimum oxidizer loadings. Furthermore, peak performance was achieved at 83% oxidizer, and even at an 80% loading a theoretical I8P of 250 seconds was obtained. 

Propellants are explosive materials with low rates of combustion diat will ideally burn at uniform rates after ignition without requiring interaction with the atmosphere [1,2], They frequently involve several components, including an energetic oxidizer, a plasticizer to facilitate processing, and a polymeric binder. The specific impulse of such propellants is necessarily that of the composite mixture. Oui focus here is on chemical and structural factors affecting the specific impulse of the oxidizer, which will be designated as a monopropellant. 

Tappan BC, Brill TB (2003) Thermal decomposition of energetic materials 85 Cryogels of nanoscale hydrazinium perchlorate in resorcinol-formaldehyde. Propellants Explosives and Pyrotechnics 28(2) 72-76. Li J, Brill TB (2005) Nanostructured energetic composites of CL-20 and binders by sol-gel methods. Propellants Explosives and Pyrotechnics 31(1) 61-69. 

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