DB propellants

Experimental observation indicates that the AP particles within the matrix of a double-base (DB) propellant appear to burn and regress in size spherically on the burning surface. Thus, the regression rate of the particles appears to depend on their instantaneous diameter. The average burning rate of each AP particle is determined as a function of pressure, as shown in Fig. 8.3. The burning rate is represented by r p = where Kj is independent of pressure, r p is the burning rate... 

DB propellants - Konkurs and HOT missiles (Russian), Milan missile (French), X-29 and 122mm rockets (Russian). 

A solid fuel containing a mixture of wood flour and DB propellant as a binder can provide adequate heat energy to warm food and to prepare tea or coffee. These fuels are highly cost-effective as the ingredients, particularly the DB propellants, are either from the waste available in plenty from the ordnance factories or life-expired DB propellants available from the armed services. This also reduces the disposal problem of DB propellant waste to a large extent. 

These propellants are also called colloidal or double-base (DB) propellants and have nitrocellulose (NC) and nitroglycerine (NG) as their principal ingredients. Some ingredients may also be added in small proportions to serve as stabilizer, non-explosive plasticizer, coolant, lubricant, opacifier and burning-rate modifier or other additives to impart desirable properties to the propellants. These propellants are processed into desired shapes by two methods, that is, extrusion and casting. They find wide applications in anti-tank missiles. 

These propellants also contain nitroglycerine (NG) in addition to NC and the proportion of NG depends on the performance desired from double-base (DB) propellants. DB propellants are more energetic than SB propellants and have Q value between 3300 and 5200Jg 1. There are two disadvantages in the use of DB propellants higher erosion of the gun-barrel as a result of higher flame temperatures and presence of a muzzle flash which discloses the location of the gun. DB propellants are used in pistols, mortars, rockets and missiles. 

The pressure exponent (n) is the characteristic of a specific propellant and also depends on the pressure range. For DB propellants, it is in the range from 0.2 to 0.5 but AP-based composite propellants exhibit relatively low values (0.1 to 0.4). The mathematical derivations clearly show that the value of n can never exceed 1 and a value close to 0 (zero) is always preferred from safety considerations. 

A new energehc azide plashcizer which is beneficial for thermal decomposihon of modified DB propellants and hexogen. Also improves combushon properhes [173]. 

Lead compounds For the first time, Avery et al. observed the unusual behavior of lead compounds on ballistics of DB propellants [234]. 

Short sections of thin metal wires (good conductor of heat) such as , Pb, Al, Cu, Ag and Mo Increase burn rates of DB propellants containing ballistic modifiers such as lead salts of salicylic and 2-ethylhexanoic add without any adverse effect on the plateau region [240]. 

Rare-earth compounds lanthanum compounds Not only increase burn rate of DB propellants but also exhibit plateau or mesa combustion in the middle or high pressure range [244]. 

Cobalt stearate, salicylate and acetyl acetonate etc. Promising platonizers and catalysts for DB Propellants [247]. 

Ultrafine carbon fibers Non-toxic burn-rate modifiers for cast DB propellants in the absence of lead salts [248]. 

Less Toxic and Non-Toxic Burn-Rate Modifiers for DB Propellants... 

The choice of material for use as inhibitor depends mainly upon the type of propellant, that is, DB, CMDB, Composite and Fuel-rich and also on the ingredients in their formulations. For double-base propellants, cellulosic materials such a cellulose acetate, ethyl cellulose and different filled or unfilled flexible polyesters are used while fuel or binder material filled with inert substances such as asbestos, mica, silica, etc. in fine powder form is used for composite propellants. Since nitroglycerine is present in CMDB propellants also as in DB propellants, the materials used for DB propellants may also be used with minor modifications for the inhibition of CMDB propellants. 

The major ingredients of composite propellants are ammonium perchlorate (AP-68%), metal powder (-16%) and polymeric binders like CTPB, HTPB and Thiokol. As total solids loading in composite propellants is -85-88%, polyesters which are commonly used for inhibition of DB propellants, have a relatively weak bond with composite propellants. This problem is further aggravated because of higher shrinkage in the case of polyesters. 

The inhibition of composite propellants is somewhat easier than that of DB propellants. The binders used for composite propellants (with or without fillers) have been reported for inhibition of composite propellants. Such inhibition systems possess stronger bonds with composite propellants and prove to be more compatible coupled with better shelf-life of the inhibited propellants. However, epoxy or novolac epoxy resin with or without inert fillers is generally preferred for the inhibition of composite propellants due to a combination of properties possessed by them. The inhibition is usually done by casting technique and inhibition thickness is usually required on higher side in order to make the missions successful. In India, thread winding technique or inhibitor sleeve technique is preferred where 2.5-3.0mm inhibition thickness is sufficient as against 3.5-4.0 mm in case of inhibition by casting technique . 

The combustion temperatures are much higher in CMDB propellants than that of DB and composite propellants and therefore, inhibition systems for CMDB propellants should have better BS and ablative properties. As major ingredients of CMDB propellants are NC and NG similar to DB propellants, it is logical to use polyesters which have already proved their potential for DB propellants for inhibition of CMDB propellants. However, the unsaturated polyesters which function... 

Camp, A.T., and Crescenzo, F.G. (1964) Copper and lead burning-rate modifiers for DB propellants containing aluminium. US Patent 3,138,499. 

L.H., and Summmerfield, M. (1973) The burning rate flexibility of plastisol DB propellants. Proc. 10th Inti Symposium on Space Technology and Science,... 

Low-toxic burning rate catalysts for DB propellants. Proc. 27th Inti Ann. Conf. ICT, Karlsruhe, Germany, June 25-28, 1996, pp. 76/1-76/9. 

Z. (1996) Effects of rare earth compounds on the combustion of DB propellants. Proc. Ind Autumn Seminar on Propellants, Explosives and Pyrotechnics, Beijing, China, Oct. 07-10, 1996, p. 206. 

Neidert, J.B., and Askins, R.E. (1994) Castable DB propellant containing ultrafine carbon fiber as a ballistic modifier. US Patent 5,372,664. 

The combustion behavior of Alex was also studied in gun propellants (up to high pressure =280 M Pa) and it was observed that the burn rate is nearly doubled compared with high-calorie conventional DB propellants [118]. Simultaneously, n decreases from >0.8 to 0.66. 

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