Aging propellants

A brief description is given in Blaster s Handbook(l9 5 2),449 50. The bomb is also mentioned by Cook( 19 53), 280 Aged Propellant, Solubilities. Solubilities of some aged gun propellants were recently detd by P.E.Gagnon et al and reported in TM 229/59 of ARDE, Canada(l959)... 

An estimation of the probable -> Shelf Life of aged propellants can be made by chromatography4). If e.g. diphenylamine is used as a stabilizer, the transformation into the nitro derivatives up to hexanitrodiphe-nylamine can be analysed if this stage is reached, decomposition of the powder occurs. 

To give an idea of the stability of an aged propellant, the relative amounts of the stabilizer and its derivatives in the propellant can be measured. The occurence of nitro- and nitroso diphenylamine derivatives is not a real proof that the propellant is unstable, indicating however that less than the original amount of stabilizer is available. 

Effect of Storage Condition Upon the Mechanical Properties of CTPB 2 Propellant P 426 Effect of Aging (70°) and Average Humidity During Processing/Testing upon, ... 

Parker, The Transformation Products of Carbamite Produced in the Ageing of Service Propellants , GtBrit AML Rept A/12(M) March 1948 8) B.L. Hollingsworth, JCS 1959, 2420... 

Mayo, The Chemistry of Aging of Hydrocarbon Binders in Solid Propellants , CP lA Publ 262, Johns Hopkins Univ, Silver Spring (1975)... 

Hydroxy-terminated polybutadiene (HTPB) is considered to be the best binder for obtaining high combustion performance, superior elongation properties at low temperatures, and superior mechanical strength properties at high temperatures. This combination of properties is difficult to achieve in double-base propellants. HTPB is characterized by terminal -OH groups on a butadiene polymer. The other type of butadiene polymer used is carboxy-terminated polybutadiene (CTPB), which is cured with an imine or an epoxy resin. It should be noted that CTPB is somewhat sensitive to humidity, which has an adverse effect on its ageing charac-... 

Though the theoretical of black powder is less than that of single-base, doublebase, and AP-based composite propellants, black powder is useful for short-duration operation of simple propulsive systems. The advantages of the use of black powder are its low cost, its minimal deterioration with age, and simple regulation of the propulsive force by adjustment of the quantities used. 

Detonation Velocity, Influence of Ageing of Gelatin Explosives an. Ageing of dynamites and its influence on their sensitivity to detonation by influence was described in Vol 1 of Encycl, pp A110 to A112, but its influence on deton velocity was not discussed. Ageing of propellants was described on p A112... 

Figure 2. Effect of age on flow properties of uncured PVC plastisol propellant (17)...

In principle any diol/triol mixture which reacts with a diisocyanate will yield a network. However, to be useful as propellant binder, additional requirements must be met. The most important are low cure shrinkage, low reaction exotherm, rubbery characteristics down to arctic temperatures, good aging stability, and ease of handling during propellant manufacture. 

Generally one distinguishes between humidity and thermal aging of propellants. 

Table X. Mechanical Properties of Polyether—Polyurethane Propellant" after Accelerated Aging...

Another means to achieve better bonding is to increase the contacting surface area. Finally, the aging stability of liners has to be at least as good as that of the propellants with which it is used. 

The problems associated with the multifunctional curing agents for CTPB and the resultant aging behavior of the cured polymers have led to a practical solution for curing binders and propellants—i.e., using mixed aziridines or a mixture of an aziridine and an epoxide. Such mixtures, when appropriately balanced, usually provide satisfactory mechanical behavior and high temperature stability. In dual curing systems such as MAPO and BITA or MAPO and a suitable multifunctional epoxide,... 

---