AP-GAP Composite Propellants

Fig. 4.15 Specific impulse, adiabatic flame temperature, and molecular mass of the combustion products for AP-GAP composite propellants.

When HNF or ADN particles are mixed with a GAP copolymer containing aluminum particles, HNF-GAP and ADN-GAP composite propellants are formed, respectively. A higher theoretical specific impulse is obtained as compared to those of aluminized AP-HTPB composite propellants.However, the ballistic properties of ADN, HNIW, and HNF composite propellants, such as pressure exponent, temperature sensitivity, combustion instability, and mechanical properties, still need to be improved if they are to be used as rocket propellants. 

The gas-generating propellants are (1) ammonium perchlorate-polybutadiene (AP-PB) composite propellants, (2) nitrocellulose-nitroglycerin (NC-NG) doublebase propellants, and (3) glycidyl azide polymer (GAP) propellants. 

Typical gas-generating propellants are (1) AP-PB composite propellant composed of 50% AP and 50% HTPB that is cured with isophorone diisocyanate (IPDI), (2) NC-NG double-base propellant composed of 70% NC and 30% NG that is plasticized with diethyl phthalate (DEP), and (3) GAP propellant composed of GAP copolymer that is cured with 12.0% hexamethylene diisocyanate (HMDI) and cross-linked with 3.2 % trimethylolpropane (TM P). 

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 polymeric binders used for nitramine composite propellants are similar to those used for AP composite propellants, i. e. HTPB, HTPE, and GAP. The combustion performance and the products of HMX composite propellants are shown in Figs. 4.17 and 4.18, respectively. Here, the binder mixed with the HMX particles is GAP, as in the AN-GAP propellants shown in Fig. 4.16. Though the maximum Tf and f, are obtained at (HMX) = 1.0, the maximum HMX loading is less than 0.80for practical HMX-GAP propellants, at which fp = 250 s and 7 =... 

Eiselle, S., and Menke, K. (2001) About the burning behaviour and other properties of smoke reduced composite propellants based on AP/CL-20/GAP. Proc. 32nd Inti. Ann. Conf. of ICT, Karlsruhe, Germany, July 03-06, pp. 149/1-149/18. 

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