HTPE binder

In order to avoid the use of lead compounds on environmental grounds, lithium fluoride (liF) has been chosen to obtain super-rate burning of nitramine composite propellants.P7281 Typical chemical compositions of HMX composite propellants-with and without liF are shown in Table 7.4. The non-catalyzed HMX propellant is used as a reference pyrolant to evaluate the effect of super-rate burning. The HMX particles are of finely divided, crystalline (3-HMX with a bimodal size distribution. Hydroxy-terminated polyether (HTPE) is used as a binder, the OH groups of which are cured with isophorone diisocyanate. The chemical properties of the HTPE binder are summarized in Table 7.5. 

Binder (fuel) HTPB, CTPB, PBAN, HTPE, HTPS, HTPA, PU, PS, PVC... 

Various types of binders are used to formulate AP composite propellants. Binders such as HTPB and HTPE decompose endothermically or exothermically at the burning surface. The burning rates of AP composite propellants thus appear to be dependent on the thermochemical properties of the binders used. Figs. 7.17 and 7.18 show In r versus In p plots for AP composite propellants made with five differ-... 

The effects of four types of binders, HTPS, HTPE, HTPA, and HTPB, on the burning rates of HMX composite propellants are shown in Fig. 7.33. The physicochemi-... 

The presence of carbonaceous fragments can be attributed to the low oxygen content in the HTPB binder, 3.6%, compared to oxygen contents in the HTPS, HTPE, and HTPA binders of more than 25 %, as shown in Table 4.3. 

Though the physicochemical properties of HTPE and HTPS are different, both are subject to a similar super-rate burning effect. However, the magnitude of the effect is dependent on the type of binder used. As in the case of double-base propellants, the combustion wave structures of the respective propellants are homogeneous, even though the propellant structures are heterogeneous and the luminous flames are produced above the burning surfaces. 

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-... 

Fig. 7.56 Effect of binder on the burning characteristics of AP composite propellants (HTPB and HTPE).

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 =... 

The effects of four types of binders, HTPS, HTPE, HTPA, and HTPB on burning rate of HMX composite propellants are shown in Fig. 7-16. The physicochemical properties of these binders are shown in Table 4-7. Each propellant is composed of 80 % HMX and 20 % binder and the HMX particles are a bimodal mixture of large sized (220 pm in diameter) 70 % and small sized (20 pm in diameter) 30 %. The oxygen concentration of HTPS is the highest and that of HTPB is the lowest in the four types of binders1191. The adiabatic flame temperatures of HTPS, HTPE, HTPA, and HTPB propellants are 1940 K, 1910 K, 2040 K, and 1800 K, respectively. 

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