BAMO-THF copolymer

Since BAMO polymer is a solid at room temperature, BAMO monomer is copolymerized with tetrahydrofuran (THF) in order to formulate a liquid BAMO copolymer that is used as a binder in propellants and explosives, as shown in Fig. 4.9. The terminal OH groups of the BAMO-THF copolymer are cured by reaction with the NCO groups of hexamethylene diisocyanate (HMDl) and then cross-linking is carried out with trimethylolpropane (TMP). The physical properties of such a copolymer with a BAMO/THF composition of 60/40 mol% are shown in Table 4.7.1151... 

BAMO is also copolymerized with nitratomethyl methyl oxetane (NIMO) to formulate the energetic liquid polymer BAMO-NIMO. Since NIMO is a nitrate ester containing an -O-NO2 bond in its molecular structure, BAMO-NIMO copolymer is more energetic than BAMO-THF copolymer. The chemical structures of BAMO and NIMO are both based on the oxetane structure, and the structure of the BAMO-NIMO copolymer is shown in Fig. 4.10. 

Fig. 5.23 The burning rate of BAMO/ THF copolymer increases as the mass fraction of BAMO is increased at constant pressure.

BAMO is perhaps the most prominent among the azido oxetanes class in terms of the number of polymers and copolymers reported so far. Due to its symmetrical azido groups, it assumes special significance as a hard block repeating unit in a thermoplastic elastomer. However, the homopolymer is solid and cannot be used directly for binder applications because of its crystal-tine nature. Also, poly(BAMO) shows relatively poor mechanical properties as a binder for solid rocket propellants [153]. Many copolymers of BAMO with non-energetic co-monomers tike tetrahydrofuran (THF) have been reported. The BAMO-THF copolymer is an excellent candidate for binder applications with its energetic BAMO content coupled with the THF block which affords... 

Structure (4.22) BAMO-TFIF Copolymer Scheme 4.5 Synthesis of poly(BAMO) and BAMO-THF copolymer. 

Fig. 5.24 Effect of initial temperature on the burning rate of BAMO/THF = 60 40 copolymer.

Fig. 5.25 Temperature gradient, conductive heat flux, convective heat flux, and heat flux by chemical reaction as a function of distance from the burning surface at 3 MPa (initial temperatures 243 K and 343 K) for BAMO/ THF = 60 40 copolymer.

During BAMO copolymer burning in a pressurized inert atmosphere gaseous and carbonaceous solid fragments are formed exothermically at the burning surface. The temperature in the combustion wave of BAMO copolymer increases from the initial temperature T0 to the burning surface temperature Ts, and to the flame temperature Tf. The burning surface temperature of BAMO copolymer composed of BAMO/THF = 6/4 increases as T0 increases at constant pressure p = 3 MPa Ts = 700 K at T0 = 243 K and Ts = 750 K at T0 = 343 K. The effect of T0 on Ts defined in (idTs/dT0)p is determined to be 0.50 31l... 

The heat of decomposition, Qj, of BAMO copolymer containing different levels of N3 bond density, KN3), is shown as a function of KN3) in Fig. 5.21. BAMO prepolymer is copolymerized with THF. The N3 bond density is varied by adjusting the mass fraction ratio of BAMO prepolymer and THF. 

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