Physicochemical Properties of Propellants

The physicochemical properties of propellants with the compositions hmx(0-4), Ihmx(0-6), and hmx(0-8) are shown in Table 7.3. Since the energy density of HMX is higher than that of GAP, the adiabatic flame temperatures of HMX-GAP propellants increase with increasing hmx- 

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Table 5 Physicochemical Properties of Chlorofluorocarbon and Alternative Hydrofluorcarbon Propellants...

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

Table 4.8 Physicochemical properties of a single-base propellant.

Since NG is highly shock-sensitive, other types of nitrate esters can be used to formulate non-NG double-base propellants. DEGDN, TEGDN, and TMETN are typical examples of energetic nitrate esters that can be mixed with NC. These nitrate esters are less energetic than NG, and their sensitivities to friction and mechanical shock are accordingly lower than those of NG. Thus, the mass fraction of desensitizer used in propellant formulation can be lower than when NG is involved. The physicochemical properties of these nitrate esters are shown in Tabs. 2.3 and 2.5-2.7. 

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. 

Table 7.7 Physicochemical properties of TAGN-GAP and HMX-GAP propellants composed of cap(0-80)-...

Table 10.7 shows the physicochemical properties of the crystalHne materials used as oxidizers. Potassium and sodium are combined with nitrate or perchlorate to form stabilized crystalline oxidizers. Metal oxides are formed as their combustion products. On the other hand, ammonium ions are combined with nitrate or perchlorate to form stabilized crystalline oxidizers such as NH4NO3 and NH4CIO4 without metal atoms. When these oxidizers are decomposed, no solid products are formed. As discussed in Section 10.1.1, for the oxidizers used for propulsion, such as in propellants for rockets and guns, the molecular mass of the combustion products needs to be as low as possible. 

Hydrocarbon polymers (HCP) are used not only as fuel components but also as binders of crystalline oxidizers and metal powders in the formulation of pyrolants, similar to composite propellants and plastic-bonded explosives. There are many types of HCP, the physicochemical properties of which are dependent on their molecular structures. The viscosity, molecular mass, and functionality of the poly-... 

Since the energetics of nitropolymer propellants composed of NC-NG or NC-TMETN are limited due to the limited concentration of oxidizer fragments, some crystalline particles are mixed within these propellants in order to increase the thermodynamic energy or specific impulse. The resulting class of propellants is termed composite-modified double-base (CMDB) propellants . The physicochemical properties of CMDB propellants are intermediate between those of composite and double-base propellants, and these systems are widely used because of their great potential to produce a high specific impulse and their flexibility of burning rate. 

The physicochemical properties of excipients used in pMDIs are different from most dosage forms and are a derivative of the propellant system that constitutes the bulk of the formulation. The transition from CFC-based formulations to HFA-based systems has been lengthened by the historically empirical formulation approach and the dissimilarity of the physicochemical properties of the replacement HFA propellants. Both HFA 134a and HFA 227 show an increased polarity, revealed in increased dipole moments and dielectric constant. The most significant practical change has therefore been a general change in the solvency properties. 

The first challenge encountered during the reformulation with HFA propellants was the altered physicochemical properties of HFA 134a and HFA 227 compared to the CFC propellants [124], Table 2 compares the physicochemical properties of the CFC and HFA propellants [124], The increased polarity of HFA 134a and HFA 227 is illustrated by the increased dipole moments and dielectric constant. From a practical point of view, the altered solvency properties of the HFA propellant for the drug, excipient, water, and, surprisingly, components of the MDI have been the... 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropo-... 

NC and NG have oxygen available in the form of 0-N02, which is attached to the organic moiety (e.g., cellulose) from which they are derived. The physicochemical properties of double-base propellants such as energy density, mechanical properties and chemical stability depend on the fractions of NC, NG, stabilizers, plasticizers, and catalysts. Though the energy density is increased by increase in the fraction of NG, the mechanical properties are adverely affected and chemical stability is decreased. 

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