Chemistry Reference
In-Depth Information
3. Combustion catalysts such as CuCr
2
O
7
and SiO
2
were not found to affect the
high-temperature decomposition of the material's condensed phase. The addition
of Fe
2
O
3
results in a significant acceleration of the high-temperature reaction and
a decrease in the activation energy value down to
E
125 kJ mol
−
1
.
Joint analysis of these results and data on low-temperature decomposition and
thermal explosions, as well as results from experiments on the effect of Fe
2
O
3
and CuCr
2
O
7
on materials burning in the chemical arc, have led to the follow-
ing conclusion. In contrast to Fe
2
O
3
, which catalytically affects high-temperature
processes in the condensed and gas phases of the burning fuel, adding CuCr
2
O
7
to
the binder mainly influences gas-phase reactions (the introduction of CuCr
2
O
7
into AP pellets is known to result in accelerated decomposition and burning).
However, in composite solid propellants, as a rule there is no a direct contact be-
tween the AP grains and the catalyst (the latter being uniformly distributed in the
binder volume which occupies intergranular space in the composite). As opposed
to other ignition techniques (radiant flux, electrically heated wires, etc.), ignition
by means of a hot heat-conducting block provides information about the kinetics
of reactions in the condensed phase. This is explained by the almost complete
suppression of the release of heat from the gas-phase reaction in the thin gap
between the sample and the block due to the “cooling” action of the latter.
4. The kinetic constants for slow-burning polyolefin-based model systems and for
fast-burning rubber resin-based material are quite similar. In this case, one can
assume that the high burning rate of the latter system is associated with the high
degree of homogeneity of the material due to the use of submicron grain-sized
AP. As a result, the degree of conversion of the condensed phase attains quite a
high value due to the high-temperature thermally self-accelerating reaction (
E
=
242 kJ mol
−
1
) before the rate of volumetric heat release in the fuel surface layer
becomes limited by dispersion and microheterogeneity effects.
5. The simple and reliable flash-block-based ignition technique can be used as an
express method for evaluating high-temperature decomposition parameters and
determining the ignition delay times for composite solid propellants under fixed
thermophysical conditions (intensive aerodynamic heating and others).
≈
References
1. Zel'dovich JaB (1939) Zh Eksp Teor Fiz 9:1530
2. Merzhanov AG (1965) In: Encyclopaedia on Physics. Sovetskaya entsiklopediya, Moscow,
p 458
3. Merzhanov AG, Dubovitsky FI (1966) Usp Khim 35:656
4. Merzhanov AG, Averson AE (1971) Combust Flame 6:89
5. Averson AE (1968) PhD thesis. Institute of Chemical Physics of the USSR Academy of
Sciences, Chernogolovka, Russia
6. Rosenband VI, Barzykin VV (1967) Combust Explos Shock Waves 4:283
7. Rosenband VI, Barzykin VV (1967) Combust Explos Shock Waves 4:96
8. Carslaw HS, Jager JC (1959) Conduction of heat in solids, 2nd edn. Clarendon, Oxford
9. Shteinberg AS, Ulybin VB, Barzykin VV, Merzhanov AG (1966) J Eng Phys Thermophys
4:282
