AP/HTPB based composite
propellants with additives such as ammonium oxalate (AO), mixture of ammonium
oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG
and FTIR experiments. The results show that the burning rates of these propellants
are decreased significantly. TG-DTG experiments indicate that decomposition
temperatures of AP with these additives are increased. Furthermore, the activation
energy of the decomposition reaction of AP is also increased in the presence
of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition
of AP. The burning rates of these propellants are decreased. The burning rate
temperature sensitivity of AP/HTPB based propellants is reduced significantly
by the addition of AO or AO/SC. But the effect of AO is less than that of
AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the
same time, to reduce pressure exponent. The reduced heat release at the burning
surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity.
Synergetic action is probably produced between AO and SC within AP/HTPB based
propellants in the pressure range tested. This synergetic effect causes the
heat release to reduce and the burning surface temperature to increase. Moreover,
it makes the net exothermal reaction of condensed phase become little dependent
on T0. Thus, the
burning rate temperature sensitivity is reduced.
The thermal decomposition of ammonium perchlorate (AP) is considered to be the first step in the combustion of AP-based composite
propellants. In this report, the effect of the specific surface area of titanium oxide (TiO2) catalysts on the thermal decomposition characteristics of AP was examined with a series of thermal analysis experiments.
It was clear that the thermal decomposition temperature of AP decreased when the specific surface area of TiO2 increased. It was also possible that TiO2 influences the frequency factor of AP decomposition because there was no observable effect on the activation energy.
The chemical stability of a propellant and its influence on the ballistic properties during aging is a subject of interest.
The effect of aging on ballistic properties, viz., ignition delay, burning rate, and heat of combustion for an aluminised
ammonium perchlorate–hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant during accelerated aging were investigated.
Samples of composite propellants were aged at 60 and 70 °C at relative humidity of 50% in a climatic chamber. The propellant
samples were tested with pressurized nitrogen gas environment for ignition delay measurement. Test results indicate that aging
does not have any appreciable effect on ignition delay. The change in ignition delay time is less than 3% within the scatter
of the data. Experiment results indicate that burn rate do affect with pressure but aging does not have much effect on burn
rate. It was also observed that the burning rate at low pressures did not undergo significant changes during the aging period.
The most significant of all the ballistic properties of this propellant is the burning rate exponent which increased by about
10% during the aging period.
Authors:W. de Klerk, A. van der Heijden, and W. Veltmans
In a search for new storable high performance propellants for the European Space Agency (ESA), the solid oxidiser hydrazinium
nitroformate (HNF) has been identified as a very promising ingredient for a new storable composite propellant.
The purity and stability of HNF after production are very important indicators for the quality of HNF. In order to characterise
HNF,many thermal analysis techniques as DSC and TG/DTA were performed to obtain more information about its stability and its
(in)compatibility with other materials. Also some less familiar techniques such as the vacuum stability test and microcalorimetry
have been performed.
In relation to the safety, a relation between the friction and impact sensitivity and the physical-chemical properties is
Authors:M. Pandey, S. Jha, R. Kumar, S. Mishra, and R. R. Jha
] investigated the effects of organo-metallic compounds of chromium- and cobalt-like chromium acetyl acetonate, cobalt oxide, cobalt stearate and cobalt 2-ethyl hexanoate on burning rate of HTPB–AN compositepropellant. The propellants were prepared using the