U.V. Varadaraju

Bio: U.V. Varadaraju is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Thermal decomposition & Ammonium perchlorate. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

Analytical Methods for Stability Assessment of Nitrate Esters-Based Propellants.

Abstract: Nitrate esters-based propellant (NEBP) belongs to the main classes of energetic materials being used in civilian and military applications. These NEBPs are not highly stable, and during aging, some of their functional characteristics may change, what can lead to serious safety problems. A thorough analytical characterization of NEBP is of fundamental importance to provide an adequate support for their stability and safe life assessment. Moreover, in order to safely store and fully exploit these energetic materials, accurate analytical techniques and strategies are indispensable to efficiently judge their properties during aging. Although various methodologies have been developed worldwide to evaluate the aging behavior of NEBP, the characterization is not a simple task and often involves the combination of several techniques, whose results have to be evaluated together. This review sought to evaluate existing analytical techniques which can be utilized for a suitable analysis of NEBP stability and aging, evidencing their respective advantages and shortcomings. The employment of each examined technique is described and discussed by relevant examples from the literature.

Experimental study on ballistic behaviour of an aluminised AP/HTPB propellant during accelerated aging

Abstract: 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.

Nitryl perchlorate as the essential intermediate in the thermal decomposition of ammonium perchlorate

Abstract: Because of its use as a solid propellent and more generally in pyrotechnic systems, the thermal decomposition of ammonium perchlorate (AP) has been extensively studied. The breakdown of this salt is complicated, an exceptional feature being that the low-temperature (<∼570K) decomposition is incomplete (∼30%), yielding a residual solid with a composition and crystal structure very similar to those of the original reactant. Extensive rate measurements and kinetic analyses1–5 have produced two alternative general hypotheses of reaction mechanisms5, in which rate control has been attributed to steps involving the transfer of either a proton4 or an electron6. In the present study, we have found that the addition of various inorganic nitrates reduces the induction period to reaction and increases the extent of the low-temperature decomposition of AP. The measured rate of decomposition was close to that estimated for reaction involving nitryl perchlorate (NO2ClO4) as an intermediate and we have detected small quantities (∼0.08%) of an oxidized nitrogenous species in partly reacted AP. We therefore propose a novel reaction mechanism in which NO2ClO4 is the essential intermediate in the thermal decomposition of ammonium perchlorate.