Studies on the Effect of Ageing on Thermal, Ballistic and Mechanical Properties of Advanced Energetic Propellants

Abstract

In order to study the ageing behaviour of advanced energetic propellants during storage and the effect of nitrate ester on the shelf life, accelerated ageing tests were conducted on two types of propellants based on nitrate esters, BTTN (as P‐1) and NG:BTTN (1 : 1) mixture (as P‐2). Mechanical and ballistic characterization of P‐1 and P‐2 propellants were carried out during storage at ambient (27 °C) and elevated temperature (40 °C and 55 °C). During ageing, tensile strength and Young‘s modulus of propellants are increasing and percentage elongation is decreasing due to depletion of nitrate ester from the locus. Also, there is a loss of stabilizer with time during ageing. Thermal decompositions of P‐1 and P‐2 were studied using differential thermal analysis at four heating rates (1 °C/min, 2 °C/min, 5 °C/min, and 10 °C/min) during ambient and accelerated ageing. Activation energies for thermal decomposition were calculated using Kissinger's and Ozawa's methods by assuming first‐order reaction kinetics for first stage decomposition in DSC studies of aged propellants. The shelf life of propellants was predicted based on the classical Arrhenius equation using zero‐order kinetics of degradation of the propellant mechanical property i. e. percentage elongation. With the 30 percentage elongation as the critical evaluation parameter, predicted shelf life at 25 °C is 23.97 years and 12.17 years for P‐1 and P‐2 respectively.

Migration of Energetic Plasticizer in Advanced Energetic Composite Propellant Grains

“…post cure reaction which will further increase the crosslinking density of cured propellant is also responsible for toughening of propellant during storage. These observations have already been discussed in our earlier work [22].…”

“…As discussed in our earlier work [22], migration of the nitrate ester plasticizers has an effect on ballistic properties. Burn rate of BTTN based P‐1 and NG/BTTN based P‐2 propellants was reported to decrease during storage at both the temperatures 27° and 55 °C.…”

A review on the effect of ageing on the ballistic properties of solid gun and rocket propellants

“…Christo da Cunha and Rocco [60] provided a detailed overview of the types of methods used to assess the combustion behaviour of solid rocket motor propellants. The acoustic emission technique has been reported for assessing rocket propellants [20]. It is also possible to determine the burning rate of small motors on a test bench [20,61,62].…”

“…The acoustic emission technique has been reported for assessing rocket propellants [20]. It is also possible to determine the burning rate of small motors on a test bench [20,61,62].…”

“…For all classes of propellant, ageing, which is essentially the deterioration and change in the chemical, physical and mechanical properties, limits the time in which the materials can be safely stored or used [14]. The kinetics of the decomposition processes [15] and the effect of ageing in order to describe the chemical and mechanical shelf life of propellants have been extensively reported [13,[16][17][18][19][20][21].…”