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2 Central European Journal of Energetic Materials

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Influence of Dispersion Methods on the Mechanical, Thermal and Rheological Properties of HTPB-based Nanocomposites: Possible Binders for Composite Propellants

100%

Ghosh K. , Kumar A. , Banerjee S. , Patro U. S. , Gupta M.

Central European Journal of Energetic Materials

2019

tom Vol. 16, no. 2

281--298

The present study reports on the methods of preparation for HTPB-clay nanocomposites and their mechanical, thermal and rheological properties for their functional utility as an improved binder system for composite propellants. HTPB-clay nanocomposites were prepared by dispersing organoclay Cloisite 30B (1-3 wt.%) in the polymer matrix by magnetic stirring and high shear mixing. Critical parameters like time, temperature and RPM were optimized. These nanocomposites were cured with toluene diisocyanate in the presence of the cure catalyst DBTDL. The dispersion of the nanoclay was evaluated by using small angle X-ray scattering (SAXS) and energy dispersive X-ray (EDX) spectroscopy. EDX suggested homogeneous distribution while SAXS revealed partial exfoliation of the clay particles in the polymer matrix. Superior dispersion of the nanoclay was obtained by high shear mixing. The tensile properties of the nanocomposites prepared by high shear mixing showed 10-20% more strength and elastic modulus. The nanocomposites showed thermal stability higher than the pristine HTPB. Swelling behavior revealed increased cross linking, and the rheological behavior exhibited higher viscosity of the nanocomposites. In addition, the clay amount was increased up to 10 wt.% and its effect on the mechanical, thermal and swelling behavior was observed. Theoretical performance predictions of composite propellants with nanocomposites revealed their possible functional utility.

Integrating Moisture Isotherms, Compatibility Assessment, and Model Propellant with ADN as an Eco-Friendly Oxidizer

86%

Yadav D. , Ghosh K. , Sadavarte V. , Jawale L. , Pawar R. B. , Kurva R.

Central European Journal of Energetic Materials

2024

tom Vol. 21, no. 3

235--254

This study delves into the use of ammonium dinitramide (ADN) as an eco-friendly substitute for ammonium perchlorate (AP) in solid rocket propellants. ADN based novel propellants were formulated with a nitrile butadiene rubber (NBR) based binder system. Employing Dynamic Vapor Sorption (DVS), ADN’s moisture characteristics were investigated at various temperatures (25, 35, 45 and 55°C) and utilized for propellant processing. Two component chemical compatibility assessments, in adherence to STANAG 4147 standard, were performed using Differential Scanning Calorimetry (DSC) and Vacuum Stability Testing (VST). Subsequently, propellant compositions containing ADN were formulated, and their performance was predicted using NASA’s CEC-71 code. The most promising formulation was processed and thereafter underwent testing for physical, ballistic, and mechanical performance against conventional AP-based propellants at a 500 g batch level. Optimal storage (≤ 25 °C, relative humidity (RH) ≤50%) and processing (35-40 °C, RH ≤35%) performance conditions were identified for ADN, contributing to the successful formulation of high-performance ADN/NBR propellant. The developed propellant showed marginal differences compared to AP/NBR in burn rate and density. However, compatibility issues with the bonding agent, hydantoin resin, led to deficiencies in mechanical strength. These findings contribute to the advancement of eco-friendly propellant technology, showcasing ADN’s potential as a transformative substance in aerospace applications.