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Aerospace 2018, 5(1), 29; https://doi.org/10.3390/aerospace5010029

Prilling and Coating of Ammonium Dinitramide (ADN) Solid Green Propellant in Toluene Mixture Using Ultrasound Sonication

1,†
,
1,†,* and 2,†
1
Department of Chemical and Environmental Engineering, University of Nottingham Malaysia Campus, Semenyih 43500, Malaysia
2
School of Engineering and Physical Science, Heriot-Watt University Malaysia, Putrajaya 62200, Malaysia
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 18 December 2017 / Revised: 6 March 2018 / Accepted: 7 March 2018 / Published: 9 March 2018
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Abstract

Ammonium Dinitramide (ADN) in its generic form has a long needle shaped structure, which hinders higher solid loading. Therefore, it is of utmost importance to optimize its crystal morphology into octagonal shapes. Moreover, the low critical humidity level of ADN renders it unusable in a humid climate. Hence, encapsulation with a hydrophobic polymer is necessary. In the present work, ADN was synthesized by nitration of potassium sulfamate with mixed acid nitration. The product was then mixed with toluene, graphene, citryl ammonium butyl, Cab-o-sil, and coating polymer (Polystyrene or HTPB) and treated with ultrasound to obtain semi-spherical ADN-coated particles. The method offers a reduction in operating temperature and elimination of ADN melting in the shape-altering process. In addition, the ADN product has a similar particle size and thermal stability compared to those in a conventional ADN melt-prilling method. The ADN product investigated under SEM confirms the particle morphological change from long needles into semi-spherical shapes. The particle size obtained, in the micrometer range, is ideal for higher theoretical maximum density. Furthermore, the ultrasound-treated ADN particles show significant reduction in moisture absorption, from 68% to 16% at 65% relative humidity. The DSC result shows no degradation of thermal stability of the coated particles. View Full-Text
Keywords: Ammonium Dinitramide (ADN); ultrasound sonication; green propellant; polymer coating Ammonium Dinitramide (ADN); ultrasound sonication; green propellant; polymer coating
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Rahman, A.; Chin, J.; Cheah, K.H. Prilling and Coating of Ammonium Dinitramide (ADN) Solid Green Propellant in Toluene Mixture Using Ultrasound Sonication. Aerospace 2018, 5, 29.

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