ADN Recrystallization and Microencapsulation with HTPB by Simple Coacervation

Author(s)

Silva, Jessica de Oliveira ^[1] ; Cardoso, Kamila Pereira ^[2] ; Campos Silva, Josiane Ribeiro ^[1] ; Kawachi, Elizabete Yoshie ^[1] ; Nagamachi, Marcio Yuji ^[2] ; de Araujo Ferrao, Luiz Fernando ^[1]

Affiliation

^[1] Inst Tecnol Aeronaut, Dept Quim, Praca Marechal Eduardo Gomes 50, BR-12228900 Sao Jose Dos Campos, SP - Brazil

^[2] Inst Aeronaut & Espaco, Div Propulsao, Praca Mal Eduardo Gomes 50, BR-12228904 Sao Jose Dos Campos, SP - Brazil

• Document type: Journal article
• Source: PROPELLANTS EXPLOSIVES PYROTECHNICS; v. 45, n. 5, p. 705-713, MAY 2020.
• Web of Science Citations: 1

Abstract

Ammonium dinitramide (ADN) has been considered the potential substitute for ammonium perchlorate in solid green propellants. However, it has also some drawbacks due to its high hygroscopicity and chemical incompatibility with some of the components present in composite propellant formulations. On the other hand, ADN melts at temperatures below degradation, which makes emulsion crystallization an important method to prepare spherical ADN particles that benefit both propellant slurry processing and casting. Spherical ADN particles were prepared by emulsion crystallization to be used for the microencapsulation studies, and whose method was assessed to better understand which parameters may affect the ADN particles formation. Microencapsulation protects ADN particles as it addresses hygroscopicity besides the given protection from chemical incompatibility. Polyurethane made of hydroxyl-terminated polybutadiene was selected as a coating material because of its common use in propellants as a binder. Also, the good performance of methylene diphenyl diisocyanate as a curing agent was such that it was used in the whole study. The number of layers and the processing time played important roles in the formation of the capsule as seen in the impermeability tests. Besides, drying at 50 degrees C for 168 h showed to be even more beneficial on average for the capsule protective property. Chemical compatibility between the capsule and ADN was confirmed at 60 degrees C which allows it to be used as a protective coating. However, the obtained average coating thickness of ten microns has to be reduced yet with more efficient protective coating materials. (AU)

• FAPESP's process: 17/00618-5 - Study and development of a particulate ADN based propellant with protective coating
• Grantee: Jessica de Oliveira Silva
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 19/03729-8 - Theoretical and experimental development of energetic materials applied to chemical propulsion
• Grantee: Luiz Fernando de Araújo Ferrão
• Support Opportunities: Regular Research Grants