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Aging of ADN rocket propellant formulations with desmophen®-based elastomer binder

: Cerri, S.; Bohn, M.A.; Menke, K.; Galfetti, L.


Propellants, explosives, pyrotechnics 39 (2014), Nr.4, S.526-537
ISSN: 0340-7462
ISSN: 0721-3115
ISSN: 1521-4087
Fraunhofer ICT ()

Desmophen® binder-based rocket propellant formulations containing ammonium dinitramide (ADN) and different fuel filler types (Al, HMX) were manufactured and investigated. Desmophen® D2220 is a polyesterpolyol. Polyesters are seen as a binder possibility, because of the relatively low temperature of the glass transition region compared to polyether-based prepolymers such as GAP. The analogous formulations with AP instead of ADN were also included for comparison. The aging was followed by SEM, DSC, and DMA measurements. The accelerated aging program was developed on the principle of thermal equivalent load and the generalized van't Hoff rule with a scaling factor equal to F=2.9. The aging was performed in air (RH<10%) at temperature values between 65 and 85°C and aging times adjusted to a thermal equivalent load of 15years at 25°C. DMA measurements of the aged ADN/Desmophen®-based propellants identified changes in the loss factor curve. In contrast to HTPB-Al-AP rocket propellant formulations, the loss factor curve of the ADN formulations with Desmophen®-based elastomer binder shows only one main apparent peak. The loss factor curves were modeled with exponentially modified Gaussian functions, which have revealed the presence of a second hidden peak. It was found that the aging could be characterized by the time-temperature dependence of the areas of the hidden peak. The area increased with aging, which is explained by scissioning of the polymer in the shell around the ADN particles. By this process the strength is reduced, which was recognized by the decrease in storage shear modulus.