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Fast burning rocket propellants based on silicone binders. New aspects of an old system

: Eisele, S.; Gerber, P.; Menke, K.


Propellants, explosives, pyrotechnics 27 (2002), No.3, pp.161-167
ISSN: 0340-7462
ISSN: 0721-3115
ISSN: 1521-4087
Journal Article
Fraunhofer ICT ()

Fast burning rocket propellants based on ammonium perchlorate (AP) and polydimethylsiloxane (PDMS) binders have been formulated and basically characterized in aluminized and non aluminized versions. The thermodynamic performance of PDMS bound propellants is limited by the evaporation point of silicon dioxide (crystobalite at 2863 K), which is formed during the combustion. The maximum specific impulses calculated with an expansion ratio of 70: 1 are I-SP = 2340 N s/kg (238 s) for AP/PDMS and Isp = 2430 N s/kg (247 s) for AP/Al/PDMS formulations. With a tri-modal AP-fraction of 200 mum, 30 mum and 2 mum it was possible to achieve processable propellants with 83% and 84% solid loading. They give burning rates close to 60 mm/s at 10 MPa and pressure exponents between 0.5 and 0.6 in the range of 7 - 25 MPa. The thermodynamic specific impulse of these systems was calculated to I-SP = 2319 N s/kg (236 s) for AP/PDMS and I-SP = 2403 N s/kg (245 s) for AP/Al/PDMS formulations at 70:1 expansion ratio. Measurements of the glass transition point by DMA and TMA detected a time dependent partial crystallization of the used PDMS close to T-G in the temperature range from -44degreesC to -60degreesC. Basic tests reveal high thermal and chemical stability with flash points over 300degreesC and zero detonation sensitivity at 50 mm diameter. The property profile, so far determined, tends to fulfil the demands for applications as propellants with high burning rates and operating pressures together with a high thermal stability and a low vulnerability.