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2016
Conference Paper
Titel
Accelerated aging and cure kinetics of butacene® containing composite propellants
Abstract
Butacene® (trademark by SNPE, France) with ferrocenyl groups chemically bonded to HTPB backbone leads to high burning rates (rb > 20 mm/s at 7 MPa) in AP-Al based solid composite rocket propellant (SCRP) formulations by keeping the pressure exponent (n) lower than 0.5. Moreover, one can pre-serve the characteristics (kneading process, mechanical properties, pot-life) of conventional HTPB binder formulations together with less sensitivity regarding formation of pyrophoric iron on inner surfaces of the propellant grain. The behavior of Butacene formulations during accelerated aging is analyzed mainly by DMA and additional results are shared with the current study. The thermo-mechanical analysis (TMA) is used to characterize SCRP for thermal expansion. But TMA can be used in part complementary to DMA as it is also sensitive to molecular mobility of the different fractions in highly filled elastomeric network. Butacene preserved insensitivity compared to a formulation with HTPB and using other materials as burning catalyst as CatoceneTM or iron oxide. The interpretation of SCRP cure kinetics is important in order to get the final product free of flaws, i.e., cracks, fissures, voids, and further on interphases with adequate mechanical properties. An important point is to be able to define final point of curing and residual post-curing time because the latter interferes with the accelerated aging and would distort the estimation of in-service time. Thus analysis of rheological and thermal cure kinetics during the evolution of liquid to gel to solid phase is investigated. The curing characteristics of such a system can be modelled in several ways in terms of viscosity build-up w.r.t. time, thermally with DSC via Kissinger method, and in Heat Flow Calorimeter (HFC) and Pressure Curing Cells (PCC). Current work comprise cure modelling in PCC with different SCRP formulations, which allows the investigation of the effect of curing catalyst TPB (triphenyl bismuth), reactivity of formulations containing HTPB and Butacene® versus the formulation based on HTPB binder alone.
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