Abstract
In the present study, the viscoelastic response of three composite solid propellants based on hydroxyl-terminated poly(butadiene), ammonium perchlorate and aluminum has been investigated. The investigation was surveyed by dynamic mechanical analysis over a wide range of temperatures and frequencies. The mechanical properties of these materials are related to the macromolecular structure of the binder as well as to the content and nature of solid fillers. The storage modulus, loss modulus, loss factor and glass transition temperature for each propellant sample have been evaluated. The master curves of storage (log G' vs log ?) and loss modulus (log G'' vs log ?) were generated for each propellant. A comparison of logaT vs temperature curves for all propellants indicate conformance to Williams-Landel-Ferry equation. Choosing the glass transition as the reference temperature, WLF equation constants are determined. Fractional free volume at the glass transition temperature and thermal coefficient of free volume expansion values are in accordance with the consideration that Al is reinforcing filler.
Highlights
In the present study, the viscoelastic response of three composite solid propellants based on hydroxyl-terminated poly(butadiene), ammonium perchlorate and aluminum has been investigated
Composite rocket propellant formulations based on hydroxyl-terminated poly(butadiene) (HTPB) as a binder, ammonium-perchlorate (AP) and aluminum (Al) as solid ingredients, are at present the state-of-the-art propellants in solid fuel rocket engines
To insure the desired degree of crosslinking, isophorone diisocyanate (IPDI) is added in an amount sufficient to generate a ratio of Correspondence: S.J
Summary
The viscoelastic response of three composite solid propellants based on hydroxyl-terminated poly(butadiene), ammonium perchlorate and aluminum has been investigated. Due to presence of a polymeric binder, as viscoelastic materials, composite propellants show time and temperature dependence of mechanical properties. If the reference temperature is such that Т0 - Тg = 50 °C, where Тg is the glass transition temperature, C1 and C2 are general constants with values of 8.86 and 101.6, respectively [2] Since this is a rough approximation, for more accurate calculations it is necessary to determine the values of a shift factor aT, and constants C1 and C2 for each type of rocket propellant. De la Fuente et al analyzed unfilled elastomeric binder and the effect of the different types of fillers on the viscoelastic behavior of a several HTPB based solid composites by dynamic mechanical measurements [3]. Borsus et al showed that Al particles (having OH-groups on the surface) make fine dispersion in polyurethane foams through a molecular bonds between the particles and the binder [5]
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