Improving Physical Properties of Wax-Based Fuels and Its Effect on Regression Rate

Abstract

Wax is a brittle thermoplastic material, and its physical properties must be improved so that it can be used as fuel in hybrid rockets. In this study, we use microcrystalline wax and paraffin wax by mixing ethylene vinyl acetate copolymer (EVA) and stearic acid; conduct tensile tests and firing tests; and measure viscosities to obtain the effect of improvement in physical properties on the regression rate. According to the results, microcrystalline wax has higher strength than paraffin wax, and the tensile strength increases as the EVA and the stearic acid contents increase. By contrast, mixing EVA with wax decreases the regression rate, but mixing stearic acid hardly affects the regression rate. The regression rates of these wax-based fuels increase almost proportionally with power of the coefficient of the viscosity of molten fuel at a constant temperature, which agrees with the results of the theoretical analysis.