This report investigates the pyrolysis properties of both extruded and additively manufactured acrylonitrileacrylonitrile-styrene at material surface temperatures from 350 to 725°C. These temperatures approximate the range of surface temperatures reached during combustion when acrylonitrile-acrylonitrile-styrene is employed as a hybrid rocket propellant. This temperature range is significantly higher than temperatures evaluated during previous acrylonitrile-acrylonitrile-styrene fire-safety combustion and pyrolysis studies. Linear regression rates of acrylonitrile-acrylonitrile-styrene fuel grain material specimens are measured during pyrolysis and used to derive estimates for both the molar and mass-based enthalpies of gasification. Molar values for enthalpy of gasification are estimated from the regression rate data using an Arrhenius-type process model. The mass-based enthalpy of ablation is calculated from the power duty cycle of the heating element used to produce the fuel pyrolysis. Test results compare favorably with the previously published enthalpies of gasification, obtained at significantly lower surface temperatures, for extruded acrylonitrile-acrylonitrile-styrene. The additively manufactured acrylonitrileacrylonitrile-styrene specimens exhibit a minor, but statistically significant, lower enthalpy of vaporization when compared to the extruded specimens.
Acrylonitrile-butadiene-styrene (ABS) is a common industrial plastic that is widely used for structural and piping applications. Because ABS possesses a variety of advantageous material properties, within the past three years ABS plastic blends have been investigated as a potential fuel for hybrid-and solid-propelled rocket systems. Promising results have been achieved. Because ABS as a rocket propellant is a very recent development, a database describing the pyrolysis properties of ABS at the temperatures and heating rates experienced by rocket systems does not exist. Especially important is the current lack of established values for the specific enthalpy of gasification (latent heat of vaporization) for various ABS material formulations. All existing ABS pyrolysis data were collected during fire prevention studies, and were performed at heating rates nearly an order of magnitude lower than those experienced during rocket combustion. This report investigates the pyrolysis properties of ABS at high flux levels and material temperatures from 350 to 700 C. Linear regression rates are measured and used to derive estimates for the specific enthalpy of gasification based on the power duty cycle of the heating element used to produce the fuel pyrolysis. Results for both extruded and additively manufactured ABS are compared. Nomenclature A= Arrhenius pre-exponential scale factor, mm/s ABS = acrylonitrile-butadiene-styrene (acronym) A burn = fuel grain surface burn area, cm 2 A c = fuel chamber cross sectional area , cm 2 A ox = effective total oxidizer injector area, cm 2 A * = nozzle throat area, sonic choke area, cm 2 B = free energy of formation curve fit slope parameter CEA = chemical equilibrium with applications (acronym) c fx = local skin friction coefficient c p = specific heat of solid propellant fuel grain, J/kg-K D final = test specimen final diameter, mm
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