PYROLYSIS BEHAVIOR OF A PARAFFIN-BASED THERMOPLASTIC POLYMER USED IN HYBRID ROCKET FUEL

Preliminary experimental studies on the flash pyrolysis behavior of low-melting-temperature thermoplastic (LT) were conducted under typical hybrid rocket operation conditions to obtain the decomposition characteristics of the fuel. LTfuel is a paraffin-added thermoplastic elastomer used in hybrid rocket fuel or solid propellant binders. The temperature profile at or near the surface was measured at 2 MPa chamber pressure and 50 kg m(-2) s(-1) oxidizer mass flux by a 25 mu m thermocouple to estimate the phase structure of the fuel. The paraffin oil was flash pyrolyzed in a pyrolysis temperature range of 758 K to 1,313 K (maximum heating rate: 6,400 K s(-1)) with a gas chromatograph mass spectrometer. Under each temperature condition, the paraffin oil produced a unique pyrolysis mass-spectrometry spectrum. In high-temperature regions, the mass spectra indicate lower molecular weight range products. Benzene, methyl benzene, and vinyl benzene were obtained as pyrolysis products from the paraffin oil at a pyrolysis temperature of 1,037 K. These results suggest that the formation of aromatic compounds dominated the paraffin-oil pyrolysis process. The pyrolysis behavior of LT fuel was observed by combining the results of the LT-fuel temperature profile and the pyrolysis process in paraffin oil. The result shows that decomposing the LT fuel may form aromatic compounds around the burning surface.