A study on thermal stability and combustion performance of hydroxyl-terminated polybutadiene-paraffin blended fuel

Abstract

ABSTRACT The conventional hydroxyl-terminated polybutadiene (HTPB) hybrid fuel exhibits a slow regression rate which hindered their potential applications. Paraffin-based fuels regress considerably faster than HTPB fuel. Adding paraffin to HTPB could upgrade the regression rate and mechanical performance of a hybrid rocket. In the current study, the thermal decomposition and combustion characteristics of pure HTPB, pure paraffin, HTPB blended with 25, 40, 60, and 80% paraffin were prepared and analyzed. The surface morphology and chemical composition of HTPB-paraffin based fuels were investigated using Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. The thermal stability and combustion characteristics of HTPB-paraffin based fuels were examined using thermogravimetry (TG) analysis and differential scanning calorimetry (DSC) under an oxygen environment. The TG analysis revealed that the thermal stability of fuels decreased with increasing the weight percentage of paraffin in the composition. The TG/DTG results showed that HTPB-paraffin blends ignition and burnout temperatures decreased with increasing the concentrations of paraffin. Finally, the heat of combustion of tested fuels was evaluated using an isothermal oxygen bomb calorimeter. The combustion enthalpy of pure HTPB sample exhibited a value of 35.3 MJ g−1 and 46.2 MJ g−1 for pure paraffin sample. The results revealed that the addition of paraffin in HTPB increased the combustion enthalpy of blended samples.