Mechanical Characteristics of Paraffin Wax-HTPB Based Hybrid Rocket Fuel

Paraffin wax has 3–4 times higher regression rate compared to conventional polymeric fuels used in hybrid rocket applications. Hydroxyl-terminated polybutadiene (HTPB) suffers poor mechanical properties and has lower tensile strength, Young’s modulus compared to pure paraffin wax. The mechanical properties of HTPB can suitably be improved by mixing paraffin wax with HTPB. In this study, paraffin wax and HTPB are mixed with different weight ratios to form nine different compositions viz, 100P, 90P, 80P, 70P, 60P, 50P, 40P, 25P and 0P (where P denotes the percentage of paraffin wax and the remaining forms the HTPB system). To understand the effect of addition of paraffin wax with HTPB, nine fuel samples were prepared and experimentally tested for their mechanical properties. It is observed that addition of paraffin wax content in solid fuel composition increases maximum stress and Young’s modulus in the range of 16–74% and 15–97% respectively. It is also observed that addition of paraffin wax content in solid fuel composition decreases percentage of elongation by 98–57%. The surface morphology and chemical composition were examined using Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) to understand the blending of paraffin wax + HTPB and to find out the occurrence of chemical reaction during mixing and curing processes.