Development of High‐Performance <scp>HTPB</scp> and Cerium Oxide‐Based Polyurethane Composite Liners for Solid Rocket Motors

ABSTRACT Polyurethanes based on hydroxyl‐terminated polybutadiene (HTPB) have been utilized as liners in solid rocket motors due to their compatibility with propellant systems and flexible mechanical properties. However, enhancing the liners' thermal stability and mechanical strength remains a significant challenge in extreme operational environments. This study focuses on the development of an advanced composite liner for solid rocket motors (SRMs) based on HTPB and cerium oxide (CeO₂) reinforced polyurethanes (PUs). The novel HTPB/CeO₂ polyurethane composite has been synthesized to enhance the mechanical and thermal properties essential for high‐performance SRMs. These composites were characterized using Fourier transform infrared spectroscopy (FTIR), rheological analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mechanical testing, x‐ray diffraction (XRD), thermal conductivity measurements, and the limited oxygen index (LOI). With increasing CeO₂ content, the pot life decreased from 377 to 201 min. In contrast, thermal stability, as indicated by T₅%, improved from 321°C to 357°C. The inclusion of CeO₂ altered the amorphous nature of the PU composites, as confirmed by both DSC and XRD results. Additionally, tensile strength increased from 3.89 to 7.94 MPa, and elongation at break increased from 495% to 600% at a CeO₂ loading of 9% before decreasing to 362% at 12% loading. CeO₂ acted as a reinforcing agent and contributed to improving flame retardancy. These findings confirm the potential of the HTPB/CeO₂‐based composite liner to outperform traditional materials in terms of mechanical properties, thermal stability, and flame retardancy.