Nano-Iron as a Catalyst in Isocyanate-Free Rocket Propellants

This study investigates the influence of selected combustion rate catalysts on the ballistic, physicochemical, and mechanical properties of non-isocyanate heterogeneous solid rocket propellants. Methods for curing prepolymers and modifying hydroxyl-terminated polybutadiene (HTPB) to obtain carboxyl-terminated polybutadiene (CTPB) and its epoxidized derivative (EHTPB) are discussed. The initial stage involved the synthesis of CTPB and EHTPB. The obtained compounds were analyzed for viscosity, comparing their properties to those of the base polymer HTPB. FTIR spectra of the synthesized compounds were recorded. Crosslinking systems were formulated based on the synthesized substances and tested for tensile strength. The final stage consisted of preparing solid heterogeneous rocket propellants containing selected catalysts-catocene and iron nanopowder-and evaluating their burning rate, hardness, and density. The results of the rocket propellant tests indicate that both catalysts perform effectively in the proposed system. Significantly higher burning rates were achieved compared to the catalyst-free formulation. The addition of 1% catocene resulted in a 2.5-fold increase in burning rate. Even better performance was observed with iron nanopowder-1% addition led to an almost threefold increase in burning rate. Neither catalyst significantly affected the hardness of the propellant; all samples exhibited hardness values in the range of 71-76 Shore A. Increasing the catocene content led to a decrease in the final propellant density, whereas the addition of iron nanopowder increased the density relative to the base formulation.