In situ synthesis of polyurethane–TiO2 nanocomposite and performance in solid propellants

Abstract

Achieving a homogeneous nanoparticle dispersion is a frequent challenge in the preparation of polymer–matrix nanocomposites. In this paper, we report a polyurethane–TiO₂ composite with improved nanoparticle dispersion by the in situ synthesis of TiO₂ nanoparticles in a solution containing the pre-polymer hydroxyl-terminated polybutadiene (HTPB). The coordination chemistry of titanium with the functional groups of HTPB was studied by ¹H NMR spectroscopy, and protective methods were developed to prevent undesired side reactions. The resulting synthesis approach produced a uniform dispersion of mesoporous anatase TiO₂ nanoparticles with minimal agglomeration in HTPB, which could then be cast and cured into bulk polyurethane composites. The performance of the polyurethane–TiO₂ composite as a solid propellant binder was investigated. The in situ TiO₂ nanoparticles demonstrated substantially higher activity as combustion catalysts compared to TiO₂ nanoparticles incorporated into polyurethane by conventional powder or solution mixing methods.